DOE Office of Scientific and Technical Information (OSTI.GOV)

Turkov, Vadim K.; Baranov, Alexander V.; Fedorov, Anatoly V.

Doped semiconductor nanocrystals is a versatile material base for contemporary photonics and optoelectronics devices. Here, for the first time to the best of our knowledge, we theoretically calculate the radiative decay rates of the lowest-energy states of donor impurity in spherical nanocrystals made of four widely used semiconductors: ZnS, CdSe, Ge, and GaAs. The decay rates were shown to vary significantly with the nanocrystal radius, increasing by almost three orders of magnitude when the radius is reduced from 15 to 5 nm. Our results suggest that spontaneous emission may dominate the decay of impurity states at low temperatures, and shouldmore » be taken into account in the design of advanced materials and devices based on doped semiconductor nanocrystals.« less

Back-side readout semiconductor photomultiplier

DOEpatents

Choong, Woon-Seng; Holland, Stephen E

2014-05-20

This disclosure provides systems, methods, and apparatus related to semiconductor photomultipliers. In one aspect, a device includes a p-type semiconductor substrate, the p-type semiconductor substrate having a first side and a second side, the first side of the p-type semiconductor substrate defining a recess, and the second side of the p-type semiconductor substrate being doped with n-type ions. A conductive material is disposed in the recess. A p-type epitaxial layer is disposed on the second side of the p-type semiconductor substrate. The p-type epitaxial layer includes a first region proximate the p-type semiconductor substrate, the first region being implanted with p-type ions at a higher doping level than the p-type epitaxial layer, and a second region disposed on the first region, the second region being doped with p-type ions at a higher doping level than the first region.

Spontaneous and strong multi-layer graphene n-doping on soda-lime glass and its application in graphene-semiconductor junctions

DOE PAGES

Dissanayake, D. M. N. M.; Ashraf, A.; Dwyer, D.; ...

2016-02-12

Scalable and low-cost doping of graphene could improve technologies in a wide range of fields such as microelectronics, optoelectronics, and energy storage. While achieving strong p-doping is relatively straightforward, non-electrostatic approaches to n-dope graphene, such as chemical doping, have yielded electron densities of 9.5 × 10 12 e/cm 2 or below. Furthermore, chemical doping is susceptible to degradation and can adversely affect intrinsic graphene’s properties. Here we demonstrate strong (1.33 × 10 13 e/cm 2), robust, and spontaneous graphene n-doping on a soda-lime-glass substrate via surface-transfer doping from Na without any external chemical, high-temperature, or vacuum processes. Remarkably, the n-dopingmore » reaches 2.11 × 10 13 e/cm 2 when graphene is transferred onto a p-type copper indium gallium diselenide (CIGS) semiconductor that itself has been deposited onto soda-lime-glass, via surface-transfer doping from Na atoms that diffuse to the CIGS surface. Using this effect, we demonstrate an n-graphene/p-semiconductor Schottky junction with ideality factor of 1.21 and strong photo-response. As a result, the ability to achieve strong and persistent graphene n-doping on low-cost, industry-standard materials paves the way toward an entirely new class of graphene-based devices such as photodetectors, photovoltaics, sensors, batteries, and supercapacitors.« less

N-Doped Hybrid Graphene and Boron Nitride Armchair Nanoribbons As Nonmagnetic Semiconductors with Widely Tunable Electronic Properties

NASA Astrophysics Data System (ADS)

Habibpour, Razieh; Kashi, Eslam; Vazirib, Raheleh

2018-03-01

The electronic and chemical properties of N-doped hybrid graphene and boron nitride armchair nanoribbons (N-doped a-GBNNRs) in comparison with graphene armchair nanoribbon (pristine a-GNR) and hybrid graphene and boron nitride armchair nanoribbon (C-3BN) are investigated using the density functional theory method. The results show that all the mentioned nanoribbons are nonmagnetic direct semiconductors and all the graphitic N-doped a-GBNNRs are n-type semiconductors while the rest are p-type semiconductors. The N-doped graphitic 2 and N-doped graphitic 3 structures have the lowest work function and the highest number of valence electrons (Lowdin charges) which confirms that they are effective for use in electronic device applications.

Rare earth doped III-nitride semiconductors for spintronic and optoelectronic applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Palai, Ratnakar

2016-10-01

Since last four decades the information and communication technologies are relying on the semiconductor materials. Currently a great deal of attention is being focused on adding spin degree-of-freedom into semiconductor to create a new area of solid-state electronics, called spintronics. In spintronics not only the current but also its spin state is controlled. Such materials need to be good semiconductors for easy integration in typical integrated circuits with high sensitivity to the spin orientation, especially room temperature ferromagnetism being an important desirable property. GaN is considered to be the most important semiconductor after silicon. It is widely used for the production of green, blue, UV, and white LEDs in full color displays, traffic lights, automotive lightings, and general room lighting using white LEDs. GaN-based systems also show promise for microwave and high power electronics intended for radar, satellite, wireless base stations and spintronic applications. Rare earth (Yb, Eu, Er, and Tm) doped GaN shows many interesting optoelectronic and magnetoptic properties e. g. sharp emission from UV through visible to IR, radiation hardness, and ferromagnetism. The talk will be focused on fabrication, optoelectronic (photoluminescence, cathodeluminescence, magnetic, and x-ray photoelectron spectroscopy) properties of some rare earth doped GaN and InGaN semiconductor nanostructures grown by plasma assisted molecular beam epitaxy (MBE) and future applications.

Insight into doping efficiency of organic semiconductors from the analysis of the density of states in n-doped C60 and ZnPc

NASA Astrophysics Data System (ADS)

Gaul, Christopher; Hutsch, Sebastian; Schwarze, Martin; Schellhammer, Karl Sebastian; Bussolotti, Fabio; Kera, Satoshi; Cuniberti, Gianaurelio; Leo, Karl; Ortmann, Frank

2018-05-01

Doping plays a crucial role in semiconductor physics, with n-doping being controlled by the ionization energy of the impurity relative to the conduction band edge. In organic semiconductors, efficient doping is dominated by various effects that are currently not well understood. Here, we simulate and experimentally measure, with direct and inverse photoemission spectroscopy, the density of states and the Fermi level position of the prototypical materials C60 and zinc phthalocyanine n-doped with highly efficient benzimidazoline radicals (2-Cyc-DMBI). We study the role of doping-induced gap states, and, in particular, of the difference Δ1 between the electron affinity of the undoped material and the ionization potential of its doped counterpart. We show that this parameter is critical for the generation of free carriers and influences the conductivity of the doped films. Tuning of Δ1 may provide alternative strategies to optimize the electronic properties of organic semiconductors.

Semiconductor P-I-N detector

DOEpatents

Sudharsanan, Rengarajan; Karam, Nasser H.

2001-01-01

A semiconductor P-I-N detector including an intrinsic wafer, a P-doped layer, an N-doped layer, and a boundary layer for reducing the diffusion of dopants into the intrinsic wafer. The boundary layer is positioned between one of the doped regions and the intrinsic wafer. The intrinsic wafer can be composed of CdZnTe or CdTe, the P-doped layer can be composed of ZnTe doped with copper, and the N-doped layer can be composed of CdS doped with indium. The boundary layers is formed of an undoped semiconductor material. The boundary layer can be deposited onto the underlying intrinsic wafer. The doped regions are then typically formed by a deposition process or by doping a section of the deposited boundary layer.

Method of manufacturing semiconductor having group II-group VI compounds doped with nitrogen

DOEpatents

Compaan, Alvin D.; Price, Kent J.; Ma, Xianda; Makhratchev, Konstantin

2005-02-08

A method of making a semiconductor comprises depositing a group II-group VI compound onto a substrate in the presence of nitrogen using sputtering to produce a nitrogen-doped semiconductor. This method can be used for making a photovoltaic cell using sputtering to apply a back contact layer of group II-group VI compound to a substrate in the presence of nitrogen, the back coating layer being doped with nitrogen. A semiconductor comprising a group II-group VI compound doped with nitrogen, and a photovoltaic cell comprising a substrate on which is deposited a layer of a group II-group VI compound doped with nitrogen, are also included.

Semiconductor-based photoelectrochemical water splitting at the limit of very wide depletion region

DOE PAGES

Liu, Mingzhao; Lyons, John L.; Yan, Danhua H.; ...

2015-11-23

In semiconductor-based photoelectrochemical (PEC) water splitting, carrier separation and delivery largely relies on the depletion region formed at the semiconductor/water interface. As a Schottky junction device, the trade-off between photon collection and minority carrier delivery remains a persistent obstacle for maximizing the performance of a water splitting photoelectrode. Here, it is demonstrated that the PEC water splitting efficiency for an n-SrTiO 3 (n-STO) photoanode is improved very significantly despite its weak indirect band gap optical absorption (α < 10⁴ cm⁻¹), by widening the depletion region through engineering its doping density and profile. Graded doped n-SrTiO 3 photoanodes are fabricated withmore » their bulk heavily doped with oxygen vacancies but their surface lightly doped over a tunable depth of a few hundred nanometers, through a simple low temperature re-oxidation technique. The graded doping profile widens the depletion region to over 500 nm, thus leading to very efficient charge carrier separation and high quantum efficiency (>70%) for the weak indirect transition. As a result, this simultaneous optimization of the light absorption, minority carrier (hole) delivery, and majority carrier (electron) transport by means of a graded doping architecture may be useful for other indirect band gap photocatalysts that suffer from a similar problem of weak optical absorption.« less

High resolution three-dimensional doping profiler

DOEpatents

Thundat, Thomas G.; Warmack, Robert J.

1999-01-01

A semiconductor doping profiler provides a Schottky contact at one surface and an ohmic contact at the other. While the two contacts are coupled to a power source, thereby establishing an electrical bias in the semiconductor, a localized light source illuminates the semiconductor to induce a photocurrent. The photocurrent changes in accordance with the doping characteristics of the semiconductor in the illuminated region. By changing the voltage of the power source the depth of the depletion layer can be varied to provide a three dimensional view of the local properties of the semiconductor.

Unraveling the mechanism of molecular doping in organic semiconductors.

PubMed

Mityashin, Alexander; Olivier, Yoann; Van Regemorter, Tanguy; Rolin, Cedric; Verlaak, Stijn; Martinelli, Nicolas G; Beljonne, David; Cornil, Jérôme; Genoe, Jan; Heremans, Paul

2012-03-22

The mechanism by which molecular dopants donate free charge carriers to the host organic semiconductor is investigated and is found to be quite different from the one in inorganic semiconductors. In organics, a strong correlation between the doping concentration and its charge donation efficiency is demonstrated. Moreover, there is a threshold doping level below which doping simply has no electrical effect. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Large Modulation of Charge Carrier Mobility in Doped Nanoporous Organic Transistors.

PubMed

Zhang, Fengjiao; Dai, Xiaojuan; Zhu, Weikun; Chung, Hyunjoong; Diao, Ying

2017-07-01

Molecular doping of organic electronics has shown promise to sensitively modulate important device metrics. One critical challenge is the disruption of structure order upon doping of highly crystalline organic semiconductors, which significantly reduces the charge carrier mobility. This paper demonstrates a new method to achieve large modulation of charge carrier mobility via channel doping without disrupting the molecular ordering. Central to the method is the introduction of nanopores into the organic semiconductor thin films via a simple and robust templated meniscus-guided coating method. Using this method, the charge carrier mobility of C 8 -benzothieno[3,2-b]benzothiophene transistors is boosted by almost sevenfold. This paper further demonstrates enhanced electron transport by close to an order of magnitude in a diketopyrrolopyrrole-based donor-acceptor polymer. Combining spectroscopic measurements, density functional theory calculations, and electrical characterizations, the doping mechanism is identified as partial-charge-transfer induced trap filling. The nanopores serve to enhance the dopant/organic semiconductor charge transfer reaction by exposing the π-electrons to the pore wall. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Large Modulation of Charge Carrier Mobility in Doped Nanoporous Organic Transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fengjiao; Dai, Xiaojuan; Zhu, Weikun

Molecular doping of organic electronics has shown promise to sensitively modulate important device metrics. One critical challenge is the disruption of structure order upon doping of highly crystalline organic semiconductors, which significantly reduces the charge carrier mobility. This paper demonstrates a new method to achieve large modulation of charge carrier mobility via channel doping without disrupting the molecular ordering. Central to the method is the introduction of nanopores into the organic semiconductor thin films via a simple and robust templated meniscus-guided coating method. Using this method, the charge carrier mobility of C8-benzothieno[3,2-b]benzothiophene transistors is boosted by almost sevenfold. This papermore » further demonstrates enhanced electron transport by close to an order of magnitude in a diketopyrrolopyrrole-based donor–acceptor polymer. Combining spectroscopic measurements, density functional theory calculations, and electrical characterizations, the doping mechanism is identified as partial-charge-transfer induced trap filling. The nanopores serve to enhance the dopant/organic semiconductor charge transfer reaction by exposing the π-electrons to the pore wall.« less

Doped polymer semiconductors with ultrahigh and ultralow work functions for ohmic contacts.

PubMed

Tang, Cindy G; Ang, Mervin C Y; Choo, Kim-Kian; Keerthi, Venu; Tan, Jun-Kai; Syafiqah, Mazlan Nur; Kugler, Thomas; Burroughes, Jeremy H; Png, Rui-Qi; Chua, Lay-Lay; Ho, Peter K H

2016-11-24

To make high-performance semiconductor devices, a good ohmic contact between the electrode and the semiconductor layer is required to inject the maximum current density across the contact. Achieving ohmic contacts requires electrodes with high and low work functions to inject holes and electrons respectively, where the work function is the minimum energy required to remove an electron from the Fermi level of the electrode to the vacuum level. However, it is challenging to produce electrically conducting films with sufficiently high or low work functions, especially for solution-processed semiconductor devices. Hole-doped polymer organic semiconductors are available in a limited work-function range, but hole-doped materials with ultrahigh work functions and, especially, electron-doped materials with low to ultralow work functions are not yet available. The key challenges are stabilizing the thin films against de-doping and suppressing dopant migration. Here we report a general strategy to overcome these limitations and achieve solution-processed doped films over a wide range of work functions (3.0-5.8 electronvolts), by charge-doping of conjugated polyelectrolytes and then internal ion-exchange to give self-compensated heavily doped polymers. Mobile carriers on the polymer backbone in these materials are compensated by covalently bonded counter-ions. Although our self-compensated doped polymers superficially resemble self-doped polymers, they are generated by separate charge-carrier doping and compensation steps, which enables the use of strong dopants to access extreme work functions. We demonstrate solution-processed ohmic contacts for high-performance organic light-emitting diodes, solar cells, photodiodes and transistors, including ohmic injection of both carrier types into polyfluorene-the benchmark wide-bandgap blue-light-emitting polymer organic semiconductor. We also show that metal electrodes can be transformed into highly efficient hole- and electron-injection contacts via the self-assembly of these doped polyelectrolytes. This consequently allows ambipolar field-effect transistors to be transformed into high-performance p- and n-channel transistors. Our strategy provides a method for producing ohmic contacts not only for organic semiconductors, but potentially for other advanced semiconductors as well, including perovskites, quantum dots, nanotubes and two-dimensional materials.

New Fluoride-arsenide Diluted Magnetic Semiconductor (Ba,K)F(Zn,Mn)As with Independent Spin and Charge Doping

NASA Astrophysics Data System (ADS)

Chen, Bijuan; Deng, Zheng; Li, Wenmin; Gao, Moran; Liu, Qingqing; Gu, C. Z.; Hu, F. X.; Shen, B. G.; Frandsen, Benjamin; Cheung, Sky; Lian, Liu; Uemura, Yasutomo J.; Ding, Cui; Guo, Shengli; Ning, Fanlong; Munsie, Timothy J. S.; Wilson, Murray Neff; Cai, Yipeng; Luke, Graeme; Guguchia, Zurab; Yonezawa, Shingo; Li, Zhi; Jin, Changqing

2016-11-01

We report the discovery of a new fluoride-arsenide bulk diluted magnetic semiconductor (Ba,K)F(Zn,Mn)As with the tetragonal ZrCuSiAs-type structure which is identical to that of the “1111” iron-based superconductors. The joint hole doping via (Ba,K) substitution & spin doping via (Zn,Mn) substitution results in ferromagnetic order with Curie temperature up to 30 K and demonstrates that the ferromagnetic interactions between the localized spins are mediated by the carriers. Muon spin relaxation measurements confirm the intrinsic nature of the long range magnetic order in the entire volume in the ferromagnetic phase. This is the first time that a diluted magnetic semiconductor with decoupled spin and charge doping is achieved in a fluoride compound. Comparing to the isostructure oxide counterpart of LaOZnSb, the fluoride DMS (Ba,K)F(Zn,Mn)As shows much improved semiconductive behavior that would be benefit for further application developments.

Molecular Electrical Doping of Organic Semiconductors: Fundamental Mechanisms and Emerging Dopant Design Rules.

PubMed

Salzmann, Ingo; Heimel, Georg; Oehzelt, Martin; Winkler, Stefanie; Koch, Norbert

2016-03-15

Today's information society depends on our ability to controllably dope inorganic semiconductors, such as silicon, thereby tuning their electrical properties to application-specific demands. For optoelectronic devices, organic semiconductors, that is, conjugated polymers and molecules, have emerged as superior alternative owing to the ease of tuning their optical gap through chemical variability and their potential for low-cost, large-area processing on flexible substrates. There, the potential of molecular electrical doping for improving the performance of, for example, organic light-emitting devices or organic solar cells has only recently been established. The doping efficiency, however, remains conspicuously low, highlighting the fact that the underlying mechanisms of molecular doping in organic semiconductors are only little understood compared with their inorganic counterparts. Here, we review the broad range of phenomena observed upon molecularly doping organic semiconductors and identify two distinctly different scenarios: the pairwise formation of both organic semiconductor and dopant ions on one hand and the emergence of ground state charge transfer complexes between organic semiconductor and dopant through supramolecular hybridization of their respective frontier molecular orbitals on the other hand. Evidence for the occurrence of these two scenarios is subsequently discussed on the basis of the characteristic and strikingly different signatures of the individual species involved in the respective doping processes in a variety of spectroscopic techniques. The critical importance of a statistical view of doping, rather than a bimolecular picture, is then highlighted by employing numerical simulations, which reveal one of the main differences between inorganic and organic semiconductors to be their respective density of electronic states and the doping induced changes thereof. Engineering the density of states of doped organic semiconductors, the Fermi-Dirac occupation of which ultimately determines the doping efficiency, thus emerges as key challenge. As a first step, the formation of charge transfer complexes is identified as being detrimental to the doping efficiency, which suggests sterically shielding the functional core of dopant molecules as an additional design rule to complement the requirement of low ionization energies or high electron affinities in efficient n-type or p-type dopants, respectively. In an extended outlook, we finally argue that, to fully meet this challenge, an improved understanding is required of just how the admixture of dopant molecules to organic semiconductors does affect the density of states: compared with their inorganic counterparts, traps for charge carriers are omnipresent in organic semiconductors due to structural and chemical imperfections, and Coulomb attraction between ionized dopants and free charge carriers is typically stronger in organic semiconductors owing to their lower dielectric constant. Nevertheless, encouraging progress is being made toward developing a unifying picture that captures the entire range of doping induced phenomena, from ion-pair to complex formation, in both conjugated polymers and molecules. Once completed, such a picture will provide viable guidelines for synthetic and supramolecular chemistry that will enable further technological advances in organic and hybrid organic/inorganic devices.

Photochemical Hydrogen Doping Induced Embedded Two-Dimensional Metallic Channel Formation in InGaZnO at Room Temperature.

PubMed

Kim, Myeong-Ho; Lee, Young-Ahn; Kim, Jinseo; Park, Jucheol; Ahn, Seungbae; Jeon, Ki-Joon; Kim, Jeong Won; Choi, Duck-Kyun; Seo, Hyungtak

2015-10-27

The photochemical tunability of the charge-transport mechanism in metal-oxide semiconductors is of great interest since it may offer a facile but effective semiconductor-to-metal transition, which results from photochemically modified electronic structures for various oxide-based device applications. This might provide a feasible hydrogen (H)-radical doping to realize the effectively H-doped metal oxides, which has not been achieved by thermal and ion-implantation technique in a reliable and controllable way. In this study, we report a photochemical conversion of InGaZnO (IGZO) semiconductor to a transparent conductor via hydrogen doping to the local nanocrystallites formed at the IGZO/glass interface at room temperature. In contrast to thermal or ionic hydrogen doping, ultraviolet exposure of the IGZO surface promotes a photochemical reaction with H radical incorporation to surface metal-OH layer formation and bulk H-doping which acts as a tunable and stable highly doped n-type doping channel and turns IGZO to a transparent conductor. This results in the total conversion of carrier conduction property to the level of metallic conduction with sheet resistance of ∼16 Ω/□, room temperature Hall mobility of 11.8 cm(2) V(-1) sec(-1), the carrier concentration at ∼10(20) cm(-3) without any loss of optical transparency. We demonstrated successful applications of photochemically highly n-doped metal oxide via optical dose control to transparent conductor with excellent chemical and optical doping stability.

Hole mobility in various transition-metal-oxides doped organic semiconductor films

NASA Astrophysics Data System (ADS)

Yoo, Seung-Jun; Lee, Jeong-Hwan; Kim, Jae-Min; Kim, Jang-Joo

2017-01-01

Hole mobility in various p-doped organic semiconductors possessing different energetic disorder parameters in low-to-moderate doping range is reported. The hole mobility is reduced by orders of magnitude and converged to 10-7-10-6 cm2/Vs at a doping concentration of 5 mol. % for all the materials, even though the pristine organic films possess orders of magnitude of different mobilities from 10-5 to 10-3 cm2/Vs. These results indicate that the ionized dopants behave as traps for generated carriers to reduce the mobility. Further increase in the doping concentration either increases or decreases the mobility depending on the energetic disorder parameters of the organic films. These phenomena are interpreted based on the Coulomb trap depth of the ionized dopants and energetic disorder of the host layers.

N-doping of organic semiconductors by bis-metallosandwich compounds

DOEpatents

Barlow, Stephen; Qi, Yabing; Kahn, Antoine; Marder, Seth; Kim, Sang Bok; Mohapatra, Swagat K.; Guo, Song

2016-01-05

The various inventions disclosed, described, and/or claimed herein relate to the field of methods for n-doping organic semiconductors with certain bis-metallosandwich compounds, the doped compositions produced, and the uses of the doped compositions in organic electronic devices. Metals can be manganese, rhenium, iron, ruthenium, osmium, rhodium, or iridium. Stable and efficient doping can be achieved.

Co-Doped ZnO nanoparticles: minireview.

PubMed

Djerdj, Igor; Jaglicić, Zvonko; Arcon, Denis; Niederberger, Markus

2010-07-01

Diluted magnetic semiconductors with a Curie temperature exceeding 300 K are promising candidates for spintronic devices and spin-based electronic technologies. We review recent achievements in the field of one of them: Co-doped ZnO at the nanoparticulate scale.

Isolated molecular dopants in pentacene observed by scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Ha, Sieu D.; Kahn, Antoine

2009-11-01

Doping is essential to the control of electronic structure and conductivity of semiconductor materials. Whereas doping of inorganic semiconductors is well established, doping of organic molecular semiconductors is still relatively poorly understood. Using scanning tunneling microscopy, we investigate, at the molecular scale, surface and subsurface tetrafluoro-tetracyanoquinodimethane p -dopants in the prototypical molecular semiconductor pentacene. Surface dopants diffuse to pentacene vacancies and appear as negatively charged centers, consistent with the standard picture of an ionized acceptor. Subsurface dopants, however, have the effect of a positive charge, evidence that the donated hole is localized by the parent acceptor counterion, in contrast to the model of doping in inorganic semiconductors. Scanning tunneling spectroscopy shows that the electron potential energy is locally lowered near a subsurface dopant feature, in agreement with the localized hole model.

Electron gas grid semiconductor radiation detectors

DOEpatents

Lee, Edwin Y.; James, Ralph B.

2002-01-01

An electron gas grid semiconductor radiation detector (EGGSRAD) useful for gamma-ray and x-ray spectrometers and imaging systems is described. The radiation detector employs doping of the semiconductor and variation of the semiconductor detector material to form a two-dimensional electron gas, and to allow transistor action within the detector. This radiation detector provides superior energy resolution and radiation detection sensitivity over the conventional semiconductor radiation detector and the "electron-only" semiconductor radiation detectors which utilize a grid electrode near the anode. In a first embodiment, the EGGSRAD incorporates delta-doped layers adjacent the anode which produce an internal free electron grid well to which an external grid electrode can be attached. In a second embodiment, a quantum well is formed between two of the delta-doped layers, and the quantum well forms the internal free electron gas grid to which an external grid electrode can be attached. Two other embodiments which are similar to the first and second embodiment involve a graded bandgap formed by changing the composition of the semiconductor material near the first and last of the delta-doped layers to increase or decrease the conduction band energy adjacent to the delta-doped layers.

Back wall solar cell

NASA Technical Reports Server (NTRS)

Brandhorst, H. W., Jr. (Inventor)

1978-01-01

A solar cell is disclosed which comprises a first semiconductor material of one conductivity type with one face having the same conductivity type but more heavily doped to form a field region arranged to receive the radiant energy to be converted to electrical energy, and a layer of a second semiconductor material, preferably highly doped, of opposite conductivity type on the first semiconductor material adjacent the first semiconductor material at an interface remote from the heavily doped field region. Instead of the opposite conductivity layer, a metallic Schottky diode layer may be used, in which case no additional back contact is needed. A contact such as a gridded contact, previous to the radiant energy may be applied to the heavily doped field region of the more heavily doped, same conductivity material for its contact.

Semiconductor systems utilizing materials that form rectifying junctions in both N and P-type doping regions, whether metallurgically or field induced, and methods of use

DOEpatents

Welch, James D.

2000-01-01

Disclosed are semiconductor systems, such as integrated circuits utilizing Schotky barrier and/or diffused junction technology, which semiconductor systems incorporate material(s) that form rectifying junctions in both metallurgically and/or field induced N and P-type doping regions, and methods of their use. Disclosed are Schottky barrier based inverting and non-inverting gate voltage channel induced semiconductor single devices with operating characteristics similar to multiple device CMOS systems and which can be operated as modulators, N and P-channel MOSFETS and CMOS formed therefrom, and (MOS) gate voltage controlled rectification direction and gate voltage controlled switching devices, and use of such material(s) to block parasitic current flow pathways. Simple demonstrative five mask fabrication procedures for inverting and non-inverting gate voltage channel induced semiconductor single devices with operating characteristics similar to multiple device CMOS systems are also presented.

Compositions of doped, co-doped and tri-doped semiconductor materials

DOEpatents

Lynn, Kelvin [Pullman, WA; Jones, Kelly [Colfax, WA; Ciampi, Guido [Watertown, MA

2011-12-06

Semiconductor materials suitable for being used in radiation detectors are disclosed. A particular example of the semiconductor materials includes tellurium, cadmium, and zinc. Tellurium is in molar excess of cadmium and zinc. The example also includes aluminum having a concentration of about 10 to about 20,000 atomic parts per billion and erbium having a concentration of at least 10,000 atomic parts per billion.

Unusually large chemical potential shift in a degenerate semiconductor: Angle-resolved photoemission study of SnSe and Na-doped SnSe

NASA Astrophysics Data System (ADS)

Maeda, M.; Yamamoto, K.; Mizokawa, T.; Saini, N. L.; Arita, M.; Namatame, H.; Taniguchi, M.; Tan, G.; Zhao, L. D.; Kanatzidis, M. G.

2018-03-01

We have studied the electronic structure of SnSe and Na-doped SnSe by means of angle-resolved photoemission spectroscopy. The valence-band top reaches the Fermi level by the Na doping, indicating that Na-doped SnSe can be viewed as a degenerate semiconductor. However, in the Na-doped system, the chemical potential shift with temperature is unexpectedly large and is apparently inconsistent with the degenerate semiconductor picture. The large chemical potential shift and anomalous spectral shape are key ingredients for an understanding of the novel metallic state with the large thermoelectric performance in Na-doped SnSe.

Unusually large chemical potential shift in a degenerate semiconductor: Angle-resolved photoemission study of SnSe and Na-doped SnSe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maeda, M.; Yamamoto, K.; Mizokawa, T.

In this work, we have studied the electronic structure of SnSe and Na-doped SnSe by means of angle-resolved photoemission spectroscopy. The valence-band top reaches the Fermi level by the Na doping, indicating that Na-doped SnSe can be viewed as a degenerate semiconductor. However, in the Na-doped system, the chemical potential shift with temperature is unexpectedly large and is apparently inconsistent with the degenerate semiconductor picture. Lastly, the large chemical potential shift and anomalous spectral shape are key ingredients for an understanding of the novel metallic state with the large thermoelectric performance in Na-doped SnSe.

Unusually large chemical potential shift in a degenerate semiconductor: Angle-resolved photoemission study of SnSe and Na-doped SnSe

DOE PAGES

Maeda, M.; Yamamoto, K.; Mizokawa, T.; ...

2018-03-23

In this work, we have studied the electronic structure of SnSe and Na-doped SnSe by means of angle-resolved photoemission spectroscopy. The valence-band top reaches the Fermi level by the Na doping, indicating that Na-doped SnSe can be viewed as a degenerate semiconductor. However, in the Na-doped system, the chemical potential shift with temperature is unexpectedly large and is apparently inconsistent with the degenerate semiconductor picture. Lastly, the large chemical potential shift and anomalous spectral shape are key ingredients for an understanding of the novel metallic state with the large thermoelectric performance in Na-doped SnSe.

Efficient n-type doping of zinc-blende III-V semiconductor nanowires

NASA Astrophysics Data System (ADS)

Besteiro, Lucas V.; Tortajada, Luis; Souto, J.; Gallego, L. J.; Chelikowsky, James R.; Alemany, M. M. G.

2014-03-01

We demonstrate that it is preferable to dope III-V semiconductor nanowires by n-type anion substitution as opposed to cation substitution. Specifically, we show the dopability of zinc-blende nanowires is more efficient when the dopants are placed at the anion site as quantified by formation energies and the stabilization of DX-like defect centers. The comparison with previous work on n - type III-V semiconductor nanocrystals also allows to determine the role of dimensionality and quantum confinement on doping characteristics of materials. Our results are based on first-principles calculations of InP nanowires by using the PARSEC code. Work supported by the Spanish MICINN (FIS2012-33126) and Xunta de Galicia (GPC2013-043) in conjunction with FEDER. JRC acknowledges support from DoE (DE-FG02-06ER46286 and DESC0008877). Computational support was provided in part by CESGA.

Transition metal doped (X = V, Cr) CdS monolayer: A DFT study

NASA Astrophysics Data System (ADS)

Deb, Jyotirmoy; Paul, Debolina; Sarkar, Utpal

2018-05-01

In this work based on density functional theory approach with generalized gradient approximation we have investigated the effect doping and co-doping of transition metal atoms in CdS monolayer sheet. On the basis cohesive energy, we have determined the stability of all the transition metal doped systems. CdS monolayer is of nonmagnetic character but the insertion of transition metal atoms introduces the spontaneous spin polarization which results in a significant value of magnetic moment. The band structure analysis reveals that three different types of conducting nature such as spin-select-half-semiconductor, half metallic and metallic nature with total spin polarization has also been observed. The versatile conducting nature of the transition metal doped CdS monolayer predicts the possibility of using these systems in spintronics mainly as a spin filter and also to form metal-semiconductor interface etc. at nanoscale level.

High efficiency photovoltaic device

DOEpatents

Guha, Subhendu; Yang, Chi C.; Xu, Xi Xiang

1999-11-02

An N-I-P type photovoltaic device includes a multi-layered body of N-doped semiconductor material which has an amorphous, N doped layer in contact with the amorphous body of intrinsic semiconductor material, and a microcrystalline, N doped layer overlying the amorphous, N doped material. A tandem device comprising stacked N-I-P cells may further include a second amorphous, N doped layer interposed between the microcrystalline, N doped layer and a microcrystalline P doped layer. Photovoltaic devices thus configured manifest improved performance, particularly when configured as tandem devices.

Doping Polymer Semiconductors by Organic Salts: Toward High-Performance Solution-Processed Organic Field-Effect Transistors.

PubMed

Hu, Yuanyuan; Rengert, Zachary D; McDowell, Caitlin; Ford, Michael J; Wang, Ming; Karki, Akchheta; Lill, Alexander T; Bazan, Guillermo C; Nguyen, Thuc-Quyen

2018-04-24

Solution-processed organic field-effect transistors (OFETs) were fabricated with the addition of an organic salt, trityl tetrakis(pentafluorophenyl)borate (TrTPFB), into thin films of donor-acceptor copolymer semiconductors. The performance of OFETs is significantly enhanced after the organic salt is incorporated. TrTPFB is confirmed to p-dope the organic semiconductors used in this study, and the doping efficiency as well as doping physics was investigated. In addition, systematic electrical and structural characterizations reveal how the doping enhances the performance of OFETs. Furthermore, it is shown that this organic salt doping method is feasible for both p- and n-doping by using different organic salts and, thus, can be utilized to achieve high-performance OFETs and organic complementary circuits.

Uniform Doping in Quantum-Dots-Based Dilute Magnetic Semiconductor.

PubMed

Saha, Avijit; Shetty, Amitha; Pavan, A R; Chattopadhyay, Soma; Shibata, Tomohiro; Viswanatha, Ranjani

2016-07-07

Effective manipulation of magnetic spin within a semiconductor leading to a search for ferromagnets with semiconducting properties has evolved into an important field of dilute magnetic semiconductors (DMS). Although a lot of research is focused on understanding the still controversial origin of magnetism, efforts are also underway to develop new materials with higher magnetic temperatures for spintronics applications. However, so far, efforts toward quantum-dots(QDs)-based DMS materials are plagued with problems of phase separation, leading to nonuniform distribution of dopant ions. In this work, we have developed a strategy to synthesize highly crystalline, single-domain DMS system starting from a small magnetic core and allowing it to diffuse uniformly inside a thick CdS semiconductor matrix and achieve DMS QDs. X-ray absorption fine structure (XAFS) spectroscopy and energy-dispersive X-ray spectroscopy-scanning transmission electron microscopy (STEM-EDX) indicates the homogeneous distribution of magnetic impurities inside the semiconductor QDs leading to superior magnetic property. Further, the versatility of this technique was demonstrated by obtaining ultra large particles (∼60 nm) with uniform doping concentration as well as demonstrating the high quality magnetic response.

Origin of poor doping efficiency in solution processed organic semiconductors.

PubMed

Jha, Ajay; Duan, Hong-Guang; Tiwari, Vandana; Thorwart, Michael; Miller, R J Dwayne

2018-05-21

Doping is an extremely important process where intentional insertion of impurities in semiconductors controls their electronic properties. In organic semiconductors, one of the convenient, but inefficient, ways of doping is the spin casting of a precursor mixture of components in solution, followed by solvent evaporation. Active control over this process holds the key to significant improvements over current poor doping efficiencies. Yet, an optimized control can only come from a detailed understanding of electronic interactions responsible for the low doping efficiencies. Here, we use two-dimensional nonlinear optical spectroscopy to examine these interactions in the course of the doping process by probing the solution mixture of doped organic semiconductors. A dopant accepts an electron from the semiconductor and the two ions form a duplex of interacting charges known as ion-pair complexes. Well-resolved off-diagonal peaks in the two-dimensional spectra clearly demonstrate the electronic connectivity among the ions in solution. This electronic interaction represents a well resolved electrostatically bound state, as opposed to a random distribution of ions. We developed a theoretical model to recover the experimental data, which reveals an unexpectedly strong electronic coupling of ∼250 cm -1 with an intermolecular distance of ∼4.5 Å between ions in solution, which is approximately the expected distance in processed films. The fact that this relationship persists from solution to the processed film gives direct evidence that Coulomb interactions are retained from the precursor solution to the processed films. This memory effect renders the charge carriers equally bound also in the film and, hence, results in poor doping efficiencies. This new insight will help pave the way towards rational tailoring of the electronic interactions to improve doping efficiencies in processed organic semiconductor thin films.

CO2 Sensors Based on Nanocrystalline SnO2 Doped with CuO

NASA Technical Reports Server (NTRS)

Xu, Jennifer C.; Hunter, Gary W.; Liu, Chung Chiun; Ward, Benjamin J.

2008-01-01

Nanocrystalline tin oxide (SnO2) doped with copper oxide (CuO) has been found to be useful as an electrical-resistance sensory material for measuring the concentration of carbon dioxide in air. SnO2 is an n-type semiconductor that has been widely used as a sensing material for detecting such reducing gases as carbon monoxide, some of the nitrogen oxides, and hydrocarbons. Without doping, SnO2 usually does not respond to carbon dioxide and other stable gases. The discovery that the electrical resistance of CuO-doped SnO2 varies significantly with the concentration of CO2 creates opportunities for the development of relatively inexpensive CO2 sensors for detecting fires and monitoring atmospheric conditions. This discovery could also lead to research that could alter fundamental knowledge of SnO2 as a sensing material, perhaps leading to the development of SnO2-based sensing materials for measuring concentrations of oxidizing gases. Prototype CO2 sensors based on CuO-doped SnO2 have been fabricated by means of semiconductor-microfabrication and sol-gel nanomaterial-synthesis batch processes that are amendable to inexpensive implementation in mass production.

Recent Advances in Inorganic Nanoparticle-Based NIR Luminescence Imaging: Semiconductor Nanoparticles and Lanthanide Nanoparticles.

PubMed

Kim, Dokyoon; Lee, Nohyun; Park, Yong Il; Hyeon, Taeghwan

2017-01-18

Several types of nanoparticle-based imaging probes have been developed to replace conventional luminescent probes. For luminescence imaging, near-infrared (NIR) probes are useful in that they allow deep tissue penetration and high spatial resolution as a result of reduced light absorption/scattering and negligible autofluorescence in biological media. They rely on either an anti-Stokes or a Stokes shift process to generate luminescence. For example, transition metal-doped semiconductor nanoparticles and lanthanide-doped inorganic nanoparticles have been demonstrated as anti-Stokes shift-based agents that absorb NIR light through two- or three-photon absorption process and upconversion process, respectively. On the other hand, quantum dots (QDs) and lanthanide-doped nanoparticles that emit in NIR-II range (∼1000 to ∼1350 nm) were suggested as promising Stokes shift-based imaging agents. In this topical review, we summarize and discuss the recent progress in the development of inorganic nanoparticle-based luminescence imaging probes working in NIR range.

Semiconductor-based optical refrigerator

DOEpatents

Epstein, Richard I.; Edwards, Bradley C.; Sheik-Bahae, Mansoor

2002-01-01

Optical refrigerators using semiconductor material as a cooling medium, with layers of material in close proximity to the cooling medium that carries away heat from the cooling material and preventing radiation trapping. In addition to the use of semiconducting material, the invention can be used with ytterbium-doped glass optical refrigerators.

Electron transport in high aspect ratio semiconductor nanowires and metal-semiconductor interfaces

NASA Astrophysics Data System (ADS)

Sun, Zhuting

We are facing variability problems for modern semiconductor transistors due to the fact that the performances of nominally identical devices in the scale of 10 100 nm could be dramatically different attributed to the small manufacturing variations. Different doping strategies give statistical variations in the number of dopant atom density ND in the channel. The material size gives variations in wire diameter dW. And the immediate environment of the material leads to an additional level of variability. E.g. vacuum-semiconductor interface causes variations in surface state density Ds, metal-semiconductor interface causes variations in Schottky barrier and dielectric semiconductor interface induces dielectric confinement at small scales. To approach these variability problems, I choose Si-doped GaAs nanowires as an example. I investigate transport in Si-doped GaAs nanowire (NW) samples contacted by lithographically patterned Gold-Titanium films as function of temperature T. I find a drastically different temperature dependence between the wire resistance RW, which is relatively weak, and the zero bias resistance RC, which is strong. I show that the data are consistent with a model based on a sharp donor energy level slightly above the bottom of the semiconductor conduction band and develop a simple method for using transport measurements for estimates of the doping density after nanowire growth. I discuss the predictions of effective free carrier density n eff as function of the surface state density Ds and wire size dW. I also describe a correction to the widely used model of Schottky contacts that improves thermodynamic consistency of the Schottky tunnel barrier profile and show that the original theory may underestimate the barrier conductance under certain conditions. I also provide analytical calculations for shallow silicon dopant energy in GaAs crystals, and find the presence of dielectrics (dielectric screening) and free carriers (Coulomb screening) cause a reduction of ionization energy and shift the donor energy level ED upward, accompanying conduction band EC shift downward due to band gap narrowing for doped semiconductor material. The theoretical results are in a reasonable agreement with previous experimental data. I also find that when the material reduces to nanoscale, dielectric confinement and surface depletion compete with both Coulomb screening and dielectric screening that shift the donor level ED down towards the band gap. The calculation should be appropriate for all types of semiconductors and dopant species.

Ferromagnetism in doped or undoped spintronics nanomaterials

NASA Astrophysics Data System (ADS)

Qiang, You

2010-10-01

Much interest has been sparked by the discovery of ferromagnetism in a range of oxide doped and undoped semiconductors. The development of ferromagnetic oxide semiconductor materials with giant magnetoresistance (GMR) offers many advantages in spintronics devices for future miniaturization of computers. Among them, TM-doped ZnO is an extensively studied n-type wide-band-gap (3.36 eV) semiconductor with a tremendous interest as future mini-computer, blue light emitting, and solar cells. In this talk, Co-doped ZnO and Co-doped Cu2O semiconductor nanoclusters are successfully synthesized by a third generation sputtering-gas-aggregation cluster technique. The Co-doped nanoclusters are ferromagnetic with Curie temperature above room temperature. Both of Co-doped nanoclusters show positive magnetoresistance (PMR) at low temperature, but the amplitude of the PMRs shows an anomalous difference. For similar Co doping concentration at 5 K, PMR is greater than 800% for Co-doped ZnO but only 5% for Co-doped Cu2O nanoclusters. Giant PMR in Co-doped ZnO which is attributed to large Zeeman splitting effect has a linear dependence on applied magnetic field with very high sensitivity, which makes it convenient for the future spintronics applications. The small PMR in Co-doped Cu2O is related to its vanishing density of states at Fermi level. Undoped Zn/ZnO core-shell nanoparticle gives high ferromagnetic properties above room temperature due to the defect induced magnetization at the interface.

Bi-Se doped with Cu, p-type semiconductor

DOEpatents

Bhattacharya, Raghu Nath; Phok, Sovannary; Parilla, Philip Anthony

2013-08-20

A Bi--Se doped with Cu, p-type semiconductor, preferably used as an absorber material in a photovoltaic device. Preferably the semiconductor has at least 20 molar percent Cu. In a preferred embodiment, the semiconductor comprises at least 28 molar percent of Cu. In one embodiment, the semiconductor comprises a molar percentage of Cu and Bi whereby the molar percentage of Cu divided by the molar percentage of Bi is greater than 1.2. In a preferred embodiment, the semiconductor is manufactured as a thin film having a thickness less than 600 nm.

Inhibition of unintentional extra carriers by Mn valence change for high insulating devices

PubMed Central

Guo, Daoyou; Li, Peigang; Wu, Zhenping; Cui, Wei; Zhao, Xiaolong; Lei, Ming; Li, Linghong; Tang, Weihua

2016-01-01

For intrinsic oxide semiconductors, oxygen vacancies served as the electron donors have long been, and inevitably still are, attributed as the primary cause of conductivity, making oxide semiconductors seem hard to act as high insulating materials. Meanwhile, the presence of oxygen vacancies often leads to a persistent photoconductivity phenomenon which is not conducive to the practical use in the fast photoelectric response devices. Herein, we propose a possible way to reduce the influence of oxygen vacancies by introducing a valence change doping in the monoclinic β-Ga2O3 epitaxial thin film. The unintentional extra electrons induced by oxygen vacancies can be strongly suppressed by the change valence of the doped Mn ions from +3 to +2. The resistance for the Mn-doped Ga2O3 increases two orders of magnitude in compared with the pure Ga2O3. As a result, photodetector based on Mn-doped Ga2O3 thin films takes on a lower dark current, a higher sensitivity, and a faster photoresponse time, exhibiting a promising candidate using in high performance solar-blind photodetector. The study presents that the intentional doping of Mn may provide a convenient and reliable method of obtaining high insulating thin film in oxide semiconductor for the application of specific device. PMID:27068227

Influence of cation choice on magnetic behavior of III-N dilute magnetic semiconductors

NASA Astrophysics Data System (ADS)

Frazier, Rachel Marian

With the increasing interest in spintronics, many attempts have been made at incorporating spin-based functionality into existing semiconductor technology. One approach, utilizing dilute magnetic semiconductors (DMS) formed via introduction of transition metal ions into III-Nitride hosts, would allow for integration of spin based phenomena into current wide bandgap device technology. To accomplish such device structures, it is necessary to achieve single phase transition metal doped GaN and AlN which exhibit room temperature magnetic behavior. Ion implantation is an effective survey method for introduction of various transition metals into AlN. In ion implanted AlN, the Co and Cr doped films showed hysteresis at 300K while the Mn doped material did not. However, it is not a technique which will allow for the development of advanced spin based devices. Such devices will require epitaxial methods of the sort currently used for synthesis of III-Nitride optoelectronics. One such technique, Gas Source Molecular Beam Epitaxy (GSMBE), has been used to synthesize AlN films doped with Cr and Mn. Room temperature ferromagnetism has been observed for AlMnN and AlCrN grown by GSMBE. In both cases, the magnetic signal was found to depend on the flux of the dopant. The magnetization of the AlCrN was found to be an order of magnitude greater than in the AlMnN. The temperature dependent magnetic behavior of AlCrN was also superior to AlMnN; however, the AlCrN was not resistant to thermal degradation. An all-semiconductor tunneling magnetoresistive device (TMR) was grown with GaMnN as a spin injector and AlMnN as a spin filter. The resistance of the device should change with applied magnetic field depending on the magnetization of the injector and filter. However, due to the impurity bands found in the AlMnN, the resistance was found to change very little with magnetic field. To overcome such obstacles as found in the transition metal doped AlN, another dopant must be used. One viable dopant is Gd, which due to the low concentration incorporated in the semiconductor matrix should provide a single impurity level within the DMS instead of an impurity band. The incorporation of Gd into GaN and AlN may be the ultimate dopant for these III-N based DMS.

Codoping method for the fabrication of low-resistivity wide band-gap semiconductors in p-type GaN, p-type AlN and n-type diamond: prediction versus experiment

NASA Astrophysics Data System (ADS)

Katayama-Yoshida, H.; Nishimatsu, T.; Yamamoto, T.; Orita, N.

2001-10-01

We review our new valence control method of a co-doping for the fabrication of low-resistivity p-type GaN, p-type AlN and n-type diamond. The co-doping method is proposed based upon ab initio electronic structure calculation in order to solve the uni-polarity and the compensation problems in the wide band-gap semiconductors. In the co-doping method, we dope both the acceptors and donors at the same time by forming the meta-stable acceptor-donor-acceptor complexes for the p-type or donor-acceptor-donor complexes for the n-type under thermal non-equilibrium crystal growth conditions. We propose the following co-doping method to fabricate the low-resistivity wide band-gap semiconductors; p-type GaN: [Si + 2 Mg (or Be)], [H + 2 Mg (or Be)], [O + 2 Mg (or Be)], p-type AlN: [O + 2 C] and n-type diamond: [B + 2 N], [H + S], [H + 2 P]. We compare our prediction of the co-doping method with the recent successful experiments to fabricate the low-resistivity p-type GaN, p-type AlN and n-type diamond. We show that the co-doping method is the efficient and universal doping method by which to avoid carrier compensation with an increase of the solubility of the dopant, to increase the activation rate by decreasing the ionization energy of acceptors and donors, and to increase the mobility of the carrier.

Diluted magnetic semiconductors with narrow band gaps

NASA Astrophysics Data System (ADS)

Gu, Bo; Maekawa, Sadamichi

2016-10-01

We propose a method to realize diluted magnetic semiconductors (DMSs) with p - and n -type carriers by choosing host semiconductors with a narrow band gap. By employing a combination of the density function theory and quantum Monte Carlo simulation, we demonstrate such semiconductors using Mn-doped BaZn2As2 , which has a band gap of 0.2 eV. In addition, we found a nontoxic DMS Mn-doped BaZn2Sb2 , of which the Curie temperature Tc is predicted to be higher than that of Mn-doped BaZn2As2 , the Tc of which was up to 230 K in a recent experiment.

Unraveling the Origin of Magnetism in Mesoporous Cu-Doped SnO₂ Magnetic Semiconductors.

PubMed

Fan, Junpeng; Menéndez, Enric; Guerrero, Miguel; Quintana, Alberto; Weschke, Eugen; Pellicer, Eva; Sort, Jordi

2017-10-25

The origin of magnetism in wide-gap semiconductors doped with non-ferromagnetic 3d transition metals still remains intriguing. In this article, insights in the magnetic properties of ordered mesoporous Cu-doped SnO₂ powders, prepared by hard-templating, have been unraveled. Whereas, both oxygen vacancies and Fe-based impurity phases could be a plausible explanation for the observed room temperature ferromagnetism, the low temperature magnetism is mainly and unambiguously arising from the nanoscale nature of the formed antiferromagnetic CuO, which results in a net magnetization that is reminiscent of ferromagnetic behavior. This is ascribed to uncompensated spins and shape-mediated spin canting effects. The reduced blocking temperature, which resides between 30 and 5 K, and traces of vertical shifts in the hysteresis loops confirm size effects in CuO. The mesoporous nature of the system with a large surface-to-volume ratio likely promotes the occurrence of uncompensated spins, spin canting, and spin frustration, offering new prospects in the use of magnetic semiconductors for energy-efficient spintronics.

Electronic and magnetic properties of SnS2 monolayer doped with 4d transition metals

NASA Astrophysics Data System (ADS)

Xiao, Wen-Zhi; Xiao, Gang; Rong, Qing-Yan; Chen, Qiao; Wang, Ling-Ling

2017-09-01

We investigate the electronic structures and magnetic properties of SnS2 monolayers substitutionally doped with 4-d transition-metal through systematic first principles calculations. The doped complexes exhibit interesting electronic and magnetic behaviors, depending on the interplay between crystal field splitting, Hund's rule, and 4d levels. The system doped with Y is nonmagnetic metal. Both the Zr- and Pd-doped systems remain nonmagnetic semiconductors. Doping results in half-metallic states for Nb-, Ru-, Rh-, Ag, and Cd doped cases, and magnetic semiconductors for systems with Mo and Tc dopants. In particular, the Nb- and Mo-doped systems display long-ranged ferromagnetic ordering with Curie temperature above room temperature, which are primarily attributable to the double-exchange mechanism, and the p-d/p-p hybridizations, respectively. Moreover, The Mo-doped system has excellent energetic stability and flexible mechanical stability, and also possesses remarkable dynamic and thermal (500 K) stability. Our studies demonstrate that Nb- and Mo-doped SnS2 monolayers are promising candidates for preparing 2D diluted magnetic semiconductors, and hence will be a helpful clue for experimentalists.

Transition-Metal Substitution Doping in Synthetic Atomically Thin Semiconductors

DOE PAGES

Gao, Jian; Kim, Young Duck; Liang, Liangbo; ...

2016-09-20

Semiconductor impurity doping has enabled an entire generation of technology. The emergence of alternative semiconductor material systems, such as transition metal dichalcogenides (TMDCs), requires the development of scalable doping strategies. We report an unprecedented one-pot synthesis for transition-metal substitution in large-area, synthetic monolayer TMDCs. Electron microscopy, optical and electronic transport characterization and ab initio calculations indicate that our doping strategy preserves the attractive qualities of TMDC monolayers, including semiconducting transport and strong direct-gap luminescence. These results are expected to encourage exploration of transition-metal substitution in two-dimensional systems, potentially enabling next-generation optoelectronic technology in the atomically-thin regime.

Band alignments in Fe/graphene/Si(001) junctions studied by x-ray photoemission spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Breton, J.-C., E-mail: jean-christophe.lebreton@univ-rennes1.fr; Tricot, S.; Delhaye, G.

2016-08-01

The control of tunnel contact resistance is of primary importance for semiconductor-based spintronic devices. This control is hardly achieved with conventional oxide-based tunnel barriers due to deposition-induced interface states. Manipulation of single 2D atomic crystals (such as graphene sheets) weakly interacting with their substrate might represent an alternative and efficient way to design new heterostructures for a variety of different purposes including spin injection into semiconductors. In the present paper, we study by x-ray photoemission spectroscopy the band alignments and interface chemistry of iron–graphene-hydrogenated passivated silicon (001) surfaces for a low and a high n-doping concentration. We find that themore » hydrogen passivation of the Si(001) surface remains efficient even with a graphene sheet on the Si(001) surface. For both doping concentrations, the semiconductor is close to flat-band conditions which indicates that the Fermi level is unpinned on the semiconductor side of the Graphene/Si(001):H interface. When iron is deposited on the graphene/Si(001):H structures, the Schottky barrier height remains mainly unaffected by the metallic overlayer with a very low barrier height for electrons, a sought-after property in semiconductor based spintronic devices. Finally, we demonstrate that the graphene layer intercalated between the metal and semiconductor also serves as a protection against iron-silicide formation even at elevated temperatures preventing from the formation of a Si-based magnetic dead layer.« less

Band alignments in Fe/graphene/Si(001) junctions studied by x-ray photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Le Breton, J.-C.; Tricot, S.; Delhaye, G.; Lépine, B.; Turban, P.; Schieffer, P.

2016-08-01

The control of tunnel contact resistance is of primary importance for semiconductor-based spintronic devices. This control is hardly achieved with conventional oxide-based tunnel barriers due to deposition-induced interface states. Manipulation of single 2D atomic crystals (such as graphene sheets) weakly interacting with their substrate might represent an alternative and efficient way to design new heterostructures for a variety of different purposes including spin injection into semiconductors. In the present paper, we study by x-ray photoemission spectroscopy the band alignments and interface chemistry of iron-graphene-hydrogenated passivated silicon (001) surfaces for a low and a high n-doping concentration. We find that the hydrogen passivation of the Si(001) surface remains efficient even with a graphene sheet on the Si(001) surface. For both doping concentrations, the semiconductor is close to flat-band conditions which indicates that the Fermi level is unpinned on the semiconductor side of the Graphene/Si(001):H interface. When iron is deposited on the graphene/Si(001):H structures, the Schottky barrier height remains mainly unaffected by the metallic overlayer with a very low barrier height for electrons, a sought-after property in semiconductor based spintronic devices. Finally, we demonstrate that the graphene layer intercalated between the metal and semiconductor also serves as a protection against iron-silicide formation even at elevated temperatures preventing from the formation of a Si-based magnetic dead layer.

Nonthermal Photocoercivity Effect in a Low-Doped (Ga,Mn)As Ferromagnetic Semiconductor

NASA Astrophysics Data System (ADS)

Astakhov, G. V.; Hoffmann, H.; Korenev, V. L.; Kiessling, T.; Schwittek, J.; Schott, G. M.; Gould, C.; Ossau, W.; Brunner, K.; Molenkamp, L. W.

2009-05-01

We report a photoinduced change of the coercive field, i.e., a photocoercivity effect (PCE), under very low intensity illumination of a low-doped (Ga,Mn)As ferromagnetic semiconductor. We find a strong correlation between the PCE and the sample resistivity. Spatially resolved dynamics of the magnetization reversal rule out any role of thermal heating in the origin of this PCE, and we propose a mechanism based on the light-induced lowering of the domain wall pinning energy. The PCE is local and reversible, allowing writing and erasing of magnetic images using light.

Nonthermal photocoercivity effect in a low-doped (Ga,Mn)As ferromagnetic semiconductor.

PubMed

Astakhov, G V; Hoffmann, H; Korenev, V L; Kiessling, T; Schwittek, J; Schott, G M; Gould, C; Ossau, W; Brunner, K; Molenkamp, L W

2009-05-08

We report a photoinduced change of the coercive field, i.e., a photocoercivity effect (PCE), under very low intensity illumination of a low-doped (Ga,Mn)As ferromagnetic semiconductor. We find a strong correlation between the PCE and the sample resistivity. Spatially resolved dynamics of the magnetization reversal rule out any role of thermal heating in the origin of this PCE, and we propose a mechanism based on the light-induced lowering of the domain wall pinning energy. The PCE is local and reversible, allowing writing and erasing of magnetic images using light.

Initiation of explosive conversions in energy-saturated nanoporous silicon-based compounds with fast semiconductor switches and energy-releasing elements

NASA Astrophysics Data System (ADS)

Savenkov, G. G.; Kardo-Sysoev, A. F.; Zegrya, A. G.; Os'kin, I. A.; Bragin, V. A.; Zegrya, G. G.

2017-10-01

The first findings concerning the initiation of explosive conversions in energy-saturated nanoporous silicon-based compounds via the electrical explosion of a semiconductor bridge are presented. The obtained results indicate that the energy parameters of an explosive conversion depend on the mass of a combustible agent—namely, nanoporous silicon—and the silicon-doping type.

Nanopatterning of Group V Elements for Tailoring the Electronic Properties of Semiconductors by Monolayer Doping.

PubMed

Thissen, Peter; Cho, Kyeongjae; Longo, Roberto C

2017-01-18

Control of the electronic properties of semiconductors is primarily achieved through doping. While scaling down the device dimensions to the molecular regime presents an increasing number of difficulties, doping control at the nanoscale is still regarded as one of the major challenges of the electronic industry. Within this context, new techniques such as monolayer doping (MLD) represent a substantial improvement toward surface doping with atomic and specific doping dose control at the nanoscale. Our previous work has explained in detail the atomistic mechanism behind MLD by means of density-functional theory calculations (Chem. Mater. 2016, 28, 1975). Here, we address the key questions that will ultimately allow one to optimize the scalability of the MLD process. First, we show that dopant coverage control cannot be achieved by simultaneous reaction of several group V elements, but stepwise reactions make it possible. Second, using ab initio molecular dynamics, we investigate the thermal decomposition of the molecular precursors, together with the stability of the corresponding binary and ternary dopant oxides, prior to the dopant diffusion into the semiconductor surface. Finally, the effect of the coverage and type of dopant on the electronic properties of the semiconductor is also analyzed. Furthermore, the atomistic characterization of the MLD process raises unexpected questions regarding possible crystal damage effects by dopant exchange with the semiconductor ions or the final distribution of the doping impurities within the crystal structure. By combining all our results, optimization recipes to create ultrashallow doped junctions at the nanoscale are finally proposed.

Tuning near-gap electronic structure, interface charge transfer and visible light response of hybrid doped graphene and Ag3PO4 composite: Dopant effects

PubMed Central

He, Chao-Ni; Huang, Wei-Qing; Xu, Liang; Yang, Yin-Cai; Zhou, Bing-Xin; Huang, Gui-Fang; Peng, P.; Liu, Wu-Ming

2016-01-01

The enhanced photocatalytic performance of doped graphene (GR)/semiconductor nanocomposites have recently been widely observed, but an understanding of the underlying mechanisms behind it is still out of reach. As a model system to study the dopant effects, we investigate the electronic structures and optical properties of doped GR/Ag3PO4 nanocomposites using the first-principles calculations, demonstrating that the band gap, near-gap electronic structure and interface charge transfer of the doped GR/Ag3PO4(100) composite can be tuned by the dopants. Interestingly, the doping atom and C atoms bonded to dopant become active sites for photocatalysis because they are positively or negatively charged due to the charge redistribution caused by interaction. The dopants can enhance the visible light absorption and photoinduced electron transfer. We propose that the N atom may be one of the most appropriate dopants for the GR/Ag3PO4 photocatalyst. This work can rationalize the available experimental results about N-doped GR-semiconductor composites, and enriches our understanding on the dopant effects in the doped GR-based composites for developing high-performance photocatalysts. PMID:26923338

Electrostatic analysis of n-doped SrTiO{sub 3} metal-insulator-semiconductor systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamerbeek, A. M., E-mail: a.m.kamerbeek@rug.nl; Banerjee, T.; Hueting, R. J. E.

2015-12-14

Electron doped SrTiO{sub 3}, a complex-oxide semiconductor, possesses novel electronic properties due to its strong temperature and electric-field dependent permittivity. Due to the high permittivity, metal/n-SrTiO{sub 3} systems show reasonably strong rectification even when SrTiO{sub 3} is degenerately doped. Our experiments show that the insertion of a sub nanometer layer of AlO{sub x} in between the metal and n-SrTiO{sub 3} interface leads to a dramatic reduction of the Schottky barrier height (from around 0.90 V to 0.25 V). This reduces the interface resistivity by 4 orders of magnitude. The derived electrostatic analysis of the metal-insulator-semiconductor (n-SrTiO{sub 3}) system is consistent with thismore » trend. When compared with a Si based MIS system, the change is much larger and mainly governed by the high permittivity of SrTiO{sub 3}. The non-linear permittivity of n-SrTiO{sub 3} leads to unconventional properties such as a temperature dependent surface potential non-existent for semiconductors with linear permittivity such as Si. This allows tuning of the interfacial band alignment, and consequently the Schottky barrier height, in a much more drastic way than in conventional semiconductors.« less

Sub-Kelvin resistance thermometer

NASA Technical Reports Server (NTRS)

Castles, Stephen H. (Inventor)

1992-01-01

A device capable of accurate temperature measurement down to 0.01 K of a particular object is discussed. The device is comprised of the following: a heat sink wafer; a first conducting pad bonded near one end of the heat sink wafer; a second conducting pad bonded near the other end of the heat sink wafer; and an oblong doped semiconductor crystal such as germanium. The oblong doped semiconductor crystal has a third conducting pad bonded on its bottom surface with the oblong doped semiconductor crystal bonded to the heat sink wafer by having the fourth conducting pad bonded to the first conducting pad. A wire is bonded between the second and third conducting pads. Current and voltage wires bonded to the first and second conducting pads measure the change in resistance of the oblong doped semiconductor crystal; this indicates the temperature of the object whose temperature is to be measured.

Beating the thermodynamic limit with photo-activation of n-doping in organic semiconductors

NASA Astrophysics Data System (ADS)

Lin, Xin; Wegner, Berthold; Lee, Kyung Min; Fusella, Michael A.; Zhang, Fengyu; Moudgil, Karttikay; Rand, Barry P.; Barlow, Stephen; Marder, Seth R.; Koch, Norbert; Kahn, Antoine

2017-12-01

Chemical doping of organic semiconductors using molecular dopants plays a key role in the fabrication of efficient organic electronic devices. Although a variety of stable molecular p-dopants have been developed and successfully deployed in devices in the past decade, air-stable molecular n-dopants suitable for materials with low electron affinity are still elusive. Here we demonstrate that photo-activation of a cleavable air-stable dimeric dopant can result in kinetically stable and efficient n-doping of host semiconductors, whose reduction potentials are beyond the thermodynamic reach of the dimer’s effective reducing strength. Electron-transport layers doped in this manner are used to fabricate high-efficiency organic light-emitting diodes. Our strategy thus enables a new paradigm for using air-stable molecular dopants to improve conductivity in, and provide ohmic contacts to, organic semiconductors with very low electron affinity.

Doping of germanium and silicon crystals with non-hydrogenic acceptors for far infrared lasers

DOEpatents

Haller, Eugene E.; Brundermann, Erik

2000-01-01

A method for doping semiconductors used for far infrared lasers with non-hydrogenic acceptors having binding energies larger than the energy of the laser photons. Doping of germanium or silicon crystals with beryllium, zinc or copper. A far infrared laser comprising germanium crystals doped with double or triple acceptor dopants permitting the doped laser to be tuned continuously from 1 to 4 terahertz and to operate in continuous mode. A method for operating semiconductor hole population inversion lasers with a closed cycle refrigerator.

Near-Unity Emitting Copper-Doped Colloidal Semiconductor Quantum Wells for Luminescent Solar Concentrators.

PubMed

Sharma, Manoj; Gungor, Kivanc; Yeltik, Aydan; Olutas, Murat; Guzelturk, Burak; Kelestemur, Yusuf; Erdem, Talha; Delikanli, Savas; McBride, James R; Demir, Hilmi Volkan

2017-08-01

Doping of bulk semiconductors has revealed widespread success in optoelectronic applications. In the past few decades, substantial effort has been engaged for doping at the nanoscale. Recently, doped colloidal quantum dots (CQDs) have been demonstrated to be promising materials for luminescent solar concentrators (LSCs) as they can be engineered for providing highly tunable and Stokes-shifted emission in the solar spectrum. However, existing doped CQDs that are aimed for full solar spectrum LSCs suffer from moderately low quantum efficiency, intrinsically small absorption cross-section, and gradually increasing absorption profiles coinciding with the emission spectrum, which together fundamentally limit their effective usage. Here, the authors show the first account of copper doping into atomically flat colloidal quantum wells (CQWs). In addition to Stokes-shifted and tunable dopant-induced photoluminescence emission, the copper doping into CQWs enables near-unity quantum efficiencies (up to ≈97%), accompanied by substantially high absorption cross-section and inherently step-like absorption profile, compared to those of the doped CQDs. Based on these exceptional properties, the authors have demonstrated by both experimental analysis and numerical modeling that these newly synthesized doped CQWs are excellent candidates for LSCs. These findings may open new directions for deployment of doped CQWs in LSCs for advanced solar light harvesting technologies. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Doping of two-dimensional MoS2 by high energy ion implantation

NASA Astrophysics Data System (ADS)

Xu, Kang; Zhao, Yuda; Lin, Ziyuan; Long, Yan; Wang, Yi; Chan, Mansun; Chai, Yang

2017-12-01

Two-dimensional (2D) materials have been demonstrated to be promising candidates for next generation electronic circuits. Analogues to conventional Si-based semiconductors, p- and n-doping of 2D materials are essential for building complementary circuits. Controllable and effective doping strategies require large tunability of the doping level and negligible structural damage to ultrathin 2D materials. In this work, we demonstrate a doping method utilizing a conventional high-energy ion-implantation machine. Before the implantation, a Polymethylmethacrylate (PMMA) protective layer is used to decelerate the dopant ions and minimize the structural damage to MoS2, thus aggregating the dopants inside MoS2 flakes. By optimizing the implantation energy and fluence, phosphorus dopants are incorporated into MoS2 flakes. Our Raman and high-resolution transmission electron microscopy (HRTEM) results show that only negligibly structural damage is introduced to the MoS2 lattice during the implantation. P-doping effect by the incorporation of p+ is demonstrated by Photoluminescence (PL) and electrical characterizations. Thin PMMA protection layer leads to large kinetic damage but also a more significant doping effect. Also, MoS2 with large thickness shows less kinetic damage. This doping method makes use of existing infrastructures in the semiconductor industry and can be extended to other 2D materials and dopant species as well.

Cobalt and Yttrium Modified TiO2 Nanotubes Based Dye-Sensitized Solar Cells for Solar-Energy Conversion

NASA Astrophysics Data System (ADS)

Shabanov, N. S.; Isaev, A. B.; Orudzhev, F. F.; Murliev, E. K.

2018-01-01

The solar-energy conversion in eosin-sensitized solar cells based on cobalt and yttrium modified TiO2 nanotubes has been studied.It is established that the doping with metal ions shifts the absorption edge for Co and Y doped titanium dioxide samples to longer and shorter wavelengths, respectively. The efficiency of solar energy conversion depends on the wide bandgap of the semiconductor anode and reaches a maximum (4.4%) for yttrium-doped TiO2 in comparison to that (4.1%) for pure titanium dioxide.

Large Bandgap Shrinkage from Doping and Dielectric Interface in Semiconducting Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Comfort, Everett; Lee, Ji Ung

2016-06-01

The bandgap of a semiconductor is one of its most important electronic properties. It is often considered to be a fixed property of the semiconductor. As the dimensions of semiconductors reduce, however, many-body effects become dominant. Here, we show that doping and dielectric, two critical features of semiconductor device manufacturing, can dramatically shrink (renormalize) the bandgap. We demonstrate this in quasi-one-dimensional semiconducting carbon nanotubes. Specifically, we use a four-gated device, configured as a p-n diode, to investigate the fundamental electronic structure of individual, partially supported nanotubes of varying diameter. The four-gated construction allows us to combine both electrical and optical spectroscopic techniques to measure the bandgap over a wide doping range.

Electric field induced spin-polarized current

DOEpatents

Murakami, Shuichi; Nagaosa, Naoto; Zhang, Shoucheng

2006-05-02

A device and a method for generating an electric-field-induced spin current are disclosed. A highly spin-polarized electric current is generated using a semiconductor structure and an applied electric field across the semiconductor structure. The semiconductor structure can be a hole-doped semiconductor having finite or zero bandgap or an undoped semiconductor of zero bandgap. In one embodiment, a device for injecting spin-polarized current into a current output terminal includes a semiconductor structure including first and second electrodes, along a first axis, receiving an applied electric field and a third electrode, along a direction perpendicular to the first axis, providing the spin-polarized current. The semiconductor structure includes a semiconductor material whose spin orbit coupling energy is greater than room temperature (300 Kelvin) times the Boltzmann constant. In one embodiment, the semiconductor structure is a hole-doped semiconductor structure, such as a p-type GaAs semiconductor layer.

The Research Laboratory of Electronics Progress Report Number 133, January 1-December 1990

DTIC Science & Technology

1990-12-31

4 6 Chapter 7 High-Frequency InAlAs/InGaAs Metal -Insulator-Doped Semiconductor...Epitaxy of Compound Semiconductors Chapter 7 High-Frequency InAlAs/InGaAs Metal -Insulator- Doped Semiconductor Field-Effect Transistors (MIDFETs) for...aligned silicided NMOS posed of refractory metals to allow a subsequentdevice fabrication. We have used cobalt deposi- high temperature anneal. This

Cation coordination reactions on nanocrystals: surface/interface, doping control and advanced photocatalysis applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhang, Jiatao

2016-10-01

Abstract: Including the shape and size effect, the controllable doping, hetero-composite and surface/interface are the prerequisite of colloidal nanocrystals for exploring their optoelectronic properties, such as fluorescence, plasmon-exciton coupling, efficient electron/hole separation, and enhanced photocatalysis applications. By controlling soft acid-base coordination reactions between cation molecular complexes and colloidal nanocrystals, we showed that chemical thermodynamics could drive nanoscale monocrystalline growth of the semiconductor shell on metal nano-substrates and the substitutional heterovalent doping in semiconductor nanocrystals. We have demonstrated evolution of relative position of Au and II-VI semiconductor in Au-Semi from symmetric to asymmetric configuration, different phosphines initiated morphology engineering, oriented attachment of quantum dots into micrometer nanosheets with synergistic control of surface/interface and doing, which can further lead to fine tuning of plasmon-exciton coupling. Therefore, different hydrogen photocatalytic performance, Plasmon enhanced photocatalysis properties have been achieved further which lead to the fine tuning of plasmon-exciton coupling. Substitutional heterovalent doping here enables the tailoring of optical, electronic properties and photocatalysis applications of semiconductor nanocrystals because of electronic impurities (p-, n-type doping) control. References: (1) J. Gui, J. Zhang*, et al. Angew. Chem. Int. Ed. 2015, 54, 3683. (2) Q. Zhao, J. Zhang*, etc., Adv. Mater. 2014, 26, 1387. (3) J. Liu, Q. Zhao, S. G. Wang*, J. Zhang*, etc., Adv. Mater. 2015, 27-2753-2761. (4) H. Qian, J. Zhang*, etc., NPG Asia Mater. (2015) 7, e152. (5) M. Ji, M. Xu, etc., J. Zhang*, Adv. Mater. 2016, in proof. (6) S. Yu, J. T. Zhang, Y. Tang, M. Ouyang*, Nano Lett. 2015, 15, 6282-6288. (7) J. Zhang, Y. Tang, K. Lee and M. Ouyang*, Science 2010, 327, 1634. (8) J. Zhang, Y. Tang, K. Lee, M. Ouyang*, Nature 2010, 466, 91.

Processing of insulators and semiconductors

DOEpatents

Quick, Nathaniel R.; Joshi, Pooran C.; Duty, Chad Edward; Jellison, Jr., Gerald Earle; Angelini, Joseph Attilio

2015-06-16

A method is disclosed for processing an insulator material or a semiconductor material. The method includes pulsing a plasma lamp onto the material to diffuse a doping substance into the material, to activate the doping substance in the material or to metallize a large area region of the material. The method may further include pulsing a laser onto a selected region of the material to diffuse a doping substance into the material, to activate the doping substance in the material or to metallize a selected region of the material.

Photoassisted physical vapor epitaxial growth of semiconductors: a review of light-induced modifications to growth processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alberi, Kirstin; Scarpulla, Michael A.

Herein, we review the remarkable range of modifications to materials properties associated with photoexcitation of the growth surface during physical vapor epitaxy of semiconductors. We concentrate on mechanisms producing measureable, utilizable changes in crystalline perfection, phase, composition, doping, and defect distribution. We outline the relevant physics of different mechanisms, concentrating on those yielding effects orthogonal to the primary growth variables of temperature and atomic or molecular fluxes and document the phenomenological effects reported. Based on experimental observations from a range of semiconductor systems and growth conditions, the primary effects include enhanced anion desorption, molecular dissociation, increased doping efficiency, modification tomore » defect populations and improvements to the crystalline quality of epilayers grown at low temperatures. Future research directions and technological applications are also discussed.« less

Photoassisted physical vapor epitaxial growth of semiconductors: a review of light-induced modifications to growth processes

DOE PAGES

Alberi, Kirstin; Scarpulla, Michael A.

2017-11-22

Herein, we review the remarkable range of modifications to materials properties associated with photoexcitation of the growth surface during physical vapor epitaxy of semiconductors. We concentrate on mechanisms producing measureable, utilizable changes in crystalline perfection, phase, composition, doping, and defect distribution. We outline the relevant physics of different mechanisms, concentrating on those yielding effects orthogonal to the primary growth variables of temperature and atomic or molecular fluxes and document the phenomenological effects reported. Based on experimental observations from a range of semiconductor systems and growth conditions, the primary effects include enhanced anion desorption, molecular dissociation, increased doping efficiency, modification tomore » defect populations and improvements to the crystalline quality of epilayers grown at low temperatures. Future research directions and technological applications are also discussed.« less

Ferroelectricity in epitaxial Y-doped HfO2 thin film integrated on Si substrate

NASA Astrophysics Data System (ADS)

Lee, K.; Lee, T. Y.; Yang, S. M.; Lee, D. H.; Park, J.; Chae, S. C.

2018-05-01

We report on the ferroelectricity of a Y-doped HfO2 thin film epitaxially grown on Si substrate, with an yttria-stabilized zirconia buffer layer pre-deposited on the substrate. Piezoresponse force microscopy results show the ferroelectric domain pattern, implying the existence of ferroelectricity in the epitaxial HfO2 film. The epitaxially stabilized HfO2 film in the form of a metal-ferroelectric-insulator-semiconductor structure exhibits ferroelectric hysteresis with a clear ferroelectric switching current in polarization-voltage measurements. The HfO2 thin film also demonstrates ferroelectric retention comparable to that of current perovskite-based metal-ferroelectric-insulator-semiconductor structures.

Thermophotovoltaic energy conversion system having a heavily doped n-type region

DOEpatents

DePoy, David M.; Charache, Greg W.; Baldasaro, Paul F.

2000-01-01

A thermophotovoltaic (TPV) energy conversion semiconductor device is provided which incorporates a heavily doped n-type region and which, as a consequence, has improved TPV conversion efficiency. The thermophotovoltaic energy conversion device includes an emitter layer having first and second opposed sides and a base layer in contact with the first side of the emitter layer. A highly doped n-type cap layer is formed on the second side of the emitter layer or, in another embodiment, a heavily doped n-type emitter layer takes the place of the cap layer.

Flexible 2D RF Nanoelectronics based on Layered Semiconductor Transistor (NBIT III)

DTIC Science & Technology

2016-11-11

Experimental and computational studies in multidisciplinary fields of electrical, mechanical engineering , and materials science were conducted to achieve...plan for this project. Experimental and computational studies in multidisciplinary fields of electrical, mechanical engineering , and materials...electrostatic or physisorption gating, defect engineering , and substitutional doping during the growth. These methods result in uniform doping or composition

Dispersion characteristic of photoluminescence decay times of phosphor YAG: Ce, Gd

NASA Astrophysics Data System (ADS)

Lisitsyn, V. M.; Ju, Yangyang; Stepanov, S. A.; Soschin, N. M.

2017-05-01

The dispersion of the characteristic decay times of gadolinium co-doped yttrium aluminum garnet doped with cerium phosphors were studied. In the present work, an ultraviolet semiconductor laser (λem=375 nm, τ = 1 ns) was used as excitation source for measuring kinetics characteristics of phosphor groups based on YAG with different content of cerium.

Biasing, operation and parasitic current limitation in single device equivalent to CMOS, and other semiconductor systems

DOEpatents

Welch, James D.

2003-09-23

Disclosed are semiconductor devices including at least one junction which is rectifying whether the semiconductor is caused to be N or P-type, by the presence of applied gate voltage field induced carriers in essentially intrinsic, essentially homogeneously simultaneously containing both N and P-type metallurgical dopants at substantially equal doping levels, essentially homogeneously simultaneously containing both N and P-type metallurgical dopants at different doping levels, and containing a single metallurgical doping type, and functional combinations thereof. In particular, inverting and non-inverting gate voltage channel induced semiconductor single devices with operating characteristics similar to conventional multiple device CMOS systems, which can be operated as modulators, are disclosed as are a non-latching SCR and an approach to blocking parasitic currents utilizing material(s) which form rectifying junctions with both N and P-type semiconductor whether metallurigically or field induced.

Semiconductor to metal transition by tuning the location of N{sub 2}{sup AA} in armchair graphene nanoribbons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Tong; Wang, Ling-Ling, E-mail: llwang@hnu.edu.cn; Li, Quan

2014-02-07

The electronic band structures and transport properties of N{sub 2}{sup AA}-doped armchair graphene nanoribbons (aGNRs) with two quasi-adjacent substitutional nitrogen atoms incorporated in pairs of neighboring carbon atoms in the same sublattice A are investigated by using non-equilibrium Green function formalism in combination with density functional theory. The results show that the coupling effect between the Pz orbitals of carbon and nitrogen atoms plays an important role in the transition between semiconductor and metal by different locations of N{sub 2}{sup AA}-doped aGNRs. And the striking negative differential resistance behaviors can be found in such devices. These tremendous properties suggest potentialmore » application of N{sub 2}{sup AA}-doped aGNRs in graphene-based nanoelectronic devices.« less

Spectroscopy of Charge Carriers and Traps in Field-Doped Single Crystal Organic Semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Xiaoyang; Frisbie, Daniel

2017-03-31

The proposed research aims to achieve quantitative, molecular level understanding of charge carriers and traps in field-doped crystalline organic semiconductors via in situ linear and nonlinear optical spectroscopy, in conjunction with transport measurements and molecular/crystal engineering.

Synthesis of n-type semiconductor diamond single crystal under high pressure and high temperature

NASA Astrophysics Data System (ADS)

Li, Yong; Li, Shangsheng; Song, Mousheng; She, Yanchao; Wang, Qiang; Guan, Xuemao

2017-12-01

In this paper, diamond single crystal co-doped with sulfur and boron was successfully synthesized at the fixed pressure of 6.0 GPa and temperature range of 1535 K. Sulfur was detected in the co-doped diamond by Fourier Transform Infrared Spectroscopy (FTIR) and the corresponding characteristic peak located at 848 cm-1. Interestingly, Hall effect measurements indicated that the diamond co-doped with sulfur and boron exhibited n-type semiconductor behaviour. Furthermore, the Hall mobility and carrier concentration of the co-doped diamond higher than those of the boron-doping diamond.

Effect of charging on silicene with alkali metal atom adsorption

NASA Astrophysics Data System (ADS)

Li, Manman; Li, Zhongyao; Gong, Shi-Jing

2018-02-01

Based on first-principles calculations, we studied the effects of charging on the structure, binding energy and electronic properties of silicene with alkali metal (AM) atom (Li, Na or K) adsorption. In AMSi2, electron doping enlarges the lattice constant of silicene, while the influence of hole doping is non-monotonic. In AMSi8, the lattice constant increases/decreases almost linearly with the increase in electron/hole doping. In addition, the AM-Si vertical distance can be greatly enlarged by excessive hole doping in both AMSi2 and AMSi8 systems. When the hole doping is as large as  +e per unit cell, both AMSi2 and AMSi8 can be transformed from metal to semiconductor. However, the binding energy would be negative in the AM+ Si2 semiconductor. It suggests AM+ Si2 is unstable in this case. In addition, the electron doping and the AM-Si vertical distance would greatly influence the band gap of silicene in LiSi8 and NaSi8, while the band gap in KSi8 is relatively stable. Therefore, KSi8 may be a more practicable material in nanotechnology.

Titanium-dioxide nanotube p-n homojunction diode

NASA Astrophysics Data System (ADS)

Alivov, Yahya; Ding, Yuchen; Singh, Vivek; Nagpal, Prashant

2014-12-01

Application of semiconductors in functional optoelectronic devices requires precise control over their doping and formation of junction between p- and n-doped semiconductors. While doped thin films have led to several semiconductor devices, need for high-surface area nanostructured devices for photovoltaic, photoelectrochemical, and photocatalytic applications has been hindered by lack of desired doping in nanostructures. Here, we show titanium-dioxide (TiO2) nanotubes doped with nitrogen (N) and niobium (Nb) as acceptors and donors, respectively, and formation of TiO2 nanotubes p-n homojunction. This TiO2:N/TiO2:Nb homojunction showed distinct diode-like behaviour with rectification ratio of 1115 at ±5 V and exhibited good photoresponse for ultraviolet light (λ = 365 nm) with sensitivity of 0.19 A/W at reverse bias of -5 V. These results can have important implications for development of nanostructured metal-oxide solar-cells, photodiodes, LED's, photocatalysts, and photoelectrochemical devices.

High-Yield Growth and Characterization of ⟨100⟩ InP p-n Diode Nanowires.

PubMed

Cavalli, Alessandro; Wang, Jia; Esmaeil Zadeh, Iman; Reimer, Michael E; Verheijen, Marcel A; Soini, Martin; Plissard, Sebastien R; Zwiller, Val; Haverkort, Jos E M; Bakkers, Erik P A M

2016-05-11

Semiconductor nanowires are nanoscale structures holding promise in many fields such as optoelectronics, quantum computing, and thermoelectrics. Nanowires are usually grown vertically on (111)-oriented substrates, while (100) is the standard in semiconductor technology. The ability to grow and to control impurity doping of ⟨100⟩ nanowires is crucial for integration. Here, we discuss doping of single-crystalline ⟨100⟩ nanowires, and the structural and optoelectronic properties of p-n junctions based on ⟨100⟩ InP nanowires. We describe a novel approach to achieve low resistance electrical contacts to nanowires via a gradual interface based on p-doped InAsP. As a first demonstration in optoelectronic devices, we realize a single nanowire light emitting diode in a ⟨100⟩-oriented InP nanowire p-n junction. To obtain high vertical yield, which is necessary for future applications, we investigate the effect of the introduction of dopants on the nanowire growth.

Mid-infrared Fe2+:ZnSe semiconductor saturable absorber mirror for passively Q-switched Er3+-doped ZBLAN fiber laser

NASA Astrophysics Data System (ADS)

Ning, Shougui; Feng, Guoying; Dai, Shenyu; Zhang, Hong; Zhang, Wei; Deng, Lijuan; Zhou, Shouhuan

2018-02-01

A mid-infrared (mid-IR) semiconductor saturable absorber mirror (SESAM) based on Fe2+:ZnSe for passively Q-switched Er3+-doped ZBLAN fiber laser has been demonstrated. Fe2+:ZnSe SESAM was fabricated by electron beam evaporation method. Fe2+ was innovatively doped into the reflective Bragg stack, in which ZnSe layer served as both doped matrix and high refractive layer during the fabricating process. By using the Fe2+:ZnSe SESAM, stable passively Q-switched pulses with the minimum pulse width of 0.43 μs under a repetition rate of 160.82 kHz were obtained. The recorded maximum average output power of 873 mW with a peak power of 12.59 W and pulse energy of 5.43 μJ were achieved. The results demonstrated a new method for fabricating Fe2+:ZnSe SESAM, which can be used in compact mid-IR Q-switched fiber laser.

Conductivity Modifications of Graphene by Electron Donative Organic Molecules

NASA Astrophysics Data System (ADS)

Masujima, Hiroaki; Mori, Takehiko; Hayamizu, Yuhei

2017-07-01

Graphene has been studied for the application of transparent electrodes in flexible electrical devices with semiconductor organics. Control of the charge carrier density in graphene is crucial to reduce the contact resistance between graphene and the active layer of organic semiconductor. Chemical doping of graphene is an approach to change the carrier density, where the adsorbed organic molecules donate or accept electrons form graphene. While various acceptor organic molecules have been demonstrated so far, investigation about donor molecules is still poor. In this work, we have investigated doping effect in graphene field-effect transistors functionalized by organic donor molecules such as dibenzotetrathiafulvalene (DBTTF), hexamethyltetrathiafulvalene (HMTTF), 1,5-diaminonaphthalene (DAN), and N, N, N', N'-tetramethyl- p-phenylenediamine (TMPD). Based on conductivity measurements of graphene transistors, the former three molecules do not have any significant effect to graphene transistors. However, TMPD shows effective n-type doping. The doping effect has a correlation with the level of highest occupied molecular orbital (HOMO) of each molecule, where TMPD has the highest HOMO level.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Usanov, D. A., E-mail: UsanovDA@info.sgu.ru; Nikitov, S. A.; Skripal, A. V.

A method is proposed for the measurement of the electrophysical characteristics of semiconductor structures: the electrical conductivity of the n layer, which plays the role of substrate for a semiconductor structure, and the thickness and electrical conductivity of the strongly doped epitaxial n{sup +} layer. The method is based on the use of a one-dimensional microwave photonic crystal with a violation of periodicity containing the semiconductor structure under investigation. The characteristics of epitaxial gallium-arsenide structures consisting of an epitaxial layer and the semi-insulating substrate measured by this method are presented.

Highly sensitive ethanol chemical sensor based on Ni-doped SnO₂ nanostructure materials.

PubMed

Rahman, Mohammed M; Jamal, Aslam; Khan, Sher Bahadar; Faisal, M

2011-10-15

Due to potential applications of semiconductor transition doped nanostructure materials and the important advantages of synthesis in cost-effective and environmental concerns, a significant effort has been consummated for improvement of Ni-doped SnO(2) nanomaterials using hydrothermal technique at room conditions. The structural and optical properties of the low-dimensional (average diameter, 52.4 nm) Ni-doped SnO(2) nanostructures were demonstrated using various conventional techniques such as UV/visible spectroscopy, FT-IR spectroscopy, X-ray powder diffraction (XRD), and Field-emission scanning electron microscopy (FE-SEM). The calcined doped material is an attractive semiconductor nanoparticle for accomplishment in chemical sensing by simple I-V technique, where toxic chemical (ethanol) is used as a target chemical. Thin-film of Ni-doped SnO(2) nanostructure materials with conducting coating agents on silver electrodes (AgE, surface area, 0.0216 cm(2)) revealed higher sensitivity and repeatability. The calibration plot is linear (R, 0.8440) over the large dynamic range (1.0 nM-1.0 mM), where the sensitivity is approximately 2.3148 μA cm(-2) mM(-1) with a detection limit of 0.6 nM, based on signal/noise ratio in short response time. Consequently on the basis of the sensitive communication among structures, morphologies, and properties, it is exemplified that the morphologies and the optical characteristics can be extended to a large scale in doping nanomaterials and proficient chemical sensors applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Structural, optical and morphological studies of Cd2+ doping in CH3NH3PbI3 perovskite semiconductor at Pb2+ site for photovoltaic applications

NASA Astrophysics Data System (ADS)

Parrey, Khursheed; Warish, Mohd.; Devi, Nisha; Niazi, A.; Aziz, A.; Ansari, S. G.

2018-05-01

Doping of semiconductors in a controlled mannner have paramount technological importance as far as the optical and electronic properties of the devices are concerned. Hybrid organic-inorganic perovskites (HOPs) as intrinsic semiconductors have sensational properties required for both the solar photovoltaics and perovskite light emitting diodes. However, undoped and complexity in the dpoing process of HOPs have limited their exploitation in the field of elcronics. In this papper we present the synthesis of HOP semiconductor (CH3NH3PbI3) doped in Pb2+ position by Cd2+. We studied the effect of the incorporation of Cd2+ into the crystalline structure and analysed the changes in the properties like crystal structure, optical absorption and the surface morphology. The structure of HOPs confirmed by X-ray diffraction analysis is tetragonal perovskite type. It can be found that the crystallinity of the samples was enhanced with the doping concentration as the intensity of diffraction peaks were observed to increase with doping. The absorption spectra as obtained from UV-Visible spectrophotometry and Tauc plot analysis indicated that the band gap observed (1.73 eV) is direct type and gets reduced to 1.67 eV with the doping concentration. The red shift may be due to the increase in the size of nanocrystalline material with doping.

Multi-layer MOS capacitor based polarization insensitive electro-optic intensity modulator.

PubMed

Qiu, Xiaoming; Ruan, Xiaoke; Li, Yanping; Zhang, Fan

2018-05-28

In this study, a multi-layer metal-oxide-semiconductor capacitor (MLMOSC) polarization insensitive modulator is proposed. The design is validated by numerical simulation with commercial software LUMERICAL SOLUTION. Based on the epsilon-near-zero (ENZ) effect of indium tin oxide (ITO), the device manages to uniformly modulate both the transverse electric (TE) and the transverse magnetic (TM) modes. With a 20μm-long double-layer metal-oxide-semiconductor capacitor (DLMOSC) polarization insensitive modulator, in which two metal-oxide-semiconductor (MOS) structures are formed by the n-doped Si/HfO 2 /ITO/HfO 2 / n-doped Si stack, the extinction ratios (ERs) of both the TE and the TM modes can be over 20dB. The polarization dependent losses of the device can be as low as 0.05dB for the "OFF" state and 0.004dB for the "ON" state. Within 1dB polarization dependent loss, the device can operate with over 20dB ERs at the S, C, and L bands. The polarization insensitive modulator offers various merits including ultra-compact size, broadband spectrum, and complementary metal oxide semiconductor (CMOS) compatibility.

Deliberate and Accidental Gas-Phase Alkali Doping of Chalcogenide Semiconductors: Cu(In,Ga)Se2

PubMed Central

Colombara, Diego; Berner, Ulrich; Ciccioli, Andrea; Malaquias, João C.; Bertram, Tobias; Crossay, Alexandre; Schöneich, Michael; Meadows, Helene J.; Regesch, David; Delsante, Simona; Gigli, Guido; Valle, Nathalie; Guillot, Jérome; El Adib, Brahime; Grysan, Patrick; Dale, Phillip J.

2017-01-01

Alkali metal doping is essential to achieve highly efficient energy conversion in Cu(In,Ga)Se2 (CIGSe) solar cells. Doping is normally achieved through solid state reactions, but recent observations of gas-phase alkali transport in the kesterite sulfide (Cu2ZnSnS4) system (re)open the way to a novel gas-phase doping strategy. However, the current understanding of gas-phase alkali transport is very limited. This work (i) shows that CIGSe device efficiency can be improved from 2% to 8% by gas-phase sodium incorporation alone, (ii) identifies the most likely routes for gas-phase alkali transport based on mass spectrometric studies, (iii) provides thermochemical computations to rationalize the observations and (iv) critically discusses the subject literature with the aim to better understand the chemical basis of the phenomenon. These results suggest that accidental alkali metal doping occurs all the time, that a controlled vapor pressure of alkali metal could be applied during growth to dope the semiconductor, and that it may have to be accounted for during the currently used solid state doping routes. It is concluded that alkali gas-phase transport occurs through a plurality of routes and cannot be attributed to one single source. PMID:28233864

Deliberate and Accidental Gas-Phase Alkali Doping of Chalcogenide Semiconductors: Cu(In,Ga)Se2.

PubMed

Colombara, Diego; Berner, Ulrich; Ciccioli, Andrea; Malaquias, João C; Bertram, Tobias; Crossay, Alexandre; Schöneich, Michael; Meadows, Helene J; Regesch, David; Delsante, Simona; Gigli, Guido; Valle, Nathalie; Guillot, Jérome; El Adib, Brahime; Grysan, Patrick; Dale, Phillip J

2017-02-24

Alkali metal doping is essential to achieve highly efficient energy conversion in Cu(In,Ga)Se 2 (CIGSe) solar cells. Doping is normally achieved through solid state reactions, but recent observations of gas-phase alkali transport in the kesterite sulfide (Cu 2 ZnSnS 4 ) system (re)open the way to a novel gas-phase doping strategy. However, the current understanding of gas-phase alkali transport is very limited. This work (i) shows that CIGSe device efficiency can be improved from 2% to 8% by gas-phase sodium incorporation alone, (ii) identifies the most likely routes for gas-phase alkali transport based on mass spectrometric studies, (iii) provides thermochemical computations to rationalize the observations and (iv) critically discusses the subject literature with the aim to better understand the chemical basis of the phenomenon. These results suggest that accidental alkali metal doping occurs all the time, that a controlled vapor pressure of alkali metal could be applied during growth to dope the semiconductor, and that it may have to be accounted for during the currently used solid state doping routes. It is concluded that alkali gas-phase transport occurs through a plurality of routes and cannot be attributed to one single source.

Ferromagnetic properties of Mn-doped HfS2 monolayer under strain

NASA Astrophysics Data System (ADS)

Ma, Xu; Zhao, Xu; Wu, Ninghua; Xin, Qianqian; Liu, Xiaomeng; Wang, Tianxing; Wei, Shuyi

2017-12-01

Using the first-principles calculations, we investigated electronic and magnetic properties of Mn-doped HfS2 monolayer for 4% and 8% Mn concentration. We study the strain tuning of electronic and magnetic properties of 4% Mn-doped HfS2 monolayer firstly. Our results show that the Mn-doped HfS2 monolayer is magnetic nanomaterial without strain. It keeps this character until the compressive strain comes to -8%, and the magnetism disappear with lager compressive strain. With the increasing tensile strain, the doped system transforms from semiconductor to half-metallic when the tensile strain is equivalent to or greater than 5%. The largest half-metallic gap is 1.307 eV at 5% tensile strain and the magnetic moment always keeps about 3μB, which indicates that Mn-doped HfS2 monolayer can be a candidate for superior half-metallic namomaterial. Furthermore, we find two Mn dopants couple ferromagnetically via antiferromagnetic (AFM) p-d exchange interaction at the environment of 8% concentration. It keeps the properties of magnetic semiconductor under two Mn-doped configurations with different Mn-Mn separations. Our studies predict Mn-doped HfS2 monolayer under strain to be candidates for dilute magnetic semiconductors.

Deposition of dopant impurities and pulsed energy drive-in

DOEpatents

Wickboldt, Paul; Carey, Paul G.; Smith, Patrick M.; Ellingboe, Albert R.

2008-01-01

A semiconductor doping process which enhances the dopant incorporation achievable using the Gas Immersion Laser Doping (GILD) technique. The enhanced doping is achieved by first depositing a thin layer of dopant atoms on a semiconductor surface followed by exposure to one or more pulses from either a laser or an ion-beam which melt a portion of the semiconductor to a desired depth, thus causing the dopant atoms to be incorporated into the molten region. After the molten region recrystallizes the dopant atoms are electrically active. The dopant atoms are deposited by plasma enhanced chemical vapor deposition (PECVD) or other known deposition techniques.

Deposition of dopant impurities and pulsed energy drive-in

DOEpatents

Wickboldt, Paul; Carey, Paul G.; Smith, Patrick M.; Ellingboe, Albert R.

1999-01-01

A semiconductor doping process which enhances the dopant incorporation achievable using the Gas Immersion Laser Doping (GILD) technique. The enhanced doping is achieved by first depositing a thin layer of dopant atoms on a semiconductor surface followed by exposure to one or more pulses from either a laser or an ion-beam which melt a portion of the semiconductor to a desired depth, thus causing the dopant atoms to be incorporated into the molten region. After the molten region recrystallizes the dopant atoms are electrically active. The dopant atoms are deposited by plasma enhanced chemical vapor deposition (PECVD) or other known deposition techniques.

Deposition of dopant impurities and pulsed energy drive-in

DOEpatents

Wickboldt, P.; Carey, P.G.; Smith, P.M.; Ellingboe, A.R.

1999-06-29

A semiconductor doping process which enhances the dopant incorporation achievable using the Gas Immersion Laser Doping (GILD) technique is disclosed. The enhanced doping is achieved by first depositing a thin layer of dopant atoms on a semiconductor surface followed by exposure to one or more pulses from either a laser or an ion-beam which melt a portion of the semiconductor to a desired depth, thus causing the dopant atoms to be incorporated into the molten region. After the molten region recrystallizes the dopant atoms are electrically active. The dopant atoms are deposited by plasma enhanced chemical vapor deposition (PECVD) or other known deposition techniques. 2 figs.

Boron, bismuth co-doping of gallium arsenide and other compounds for photonic and heterojunction bipolar transistor devices

DOEpatents

Mascarenhas, Angelo

2015-07-07

Isoelectronic co-doping of semiconductor compounds and alloys with acceptors and deep donors is sued to decrease bandgap, to increase concentration of the dopant constituents in the resulting alloys, and to increase carrier mobilities lifetimes. For example, Group III-V compounds and alloys, such as GaAs and GaP, are isoelectronically co-doped with, for example, B and Bi, to customize solar cells, and other semiconductor devices. Isoelectronically co-doped Group II-VI compounds and alloys are also included.

Metal contact engineering and registration-free fabrication of complementary metal-oxide semiconductor integrated circuits using aligned carbon nanotubes.

PubMed

Wang, Chuan; Ryu, Koungmin; Badmaev, Alexander; Zhang, Jialu; Zhou, Chongwu

2011-02-22

Complementary metal-oxide semiconductor (CMOS) operation is very desirable for logic circuit applications as it offers rail-to-rail swing, larger noise margin, and small static power consumption. However, it remains to be a challenging task for nanotube-based devices. Here in this paper, we report our progress on metal contact engineering for n-type nanotube transistors and CMOS integrated circuits using aligned carbon nanotubes. By using Pd as source/drain contacts for p-type transistors, small work function metal Gd as source/drain contacts for n-type transistors, and evaporated SiO(2) as a passivation layer, we have achieved n-type transistor, PN diode, and integrated CMOS inverter with an air-stable operation. Compared with other nanotube n-doping techniques, such as potassium doping, PEI doping, hydrazine doping, etc., using low work function metal contacts for n-type nanotube devices is not only air stable but also integrated circuit fabrication compatible. Moreover, our aligned nanotube platform for CMOS integrated circuits shows significant advantage over the previously reported individual nanotube platforms with respect to scalability and reproducibility and suggests a practical and realistic approach for nanotube-based CMOS integrated circuit applications.

Low-Resistivity Zinc Selenide for Heterojunctions

NASA Technical Reports Server (NTRS)

Stirn, R. J.

1986-01-01

Magnetron reactive sputtering enables doping of this semiconductor. Proposed method of reactive sputtering combined with doping shows potential for yielding low-resistivity zinc selenide films. Zinc selenide attractive material for forming heterojunctions with other semiconductor compounds as zinc phosphide, cadmium telluride, and gallium arsenide. Semiconductor junctions promising for future optoelectronic devices, including solar cells and electroluminescent displays. Resistivities of zinc selenide layers deposited by evaporation or chemical vapor deposition too high to form practical heterojunctions.

Neutron Transmutation Doped (NTD) germanium thermistors for sub-mm bolometer applications

NASA Technical Reports Server (NTRS)

Haller, E. E.; Itoh, K. M.; Beeman, J. W.

1996-01-01

Recent advances in the development of neutron transmutation doped (NTD) semiconductor thermistors fabricated from natural and controlled isotopic composition germanium are reported. The near ideal doping uniformity that can be achieved with the NTD process, the device simplicity of NTD Ge thermistors and the high performance of cooled junction field effect transistor preamplifiers led to the widespread acceptance of these thermal sensors in ground-based, airborne and spaceborne radio telescopes. These features made possible the development of efficient bolometer arrays.

Terahertz optoelectronics with surface plasmon polariton diode.

PubMed

Vinnakota, Raj K; Genov, Dentcho A

2014-05-09

The field of plasmonics has experience a renaissance in recent years by providing a large variety of new physical effects and applications. Surface plasmon polaritons, i.e. the collective electron oscillations at the interface of a metal/semiconductor and a dielectric, may bridge the gap between electronic and photonic devices, provided a fast switching mechanism is identified. Here, we demonstrate a surface plasmon-polariton diode (SPPD) an optoelectronic switch that can operate at exceedingly large signal modulation rates. The SPPD uses heavily doped p-n junction where surface plasmon polaritons propagate at the interface between n and p-type GaAs and can be switched by an external voltage. The devices can operate at transmission modulation higher than 98% and depending on the doping and applied voltage can achieve switching rates of up to 1 THz. The proposed switch is compatible with the current semiconductor fabrication techniques and could lead to nanoscale semiconductor-based optoelectronics.

Electrical properties of zinc-oxide-based thin-film transistors using strontium-oxide-doped semiconductors

NASA Astrophysics Data System (ADS)

Wu, Shao-Hang; Zhang, Nan; Hu, Yong-Sheng; Chen, Hong; Jiang, Da-Peng; Liu, Xing-Yuan

2015-10-01

Strontium-zinc-oxide (SrZnO) films forming the semiconductor layers of thin-film transistors (TFTs) are deposited by using ion-assisted electron beam evaporation. Using strontium-oxide-doped semiconductors, the off-state current can be dramatically reduced by three orders of magnitude. This dramatic improvement is attributed to the incorporation of strontium, which suppresses carrier generation, thereby improving the TFT. Additionally, the presence of strontium inhibits the formation of zinc oxide (ZnO) with the hexagonal wurtzite phase and permits the formation of an unusual phase of ZnO, thus significantly changing the surface morphology of ZnO and effectively reducing the trap density of the channel. Project supported by the National Natural Science Foundation of China (Grant No. 6140031454) and the Innovation Program of Chinese Academy of Sciences and State Key Laboratory of Luminescence and Applications.

High-efficiency, thin-film cadmium telluride photovoltaic cells

NASA Astrophysics Data System (ADS)

Compaan, A. D.; Bohn, R. G.; Rajakarunanayake, Y.

1995-08-01

This report describes work performed to develop and optimize the process of radio frequency (RF) sputtering for the fabrication of thin-film solar cells on glass. The emphasis is on CdTe-related materials including CdTe, CdS, ZnTe, and ternary alloy semiconductors. Pulsed laser physical vapor deposition (LPVD) was used for exploratory work on these materials, especially where alloying or doping are involved, and for the deposition of cadmium chloride layers. For the sputtering work, a two-gun sputtering chamber was implemented, with optical access for monitoring temperature and growth rate. We studied the optical and electrical properties of the plasmas produced by two different kinds of planar magnetron sputter guns with different magnetic field configurations and strengths. Using LPVD, we studied alloy semiconductors such as CdZnTe and heavily doped semiconductors such as ZnTe:Cu for possible incorporation into graded band gap CdTe-based photovoltaic devices.

Electronic theoretical study on the influence of torsional deformation on the electronic structure and optical properties of BN-doped graphene

NASA Astrophysics Data System (ADS)

Fan, Dazhi; Liu, Guili; Wei, Lin

2018-06-01

Based on the density functional theory, the effect of torsional deformation on the electronic structure and optical properties of boron nitride (BN)-doped graphene is studied by using the first-principles calculations. The band structure calculations show that the intrinsic graphene is a semi-metallic material with zero band gap and the torsional deformation has a large effect on its band gap, opening its band gap and turning it from the semi-metal to the medium band gap semiconductor. The doping of BN in graphene makes its band gap open and becomes a medium band gap semiconductor. When it is subjected to a torsional effect, it is found to have a weak influence on its band gap. In other words, the doping of BN makes the changes of the band gap of graphene no longer sensitive to torsional deformation. Optical properties show that the doping of BN leads to a significant decrease in the light absorption coefficient and reflectivity of the graphene at the characteristic peak and that of BN-doped graphene system is also weakened by torsional deformation at the characteristic peak. In the absorption spectrum, the absorption peaks of the doping system of the torsion angle of 2-20∘ are redshifted compared with that of the BN-doped system (the torsion angle is 0∘). In the reflection spectrum, the two reflection peaks are all redshifted relative to that of the BN-doped system (the torsion angle is 0∘) and when the torsion angle exceeds 12∘, the size relationship between the two peaks is interchanged. The results of this paper are of guiding significance for the study of graphene-based nanotube devices in terms of deformation.

Nonthermal Photocoercivity Effect in Low-Doped (Ga,Mn)As Ferromagnetic Semiconductor

NASA Astrophysics Data System (ADS)

Kiessling, T.; Astakhov, G. V.; Hoffmann, H.; Korenev, V. L.; Schwittek, J.; Schott, G. M.; Gould, C.; Ossau, W.; Brunner, K.; Molenkamp, L. W.

2011-12-01

We report a photoinduced change of the coercive field of a low doped Ga1-xMnxAs ferromagnetic semiconductor under very low intensity illumination. This photocoercivity effect (PCE) is local and reversible, which enables the controlled formation of localized magnetization domains. The PCE arises from a light induced lowering of the domain wall pinning energy as confirmed by test experiments on high doped, fully metallic ferromagnetic Ga1-xMnxAs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mascarenhas, Angelo

Isoelectronic co-doping of semiconductor compounds and alloys with acceptors and deep donors is used to decrease bandgap, to increase concentration of the dopant constituents in the resulting alloys, and to increase carrier mobilities lifetimes. For example, Group III-V compounds and alloys, such as GaAs and GaP, are isoelectronically co-doped with, for example, B and Bi, to customize solar cells, and other semiconductor devices. Isoelectronically co-doped Group II-VI compounds and alloys are also included.

Hole doping and pressure effects on the II-II-V-based diluted magnetic semiconductor ( B a 1 - x K x ) ( Z n 1 - y M n y ) 2 A s 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, F.; Zhao, G. Q.; Escanhoela, Jr., C. A.

We investigate doping- and pressure-induced changes in the electronic state of Mn 3d and As 4p orbitals in II-II-V based diluted magnetic semiconductor (Ba 1-x,K x)(Zn 1-y,Mn y) 2As 2 to shed light into the mechanism of indirect exchange interactions leading to high ferromagnetic ordering temperature (T c = 230 K in optimally doped samples). A suite of x-ray spectroscopy experiments (emission, absorption and dichroism) show that the emergence, and further enhancement of ferromagnetic interactions with increased hole doping into the As 4p band is accompanied by a decrease in local 3d spin density at Mn sites. This is amore » result of increasing Mn 3d - As 4p hybridization with hole doping which enhances indirect exchange interactions between Mn dopants and gives rise to induced magnetic polarization in As 4p states. On the contrary, application of pressure suppresses exchange interactions. While Mn Kβ emission spectra show a weak response of 3d state to pressure, clear As 4p band broadening (hole delocalization) is observed under pressure ultimately leading to loss of ferromagnetism concomitant with a semiconductor to metal transition. The pressure response of As 4p and Mn 3d states is intimately connected with the evolution of the As-As interlayer distance and the geometry of the MnAs 4 tetrahedral units, which we probed with X-ray diffraction. Our results indicate that hole doping increases the degree of covalency between the anion (As) p states and cation (Mn) d states in the MnA s4 tetrahedron, a crucial ingredient to promote indirect exchange interactions between Mn dopants and high T c ferromagnetism. As a result, the instability of ferromagnetism and semiconducting state against pressure is mainly dictated by delocalization of anion p states.« less

Hole doping and pressure effects on the II-II-V-based diluted magnetic semiconductor ( B a 1 - x K x ) ( Z n 1 - y M n y ) 2 A s 2

DOE PAGES

Sun, F.; Zhao, G. Q.; Escanhoela, Jr., C. A.; ...

2017-03-13

We investigate doping- and pressure-induced changes in the electronic state of Mn 3d and As 4p orbitals in II-II-V based diluted magnetic semiconductor (Ba 1-x,K x)(Zn 1-y,Mn y) 2As 2 to shed light into the mechanism of indirect exchange interactions leading to high ferromagnetic ordering temperature (T c = 230 K in optimally doped samples). A suite of x-ray spectroscopy experiments (emission, absorption and dichroism) show that the emergence, and further enhancement of ferromagnetic interactions with increased hole doping into the As 4p band is accompanied by a decrease in local 3d spin density at Mn sites. This is amore » result of increasing Mn 3d - As 4p hybridization with hole doping which enhances indirect exchange interactions between Mn dopants and gives rise to induced magnetic polarization in As 4p states. On the contrary, application of pressure suppresses exchange interactions. While Mn Kβ emission spectra show a weak response of 3d state to pressure, clear As 4p band broadening (hole delocalization) is observed under pressure ultimately leading to loss of ferromagnetism concomitant with a semiconductor to metal transition. The pressure response of As 4p and Mn 3d states is intimately connected with the evolution of the As-As interlayer distance and the geometry of the MnAs 4 tetrahedral units, which we probed with X-ray diffraction. Our results indicate that hole doping increases the degree of covalency between the anion (As) p states and cation (Mn) d states in the MnA s4 tetrahedron, a crucial ingredient to promote indirect exchange interactions between Mn dopants and high T c ferromagnetism. As a result, the instability of ferromagnetism and semiconducting state against pressure is mainly dictated by delocalization of anion p states.« less

Hole doping and pressure effects on the II-II-V-based diluted magnetic semiconductor (B a1 -xKx ) (Zn1-yM ny ) 2A s2

NASA Astrophysics Data System (ADS)

Sun, F.; Zhao, G. Q.; Escanhoela, C. A.; Chen, B. J.; Kou, R. H.; Wang, Y. G.; Xiao, Y. M.; Chow, P.; Mao, H. K.; Haskel, D.; Yang, W. G.; Jin, C. Q.

2017-03-01

We investigate doping- and pressure-induced changes in the electronic state of Mn 3 d and As 4 p orbitals in II-II-V-based diluted magnetic semiconductor (B a1 -xKx ) (Zn1-yM ny ) 2A s2 to shed light into the mechanism of indirect exchange interactions leading to high ferromagnetic ordering temperature (T c =230 K in optimally doped samples). A suite of x-ray spectroscopy experiments (emission, absorption, and dichroism) show that the emergence and further enhancement of ferromagnetic interactions with increased hole doping into the As 4 p band is accompanied by a decrease in local 3 d spin density at Mn sites. This is a result of increasing Mn 3 d -As 4 p hybridization with hole doping, which enhances indirect exchange interactions between Mn dopants and gives rise to induced magnetic polarization in As 4 p states. On the contrary, application of pressure suppresses exchange interactions. While Mn K β emission spectra show a weak response of 3 d states to pressure, clear As 4 p band broadening (hole delocalization) is observed under pressure, ultimately leading to loss of ferromagnetism concomitant with a semiconductor to metal transition. The pressure response of As 4 p and Mn 3 d states is intimately connected with the evolution of the As-As interlayer distance and the geometry of the MnA s4 tetrahedral units, which we probed with x-ray diffraction. Our results indicate that hole doping increases the degree of covalency between the anion (As) p states and cation (Mn) d states in the MnA s4 tetrahedron, a crucial ingredient to promote indirect exchange interactions between Mn dopants and high T c ferromagnetism. The instability of ferromagnetism and semiconducting states against pressure is mainly dictated by delocalization of anion p states.

Size Dependence of Doping by a Vacancy Formation Reaction in Copper Sulfide Nanocrystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elimelech, Orian; Liu, Jing; Plonka, Anna M.

Doping of nanocrystals (NCs) is a key, yet underexplored, approach for tuning of the electronic properties of semiconductors. An important route for doping of NCs is by vacancy formation. The size and concentration dependence of doping was studied in copper(I) sulfide (Cu2S) NCs through a redox reaction with iodine molecules (I2), which formed vacancies accompanied by a localized surface plasmon response. X-ray spectroscopy and diffraction reveal transformation from Cu2S to Cu-depleted phases, along with CuI formation. Greater reaction efficiency was observed for larger NCs. This behavior is attributed to interplay of the vacancy formation energy, which decreases for smaller sizedmore » NCs, and the growth of CuI on the NC surface, which is favored on well-defined facets of larger NCs. This doping process allows tuning of the plasmonic properties of a semiconductor across a wide range of plasmonic frequencies by varying the size of NCs and the concentration of iodine. Controlled vacancy doping of NCs may be used to tune and tailor semiconductors for use in optoelectronic applications.« less

Effect on Electron Structure and Magneto-Optic Property of Heavy W-Doped Anatase TiO2.

PubMed

Hou, Qingyu; Zhao, Chunwang; Guo, Shaoqiang; Mao, Fei; Zhang, Yue

2015-01-01

The spin or nonspin state of electrons in W-doped anatase TiO2 is very difficult to judge experimentally because of characterization method limitations. Hence, the effect on the microscopic mechanism underlying the visible-light effect of W-doped anatase TiO2 through the consideration of electronic spin or no-spin states is still unknown. To solve this problem, we establish supercell models of W-doped anatase TiO2 at different concentrations, followed by geometry optimization and energy calculation based on the first-principle planewave norm conserving pseudo-potential method of the density functional theory. Calculation results showed that under the condition of nonspin the doping concentration of W becomes heavier, the formation energy becomes greater, and doping becomes more difficult. Meanwhile, the total energy increases, the covalent weakens and ionic bonds strengthens, the stability of the W-doped anatase TiO2 decreases, the band gap increases, and the blue-shift becomes more significant with the increase of W doping concentration. However, under the condition of spin, after the band gap correction by the GGA+U method, it is found that the semimetal diluted magnetic semiconductors can be formed by heavy W-doped anatase TiO2. Especially, a conduction electron polarizability of as high as near 100% has been found for the first time in high concentration W-doped anatase TiO2. It will be able to be a promising new type of dilute magnetic semiconductor. And the heavy W-doped anatase TiO2 make the band gap becomes narrower and absorption spectrum red-shift.

Novel room temperature ferromagnetic semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Amita

2004-06-01

Today's information world, bits of data are processed by semiconductor chips, and stored in the magnetic disk drives. But tomorrow's information technology may see magnetism (spin) and semiconductivity (charge) combined in one 'spintronic' device that exploits both charge and 'spin' to carry data (the best of two worlds). Spintronic devices such as spin valve transistors, spin light emitting diodes, non-volatile memory, logic devices, optical isolators and ultra-fast optical switches are some of the areas of interest for introducing the ferromagnetic properties at room temperature in a semiconductor to make it multifunctional. The potential advantages of such spintronic devices will bemore » higher speed, greater efficiency, and better stability at a reduced power consumption. This Thesis contains two main topics: In-depth understanding of magnetism in Mn doped ZnO, and our search and identification of at least six new above room temperature ferromagnetic semiconductors. Both complex doped ZnO based new materials, as well as a number of nonoxides like phosphides, and sulfides suitably doped with Mn or Cu are shown to give rise to ferromagnetism above room temperature. Some of the highlights of this work are discovery of room temperature ferromagnetism in: (1) ZnO:Mn (paper in Nature Materials, Oct issue, 2003); (2) ZnO doped with Cu (containing no magnetic elements in it); (3) GaP doped with Cu (again containing no magnetic elements in it); (4) Enhancement of Magnetization by Cu co-doping in ZnO:Mn; (5) CdS doped with Mn, and a few others not reported in this thesis. We discuss in detail the first observation of ferromagnetism above room temperature in the form of powder, bulk pellets, in 2-3 mu-m thick transparent pulsed laser deposited films of the Mn (<4 at. percent) doped ZnO. High-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) spectra recorded from 2 to 200nm areas showed homogeneous distribution of Mn substituting for Zn a 2 + state in the ZnO lattice. Ferromagnetic Resonance (FMR) technique is used to confirm the existence of ferromagnetic ordering at temperatures as high as 425K. The ab initio calculations were found to be consistent with the observation of ferromagnetism arising from fully polarized Mn 2 + state. The key to observed room temperature ferromagnetism in this system is the low temperature processing, which prevents formation of clusters, secondary phases and the host ZnO from becoming n-type. The electronic structure of the same Mn doped ZnO thin films studied using XAS, XES and RIXS, revealed a strong hybridization between Mn 3d and O 2p states, which is an important characteristic of a Dilute magnetic Semiconductor (DMS). It is shown that the various processing conditions like sintering temperature, dopant concentration and the properties of precursors used for making of DMS have a great influence on the final properties. Use of various experimental techniques to verify the physical properties, and to understand the mechanism involved to give rise to ferromagnetism is presented. Methods to improve the magnetic moment in Mn doped ZnO are also described. New promising DMS materials (such as Cu doped ZnO are explored). The demonstrated new capability to fabricate powder, pellets, and thin films of room temperature ferromagnetic semiconductors thus makes possible the realization of a wide range of complex elements for a variety of new multifunctional phenomena related to Spintronic devices as well as magneto-optic components.« less

Controlled Chemical Doping of Semiconductor Nanocrystals Using Redox Buffers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Engel, Jesse H.; Surendranath, Yogesh; Alivisatos, Paul

Semiconductor nanocrystal solids are attractive materials for active layers in next-generation optoelectronic devices; however, their efficient implementation has been impeded by the lack of precise control over dopant concentrations. Herein we demonstrate a chemical strategy for the controlled doping of nanocrystal solids under equilibrium conditions. Exposing lead selenide nanocrystal thin films to solutions containing varying proportions of decamethylferrocene and decamethylferrocenium incrementally and reversibly increased the carrier concentration in the solid by 2 orders of magnitude from their native values. This application of redox buffers for controlled doping provides a new method for the precise control of the majority carrier concentrationmore » in porous semiconductor thin films.« less

Enhanced doping effect on tuning structural phases of monolayer antimony

NASA Astrophysics Data System (ADS)

Wang, Jizhang; Yang, Teng; Zhang, Zhidong; Yang, Li

2018-05-01

Doping is capable to control the atomistic structure, electronic structure, and even to dynamically realize a semiconductor-metal transition in two-dimensional (2D) transition metal dichalcogenides (TMDs). However, the high critical doping density (˜1014 electron/cm2), compound nature, and relatively low carrier mobility of TMDs limits broader applications. Using first-principles calculations, we predict that, via a small transition potential, a substantially lower hole doping density (˜6 × 1012 hole/cm2) can switch the ground-state structure of monolayer antimony from the hexagonal β-phase, a 2D semiconductor with excellent transport performance and air stability but an indirect bandgap, to the orthorhombic α phase with a direct bandgap and potentially better carrier mobility. We further show that this structural engineering can be achieved by the established electrostatic doping, surface functional adsorption, or directly using graphene substrate. This gives hope to dynamically tuning and large-scale production of 2D single-element semiconductors that simultaneously exhibit remarkable transport and optical performance.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elimelech, Orian; Liu, Jing; Plonka, Anna M.

Doping of nanocrystals (NCs) is a key, yet underexplored, approach for tuning of the electronic properties of semiconductors. An important route for doping of NCs is by vacancy formation. The size and concentration dependence of doping was studied in copper(I) sulfide (Cu2S) NCs through a redox reaction with iodine molecules (I2), which formed vacancies accompanied by a localized surface plasmon response. X-ray spectroscopy and diffraction reveal transformation from Cu2S to Cu-depleted phases, along with CuI formation. Greater reaction efficiency was observed for larger NCs. This behavior is attributed to interplay of the vacancy formation energy, which decreases for smaller sizedmore » NCs, and the growth of CuI on the NC surface, which is favored on well-defined facets of larger NCs. This doping process allows tuning of the plasmonic properties of a semiconductor across a wide range of plasmonic frequencies by varying the size of NCs and the concentration of iodine. Controlled vacancy doping of NCs may be used to tune and tailor semiconductors for use in optoelectronic applications.« less

Size-Dependent Optoelectronic Properties and Controlled Doping of Semiconductor Quantum Dots

NASA Astrophysics Data System (ADS)

Engel, Jesse Hart

Given a rapidly developing world, the need exists for inexpensive renewable energy alternatives to help avoid drastic climate change. Photovoltaics have the potential to fill the energy needs of the future, but significant cost decreases are necessary for widespread adoption. Semiconductor nanocrystals, also known as quantum dots, are a nascent technology with long term potential to enable inexpensive and high efficiency photovoltaics. When deposited as a film, quantum dots form unique nanocomposites whose electronic and optical properties can be broadly tuned through manipulation of their individual constituents. The contents of this thesis explore methods to understand and optimize the optoelectronic properties of PbSe quantum dot films for use in photovoltaic applications. Systematic optimization of photovoltaic performance is demonstrated as a function of nanocrystal size, establishing the potential for utilizing extreme quantum confinement to improve device energetics and alignment. Detailed investigations of the mechanisms of electrical transport are performed, revealing that electronic coupling in quantum dot films is significantly less than often assumed based on optical shifts. A method is proposed to employ extended regions of built-in electrical field, through controlled doping, to sidestep issues of poor transport. To this end, treatments with chemical redox agents are found to effect profound and reversible doping within nanocrystal films, sufficient to enable their use as chemical sensors, but lacking the precision required for optoelectronic applications. Finally, a novel doping method employing "redox buffers" is presented to enact precise, stable, and reversible charge-transfer doping in porous semiconductor films. An example of oxidatively doping PbSe quantum dot thin films is presented, and the future potential for redox buffers in photovoltaic applications is examined.

Mechanically induced strong red emission in samarium ions doped piezoelectric semiconductor CaZnOS for dynamic pressure sensing and imaging

NASA Astrophysics Data System (ADS)

Wang, Wei; Peng, Dengfeng; Zhang, Hanlu; Yang, Xiaohong; Pan, Caofeng

2017-07-01

Piezoelectric semiconductor with optical, electrical and mechanical multifunctions has great potential applications in future optoelectronic devices. The rich properties and applications mainly encompass the intrinsic structures and their coupling effects. Here, we report that lanthanide ions doped piezoelectric semiconductor CaZnOS:Sm3+ showing strong red emission induced by dynamic mechanical stress. Under moderate mechanical load, the doped piezoelectric semiconductor exhibits strong visible red emission to the naked eyes even under the day light. A flexible dynamic pressure sensor device is fabricated based on the prepared CaZnOS:Sm3+ powders. The mechanical-induced emission properties of the device are investigated by the optical fiber spectrometer. The linear characteristic emissions are attributed to the 4G5/2→6H5/2 (566 nm), 4G5/2→6H7/2 (580-632 nm), 4G5/2→6H9/2 (653-673 nm) and 4G5/2→6H11/2 (712-735 nm) f-f transitions of Sm3+ ions. The integral emission intensity is proportional to the value of applied pressure. By using the linear relationship between integrated emission intensity and the dynamic pressure, the real-time pressure distribution is visualized and recorded. Our results highlight that the incorporation of lanthanide luminescent ions into piezoelectric semiconductors as smart materials could be applied into the flexible mechanical-optical sensor device without additional auxiliary power, which has great potential for promising applications such as mapping of personalized handwriting, smart display, and human machine interface.

Doped titanium oxide photcatalysts: Preparation, structure and interaction with viruses

NASA Astrophysics Data System (ADS)

Li, Qi

Since the discovery of photoelectrochemical splitting of water on n-titanium oxide (n-TiO2) electrodes by Fujishima and Honda in 1972, there has been much interest in semiconductor-based materials as photocatalysts for both solar energy conversion and environmental applications in the past several decades. Among various semiconductor-based photocatalysts, TiO2 is the only candidate suitable for industrial use because of its high chemical stability, good photoactivity, relatively low cost, and nontoxicity. However, the photocatalytic capability of TiO 2 is limited to only ultraviolet (UV) light (wavelength, lambda, < 400 nm), seriously limiting its solar efficiency. In this study, both chemical and physical modification approaches were developed to extend the absorption band-edge of TiO2 into the visible light region with improved stability, photocatalytic efficiency and ease of the doping process. Two major approaches were used in the material synthesis and processing, including the ion-beam-assisted-deposition (IBAD) technique and sol-gel based processes. Both nitrogen-doped TiO2 (TiON) and nitrogen/palladium co-doped TiO2 (TiON/PdO) photocatalysts were created and their photocatalytic activity was investigated by the degradation of methylene blue (MB) and disinfection of bacteria and viruses under visible light illumination. The sol-gel process was optimized to produce high quality TiON-based photocatalysts by carefully modulating the precursor ratio and calcination temperature. A TiON inverse opal structure was created, which demonstrated enhanced visible light absorption and subsequently improved photocatalytic efficiency by the combination of chemical and physical modifications on n-TiO2. The effect of palladium dopant on the optical and photocatalytic properties of TiON/PdO photocatalyst was examined, which suggests that a careful optimization of the transition metal ion dopant concentration is needed to achieve high photocatalytic efficiency in these anion and transition metal ion co-doped TiO2 photocatalysts. High photocatalytic virus disinfection efficiency under visible-light illumination was observed for the first time with TiON/PdO photocatalyst, and the interaction between MS2 virus and TiO2-based semiconductor surfaces was successfully modulated. A strategy to use atomic force microscope (AFM) to conduct in-situ observation of viruses on semiconductor surfaces in aqueous environment was developed, which combines information from both height profile and phase profile and solves the difficulty of observing small nanosized biomolecules on substrates with similar feature sizes.

Photovoltaic Device Including A Boron Doping Profile In An I-Type Layer

DOEpatents

Yang, Liyou

1993-10-26

A photovoltaic cell for use in a single junction or multijunction photovoltaic device, which includes a p-type layer of a semiconductor compound including silicon, an i-type layer of an amorphous semiconductor compound including silicon, and an n-type layer of a semiconductor compound including silicon formed on the i-type layer. The i-type layer including an undoped first sublayer formed on the p-type layer, and a boron-doped second sublayer formed on the first sublayer.

Charge Saturation and Intrinsic Doping in Electrolyte-Gated Organic Semiconductors.

PubMed

Atallah, Timothy L; Gustafsson, Martin V; Schmidt, Elliot; Frisbie, C Daniel; Zhu, X-Y

2015-12-03

Electrolyte gating enables low voltage operation of organic thin film transistors, but little is known about the nature of the electrolyte/organic interface. Here we apply charge-modulation Fourier transform infrared spectroscopy, in conjunction with electrical measurements, on a model electrolyte gated organic semiconductor interface: single crystal rubrene/ion-gel. We provide spectroscopic signature for free-hole like carriers in the organic semiconductor and unambiguously show the presence of a high density of intrinsic doping of the free holes upon formation of the rubrene/ion-gel interface, without gate bias (Vg = 0 V). We explain this intrinsic doping as resulting from a thermodynamic driving force for the stabilization of free holes in the organic semiconductor by anions in the ion-gel. Spectroscopy also reveals the saturation of free-hole like carrier density at the rubrene/ion-gel interface at Vg < -0.5 V, which is commensurate with the negative transconductance seen in transistor measurements.

A Solution-Doped Polymer Semiconductor:Insulator Blend for Thermoelectrics.

PubMed

Kiefer, David; Yu, Liyang; Fransson, Erik; Gómez, Andrés; Primetzhofer, Daniel; Amassian, Aram; Campoy-Quiles, Mariano; Müller, Christian

2017-01-01

Poly(ethylene oxide) is demonstrated to be a suitable matrix polymer for the solution-doped conjugated polymer poly(3-hexylthiophene). The polarity of the insulator combined with carefully chosen processing conditions permits the fabrication of tens of micrometer-thick films that feature a fine distribution of the F4TCNQ dopant:semiconductor complex. Changes in electrical conductivity from 0.1 to 0.3 S cm -1 and Seebeck coefficient from 100 to 60 μV K -1 upon addition of the insulator correlate with an increase in doping efficiency from 20% to 40% for heavily doped ternary blends. An invariant bulk thermal conductivity of about 0.3 W m -1 K -1 gives rise to a thermoelectric Figure of merit ZT ∼ 10 -4 that remains unaltered for an insulator content of more than 60 wt%. Free-standing, mechanically robust tapes illustrate the versatility of the developed dopant:semiconductor:insulator ternary blends.

A Solution‐Doped Polymer Semiconductor:Insulator Blend for Thermoelectrics

PubMed Central

Kiefer, David; Yu, Liyang; Fransson, Erik; Gómez, Andrés; Primetzhofer, Daniel; Amassian, Aram; Campoy‐Quiles, Mariano

2016-01-01

Poly(ethylene oxide) is demonstrated to be a suitable matrix polymer for the solution‐doped conjugated polymer poly(3‐hexylthiophene). The polarity of the insulator combined with carefully chosen processing conditions permits the fabrication of tens of micrometer‐thick films that feature a fine distribution of the F4TCNQ dopant:semiconductor complex. Changes in electrical conductivity from 0.1 to 0.3 S cm−1 and Seebeck coefficient from 100 to 60 μV K−1 upon addition of the insulator correlate with an increase in doping efficiency from 20% to 40% for heavily doped ternary blends. An invariant bulk thermal conductivity of about 0.3 W m−1 K−1 gives rise to a thermoelectric Figure of merit ZT ∼ 10−4 that remains unaltered for an insulator content of more than 60 wt%. Free‐standing, mechanically robust tapes illustrate the versatility of the developed dopant:semiconductor:insulator ternary blends. PMID:28105396

Simulation of hole-mobility in doped relaxed and strained Ge layers

NASA Astrophysics Data System (ADS)

Watling, Jeremy R.; Riddet, Craig; Chan, Morgan Kah H.; Asenov, Asen

2010-11-01

As silicon based metal-oxide-semiconductor field-effect transistors (MOSFETs) are reaching the limits of their performance with scaling, alternative channel materials are being considered to maintain performance in future complementary metal-oxide semiconductor technology generations. Thus there is renewed interest in employing Ge as a channel material in p-MOSFETs, due to the significant improvement in hole mobility as compared to Si. Here we employ full-band Monte Carlo to study hole transport properties in Ge. We present mobility and velocity-field characteristics for different transport directions in p-doped relaxed and strained Ge layers. The simulations are based on a method for over-coming the potentially large dynamic range of scattering rates, which results from the long-range nature of the unscreened Coulombic interaction. Our model for ionized impurity scattering includes the affects of dynamic Lindhard screening, coupled with phase-shift, and multi-ion corrections along with plasmon scattering. We show that all these effects play a role in determining the hole carrier transport in doped Ge layers and cannot be neglected.

Analysis of fluctuations in semiconductor devices

NASA Astrophysics Data System (ADS)

Andrei, Petru

The random nature of ion implantation and diffusion processes as well as inevitable tolerances in fabrication result in random fluctuations of doping concentrations and oxide thickness in semiconductor devices. These fluctuations are especially pronounced in ultrasmall (nanoscale) semiconductor devices when the spatial scale of doping and oxide thickness variations become comparable with the geometric dimensions of devices. In the dissertation, the effects of these fluctuations on device characteristics are analyzed by using a new technique for the analysis of random doping and oxide thickness induced fluctuations. This technique is universal in nature in the sense that it is applicable to any transport model (drift-diffusion, semiclassical transport, quantum transport etc.) and it can be naturally extended to take into account random fluctuations of the oxide (trapped) charges and channel length. The technique is based on linearization of the transport equations with respect to the fluctuating quantities. It is computationally much (a few orders of magnitude) more efficient than the traditional Monte-Carlo approach and it yields information on the sensitivity of fluctuations of parameters of interest (e.g. threshold voltage, small-signal parameters, cut-off frequencies, etc.) to the locations of doping and oxide thickness fluctuations. For this reason, it can be very instrumental in the design of fluctuation-resistant structures of semiconductor devices. Quantum mechanical effects are taken into account by using the density-gradient model as well as through self-consistent Poisson-Schrodinger computations. Special attention is paid to the presenting of the technique in a form that is suitable for implementation on commercial device simulators. The numerical implementation of the technique is discussed in detail and numerous computational results are presented and compared with those previously published in literature.

High-temperature ferromagnetism in new n-type Fe-doped ferromagnetic semiconductor (In,Fe)Sb

NASA Astrophysics Data System (ADS)

Thanh Tu, Nguyen; Hai, Pham Nam; Anh, Le Duc; Tanaka, Masaaki

2018-06-01

Over the past two decades, intensive studies on various ferromagnetic semiconductor (FMS) materials have failed to realize reliable FMSs that have a high Curie temperature (T C > 300 K), good compatibility with semiconductor electronics, and characteristics superior to those of their nonmagnetic host semiconductors. Here, we demonstrate a new n-type Fe-doped narrow-gap III–V FMS, (In1‑ x ,Fe x )Sb. Its T C is unexpectedly high, reaching ∼335 K at a modest Fe concentration (x) of 16%. The anomalous Hall effect and magnetic circular dichroism (MCD) spectroscopy indicate that the high-temperature ferromagnetism in (In,Fe)Sb thin films is intrinsic and originates from the zinc-blende (In,Fe)Sb alloy semiconductor.

Method for sputtering a PIN microcrystalline/amorphous silicon semiconductor device with the P and N-layers sputtered from boron and phosphorous heavily doped targets

DOEpatents

Moustakas, Theodore D.; Maruska, H. Paul

1985-04-02

A silicon PIN microcrystalline/amorphous silicon semiconductor device is constructed by the sputtering of N, and P layers of silicon from silicon doped targets and the I layer from an undoped target, and at least one semi-transparent ohmic electrode.

Structurally controllable spin spatial splitter in a hybrid ferromagnet and semiconductor nanostructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Mao-Wang, E-mail: maowanglu@126.com; Cao, Xue-Li; Huang, Xin-Hong

2014-05-07

We theoretically investigate modulation of a tunable δ-potential to the lateral displacement of electrons across a magnetically modulated semiconductor nanostructure. Experimentally, this nanostructure can be produced by depositing a nanosized ferromagnetic stripe with in-plane magnetization on top of a semiconductor heterostructure, while the δ-potential can be realized by means of the atomic layer doping technique. Theoretical analysis reveals that this δ-doping can break the intrinsic symmetry in nanostructure and a considerable spin polarization in the lateral displacement will appear. Numerical calculations demonstrate that both magnitude and sign of spin polarization can be manipulated by changing the height and/or position ofmore » the δ-doping, giving rise to a structurally tunable spin spatial splitter.« less

Correlated electron-hole mechanism for molecular doping in organic semiconductors

NASA Astrophysics Data System (ADS)

Li, Jing; D'Avino, Gabriele; Pershin, Anton; Jacquemin, Denis; Duchemin, Ivan; Beljonne, David; Blase, Xavier

2017-07-01

The electronic and optical properties of the paradigmatic F4TCNQ-doped pentacene in the low-doping limit are investigated by a combination of state-of-the-art many-body ab initio methods accounting for environmental screening effects, and a carefully parametrized model Hamiltonian. We demonstrate that while the acceptor level lies very deep in the gap, the inclusion of electron-hole interactions strongly stabilizes dopant-semiconductor charge transfer states and, together with spin statistics and structural relaxation effects, rationalize the possibility for room-temperature dopant ionization. Our findings reconcile available experimental data, shedding light on the partial vs. full charge transfer scenario discussed in the literature, and question the relevance of the standard classification in shallow or deep impurity levels prevailing for inorganic semiconductors.

Manipulating semiconductor colloidal stability through doping.

PubMed

Fleharty, Mark E; van Swol, Frank; Petsev, Dimiter N

2014-10-10

The interface between a doped semiconductor material and electrolyte solution is of considerable fundamental interest, and is relevant to systems of practical importance. Both adjacent domains contain mobile charges, which respond to potential variations. This is exploited to design electronic and optoelectronic sensors, and other enabling semiconductor colloidal materials. We show that the charge mobility in both phases leads to a new type of interaction between semiconductor colloids suspended in aqueous electrolyte solutions. This interaction is due to the electrostatic response of the semiconductor interior to disturbances in the external field upon the approach of two particles. The electrostatic repulsion between two charged colloids is reduced from the one governed by the charged groups present at the particles surfaces. This type of interaction is unique to semiconductor particles and may have a substantial effect on the suspension dynamics and stability.

Recent progress in high-mobility thin-film transistors based on multilayer 2D materials

NASA Astrophysics Data System (ADS)

Hong, Young Ki; Liu, Na; Yin, Demin; Hong, Seongin; Kim, Dong Hak; Kim, Sunkook; Choi, Woong; Yoon, Youngki

2017-04-01

Two-dimensional (2D) layered semiconductors are emerging as promising candidates for next-generation thin-film electronics because of their high mobility, relatively large bandgap, low-power switching, and the availability of large-area growth methods. Thin-film transistors (TFTs) based on multilayer transition metal dichalcogenides or black phosphorus offer unique opportunities for next-generation electronic and optoelectronic devices. Here, we review recent progress in high-mobility transistors based on multilayer 2D semiconductors. We describe the theoretical background on characterizing methods of TFT performance and material properties, followed by their applications in flexible, transparent, and optoelectronic devices. Finally, we highlight some of the methods used in metal-semiconductor contacts, hybrid structures, heterostructures, and chemical doping to improve device performance.

Effect on Electron Structure and Magneto-Optic Property of Heavy W-Doped Anatase TiO2

PubMed Central

Hou, Qingyu; Zhao, Chunwang; Guo, Shaoqiang; Mao, Fei; Zhang, Yue

2015-01-01

The spin or nonspin state of electrons in W-doped anatase TiO2 is very difficult to judge experimentally because of characterization method limitations. Hence, the effect on the microscopic mechanism underlying the visible-light effect of W-doped anatase TiO2 through the consideration of electronic spin or no-spin states is still unknown. To solve this problem, we establish supercell models of W-doped anatase TiO2 at different concentrations, followed by geometry optimization and energy calculation based on the first-principle planewave norm conserving pseudo-potential method of the density functional theory. Calculation results showed that under the condition of nonspin the doping concentration of W becomes heavier, the formation energy becomes greater, and doping becomes more difficult. Meanwhile, the total energy increases, the covalent weakens and ionic bonds strengthens, the stability of the W-doped anatase TiO2 decreases, the band gap increases, and the blue-shift becomes more significant with the increase of W doping concentration. However, under the condition of spin, after the band gap correction by the GGA+U method, it is found that the semimetal diluted magnetic semiconductors can be formed by heavy W-doped anatase TiO2. Especially, a conduction electron polarizability of as high as near 100% has been found for the first time in high concentration W-doped anatase TiO2. It will be able to be a promising new type of dilute magnetic semiconductor. And the heavy W-doped anatase TiO2 make the band gap becomes narrower and absorption spectrum red-shift. PMID:25955308

Doping effect in Si nanocrystals

NASA Astrophysics Data System (ADS)

Li, Dongke; Xu, Jun; Zhang, Pei; Jiang, Yicheng; Chen, Kunji

2018-06-01

Intentional doping in semiconductors is a fundamental issue since it can control the conduction type and ability as well as modify the optical and electronic properties. To realize effective doping is the basis for developing semiconductor devices. However, by reducing the size of a semiconductor, like Si, to the nanometer scale, the doping effects become complicated due to the coupling between the quantum confinement effect and the surfaces and/or interfaces effect. In particular, by introducing phosphorus or boron impurities as dopants into material containing Si nanocrystals with a dot size of less than 10 nm, it exhibits different behaviors and influences on the physical properties from its bulk counterpart. Understanding the doping effects in Si nanocrystals is currently a challenge in order to further improve the performance of the next generation of nano-electronic and photonic devices. In this review, we present an overview of the latest theoretical studies and experimental results on dopant distributions and their effects on the electronic and optical properties of Si nanocrystals. In particular, the advanced characterization techniques on dopant distribution, the carrier transport process as well as the linear and nonlinear optical properties of doped Si nanocrystals, are systematically summarized.

Doping-tunable thermal emission from plasmon polaritons in semiconductor epsilon-near-zero thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jun, Young Chul; Luk, Ting S.; Robert Ellis, A.

2014-09-29

Here, we utilize the unique dispersion properties of leaky plasmon polaritons in epsilon-near-zero (ENZ) thin films to demonstrate thermal radiation control. Owing to its highly flat dispersion above the light line, a thermally excited leaky wave at the ENZ frequency out-couples into free space without any scattering structures, resulting in a narrowband, wide-angle, p-polarized thermal emission spectrum. We demonstrate this idea by measuring angle- and polarization-resolved thermal emission spectra from a single layer of unpatterned, doped semiconductors with deep-subwavelength film thickness (d/λ0 ~ 6 ×10 -3, where d is the film thickness and λ0 is the free space wavelength). Wemore » show that this semiconductor ENZ film effectively works as a leaky wave thermal radiation antenna, which generates far-field radiation from a thermally excited mode. The use of semiconductors makes the radiation frequency highly tunable by controlling doping densities and also facilitates device integration with other components. Therefore, this leaky plasmon polariton emission from semiconductor ENZ films provides an avenue for on-chip control of thermal radiation.« less

Spin polarized first principles study of Mn doped gallium nitride monolayer nanosheet

NASA Astrophysics Data System (ADS)

Sharma, Venus; Kaur, Sumandeep; Srivastava, Sunita; Kumar, Tankeshwar

2017-05-01

The structural, electronic and magnetic properties of gallium nitride nanosheet (GaNs) doped with Mn atoms have been studied using spin polarized density functional theory. The binding energy per atom, Energy Band gap, Fermi energy, magnetic moment, electric dipole moment have been found. The doped nanosheet is found to be more stable than pure GaN monolayer nanosheet. Adsorption of Mn atom has been done at four different sites on GaNs which affects the fermi level position. It is found that depending on the doping site, Mn can behave both like p-type semiconductor and also as n-type semiconductor. Also, it is ascertained that Mn doped GaNs (GaNs-Mn) exhibits ferromagnetic behavior.

Frontiers of controlling energy levels at interfaces

NASA Astrophysics Data System (ADS)

Koch, Norbert

The alignment of electron energy levels at interfaces between semiconductors, dielectrics, and electrodes determines the function and efficiency of all electronic and optoelectronic devices. Reliable guidelines for predicting the level alignment for a given material combination and methods to adjust the intrinsic energy landscape are needed to enable efficient engineering approaches. These are sufficiently understood for established electronic materials, e.g., Si, but for the increasing number of emerging materials, e.g., organic and 2D semiconductors, perovskites, this is work in progress. The intrinsic level alignment and the underlying mechanisms at interfaces between organic and inorganic semiconductors are discussed first. Next, methods to alter the level alignment are introduced, which all base on proper charge density rearrangement at a heterojunction. As interface modification agents we use molecular electron acceptors and donors, as well as molecular photochromic switches that add a dynamic aspect and allow device multifunctionality. For 2D semiconductors surface transfer doping with molecular acceptors/donors transpires as viable method to locally tune the Fermi-level position in the energy gap. The fundamental electronic properties of a prototypical 1D interface between intrinsic and p-doped 2D semiconductor regions are derived from local (scanning probe) and area-averaged (photoemission) spectroscopy experiments. Future research opportunities for attaining unsurpassed interface control through charge density management are discussed.

Development of p-type oxide semiconductors based on tin oxide and its alloys: application to thin film transistors

NASA Astrophysics Data System (ADS)

Barros, Ana Raquel Xarouco de

In spite of the recent p-type oxide TFTs developments based on SnOx and CuxO, the results achieved so far refer to devices processed at high temperatures and are limited by a low hole mobility and a low On-Off ratio and still there is no report on p-type oxide TFTs with performance similar to n-type, especially when comparing their field-effect mobility values, which are at least one order of magnitude higher on n-type oxide TFTs. Achieving high performance p-type oxide TFTs will definitely promote a new era for electronics in rigid and flexible substrates, away from silicon. None of the few reported p-channel oxide TFTs is suitable for practical applications, which demand significant improvements in the device engineering to meet the real-world electronic requirements, where low processing temperatures together with high mobility and high On-Off ratio are required for TFT and CMOS applications. The present thesis focuses on the study and optimization of p-type thin film transistors based on oxide semiconductors deposited by r.f. magnetron sputtering without intentional substrate heating. In this work several p-type oxide semiconductors were studied and optimized based on undoped tin oxide, Cu-doped SnOx and In-doped SnO2.

Understanding and control of bipolar self-doping in copper nitride

NASA Astrophysics Data System (ADS)

Fioretti, Angela N.; Schwartz, Craig P.; Vinson, John; Nordlund, Dennis; Prendergast, David; Tamboli, Adele C.; Caskey, Christopher M.; Tuomisto, Filip; Linez, Florence; Christensen, Steven T.; Toberer, Eric S.; Lany, Stephan; Zakutayev, Andriy

2016-05-01

Semiconductor materials that can be doped both n-type and p-type are desirable for diode-based applications and transistor technology. Copper nitride (Cu3N) is a metastable semiconductor with a solar-relevant bandgap that has been reported to exhibit bipolar doping behavior. However, deeper understanding and better control of the mechanism behind this behavior in Cu3N is currently lacking in the literature. In this work, we use combinatorial growth with a temperature gradient to demonstrate both conduction types of phase-pure, sputter-deposited Cu3N thin films. Room temperature Hall effect and Seebeck effect measurements show n-type Cu3N with 1017 electrons/cm3 for low growth temperature (≈35 °C) and p-type with 1015 holes/cm3-1016 holes/cm3 for elevated growth temperatures (50 °C-120 °C). Mobility for both types of Cu3N was ≈0.1 cm2/Vs-1 cm2/Vs. Additionally, temperature-dependent Hall effect measurements indicate that ionized defects are an important scattering mechanism in p-type films. By combining X-ray absorption spectroscopy and first-principles defect theory, we determined that VCu defects form preferentially in p-type Cu3N, while Cui defects form preferentially in n-type Cu3N, suggesting that Cu3N is a compensated semiconductor with conductivity type resulting from a balance between donor and acceptor defects. Based on these theoretical and experimental results, we propose a kinetic defect formation mechanism for bipolar doping in Cu3N that is also supported by positron annihilation experiments. Overall, the results of this work highlight the importance of kinetic processes in the defect physics of metastable materials and provide a framework that can be applied when considering the properties of such materials in general.

Simulations of terahertz pulse emission from thin-film semiconductor structures

NASA Astrophysics Data System (ADS)

Semichaevsky, Andrey

The photo-Dember effect is the formation of transient electric dipoles due to the interaction of semiconductors with ultrashort optical pulses. Typically the optically-induced dipole moments vary on the ns- or ps- scales, leading to the emission of electromagnetic pulses with terahertz (THz) bandwidths. One of the applications of the photo-Dember effect is a photoconductive dipole antenna (PDA). This work presents a computational model of a PDA based on Maxwell's equations coupled to the Boltzmann transport equation. The latter is solved semiclassically for the doped GaAs using a continuum approach. The emphasis is on the accurate prediction of the emitted THz pulse shape and bandwidth, particularly when materials are doped with a rare-earth metal such as erbium or terbium that serve as carrier recombination centers. Field-dependent carrier mobility is determined from particle-based simulations. Some of the previous experimental results are used as a basis for comparison with our model.

Doping enhanced barrier lowering in graphene-silicon junctions

NASA Astrophysics Data System (ADS)

Zhang, Xintong; Zhang, Lining; Chan, Mansun

2016-06-01

Rectifying properties of graphene-semiconductor junctions depend on the Schottky barrier height. We report an enhanced barrier lowering in graphene-Si junction and its essential doping dependence in this paper. The electric field due to ionized charge in n-type Si induces the same type doping in graphene and contributes another Schottky barrier lowering factor on top of the image-force-induced lowering (IFIL). We confirm this graphene-doping-induced lowering (GDIL) based on well reproductions of the measured reverse current of our fabricated graphene-Si junctions by the thermionic emission theory. Excellent matching between the theoretical predictions and the junction data of the doping-concentration dependent barrier lowering serves as another evidence of the GDIL. While both GDIL and IFIL are enhanced with the Si doping, GDIL exceeds IFIL with a threshold doping depending on the as-prepared graphene itself.

Bipolar resistive switching in metal-insulator-semiconductor nanostructures based on silicon nitride and silicon oxide

NASA Astrophysics Data System (ADS)

Koryazhkina, M. N.; Tikhov, S. V.; Mikhaylov, A. N.; Belov, A. I.; Korolev, D. S.; Antonov, I. N.; Karzanov, V. V.; Gorshkov, O. N.; Tetelbaum, D. I.; Karakolis, P.; Dimitrakis, P.

2018-03-01

Bipolar resistive switching in metal-insulator-semiconductor (MIS) capacitor-like structures with an inert Au top electrode and a Si3N4 insulator nanolayer (6 nm thick) has been observed. The effect of a highly doped n +-Si substrate and a SiO2 interlayer (2 nm) is revealed in the changes in the semiconductor space charge region and small-signal parameters of parallel and serial equivalent circuit models measured in the high- and low-resistive capacitor states, as well as under laser illumination. The increase in conductivity of the semiconductor capacitor plate significantly reduces the charging and discharging times of capacitor-like structures.

First Principles Electronic Structure of Mn doped GaAs, GaP, and GaN Semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulthess, Thomas C; Temmerman, Walter M; Szotek, Zdzislawa

We present first-principles electronic structure calculations of Mn doped III-V semiconductors based on the local spin-density approximation (LSDA) as well as the self-interaction corrected local spin density method (SIC-LSD). We find that it is crucial to use a self-interaction free approach to properly describe the electronic ground state. The SIC-LSD calculations predict the proper electronic ground state configuration for Mn in GaAs, GaP, and GaN. Excellent quantitative agreement with experiment is found for magnetic moment and p-d exchange in (GaMn)As. These results allow us to validate commonly used models for magnetic semiconductors. Furthermore, we discuss the delicate problem of extractingmore » binding energies of localized levels from density functional theory calculations. We propose three approaches to take into account final state effects to estimate the binding energies of the Mn-d levels in GaAs. We find good agreement between computed values and estimates from photoemisison experiments.« less

Point Defects in Two-Dimensional Layered Semiconductors: Physics and Its Applications

NASA Astrophysics Data System (ADS)

Suh, Joonki

Recent advances in material science and semiconductor processing have been achieved largely based on in-depth understanding, efficient management and advanced application of point defects in host semiconductors, thus finding the relevant techniques such as doping and defect engineering as a traditional scientific and technological solution. Meanwhile, two- dimensional (2D) layered semiconductors currently draw tremendous attentions due to industrial needs and their rich physics at the nanoscale; as we approach the end of critical device dimensions in silicon-based technology, ultra-thin semiconductors have the potential as next- generation channel materials, and new physics also emerges at such reduced dimensions where confinement of electrons, phonons, and other quasi-particles is significant. It is therefore rewarding and interesting to understand and redefine the impact of lattice defects by investigating their interactions with energy/charge carriers of the host matter. Potentially, the established understanding will provide unprecedented opportunities for realizing new functionalities and enhancing the performance of energy harvesting and optoelectronic devices. In this thesis, multiple novel 2D layered semiconductors, such as bismuth and transition- metal chalcogenides, are explored. Following an introduction of conventional effects induced by point defects in semiconductors, the related physics of electronically active amphoteric defects is revisited in greater details. This can elucidate the complication of a two-dimensional electron gas coexisting with the topological states on the surface of bismuth chalcogenides, recently suggested as topological insulators. Therefore, native point defects are still one of the keys to understand and exploit topological insulators. In addition to from a fundamental science point of view, the effects of point defects on the integrated thermal-electrical transport, as well as the entropy-transporting process in thermoelectric materials are thoroughly investigated. Point defects can potentially beat the undesired coupling, often term "thermoelectric Bermuda triangle", among electrical conductivity, thermal conductivity and thermopower. The maximum thermoelectric performance is demonstrated with an intermediate density of defects when they beneficially and multi-functionally act as electron donors, as well as strongly energy-dependent electron and phonon scatterers. Therefore, this is a good example of how fundamental defect physics can be applied for practical devices toward renewable energy technology. Another interesting field of layered nanomaterials is on transition-metal dichalcogenides (TMDs), sensational candidates for 2D semiconductor physics and applications. At the reduced dimensionality of 2D where a far stronger correlation between point defects and charge carriers is expected, it is studied how chalcogen vacancies alter optical properties of monolayer TMDs. A new, sub-bandgap broad emission lines as well as increase in the overall photoluminescence intensity at low temperatures are reported as a result of high quantum efficiency of excitons, i.e., bound electron-hole pairs, localized at defect sites. On electrical transport, both n- and p-type materials are needed to form junctions and support bipolar carrier conduction while typically only one type of doping is stable for a particular TMD. For example, MoS2 is natively n-type, thus the lack of p-type doping hampers the development of charge-splitting p-n junctions of MoS2. To address this issue, we demonstrate stable p-type conduction in MoS2 by substitutional Nb doping up to the degenerate level. Proof-of-concept, van der Waals p-n homo-junctions based on vertically stacked MoS2 layers are also fabricated which enable gate-tuneable current rectification. Various electronic devices fabricated are stable in ambient air even without additional treatment such as capping layer protection, thanks to the substitutionality nature of the doping; this is in stark contrast to the existing approach of using molecular doping, which usually suffers from volatility and reactivity with air and/or water molecules.

A room-temperature magnetic semiconductor from a ferromagnetic metallic glass

NASA Astrophysics Data System (ADS)

Liu, Wenjian; Zhang, Hongxia; Shi, Jin-An; Wang, Zhongchang; Song, Cheng; Wang, Xiangrong; Lu, Siyuan; Zhou, Xiangjun; Gu, Lin; Louzguine-Luzgin, Dmitri V.; Chen, Mingwei; Yao, Kefu; Chen, Na

2016-12-01

Emerging for future spintronic/electronic applications, magnetic semiconductors have stimulated intense interest due to their promises for new functionalities and device concepts. So far, the so-called diluted magnetic semiconductors attract many attentions, yet it remains challenging to increase their Curie temperatures above room temperature, particularly those based on III-V semiconductors. In contrast to the concept of doping magnetic elements into conventional semiconductors to make diluted magnetic semiconductors, here we propose to oxidize originally ferromagnetic metals/alloys to form new species of magnetic semiconductors. We introduce oxygen into a ferromagnetic metallic glass to form a Co28.6Fe12.4Ta4.3B8.7O46 magnetic semiconductor with a Curie temperature above 600 K. The demonstration of p-n heterojunctions and electric field control of the room-temperature ferromagnetism in this material reflects its p-type semiconducting character, with a mobility of 0.1 cm2 V-1 s-1. Our findings may pave a new way to realize high Curie temperature magnetic semiconductors with unusual multifunctionalities.

Chemical trend of exchange coupling in diluted magnetic II-VI semiconductors: Ab initio calculations

NASA Astrophysics Data System (ADS)

Chanier, T.; Virot, F.; Hayn, R.

2009-05-01

We have calculated the chemical trend of magnetic exchange parameters ( Jdd , Nα , and Nβ ) of Zn-based II-VI semiconductors ZnA ( A=O , S, Se, and Te) doped with Co or Mn. We show that a proper treatment of electron correlations by the local spin-density approximation (LSDA)+U method leads to good agreement between experimental and theoretical values of the nearest-neighbor exchange coupling Jdd between localized 3d spins in contrast to the LSDA method. The exchange couplings between localized spins and doped electrons in the conduction band Nα are in good agreement with experiment as well. But the values for Nβ (coupling to doped holes in the valence band) indicate a crossover from weak coupling (for A=Te and Se) to strong coupling (for A=O ) and a localized hole state in ZnO:Mn. This hole localization explains the apparent discrepancy between photoemission and magneto-optical data for ZnO:Mn.

Remarkable Enhancement of the Hole Mobility in Several Organic Small-Molecules, Polymers, and Small-Molecule:Polymer Blend Transistors by Simple Admixing of the Lewis Acid p-Dopant B(C6F5)3.

PubMed

Panidi, Julianna; Paterson, Alexandra F; Khim, Dongyoon; Fei, Zhuping; Han, Yang; Tsetseris, Leonidas; Vourlias, George; Patsalas, Panos A; Heeney, Martin; Anthopoulos, Thomas D

2018-01-01

Improving the charge carrier mobility of solution-processable organic semiconductors is critical for the development of advanced organic thin-film transistors and their application in the emerging sector of printed electronics. Here, a simple method is reported for enhancing the hole mobility in a wide range of organic semiconductors, including small-molecules, polymers, and small-molecule:polymer blends, with the latter systems exhibiting the highest mobility. The method is simple and relies on admixing of the molecular Lewis acid B(C 6 F 5 ) 3 in the semiconductor formulation prior to solution deposition. Two prototypical semiconductors where B(C 6 F 5 ) 3 is shown to have a remarkable impact are the blends of 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene:poly(triarylamine) (diF-TESADT:PTAA) and 2,7-dioctyl[1]-benzothieno[3,2-b][1]benzothiophene:poly(indacenodithiophene-co-benzothiadiazole) (C8-BTBT:C16-IDTBT), for which hole mobilities of 8 and 11 cm 2 V -1 s -1 , respectively, are obtained. Doping of the 6,13-bis(triisopropylsilylethynyl)pentacene:PTAA blend with B(C 6 F 5 ) 3 is also shown to increase the maximum hole mobility to 3.7 cm 2 V -1 s -1 . Analysis of the single and multicomponent materials reveals that B(C 6 F 5 ) 3 plays a dual role, first acting as an efficient p-dopant, and secondly as a microstructure modifier. Semiconductors that undergo simultaneous p-doping and dopant-induced long-range crystallization are found to consistently outperform transistors based on the pristine materials. Our work underscores Lewis acid doping as a generic strategy towards high performance printed organic microelectronics.

Towards a new class of heavy ion doped magnetic semiconductors for room temperature applications

PubMed Central

Lee, Juwon; Subramaniam, Nagarajan Ganapathi; Agnieszka Kowalik, Iwona; Nisar, Jawad; Lee, Jaechul; Kwon, Younghae; Lee, Jaechoon; Kang, Taewon; Peng, Xiangyang; Arvanitis, Dimitri; Ahuja, Rajeev

2015-01-01

The article presents, using Bi doped ZnO, an example of a heavy ion doped oxide semiconductor, highlighting a novel p-symmetry interaction of the electronic states to stabilize ferromagnetism. The study includes both ab initio theory and experiments, which yield clear evidence for above room temperature ferromagnetism. ZnBixO1−x thin films are grown using the pulsed laser deposition technique. The room temperature ferromagnetism finds its origin in the holes introduced by the Bi doping and the p-p coupling between Bi and the host atoms. A sizeable magnetic moment is measured by means of x-ray magnetic circular dichroism at the O K-edge, probing directly the spin polarization of the O(2p) states. This result is in agreement with the theoretical predictions and inductive magnetometry measurements. Ab initio calculations of the electronic and magnetic structure of ZnBixO1−x at various doping levels allow to trace the origin of the ferromagnetic character of this material. It appears, that the spin-orbit energy of the heavy ion Bi stabilizes the ferromagnetic phase. Thus, ZnBixO1−x doped with a heavy non-ferromagnetic element, such as Bi, is a credible example of a candidate material for a new class of compounds for spintronics applications, based on the spin polarization of the p states. PMID:26592564

Pseudo-Boltzmann model for modeling the junctionless transistors

NASA Astrophysics Data System (ADS)

Avila-Herrera, F.; Cerdeira, A.; Roldan, J. B.; Sánchez-Moreno, P.; Tienda-Luna, I. M.; Iñiguez, B.

2014-05-01

Calculation of the carrier concentrations in semiconductors using the Fermi-Dirac integral requires complex numerical calculations; in this context, practically all analytical device models are based on Boltzmann statistics, even though it is known that it leads to an over-estimation of carriers densities for high doping concentrations. In this paper, a new approximation to Fermi-Dirac integral, called Pseudo-Boltzmann model, is presented for modeling junctionless transistors with high doping concentrations.

Electrically tunable infrared metamaterial devices

DOEpatents

Brener, Igal; Jun, Young Chul

2015-07-21

A wavelength-tunable, depletion-type infrared metamaterial optical device is provided. The device includes a thin, highly doped epilayer whose electrical permittivity can become negative at some infrared wavelengths. This highly-doped buried layer optically couples with a metamaterial layer. Changes in the transmission spectrum of the device can be induced via the electrical control of this optical coupling. An embodiment includes a contact layer of semiconductor material that is sufficiently doped for operation as a contact layer and that is effectively transparent to an operating range of infrared wavelengths, a thin, highly doped buried layer of epitaxially grown semiconductor material that overlies the contact layer, and a metallized layer overlying the buried layer and patterned as a resonant metamaterial.

Boron doping a semiconductor particle

DOEpatents

Stevens, G.D.; Reynolds, J.S.; Brown, L.K.

1998-06-09

A method of boron doping a semiconductor particle using boric acid to obtain a p-type doped particle. Either silicon spheres or silicon powder is mixed with a diluted solution of boric acid having a predetermined concentration. The spheres are dried, with the boron film then being driven into the sphere. A melt procedure mixes the driven boron uniformly throughout the sphere. In the case of silicon powder, the powder is metered out into piles and melted/fused with an optical furnace. Both processes obtain a p-type doped silicon sphere with desired resistivity. Boric acid is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirements. 2 figs.

Boron doping a semiconductor particle

DOEpatents

Stevens, Gary Don; Reynolds, Jeffrey Scott; Brown, Louanne Kay

1998-06-09

A method (10,30) of boron doping a semiconductor particle using boric acid to obtain a p-type doped particle. Either silicon spheres or silicon powder is mixed with a diluted solution of boric acid having a predetermined concentration. The spheres are dried (16), with the boron film then being driven (18) into the sphere. A melt procedure mixes the driven boron uniformly throughout the sphere. In the case of silicon powder, the powder is metered out (38) into piles and melted/fused (40) with an optical furnace. Both processes obtain a p-type doped silicon sphere with desired resistivity. Boric acid is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirements.

Method for making defect-free zone by laser-annealing of doped silicon

DOEpatents

Narayan, Jagdish; White, Clark W.; Young, Rosa T.

1980-01-01

This invention is a method for improving the electrical properties of silicon semiconductor material. The method comprises irradiating a selected surface layer of the semiconductor material with high-power laser pulses characterized by a special combination of wavelength, energy level, and duration. The combination effects melting of the layer without degrading electrical properties, such as minority-carrier diffusion length. The method is applicable to improving the electrical properties of n- and p-type silicon which is to be doped to form an electrical junction therein. Another important application of the method is the virtually complete removal of doping-induced defects from ion-implanted or diffusion-doped silicon substrates.

Influence of nitrogen-doping concentration on the electronic structure of CuAlO2 by first-principles studies

NASA Astrophysics Data System (ADS)

Liu, Wei-wei; Chen, Hong-xia; Liu, Cheng-lin; Wang, Rong

2017-02-01

Effect of N doping concentration on the electronic structure of N-doped CuAlO2 was investigated by density functional theory based on generalized-gradient approximation plus orbital potential. Lattice parameters a and c both increase with increasing N-doping concentration. Formation energies increase with increasing N doping concentration and all N-doped CuAlO2 were structurally stable. The calculated band gaps for N-doped CuAlO2 narrowed compared to pure CuAlO2, which was attributed to the stronger hybridization between Cu-3d and N-2p states and the downward shift of Cu-3p states in conduction bands. The higher the N-doping concentration is, the narrower the band gap. N-doped CuAlO2 shows a typical p-type semiconductor. The band structure changed from indirect to direct after N doping which will benefit the application of the CuAlO2 materials in optoelectronic and electronic devices.

N doped ZnO and ZnO nanorods based p-n homojunction fabricated by ion implantation

NASA Astrophysics Data System (ADS)

Chakraborty, Mohua; Thangavel, R.; Asokan, K.

2018-05-01

Nitrogen (N) doped and undoped Zinc Oxide (ZnO) nanorod p-n homojunctions were fabricated by ion implantation method. The structural and optical characterizations showed that the N atoms doped into the ZnO crystal lattice. The UV-Vis absorption spectra revealed shift in optical absorption edge towards higher wavelength with ion implantation on ZnO, which attributed N acceptor levels above the valence band. The current-voltage (I-V) measurements exhibit a typical semiconductor rectification characteristic indicating the electrical conductivity of the N-doped ZnO nanorod have p-type conductivity. Moreover, a high photocurrent response has been observed with these p-n homojunctions.

Metal-doped semiconductor nanoparticles and methods of synthesis thereof

NASA Technical Reports Server (NTRS)

Ren, Zhifeng (Inventor); Wang, Wenzhong (Inventor); Chen, Gang (Inventor); Dresselhaus, Mildred (Inventor); Poudel, Bed (Inventor); Kumar, Shankar (Inventor)

2009-01-01

The present invention generally relates to binary or higher order semiconductor nanoparticles doped with a metallic element, and thermoelectric compositions incorporating such nanoparticles. In one aspect, the present invention provides a thermoelectric composition comprising a plurality of nanoparticles each of which includes an alloy matrix formed of a Group IV element and Group VI element and a metallic dopant distributed within the matrix.

Metal-doped semiconductor nanoparticles and methods of synthesis thereof

DOEpatents

Ren, Zhifeng [Newton, MA; Chen, Gang [Carlisle, MA; Poudel, Bed [West Newton, MA; Kumar, Shankar [Newton, MA; Wang, Wenzhong [Beijing, CN; Dresselhaus, Mildred [Arlington, MA

2009-09-08

The present invention generally relates to binary or higher order semiconductor nanoparticles doped with a metallic element, and thermoelectric compositions incorporating such nanoparticles. In one aspect, the present invention provides a thermoelectric composition comprising a plurality of nanoparticles each of which includes an alloy matrix formed of a Group IV element and Group VI element and a metallic dopant distributed within the matrix.

Controlling the stoichiometry and doping of semiconductor materials

DOEpatents

Albin, David; Burst, James; Metzger, Wyatt; Duenow, Joel; Farrell, Stuart; Colegrove, Eric

2016-08-16

Methods for treating a semiconductor material are provided. According to an aspect of the invention, the method includes annealing the semiconductor material in the presence of a compound that includes a first element and a second element. The first element provides an overpressure to achieve a desired stoichiometry of the semiconductor material, and the second element provides a dopant to the semiconductor material.

Doping-tunable thermal emission from plasmon polaritons in semiconductor epsilon-near-zero thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jun, Young Chul, E-mail: youngchul.jun@inha.ac.kr; Luk, Ting S., E-mail: tsluk@sandia.gov; Brener, Igal

2014-09-29

We utilize the unique dispersion properties of leaky plasmon polaritons in epsilon-near-zero (ENZ) thin films to demonstrate thermal radiation control. Owing to its highly flat dispersion above the light line, a thermally excited leaky wave at the ENZ frequency out-couples into free space without any scattering structures, resulting in a narrowband, wide-angle, p-polarized thermal emission spectrum. We demonstrate this idea by measuring angle- and polarization-resolved thermal emission spectra from a single layer of unpatterned, doped semiconductors with deep-subwavelength film thickness (d/λ{sub 0} ∼ 6×10{sup −3}, where d is the film thickness and  λ{sub 0} is the free space wavelength). We show thatmore » this semiconductor ENZ film effectively works as a leaky wave thermal radiation antenna, which generates far-field radiation from a thermally excited mode. The use of semiconductors makes the radiation frequency highly tunable by controlling doping densities and also facilitates device integration with other components. Therefore, this leaky plasmon polariton emission from semiconductor ENZ films provides an avenue for on-chip control of thermal radiation.« less

Integrated Graphene-Based Optoelectronic Devices Used for Ultrafast Optical-THz Photodetectors, Modulators and Emitters

DTIC Science & Technology

2015-04-03

08 and AFRL/ CA policy clarification memorandum dated 16 Jan 09. This report is available to the general public, including foreign nationals. Copies... doped graphene micro-ribbon array and a quantum-well electron gas sitting at an interface between a half-space of air and another half-space of a... doped semiconductor substrate which supports a surface-plasmon mode in our system. The coupling between a spatially-modulated total electromagnetic

Spatially controlled doping of two-dimensional SnS 2 through intercalation for electronics

DOE PAGES

Gong, Yongji; Yuan, Hongtao; Wu, Chun-Lan; ...

2018-02-26

Doped semiconductors are the most important building elements for modern electronic devices. In silicon-based integrated circuits, facile and controllable fabrication and integration of these materials can be realized without introducing a high-resistance interface. Besides, the emergence of two-dimensional (2D) materials enables the realization of atomically thin integrated circuits. However, the 2D nature of these materials precludes the use of traditional ion implantation techniques for carrier doping and further hinders device development10. Here, we demonstrate a solvent-based intercalation method to achieve p-type, n-type and degenerately doped semiconductors in the same parent material at the atomically thin limit. In contrast to naturallymore » grown n-type S-vacancy SnS 2, Cu intercalated bilayer SnS 2 obtained by this technique displays a hole field-effect mobility of ~40 cm 2 V -1 s -1, and the obtained Co-SnS 2 exhibits a metal-like behaviour with sheet resistance comparable to that of few-layer graphene. Combining this intercalation technique with lithography, an atomically seamless p–n–metal junction could be further realized with precise size and spatial control, which makes in-plane heterostructures practically applicable for integrated devices and other 2D materials. Therefore, the presented intercalation method can open a new avenue connecting the previously disparate worlds of integrated circuits and atomically thin materials.« less

Spatially controlled doping of two-dimensional SnS 2 through intercalation for electronics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Yongji; Yuan, Hongtao; Wu, Chun-Lan

Doped semiconductors are the most important building elements for modern electronic devices. In silicon-based integrated circuits, facile and controllable fabrication and integration of these materials can be realized without introducing a high-resistance interface. Besides, the emergence of two-dimensional (2D) materials enables the realization of atomically thin integrated circuits. However, the 2D nature of these materials precludes the use of traditional ion implantation techniques for carrier doping and further hinders device development10. Here, we demonstrate a solvent-based intercalation method to achieve p-type, n-type and degenerately doped semiconductors in the same parent material at the atomically thin limit. In contrast to naturallymore » grown n-type S-vacancy SnS 2, Cu intercalated bilayer SnS 2 obtained by this technique displays a hole field-effect mobility of ~40 cm 2 V -1 s -1, and the obtained Co-SnS 2 exhibits a metal-like behaviour with sheet resistance comparable to that of few-layer graphene. Combining this intercalation technique with lithography, an atomically seamless p–n–metal junction could be further realized with precise size and spatial control, which makes in-plane heterostructures practically applicable for integrated devices and other 2D materials. Therefore, the presented intercalation method can open a new avenue connecting the previously disparate worlds of integrated circuits and atomically thin materials.« less

Spatially controlled doping of two-dimensional SnS2 through intercalation for electronics

NASA Astrophysics Data System (ADS)

Gong, Yongji; Yuan, Hongtao; Wu, Chun-Lan; Tang, Peizhe; Yang, Shi-Ze; Yang, Ankun; Li, Guodong; Liu, Bofei; van de Groep, Jorik; Brongersma, Mark L.; Chisholm, Matthew F.; Zhang, Shou-Cheng; Zhou, Wu; Cui, Yi

2018-04-01

Doped semiconductors are the most important building elements for modern electronic devices1. In silicon-based integrated circuits, facile and controllable fabrication and integration of these materials can be realized without introducing a high-resistance interface2,3. Besides, the emergence of two-dimensional (2D) materials enables the realization of atomically thin integrated circuits4-9. However, the 2D nature of these materials precludes the use of traditional ion implantation techniques for carrier doping and further hinders device development10. Here, we demonstrate a solvent-based intercalation method to achieve p-type, n-type and degenerately doped semiconductors in the same parent material at the atomically thin limit. In contrast to naturally grown n-type S-vacancy SnS2, Cu intercalated bilayer SnS2 obtained by this technique displays a hole field-effect mobility of 40 cm2 V-1 s-1, and the obtained Co-SnS2 exhibits a metal-like behaviour with sheet resistance comparable to that of few-layer graphene5. Combining this intercalation technique with lithography, an atomically seamless p-n-metal junction could be further realized with precise size and spatial control, which makes in-plane heterostructures practically applicable for integrated devices and other 2D materials. Therefore, the presented intercalation method can open a new avenue connecting the previously disparate worlds of integrated circuits and atomically thin materials.

The structural, electronic and optical properties of Nd doped ZnO using first-principles calculations

NASA Astrophysics Data System (ADS)

Wen, Jun-Qing; Zhang, Jian-Min; Chen, Guo-Xiang; Wu, Hua; Yang, Xu

2018-04-01

The density functional theory calculations using general gradient approximation (GGA) applying Perdew-Burke-Ernzerhof (PBE) as correlation functional have been systematically performed to research the formation energy, the electronic structures, band structures, total and partial DOS, and optical properties of Nd doping ZnO with the content from 6.25% to 12.5%. The formation energies are negative for both models, which show that two structures are energetically stable. Nd doping ZnO crystal is found to be a direct band gap semiconductor and Fermi level shifts upward into conduction band, which show the properties of n-type semiconductor. Band structures are more compact after Nd doping ZnO, implying that Nd doping induces the strong interaction between different atoms. Nd doping ZnO crystal presents occupied states at near Fermi level, which mainly comes from the Nd 4f orbital. The calculated optical properties imply that Nd doping causes a red-shift of absorption peaks, and enhances the absorption of the visible light.

Screening-Engineered Field-Effect Solar Cells

DTIC Science & Technology

2012-01-01

virtually any semiconductor, including the promising but hard-to- dope metal oxides, sulfides, and phosphides.3 Prototype SFPV devices have been...MIS interface. Unfortu- nately, MIS cells, though sporting impressive efficiencies,4−6 typically have short operating lifetimes due to surface state...instability at the MIS interface.7 Methods aimed at direct field- effect “ doping ” of semiconductors, in which the voltage is externally applied to a gate

Charge transport in electrically doped amorphous organic semiconductors.

PubMed

Yoo, Seung-Jun; Kim, Jang-Joo

2015-06-01

This article reviews recent progress on charge generation by doping and its influence on the carrier mobility in organic semiconductors (OSs). The doping induced charge generation efficiency is generally low in OSs which was explained by the integer charge transfer model and the hybrid charge transfer model. The ionized dopants formed by charge transfer between hosts and dopants can act as Coulomb traps for mobile charges, and the presence of Coulomb traps in OSs broadens the density of states (DOS) in doped organic films. The Coulomb traps strongly reduce the carrier hopping rate and thereby change the carrier mobility, which was confirmed by experiments in recent years. In order to fully understand the doping mechanism in OSs, further quantitative and systematic analyses of charge transport characteristics must be accomplished. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultrahigh sensitivity of anomalous Hall effect sensor based on Cr-doped Bi 2Te 3 topological insulator thin films

DOE PAGES

Ni, Y.; Zhang, Z.; Nlebedim, I. C.; ...

2016-07-01

Anomalous Hall effect (AHE) was recently discovered in magnetic element-doped topological insulators (TIs), which promises low power consumption and high efficiency spintronics and electronics. This discovery broadens the family of Hall sensors. In this paper, AHE sensors based on Cr-doped Bi 2Te 3 topological insulator thin films are studied with two thicknesses (15 and 65 nm). It is found, in both cases, that ultrahigh Hall sensitivity can be obtained in Cr-doped Bi 2Te 3. Hall sensitivity reaches 1666 Ω/T in the sensor with the 15 nm TI thin film, which is higher than that of the conventional semiconductor HE sensor.more » The AHE of 65 nm sensors is even stronger, which causes the sensitivity increasing to 2620 Ω/T. Furthermore, after comparing Cr-doped Bi 2Te 3 with the previously studied Mn-doped Bi 2Te 3 TI Hall sensor, the sensitivity of the present AHE sensor shows about 60 times higher in 65 nm sensors. Furthermore, the implementation of AHE sensors based on a magnetic-doped TI thin film indicates that the TIs are good candidates for ultrasensitive AHE sensors.« less

Magnetism in Mn-nanowires and -clusters as δ-doped layers in group IV semiconductors (Si, Ge)

NASA Astrophysics Data System (ADS)

Simov, K. R.; Glans, P.-A.; Jenkins, C. A.; Liberati, M.; Reinke, P.

2018-01-01

Mn doping of group-IV semiconductors (Si/Ge) is achieved by embedding nanostructured Mn-layers in group-IV matrix. The Mn-nanostructures are monoatomic Mn-wires or Mn-clusters and capped with an amorphous Si or Ge layer. The precise fabrication of δ-doped Mn-layers is combined with element-specific detection of the magnetic signature with x-ray magnetic circular dichroism. The largest moment (2.5 μB/Mn) is measured for Mn-wires with ionic bonding character and a-Ge overlayer cap; a-Si capping reduces the moment due to variations of bonding in agreement with theoretical predictions. The moments in δ-doped layers dominated by clusters is quenched with an antiferromagnetic component from Mn-Mn bonding.

Itinerant magnetism in doped semiconducting β-FeSi2 and CrSi2

PubMed Central

Singh, David J.; Parker, David

2013-01-01

Novel or unusual magnetism is a subject of considerable interest, particularly in metals and degenerate semiconductors. In such materials the interplay of magnetism, transport and other Fermi liquid properties can lead to fascinating physical behavior. One example is in magnetic semiconductors, where spin polarized currents may be controlled and used. We report density functional calculations predicting magnetism in doped semiconducting β-FeSi2 and CrSi2 at relatively low doping levels particularly for n-type. In this case, there is a rapid cross-over to a half-metallic state as a function of doping level. The results are discussed in relation to the electronic structure and other properties of these compounds. PMID:24343332

Development of Room Temperature Excitonic Lasing From ZnO and MgZnO Thin Film Based Metal-Semiconductor-Metal Devices

NASA Astrophysics Data System (ADS)

Suja, Mohammad Zahir Uddin

Room temperature excitonic lasing is demonstrated and developed by utilizing metal-semiconductor-metal devices based on ZnO and MgZnO materials. At first, Cu-doped p-type ZnO films are grown on c-sapphire substrates by plasma-assisted molecular beam epitaxy. Photoluminescence (PL) experiments reveal a shallow acceptor state at 0.15 eV above the valence band edge. Hall effect results indicate that a growth condition window is found for the formation of p-type ZnO thin films and the best conductivity is achieved with a high hole concentration of 1.54x1018 cm-3, a low resistivity of 0.6 O cm and a moderate mobility of 6.65 cm2 V -1 s-1 at room temperature. Metal oxide semiconductor (MOS) capacitor devices have been fabricated on the Cu-doped ZnO films and the characteristics of capacitance-voltage measurements demonstrate that the Cu-doped ZnO thin films under proper growth conditions are p-type. Seebeck measurements on these Cu-doped ZnO samples lead to positive Seebeck coefficients and further confirm the p-type conductivity. Other measurements such as XRD, XPS, Raman and absorption are also performed to elucidate the structural and optical characteristics of the Cu-doped p-type ZnO films. The p-type conductivity is explained to originate from Cu substitution of Zn with a valency of +1 state. However, all p-type samples are converted to n-type over time, which is mostly due to the carrier compensation from extrinsic defects of ZnO. To overcome the stability issue of p-type ZnO film, alternate devices other than p-n junction has been developed. Electrically driven plasmon-exciton coupled random lasing is demonstrated by incorporating Ag nanoparticles on Cu-doped ZnO metal-semiconductor-metal (MSM) devices. Both photoluminescence and electroluminescence studies show that emission efficiencies have been enhanced significantly due to coupling between ZnO excitons and Ag surface plasmons. With the incorporation of Ag nanoparticles on ZnO MSM structures, internal quantum efficiency up to 6 times is demonstrated. Threshold current for lasing is decreased by as much as 30% while the output power is increased up to 350% at an injection current of 40 mA. A numerical simulation study reveals that hole carriers are generated in the ZnO MSM devices from impact ionization processes for subsequent plasmon-exciton coupled lasing. Our results suggest that plasmon-enhanced ZnO MSM random lasers can become a competitive candidate of efficient ultraviolet light sources. Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. In this thesis, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM) random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29 33 A/cm2 are achieved. Numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.

A room-temperature magnetic semiconductor from a ferromagnetic metallic glass.

PubMed

Liu, Wenjian; Zhang, Hongxia; Shi, Jin-An; Wang, Zhongchang; Song, Cheng; Wang, Xiangrong; Lu, Siyuan; Zhou, Xiangjun; Gu, Lin; Louzguine-Luzgin, Dmitri V; Chen, Mingwei; Yao, Kefu; Chen, Na

2016-12-08

Emerging for future spintronic/electronic applications, magnetic semiconductors have stimulated intense interest due to their promises for new functionalities and device concepts. So far, the so-called diluted magnetic semiconductors attract many attentions, yet it remains challenging to increase their Curie temperatures above room temperature, particularly those based on III-V semiconductors. In contrast to the concept of doping magnetic elements into conventional semiconductors to make diluted magnetic semiconductors, here we propose to oxidize originally ferromagnetic metals/alloys to form new species of magnetic semiconductors. We introduce oxygen into a ferromagnetic metallic glass to form a Co 28.6 Fe 12.4 Ta 4.3 B 8.7 O 46 magnetic semiconductor with a Curie temperature above 600 K. The demonstration of p-n heterojunctions and electric field control of the room-temperature ferromagnetism in this material reflects its p-type semiconducting character, with a mobility of 0.1 cm 2  V -1  s -1 . Our findings may pave a new way to realize high Curie temperature magnetic semiconductors with unusual multifunctionalities.

A room-temperature magnetic semiconductor from a ferromagnetic metallic glass

PubMed Central

Liu, Wenjian; Zhang, Hongxia; Shi, Jin-an; Wang, Zhongchang; Song, Cheng; Wang, Xiangrong; Lu, Siyuan; Zhou, Xiangjun; Gu, Lin; Louzguine-Luzgin, Dmitri V.; Chen, Mingwei; Yao, Kefu; Chen, Na

2016-01-01

Emerging for future spintronic/electronic applications, magnetic semiconductors have stimulated intense interest due to their promises for new functionalities and device concepts. So far, the so-called diluted magnetic semiconductors attract many attentions, yet it remains challenging to increase their Curie temperatures above room temperature, particularly those based on III–V semiconductors. In contrast to the concept of doping magnetic elements into conventional semiconductors to make diluted magnetic semiconductors, here we propose to oxidize originally ferromagnetic metals/alloys to form new species of magnetic semiconductors. We introduce oxygen into a ferromagnetic metallic glass to form a Co28.6Fe12.4Ta4.3B8.7O46 magnetic semiconductor with a Curie temperature above 600 K. The demonstration of p–n heterojunctions and electric field control of the room-temperature ferromagnetism in this material reflects its p-type semiconducting character, with a mobility of 0.1 cm2 V−1 s−1. Our findings may pave a new way to realize high Curie temperature magnetic semiconductors with unusual multifunctionalities. PMID:27929059

INAS hole-immobilized doping superlattice long-wave-infrared detector

NASA Technical Reports Server (NTRS)

Maserjian, Joseph (Inventor)

1992-01-01

An approach to long-wave-infrared (LWIR) technology is discussed. The approach is based on molecular beam epitaxy (MBE) growth of hole immobilized doping superlattices in narrow band gap 3-5 semiconductors, specifically, InAs and InSb. Such superlattices are incorporated into detector structures suitable for focal plane arrays. An LWIR detector that has high detectivity performance to wavelengths of about 16 microns at operating temperatures of 65K, where long-duration space refrigeration is plausible, is presented.

A position-dependent mass model for the Thomas–Fermi potential: Exact solvability and relation to δ-doped semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulze-Halberg, Axel, E-mail: xbataxel@gmail.com; García-Ravelo, Jesús; Pacheco-García, Christian

We consider the Schrödinger equation in the Thomas–Fermi field, a model that has been used for describing electron systems in δ-doped semiconductors. It is shown that the problem becomes exactly-solvable if a particular effective (position-dependent) mass distribution is incorporated. Orthogonal sets of normalizable bound state solutions are constructed in explicit form, and the associated energies are determined. We compare our results with the corresponding findings on the constant-mass problem discussed by Ioriatti (1990) [13]. -- Highlights: ► We introduce an exactly solvable, position-dependent mass model for the Thomas–Fermi potential. ► Orthogonal sets of solutions to our model are constructed inmore » closed form. ► Relation to delta-doped semiconductors is discussed. ► Explicit subband bottom energies are calculated and compared to results obtained in a previous study.« less

Use of separate ZnTe interface layers to form ohmic contacts to p-CdTe films

DOEpatents

Gessert, T.A.

1999-06-01

A method of is disclosed improving electrical contact to a thin film of a p-type tellurium-containing II-VI semiconductor comprising: depositing a first undoped layer of ZnTe on a thin film of p-type tellurium containing II-VI semiconductor with material properties selected to limit the formation of potential barriers at the interface between the p-CdTe and the undoped layer, to a thickness sufficient to control diffusion of the metallic-doped ZnTe into the p-type tellurium-containing II-VI semiconductor, but thin enough to minimize affects of series resistance; depositing a second heavy doped p-type ZnTe layer to the first layer using an appropriate dopant; and depositing an appropriate metal onto the outer-most surface of the doped ZnTe layer for connecting an external electrical conductor to an ohmic contact. 11 figs.

Use of separate ZnTe interface layers to form OHMIC contacts to p-CdTe films

DOEpatents

Gessert, Timothy A.

1999-01-01

A method of improving electrical contact to a thin film of a p-type tellurium-containing II-VI semiconductor comprising: depositing a first undoped layer of ZnTe on a thin film of p-type tellurium containing II-VI semiconductor with material properties selected to limit the formation of potential barriers at the interface between the p-CdTe and the undoped layer, to a thickness sufficient to control diffusion of the metallic-doped ZnTe into the p-type tellurim-containing II-VI semiconductor, but thin enough to minimize affects of series resistance; depositing a second heavy doped p-type ZnTe layer to the first layer using an appropriate dopant; and depositing an appropriate metal onto the outer-most surface of the doped ZnTe layer for connecting an external electrical conductor to an ohmic contact.

Temperature effects in contacts between a metal and a semiconductor nanowire near the degenerate doping

NASA Astrophysics Data System (ADS)

Sun, Zhuting; Burgess, Tim; Tan, H. H.; Jagadish, Chennupati; Kogan, Andrei

2018-04-01

We have investigated the nonlinear conductance in diffusion-doped Si:GaAs nanowires contacted by patterned metal films in a wide range of temperatures T. The wire resistance R W and the zero bias resistance R C, dominated by the contacts, exhibit very different responses to temperature changes. While R W shows almost no dependence on T, R C varies by several orders of magnitude as the devices are cooled from room temperature to T = 5 K. We develop a model that employs a sharp donor level very low in the GaAs conduction band and show that our observations are consistent with the model predictions. We then demonstrate that such measurements can be used to estimate carrier properties in nanostructured semiconductors and obtain an estimate for N D, the doping density in our samples. We also discuss the effects of surface states and dielectric confinement on carrier density in semiconductor nanowires.

Features of conductivity mechanisms in heavily doped compensated V{sub 1–x}Ti{sub x}FeSb Semiconductor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romaka, V. A., E-mail: vromaka@polynet.lviv.ua; Rogl, P.; Romaka, V. V.

2016-07-15

The crystal and electronic structure and also the energy and kinetic properties of n-VFeSb semiconductor heavily doped with the Ti acceptor impurity are investigated in the temperature and Ti concentration ranges of T = 4.2–400 K and N{sub A}{sup Ti} ≈ 9.5 × 10{sup 19}–3.6 × 10{sup 21} cm{sup –3} (x = 0.005–0.20), respectively. The complex mechanism of the generation of acceptor and donor structural defects is established. It is demonstrated that the presence of vacancies at Sb atomic sites in n-VFeSb gives rise to donor structural defects (“a priori doping”). Substitution of the Ti dopant for V in VFeSbmore » leads simultaneously to the generation of acceptortype structural defects, a decrease in the number of donor defects, and their removal in the concentration range of 0 ≤ x ≤ 0.03 via the occupation of vacancies by Sb atoms, and the generation of donor defects due to the occurrence of vacancies and an increase in their number. The result obtained underlies the technique for fabricating new n-VFeSb-based thermoelectric materials. The results are discussed in the context of the Shklovsky–Efros model for a heavily doped compensated semiconductor.« less

Enhanced adhesion of films to semiconductors or metals by high energy bombardment

NASA Technical Reports Server (NTRS)

Tombrello, Thomas A. (Inventor); Qiu, Yuanxun (Inventor); Mendenhall, Marcus H. (Inventor)

1985-01-01

Films (12) of a metal such as gold or other non-insulator materials are firmly bonded to other non-insulators such as semiconductor substrates (10), suitably silicon or gallium arsenide by irradiating the interface with high energy ions. The process results in improved adhesion without excessive doping and provides a low resistance contact to the semiconductor. Thick layers can be bonded by depositing or doping the interfacial surfaces with fissionable elements or alpha emitters. The process can be utilized to apply very small, low resistance electrodes (78) to light-emitting solid state laser diodes (60) to form a laser device 70.

Vanadium doped tin dioxide as a novel sulfur dioxide sensor.

PubMed

Das, S; Chakraborty, S; Parkash, O; Kumar, D; Bandyopadhyay, S; Samudrala, S K; Sen, A; Maiti, H S

2008-04-15

Considering the short-term exposure limit of SO2 to be 5 ppm, we first time report that semiconductor sensors based on vanadium doped SnO2 can be used for SO2 leak detection because of their good sensitivity towards SO2 at concentrations down to 5 ppm. Such sensors are quite selective in presence of other gases like carbon monoxide, methane and butane. The high sensitivity of vanadium doped tin dioxide towards SO2 may be understood by considering the oxidation of sulfur dioxide to sulfur trioxide on SnO2 surface through redox cycles of vanadium-sulfur-oxygen adsorbed species.

Activities of Combined TiO2 Semiconductor Nanocatalysts Under Solar Light on the Reduction of CO2.

PubMed

Liu, Hongfang; Dao, Anh Quang; Fu, Chaoyang

2016-04-01

The materials based on TiO2 semiconductors are a promising option for electro-photocatalytic systems working as solar energy low-carbon fuels exchanger. These materials' structures are modified by doping metals and metal oxides, by metal sulfides sensitization, or by graphene supported membrane, enhancing their catalytic activity. The basic phenomenon of CO2 reduction to CH4 on Pd modified TiO2 under UV irradiation could be enhanced by Pd, or RuO2 co-doped TiO2. Sensitization with metal sulfide QDs is effective by moving of photo-excited electron from QDs to TiO2 particles. Based on characteristics of the catalysts various combinations of catalysts are proposed in order to creat catalyst systems with good CO2 reduction efficiency. From this critical review of the CO2 reduction to organic compounds by converting solar light and CO2 to storable fuels it is clear that more studies are still attractive and needed.

(Cu 0.5Tl 0.5)Ba 2Ca n-1 Cu n- yGe yO 2 n+4- δ ( n = 3, 4 and y = 0.5, 0.75, 1.0); superconductors with GeO 2 planes

NASA Astrophysics Data System (ADS)

Khan, Nawazish A.; Irfan, M.

2008-12-01

We have successfully synthesized germanium doped (Cu 0.5Tl 0.5)Ba 2Ca n-1 Cu n- yGe yO 2 n+4- δ ( n = 3, 4 and y = 0, 0.5, 0.75, 1.0) superconductors and investigated the effect of Ge doping on the superconducting properties of these compounds. The solubility of Ge till y = 1 in the CuO 2 planes of (Cu 0.5Tl 0.5)Ba 2Ca 2Cu 3- yGe yO 10- δ, have been found to give superconductivity above 77 K. To our surprise an enhanced superconductivity is observed with the doping of semiconductor germanium in some samples. The enhanced superconductivity associated with mixed CuO 2/GeO 2 planes can be extremely useful for the understanding of mechanism of superconductivity; since we very well know the properties of germanium based semiconductors.

2D coherent charge transport in highly ordered conducting polymers doped by solid state diffusion

NASA Astrophysics Data System (ADS)

Kang, Keehoon; Watanabe, Shun; Broch, Katharina; Sepe, Alessandro; Brown, Adam; Nasrallah, Iyad; Nikolka, Mark; Fei, Zhuping; Heeney, Martin; Matsumoto, Daisuke; Marumoto, Kazuhiro; Tanaka, Hisaaki; Kuroda, Shin-Ichi; Sirringhaus, Henning

2016-08-01

Doping is one of the most important methods to control charge carrier concentration in semiconductors. Ideally, the introduction of dopants should not perturb the ordered microstructure of the semiconducting host. In some systems, such as modulation-doped inorganic semiconductors or molecular charge transfer crystals, this can be achieved by spatially separating the dopants from the charge transport pathways. However, in conducting polymers, dopants tend to be randomly distributed within the conjugated polymer, and as a result the transport properties are strongly affected by the resulting structural and electronic disorder. Here, we show that in the highly ordered lamellar microstructure of a regioregular thiophene-based conjugated polymer, a small-molecule p-type dopant can be incorporated by solid state diffusion into the layers of solubilizing side chains without disrupting the conjugated layers. In contrast to more disordered systems, this allows us to observe coherent, free-electron-like charge transport properties, including a nearly ideal Hall effect in a wide temperature range, a positive magnetoconductance due to weak localization and the Pauli paramagnetic spin susceptibility.

Breaking the GaN material limits with nanoscale vertical polarisation super junction structures: A simulation analysis

NASA Astrophysics Data System (ADS)

Unni, Vineet; Sankara Narayanan, E. M.

2017-04-01

This is the first report on the numerical analysis of the performance of nanoscale vertical superjunction structures based on impurity doping and an innovative approach that utilizes the polarisation properties inherent in III-V nitride semiconductors. Such nanoscale vertical polarisation super junction structures can be realized by employing a combination of epitaxial growth along the non-polar crystallographic axes of Wurtzite GaN and nanolithography-based processing techniques. Detailed numerical simulations clearly highlight the limitations of a doping based approach and the advantages of the proposed solution for breaking the unipolar one-dimensional material limits of GaN by orders of magnitude.

Synthesis and characterization of UV-treated Fe-doped bismuth lanthanum titanate-doped TiO2 layers in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Song, Myoung Geun; Bark, Chung Wung

2016-06-01

Dye-sensitized solar cells (DSSCs) based on titanium dioxide (TiO2) have been extensively studied because they constitute promising low-cost alternatives to their conventional semiconductor-based counterparts. However, much of the effort aimed at achieving high conversion efficiencies has focused on dye and liquid electrolytes. In this work, we report the photovoltaic characteristics of DSSCs fabricated by mixing TiO2 with Fe-doped bismuth lanthanum titanate (Fe-BLT). These nanosized Fe-BLT powders were prepared by using a high-energy ball-milling process. In addition, we used a UV radiation-ozone (UV-O3) treatment to change the surface wettability of TiO2 from hydrophobic to hydrophilic and thereby prevented the easy separation of the Fe-BLT-mixed TiO2 from the fluorine-doped tin-oxide (FTO) coating glass.

Influence of chemically p-type doped active organic semiconductor on the film thickness versus performance trend in cyanine/C60 bilayer solar cells

PubMed Central

Jenatsch, Sandra; Geiger, Thomas; Heier, Jakob; Kirsch, Christoph; Nüesch, Frank; Paracchino, Adriana; Rentsch, Daniel; Ruhstaller, Beat; C Véron, Anna; Hany, Roland

2015-01-01

Simple bilayer organic solar cells rely on very thin coated films that allow for effective light absorption and charge carrier transport away from the heterojunction at the same time. However, thin films are difficult to coat on rough substrates or over large areas, resulting in adverse shorting and low device fabrication yield. Chemical p-type doping of organic semiconductors can reduce Ohmic losses in thicker transport layers through increased conductivity. By using a Co(III) complex as chemical dopant, we studied doped cyanine dye/C60 bilayer solar cell performance for increasing dye film thickness. For films thicker than 50 nm, doping increased the power conversion efficiency by more than 30%. At the same time, the yield of working cells increased to 80%. We addressed the fate of the doped cyanine dye, and found no influence of doping on solar cell long term stability. PMID:27877804

Determination of n-Type Doping Level in Single GaAs Nanowires by Cathodoluminescence.

PubMed

Chen, Hung-Ling; Himwas, Chalermchai; Scaccabarozzi, Andrea; Rale, Pierre; Oehler, Fabrice; Lemaître, Aristide; Lombez, Laurent; Guillemoles, Jean-François; Tchernycheva, Maria; Harmand, Jean-Christophe; Cattoni, Andrea; Collin, Stéphane

2017-11-08

We present an effective method of determining the doping level in n-type III-V semiconductors at the nanoscale. Low-temperature and room-temperature cathodoluminescence (CL) measurements are carried out on single Si-doped GaAs nanowires. The spectral shift to higher energy (Burstein-Moss shift) and the broadening of luminescence spectra are signatures of increased electron densities. They are compared to the CL spectra of calibrated Si-doped GaAs layers, whose doping levels are determined by Hall measurements. We apply the generalized Planck's law to fit the whole spectra, taking into account the electron occupation in the conduction band, the bandgap narrowing, and band tails. The electron Fermi levels are used to determine the free electron concentrations, and we infer nanowire doping of 6 × 10 17 to 1 × 10 18  cm -3 . These results show that cathodoluminescence provides a robust way to probe carrier concentrations in semiconductors with the possibility of mapping spatial inhomogeneities at the nanoscale.

Transition-metal-doped group-IV monochalcogenides: a combination of two-dimensional triferroics and diluted magnetic semiconductors

NASA Astrophysics Data System (ADS)

Yang, Liu; Wu, Menghao; Yao, Kailun

2018-05-01

We report the first-principles evidence of a series of two-dimensional triferroics (ferromagnetic + ferroelectric + ferroelastic), which can be obtained by doping transition-metal ions in group-IV monochalcogenide (SnS, SnSe, GeS, GeSe) monolayers, noting that a ferromagnetic Fe-doped SnS2 monolayer has recently been realized (Li B et al 2017 Nat. Commun. 8 1958). The ferroelectricity, ferroelasticity and ferromagnetism can be coupled and the magnetization direction may be switched upon ferroelectric/ferroelastic switching, rendering electrical writing + magnetic reading possible. They can be also two-dimensional half-metals or diluted magnetic semiconductors, where p/n channels or even multiferroic tunneling junctions can be designed by variation in doping and incorporated into a monolayer wafer.

Transition-metal-doped group-IV monochalcogenides: a combination of two-dimensional triferroics and diluted magnetic semiconductors.

PubMed

Yang, Liu; Wu, Menghao; Yao, Kailun

2018-05-25

We report the first-principles evidence of a series of two-dimensional triferroics (ferromagnetic + ferroelectric + ferroelastic), which can be obtained by doping transition-metal ions in group-IV monochalcogenide (SnS, SnSe, GeS, GeSe) monolayers, noting that a ferromagnetic Fe-doped SnS 2 monolayer has recently been realized (Li B et al 2017 Nat. Commun. 8 1958). The ferroelectricity, ferroelasticity and ferromagnetism can be coupled and the magnetization direction may be switched upon ferroelectric/ferroelastic switching, rendering electrical writing + magnetic reading possible. They can be also two-dimensional half-metals or diluted magnetic semiconductors, where p/n channels or even multiferroic tunneling junctions can be designed by variation in doping and incorporated into a monolayer wafer.

Effects of Excess Carriers on Charged Defect Concentrations in Wide Bandgap Semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alberi, Kirstin M; Scarpulla, Michael A.

Unintentional doping and doping limits in semiconductors are typically caused by compensating defects with low formation energies. Since the formation enthalpy of a charged defect depends linearly on the Fermi level, doping limits can be especially pronounced in wide bandgap semiconductors where the Fermi level can vary substantially. Introduction of non-equilibrium carrier concentrations during growth or processing alters the chemical potentials of band carriers and allows populations of charged defects to be modified in ways impossible at thermal equilibrium. We demonstrate that in the presence of excess carriers, the rates of carrier capture and emission involving a defect charge transitionmore » level determine the admixture of electron and hole quasi-Fermi levels involved in the formation enthalpy of non-zero charge defect states. To understand the range of possible responses, we investigate the behavior of a single donor-like defect as functions of extrinsic doping and charge transition level energy. We find that that excess carriers will increase the formation enthalpy of compensating defects for most values of the charge transition level in the bandgap. Thus, it may be possible to use non-equilibrium carrier concentrations to overcome limitations on doping imposed by native defects. Cases also exist in which the concentration of defects with the same charge polarity as the majority dopant is either left unchanged or actually increases. This surprising effect arises when emission rates are suppressed relative to the capture rates and is most pronounced in wide bandgap semiconductors. We provide guidelines for carrying out experimental tests of this model.« less

Effects of excess carriers on charged defect concentrations in wide bandgap semiconductors

NASA Astrophysics Data System (ADS)

Alberi, Kirstin; Scarpulla, Michael A.

2018-05-01

Unintentional doping and doping limits in semiconductors are typically caused by compensating defects with low formation energies. Since the formation enthalpy of a charged defect depends linearly on the Fermi level, doping limits can be especially pronounced in wide bandgap semiconductors where the Fermi level can vary substantially. Introduction of non-equilibrium carrier concentrations during growth or processing alters the chemical potentials of band carriers and allows populations of charged defects to be modified in ways impossible at thermal equilibrium. We demonstrate that in the presence of excess carriers, the rates of carrier capture and emission involving a defect charge transition level determine the admixture of electron and hole quasi-Fermi levels involved in the formation enthalpy of non-zero charge defect states. To understand the range of possible responses, we investigate the behavior of a single donor-like defect as functions of extrinsic doping and charge transition level energy. We find that that excess carriers will increase the formation enthalpy of compensating defects for most values of the charge transition level in the bandgap. Thus, it may be possible to use non-equilibrium carrier concentrations to overcome limitations on doping imposed by native defects. Cases also exist in which the concentration of defects with the same charge polarity as the majority dopant is either left unchanged or actually increases. This surprising effect arises when emission rates are suppressed relative to the capture rates and is most pronounced in wide bandgap semiconductors. We provide guidelines for carrying out experimental tests of this model.

Probing resistivity and doping concentration of semiconductors at the nanoscale using scanning microwave microscopy

NASA Astrophysics Data System (ADS)

Brinciotti, Enrico; Gramse, Georg; Hommel, Soeren; Schweinboeck, Thomas; Altes, Andreas; Fenner, Matthias A.; Smoliner, Juergen; Kasper, Manuel; Badino, Giorgio; Tuca, Silviu-Sorin; Kienberger, Ferry

2015-08-01

We present a new method to extract resistivity and doping concentration of semiconductor materials from Scanning Microwave Microscopy (SMM) S11 reflection measurements. Using a three error parameters de-embedding workflow, the S11 raw data are converted into calibrated capacitance and resistance images where no calibration sample is required. The SMM capacitance and resistance values were measured at 18 GHz and ranged from 0 to 100 aF and from 0 to 1 MΩ, respectively. A tip-sample analytical model that includes tip radius, microwave penetration skin depth, and semiconductor depletion layer width has been applied to extract resistivity and doping concentration from the calibrated SMM resistance. The method has been tested on two doped silicon samples and in both cases the resistivity and doping concentration are in quantitative agreement with the data-sheet values over a range of 10-3 Ω cm to 101 Ω cm, and 1014 atoms per cm3 to 1020 atoms per cm3, respectively. The measured dopant density values, with related uncertainties, are [1.1 +/- 0.6] × 1018 atoms per cm3, [2.2 +/- 0.4] × 1017 atoms per cm3, [4.5 +/- 0.2] × 1016 atoms per cm3, [4.5 +/- 1.3] × 1015 atoms per cm3, [4.5 +/- 1.7] × 1014 atoms per cm3. The method does not require sample treatment like cleavage and cross-sectioning, and high contact imaging forces are not necessary, thus it is easily applicable to various semiconductor and materials science investigations.

Phosphorus Doping Effect in a Zinc Oxide Channel Layer to Improve the Performance of Oxide Thin-Film Transistors

NASA Astrophysics Data System (ADS)

Han, Dong-Suk; Moon, Yeon-Keon; Lee, Sih; Kim, Kyung-Taek; Moon, Dae-Yong; Lee, Sang-Ho; Kim, Woong-Sun; Park, Jong-Wan

2012-09-01

In this study, we fabricated phosphorus-doped zinc oxide-based thin-film transistors (TFTs) using direct current (DC) magnetron sputtering at a relatively low temperature of 100°C. To improve the TFT device performance, including field-effect mobility and bias stress stability, phosphorus dopants were employed to suppress the generation of intrinsic defects in the ZnO-based semiconductor. The positive and negative bias stress stabilities were dramatically improved by introducing the phosphorus dopants, which could prevent turn-on voltage ( V ON) shift in the TFTs caused by charge trapping within the active channel layer. The study showed that phosphorus doping in ZnO was an effective method to control the electrical properties of the active channel layers and improve the bias stress stability of oxide-based TFTs.

Fabrication of Smart Chemical Sensors Based on Transition-Doped-Semiconductor Nanostructure Materials with µ-Chips

PubMed Central

Rahman, Mohammed M.; Khan, Sher Bahadar; Asiri, Abdullah M.

2014-01-01

Transition metal doped semiconductor nanostructure materials (Sb2O3 doped ZnO microflowers, MFs) are deposited onto tiny µ-chip (surface area, ∼0.02217 cm2) to fabricate a smart chemical sensor for toxic ethanol in phosphate buffer solution (0.1 M PBS). The fabricated chemi-sensor is also exhibited higher sensitivity, large-dynamic concentration ranges, long-term stability, and improved electrochemical performances towards ethanol. The calibration plot is linear (r2 = 0.9989) over the large ethanol concentration ranges (0.17 mM to 0.85 M). The sensitivity and detection limit is ∼5.845 µAcm−2mM−1 and ∼0.11±0.02 mM (signal-to-noise ratio, at a SNR of 3) respectively. Here, doped MFs are prepared by a wet-chemical process using reducing agents in alkaline medium, which characterized by UV/vis., FT-IR, Raman, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and field-emission scanning electron microscopy (FE-SEM) etc. The fabricated ethanol chemical sensor using Sb2O3-ZnO MFs is simple, reliable, low-sample volume (<70.0 µL), easy of integration, high sensitivity, and excellent stability for the fabrication of efficient I–V sensors on μ-chips. PMID:24454785

Fabrication of smart chemical sensors based on transition-doped-semiconductor nanostructure materials with µ-chips.

PubMed

Rahman, Mohammed M; Khan, Sher Bahadar; Asiri, Abdullah M

2014-01-01

Transition metal doped semiconductor nanostructure materials (Sb2O3 doped ZnO microflowers, MFs) are deposited onto tiny µ-chip (surface area, ∼0.02217 cm(2)) to fabricate a smart chemical sensor for toxic ethanol in phosphate buffer solution (0.1 M PBS). The fabricated chemi-sensor is also exhibited higher sensitivity, large-dynamic concentration ranges, long-term stability, and improved electrochemical performances towards ethanol. The calibration plot is linear (r(2) = 0.9989) over the large ethanol concentration ranges (0.17 mM to 0.85 M). The sensitivity and detection limit is ∼5.845 µAcm(-2)mM(-1) and ∼0.11±0.02 mM (signal-to-noise ratio, at a SNR of 3) respectively. Here, doped MFs are prepared by a wet-chemical process using reducing agents in alkaline medium, which characterized by UV/vis., FT-IR, Raman, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and field-emission scanning electron microscopy (FE-SEM) etc. The fabricated ethanol chemical sensor using Sb2O3-ZnO MFs is simple, reliable, low-sample volume (<70.0 µL), easy of integration, high sensitivity, and excellent stability for the fabrication of efficient I-V sensors on μ-chips.

Shallow versus deep nature of Mg acceptors in nitride semiconductors

NASA Astrophysics Data System (ADS)

Lyons, John; Janotti, Anderson; van de Walle, Chris G.

2012-02-01

Although Mg doping is the only known method for achieving p-type conductivity in nitride semiconductors, Mg is not a perfect acceptor. Hydrogen is known to passivate the Mg acceptor, necessitating a post-growth anneal for acceptor activation. Furthermore, the acceptor ionization energy of Mg is relatively large (200 meV) in GaN, thus only a few percent of Mg acceptors are ionized at room temperature. Surprisingly, despite the importance of this impurity, open questions remain regarding the nature of the acceptor. Optical and magnetic resonance measurements on Mg-doped GaN indicate intriguing and complex behavior that depends on the growth, doping level, and thermal treatment of the samples. Motivated by these studies, we have revisited this topic by performing first-principles calculations based on a hybrid functional. We investigate the electrical and optical properties of the isolated Mg acceptor and its complexes with hydrogen in GaN, InN, and AlN. With the help of these advanced techniques we explain the deep or shallow nature of the Mg acceptor and its relation to optical signals often seen in Mg-doped GaN. We also explore the properties of the Mg acceptor in InN and AlN, allowing predictions of the behavior of the Mg dopant in ternary nitride alloys.

Method for measuring the drift mobility in doped semiconductors

DOEpatents

Crandall, Richard S.

1982-01-01

A method for measuring the drift mobility of majority carriers in semiconductors consists of measuring the current transient in a Schottky-barrier device following the termination of a forward bias pulse. An example is given using an amorphous silicon hydrogenated material doped with 0.2% phosphorous. The method is particularly useful with material in which the dielectric relaxation time is shorter than the carrier transit time. It is particularly useful in material useful in solar cells.

New diluted ferromagnetic semiconductor with Curie temperature up to 180 K and isostructural to the '122' iron-based superconductors.

PubMed

Zhao, K; Deng, Z; Wang, X C; Han, W; Zhu, J L; Li, X; Liu, Q Q; Yu, R C; Goko, T; Frandsen, B; Liu, Lian; Ning, Fanlong; Uemura, Y J; Dabkowska, H; Luke, G M; Luetkens, H; Morenzoni, E; Dunsiger, S R; Senyshyn, A; Böni, P; Jin, C Q

2013-01-01

Diluted magnetic semiconductors have received much attention due to their potential applications for spintronics devices. A prototypical system (Ga,Mn)As has been widely studied since the 1990s. The simultaneous spin and charge doping via hetero-valent (Ga(3+),Mn(2+)) substitution, however, resulted in severely limited solubility without availability of bulk specimens. Here we report the synthesis of a new diluted magnetic semiconductor (Ba(1-x)K(x))(Zn(1-y)Mn(y))(2)As(2), which is isostructural to the 122 iron-based superconductors with the tetragonal ThCr(2)Si(2) (122) structure. Holes are doped via (Ba(2+), K(1+)) replacements, while spins via isovalent (Zn(2+),Mn(2+)) substitutions. Bulk samples with x=0.1-0.3 and y=0.05-0.15 exhibit ferromagnetic order with T(C) up to 180 K, which is comparable to the highest T(C) for (Ga,Mn)As and significantly enhanced from T(C) up to 50 K of the '111'-based Li(Zn,Mn)As. Moreover, ferromagnetic (Ba,K)(Zn,Mn)(2)As(2) shares the same 122 crystal structure with semiconducting BaZn(2)As(2), antiferromagnetic BaMn(2)As(2) and superconducting (Ba,K)Fe(2)As(2), which makes them promising for the development of multilayer functional devices.

P-doped strontium titanate grown using two target pulsed laser deposition for thin film solar cells

NASA Astrophysics Data System (ADS)

Man, Hamdi

Thin-film solar cells made of Mg-doped SrTiO3 p-type absorbers are promising candidates for clean energy generation. This material shows p-type conductivity and also demonstrates reasonable absorption of light. In addition, p-type SrTiO3 can be deposited as thin films so that the cost can be lower than the competing methods. In this work, Mg-doped SrTiO3 (STO) thin-films were synthesized and analyzed in order to observe their potential to be employed as the base semiconductor in photovoltaic applications. Mg-doped STO thin-films were grown by using pulsed laser deposition (PLD) using a frequency quadrupled Yttrium Aluminum Garnet (YAG) laser and with a substrate that was heated by back surface absorption of infrared (IR) laser light. The samples were characterized using X-ray photoelectron spectroscopy (XPS) and it was observed that Mg atoms were doped successfully in the stoichiometry. Reflection high energy electron diffraction (RHEED) spectroscopy proved that the thin films were polycrystalline. Kelvin Probe work function measurements indicated that the work function of the films were 4.167 eV after annealing. UV/Vis Reflection spectroscopy showed that Mg-doped STO thin-films do not reflect significantly except in the ultraviolet region of the spectrum where the reflection percentage increased up to 80%. Self-doped STO thin-films, Indium Tin Oxide (ITO) thin films and stainless steel foil (SSF) were studied in order to observe their characteristics before employing them in Mg-doped STO based solar cells. Self-doped STO thin films were grown using PLD and the results showed that they are capable of serving as the n-type semiconductor in solar cell applications with oxygen vacancies in their structure and low reflectivity. Indium Tin Oxide thin-films grown by PLD system showed low 25-50 ?/square sheet resistance and very low reflection features. Finally, commercially available stainless steel foil substrates were excellent substrates for the inexpensive growth of these novel solar cells.

Understanding and Control of Bipolar Self-Doping in Copper Nitride

PubMed Central

Fioretti, Angela N.; Schwartz, Craig P.; Vinson, John; Nordlund, Dennis; Prendergast, David; Tamboli, Adele C.; Caskey, Christopher M.; Tuomisto, Filip; Linez, Florence; Christensen, Steven T.; Toberer, Eric S.; Lany, Stephan; Zakutayev, Andriy

2016-01-01

Semiconductor materials that can be doped both n-type and p-type are desirable for diode-based applications and transistor technology. Copper nitride (Cu3N) is a metastable semiconductor with a solar-relevant bandgap that has been reported to exhibit bipolar doping behavior. However, deeper understanding and better control of the mechanism behind this behavior in Cu3N is currently lacking in the literature. In this work, we use combinatorial growth with a temperature gradient to demonstrate both conduction types of phase-pure, sputter-deposited Cu3N thin films. Room temperature Hall effect and Seebeck effect measurements show n-type Cu3N with an electron density of 1017 cm−3 for low growth temperature (≈ 35 °C) and p-type with a hole density between 1015 cm−3 and 1016 cm−3 for elevated growth temperatures (50 °C to 120 °C). Mobility for both types of Cu3N was ≈ 0.1 cm2/Vs to 1 cm2/V. Additionally, temperature-dependent Hall effect measurements indicate that ionized defects are an important scattering mechanism in p-type films. By combining X-ray absorption spectroscopy and first-principles defect theory, we determined that VCu defects form preferentially in p-type Cu3N while Cui defects form preferentially in n-type Cu3N; suggesting that Cu3N is a compensated semiconductor with conductivity type resulting from a balance between donor and acceptor defects. Based on these theoretical and experimental results, we propose a kinetic defect formation mechanism for bipolar doping in Cu3N, that is also supported by positron annihilation experiments. Overall, the results of this work highlight the importance of kinetic processes in the defect physics of metastable materials, and provide a framework that can be applied when considering the properties of such materials in general. PMID:27746508

Understanding and Control of Bipolar Self-Doping in Copper Nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fioretti, Angela N.; Schwartz, Craig P.; Vinson, John

2016-05-14

Semiconductor materials that can be doped both n-type and p-type are desirable for diode-based applications and transistor technology. Copper nitride (Cu3N) is a metastable semiconductor with a solar-relevant bandgap that has been reported to exhibit bipolar doping behavior. However, deeper understanding and better control of the mechanism behind this behavior in Cu3N is currently lacking in the literature. In this work, we use combinatorial growth with a temperature gradient to demonstrate both conduction types of phase-pure, sputter-deposited Cu3N thin films. Room temperature Hall effect and Seebeck effect measurements show n-type Cu3N with 1017 electrons/cm3 for low growth temperature (approximately 35more » degrees C) and p-type with 1015 holes/cm3-1016 holes/cm3 for elevated growth temperatures (50 degrees C-120 degrees C). Mobility for both types of Cu3N was approximately 0.1 cm2/Vs-1 cm2/Vs. Additionally, temperature-dependent Hall effect measurements indicate that ionized defects are an important scattering mechanism in p-type films. By combining X-ray absorption spectroscopy and first-principles defect theory, we determined that VCu defects form preferentially in p-type Cu3N, while Cui defects form preferentially in n-type Cu3N, suggesting that Cu3N is a compensated semiconductor with conductivity type resulting from a balance between donor and acceptor defects. Based on these theoretical and experimental results, we propose a kinetic defectformation mechanism for bipolar doping in Cu3N that is also supported by positron annihilation experiments. Overall, the results of this work highlight the importance of kinetic processes in the defect physics of metastable materials and provide a framework that can be applied when considering the properties of such materials in general.« less

Contribution of nanointerfaces to colossal permittivity of doped Ba(Ti,Sn)O3 ceramics

NASA Astrophysics Data System (ADS)

V'yunov, Oleg; Reshytko, Borys; Belous, Anatolii; Kovalenko, Leonid

2018-03-01

The microstructure, crystal chemical parameters and electrical-physical properties of samples of barium titanate-based dielectric and semiconductor ceramics were investigated in a wide frequency range. The contributions of different nanointerfaces to the permittivity of samples under investigation have been determined.

A Quasi-Classical Model of the Hubbard Gap in Lightly Compensated Semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poklonski, N. A.; Vyrko, S. A.; Kovalev, A. I.

2016-03-15

A quasi-classical method for calculating the narrowing of the Hubbard gap between the A{sup 0} and A{sup +} acceptor bands in a hole semiconductor or the D{sup 0} and D{sup –} donor bands in an electron semiconductor is suggested. This narrowing gives rise to the phenomenon of a semiconductor transition from the insulator to metal state with an increase in doping level. The major (doping) impurity can be in one of three charge states (–1, 0, or +1), while the compensating impurity can be in states (+1) or (–1). The impurity distribution over the crystal is assumed to be randommore » and the width of Hubbard bands (levels), to be much smaller than the gap between them. It is shown that narrowing of the Hubbard gap is due to the formation of electrically neutral acceptor (donor) states of the quasicontinuous band of allowed energies for holes (electrons) from excited states. This quasicontinuous band merges with the top of the valence band (v band) for acceptors or with the bottom of the conduction band (c band) for donors. In other words, the top of the v band for a p-type semiconductor or the bottom of the c band for an n-type semiconductor is shifted into the band gap. The value of this shift is determined by the maximum radius of the Bohr orbit of the excited state of an electrically neutral major impurity atom, which is no larger than half the average distance between nearest impurity atoms. As a result of the increasing dopant concentration, the both Hubbard energy levels become shallower and the gap between them narrows. Analytical formulas are derived to describe the thermally activated hopping transition of holes (electrons) between Hubbard bands. The calculated gap narrowing with increasing doping level, which manifests itself in a reduction in the activation energy ε{sub 2} is consistent with available experimental data for lightly compensated p-Si crystals doped with boron and n-Ge crystals doped with antimony.« less

Remarkable Enhancement of the Hole Mobility in Several Organic Small‐Molecules, Polymers, and Small‐Molecule:Polymer Blend Transistors by Simple Admixing of the Lewis Acid p‐Dopant B(C6F5)3

PubMed Central

Panidi, Julianna; Paterson, Alexandra F.; Khim, Dongyoon; Fei, Zhuping; Han, Yang; Tsetseris, Leonidas; Vourlias, George; Patsalas, Panos A.; Heeney, Martin

2017-01-01

Abstract Improving the charge carrier mobility of solution‐processable organic semiconductors is critical for the development of advanced organic thin‐film transistors and their application in the emerging sector of printed electronics. Here, a simple method is reported for enhancing the hole mobility in a wide range of organic semiconductors, including small‐molecules, polymers, and small‐molecule:polymer blends, with the latter systems exhibiting the highest mobility. The method is simple and relies on admixing of the molecular Lewis acid B(C6F5)3 in the semiconductor formulation prior to solution deposition. Two prototypical semiconductors where B(C6F5)3 is shown to have a remarkable impact are the blends of 2,8‐difluoro‐5,11‐bis(triethylsilylethynyl)anthradithiophene:poly(triarylamine) (diF‐TESADT:PTAA) and 2,7‐dioctyl[1]‐benzothieno[3,2‐b][1]benzothiophene:poly(indacenodithiophene‐co‐benzothiadiazole) (C8‐BTBT:C16‐IDTBT), for which hole mobilities of 8 and 11 cm2 V−1 s−1, respectively, are obtained. Doping of the 6,13‐bis(triisopropylsilylethynyl)pentacene:PTAA blend with B(C6F5)3 is also shown to increase the maximum hole mobility to 3.7 cm2 V−1 s−1. Analysis of the single and multicomponent materials reveals that B(C6F5)3 plays a dual role, first acting as an efficient p‐dopant, and secondly as a microstructure modifier. Semiconductors that undergo simultaneous p‐doping and dopant‐induced long‐range crystallization are found to consistently outperform transistors based on the pristine materials. Our work underscores Lewis acid doping as a generic strategy towards high performance printed organic microelectronics. PMID:29375962

A computational study on tuning the field emission and electronic properties of BN nanocones by impurity atom doping

NASA Astrophysics Data System (ADS)

Ahmadi, S.; Delir Kheirollahi Nezhad, P.; Hosseinian, A.; Vessally, E.

2018-06-01

We have inspected the effect of substituting a boron or nitrogen atom of a BN nanocone (BNNC) by two impurity atoms with lower and higher atomic numbers based on the density functional theory calculations. Our results explain the experimental observations in a molecular level. Orbital and partial density of states analyses show that the doping processes increase the electrical conductivity by creating new states within the gap of BNNC as follows: BeB > ON > CB > CN. The electron emission current from the surface of BNNC is improved after the CB and BeB dopings, and it is decreased by CN and ON dopings. The BeB and CN dopings make the BNNC a p-type semiconductor and the CB and ON dopings make it an n-type one in good agreement with the experimental results. The ON and BeB doping processes are suggested for the field emission current, and electrical conductivity enhancement, respectively.

Semiconductor Heterojunctions for Enhanced Visible Light Photocatalytic H 2 Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adhikari, Shiba P.; Hood, Zachary D.; Lachgar, Abdou

Semiconductor-based heterojunctions have been shown to be effective photocatalytic materials to overcome the drawbacks of low photocatalytic efficiency that results from a high rate of electron-hole recombination and narrow photo-response range. In this study, we report on the study of heterojunctions made from visible light active, graphitic carbon nitride, g-C 3N 4), and UV light active, strontium pyroniobate, Sr 2Nb 2O 7. Heterojunctions made from a combination of g-C 3N 4 and nitrogen-doped Sr 2Nb 2O 7 obtained at different temperatures were also studied to determine the effect of N doping. The photocatalytic performance was evaluated by using photocatalytic hydrogenmore » evolution reaction (HER)from water g under visible light irradiation. It was found that the photocatalytic activities of as prepared heterojunctions are significantly higher than that of individual components under similar conditions. Heterojunction formed from g-C 3N 4 and N-doped Sr 2Nb 2O 7 at 700 °C (CN/SNON-700) showed better performance than heterojunction made from g-C 3N 4 and Sr 2Nb 2O 7 (CN/SNO). Finally, a plausible mechanism for the heterojunction enhanced photocatalytic activity is proposed based on, relative band positions, and photoluminescence data.« less

Semiconductor Heterojunctions for Enhanced Visible Light Photocatalytic H 2 Production

DOE PAGES

Adhikari, Shiba P.; Hood, Zachary D.; Lachgar, Abdou

2018-04-17

Semiconductor-based heterojunctions have been shown to be effective photocatalytic materials to overcome the drawbacks of low photocatalytic efficiency that results from a high rate of electron-hole recombination and narrow photo-response range. In this study, we report on the study of heterojunctions made from visible light active, graphitic carbon nitride, g-C 3N 4), and UV light active, strontium pyroniobate, Sr 2Nb 2O 7. Heterojunctions made from a combination of g-C 3N 4 and nitrogen-doped Sr 2Nb 2O 7 obtained at different temperatures were also studied to determine the effect of N doping. The photocatalytic performance was evaluated by using photocatalytic hydrogenmore » evolution reaction (HER)from water g under visible light irradiation. It was found that the photocatalytic activities of as prepared heterojunctions are significantly higher than that of individual components under similar conditions. Heterojunction formed from g-C 3N 4 and N-doped Sr 2Nb 2O 7 at 700 °C (CN/SNON-700) showed better performance than heterojunction made from g-C 3N 4 and Sr 2Nb 2O 7 (CN/SNO). Finally, a plausible mechanism for the heterojunction enhanced photocatalytic activity is proposed based on, relative band positions, and photoluminescence data.« less

X-ray Characterization of Oxide-based Magnetic Semiconductors

NASA Astrophysics Data System (ADS)

Idzerda, Yves

2008-05-01

Although the evidence for magnetic semiconductors (not simply semiconductors which are ferromagnetic) is compelling, there is much uncertainty in the mechanism for the polarization of the carriers, suggesting that it must be quite novel. Recent experimental evidence suggests that this mechanism is similar to the polaron percolation theory proposed by Kaminski and Das Sarma,ootnotetextKaminski and S. Das Sarma, Physical Review Letters 88, 247202 (2002). which was recently applied specifically to doped oxides by Coey et al.ootnotetextJ. M. D. Coey, M. Venkatesan, and C. B. Fitzgerald, Nature Materials 4, 173 (2005). where the ferromagnetism is driven by the percolation of polarons generated by defects or dopants. We have used X-ray absorption spectroscopy at the L-edges and K-edges for low concentrations transition metal (TM) doped magnetic oxides (including TiO2, La1-xSrxO3, HfO2, and In2O3). We have found that in most cases, the transition metal assumes a valence consistent with being at a substitutional, and not interstitial site. We have also measured the X-ray Magnetic Circular Dichroism spectra. Although these materials show strong bulk magnetization, we are unable to detect a robust dichroism feature associated with magnetic elements in the host semiconductor. In the cases where a dichroism signal was observed, it was very weak and could be ascribed to a distinct ferromagnetic phase (TM metal cluster, TM oxide particulate, etc.) separate from the host material. This fascinating absence of a dichroic signal and its significant substantiation of important features of the polaron percolation model may help to finally resolve the issue of ferromagnetism in magnetically doped oxides.

P-type Al-doped Cr-deficient CrN thin films for thermoelectrics

NASA Astrophysics Data System (ADS)

le Febvrier, Arnaud; Van Nong, Ngo; Abadias, Gregory; Eklund, Per

2018-05-01

Thermoelectric properties of chromium nitride (CrN)-based films grown on c-plane sapphire by dc reactive magnetron sputtering were investigated. In this work, aluminum doping was introduced in CrN (degenerate n-type semiconductor) by co-deposition. Under the present deposition conditions, over-stoichiometry in nitrogen (CrN1+δ) rock-salt structure is obtained. A p-type conduction is observed with nitrogen-rich CrN combined with aluminum doping. The Cr0.96Al0.04N1.17 film exhibited a high Seebeck coefficient and a sufficient power factor at 300 °C. These results are a starting point for designing p-type/n-type thermoelectric materials based on chromium nitride films, which are cheap and routinely grown on the industrial scale.

Selective epitaxy using the gild process

DOEpatents

Weiner, Kurt H.

1992-01-01

The present invention comprises a method of selective epitaxy on a semiconductor substrate. The present invention provides a method of selectively forming high quality, thin GeSi layers in a silicon circuit, and a method for fabricating smaller semiconductor chips with a greater yield (more error free chips) at a lower cost. The method comprises forming an upper layer over a substrate, and depositing a reflectivity mask which is then removed over selected sections. Using a laser to melt the unmasked sections of the upper layer, the semiconductor material in the upper layer is heated and diffused into the substrate semiconductor material. By varying the amount of laser radiation, the epitaxial layer is formed to a controlled depth which may be very thin. When cooled, a single crystal epitaxial layer is formed over the patterned substrate. The present invention provides the ability to selectively grow layers of mixed semiconductors over patterned substrates such as a layer of Ge.sub.x Si.sub.1-x grown over silicon. Such a process may be used to manufacture small transistors that have a narrow base, heavy doping, and high gain. The narrowness allows a faster transistor, and the heavy doping reduces the resistance of the narrow layer. The process does not require high temperature annealing; therefore materials such as aluminum can be used. Furthermore, the process may be used to fabricate diodes that have a high reverse breakdown voltage and a low reverse leakage current.

Methods of measurement for semiconductor materials, process control, and devices

NASA Technical Reports Server (NTRS)

Bullis, W. M. (Editor)

1972-01-01

Activities directed toward the development of methods of measurement for semiconductor materials, process control, and devices are described. Accomplishments include the determination of the reasons for differences in measurements of transistor delay time, identification of an energy level model for gold-doped silicon, and the finding of evidence that it does not appear to be necessary for an ultrasonic bonding tool to grip the wire and move it across the substrate metallization to make the bond. Work is continuing on measurement of resistivity of semiconductor crystals; study of gold-doped silicon; development of the infrared response technique; evaluation of wire bonds and die attachment; measurement of thermal properties of semiconductor devices, delay time, and related carrier transport properties in junction devices, and noise properties of microwave diodes; and characterization of silicon nuclear radiation detectors.

Electrical transport engineering of semiconductor superlattice structures

NASA Astrophysics Data System (ADS)

Shokri, Aliasghar

2014-04-01

We investigate the influence of doping concentration on band structures of electrons and electrical transmission in a typical aperiodic semiconductor superlattice consisting of quantum well and barrier layers, theoretically. For this purpose, we assume that each unit cell of the superlattice contains alternately two types of material GaAs (as a well) and GaAlAs (as a barrier) with six sublayers of two materials. Our calculations are based on the generalized Kronig-Penny (KP) model and the transfer matrix method within the framework of the parabolic conductance band effective mass approximation in the coherent regime. This model reduces the numerical calculation time and enables us to use the transfer matrix method to investigate transport in the superlattices. We show that by varying the doping concentration and geometrical parameters, one can easily block the transmission of the electrons. The numerical results may be useful in designing of nanoenergy filter devices.

Watt-level passively Q-switched heavily Er3+-doped ZBLAN fiber laser with a semiconductor saturable absorber mirror

PubMed Central

Shen, Yanlong; Wang, Yishan; Luan, Kunpeng; Huang, Ke; Tao, Mengmeng; Chen, Hongwei; Yi, Aiping; Feng, Guobin; Si, Jinhai

2016-01-01

A diode-cladding pumped mid-infrared passively Q-switched Er3+-doped ZBLAN fiber laser with an average output power of watt-level based on a semiconductor saturable absorber mirror (SESAM) is demonstrated. Stable pulse train was produced at a slope efficiency of 17.8% with respect to launched pump power. The maximum average power of 1.01 W at a repetition rate of 146.3 kHz was achieved with a corresponding pulse energy of 6.9 μJ, from which the maximum peak power was calculated to be 21.9 W. To the best of our knowledge, the average power and the peak power are the highest in 3 μm region passively Q-switched fiber lasers. The influence of gain fiber length on the operation regime of the fiber laser has been investigated in detail. PMID:27225029

Chemically Modified Metal Oxide Nanostructure for Photoelectrochemical Water Splitting

NASA Astrophysics Data System (ADS)

Wang, Gongming

Hydrogen gas is chemical fuel with high energy density, and represents a clean, renewable and carbon-free burning fuel, which has the potential to solve the more and more urgent energy crisis in today's society. Inspired by natural photosynthesis, artificial photosynthesis to generate hydrogen energy has attracted a lot of attentions in the field of chemistry, physics and material. Photoelectrochemical water splitting based on semiconductors represents a green and low cost method to generate hydrogen fuel. However, the current overall efficiency of solar to hydrogen is quite low, due to some intrinsic limitations such as bandgap, diffusion distance, carrier lifetime and photostability of semiconductors. Although nanostructured semiconductors can improve their photoelectrochemical water splitting performance to some extent, by increasing electrolyte accessible area and shortening minority carrier diffusion distance, nanostructure engineering cannot change their intrinsic electronic properties. Recent development in chemically modified nanostructures such as surface catalyst decoration, element doping, plasmonic modification and interfacial hetero-junction design have led to significant advancement in the photoelectrochemical water splitting, by improving surface reaction kinetics and charge separation, transportation and collection efficiency. In this thesis, I will give a detailed discussion on the chemically modified metal oxide nanostructures for photoelectrocemical hydrogen generation, with a focus on the element doping, hydrogen treatment and catalyst modification. I have demonstrated nitrogen doping on ZnO and Ti doping on hematite can improve their photoelectrochemical performance. In addition, we found hydrogen treatment is a general and effective method to improve the photocatalytic performance, by increasing their carrier desities. Hydrogen treatment has been demonstrated on TiO2, WO3 and BiVO4. In the end, we also used electrochemical catalyt to modify these metal oxide photoelectrode for waste water treatment and chemical fuel generation.

Decrease of oxygen vacancy by Zn-doped for improving solar-blind photoelectric performance in β-Ga2O3 thin films

NASA Astrophysics Data System (ADS)

Guo, Daoyou; Qin, Xinyuan; Lv, Ming; Shi, Haoze; Su, Yuanli; Yao, Guosheng; Wang, Shunli; Li, Chaorong; Li, Peigang; Tang, Weihua

2017-11-01

Highly (201) oriented Zn-doped β-Ga2O3 thin films with different dopant concentrations were grown on (0001) sapphire substrates by radio frequency magnetron sputtering. With the increase of Zn dopant concentration, the crystal lattice expands, the energy band gap shrinks, and the oxygen vacancy concentration decreases. Both the metal semiconductor metal (MSM) structure photodetectors based on the pure and Zn-doped β-Ga2O3 thin films exhibit solar blind UV photoelectric property. Compared to the pure β-Ga2O3 photodetector, the Zn-doped one exhibits a lower dark current, a higher photo/dark current ratio, a faster photoresponse speed, which can be attributed to the decreases of oxygen vacancy concentration.[Figure not available: see fulltext.

Micro-patterned ZnO semiconductors for high performance thin film transistors via chemical imprinting with a PDMS stamp.

PubMed

Seong, Kieun; Kim, Kyongjun; Park, Si Yun; Kim, Youn Sang

2013-04-07

Chemical imprinting was conducted on ZnO semiconductor films via a chemical reaction at the contact regions between a micro-patterned PDMS stamp and ZnO films. In addition, we applied the chemical imprinting on Li doped ZnO thin films for high performance TFTs fabrication. The representative micro-patterned Li doped ZnO TFTs showed a field effect mobility of 4.2 cm(2) V(-1) s(-1) after sintering at 300 °C.

Multifunctional Organic-Semiconductor Interfacial Layers for Solution-Processed Oxide-Semiconductor Thin-Film Transistor.

PubMed

Kwon, Guhyun; Kim, Keetae; Choi, Byung Doo; Roh, Jeongkyun; Lee, Changhee; Noh, Yong-Young; Seo, SungYong; Kim, Myung-Gil; Kim, Choongik

2017-06-01

The stabilization and control of the electrical properties in solution-processed amorphous-oxide semiconductors (AOSs) is crucial for the realization of cost-effective, high-performance, large-area electronics. In particular, impurity diffusion, electrical instability, and the lack of a general substitutional doping strategy for the active layer hinder the industrial implementation of copper electrodes and the fine tuning of the electrical parameters of AOS-based thin-film transistors (TFTs). In this study, the authors employ a multifunctional organic-semiconductor (OSC) interlayer as a solution-processed thin-film passivation layer and a charge-transfer dopant. As an electrically active impurity blocking layer, the OSC interlayer enhances the electrical stability of AOS TFTs by suppressing the adsorption of environmental gas species and copper-ion diffusion. Moreover, charge transfer between the organic interlayer and the AOS allows the fine tuning of the electrical properties and the passivation of the electrical defects in the AOS TFTs. The development of a multifunctional solution-processed organic interlayer enables the production of low-cost, high-performance oxide semiconductor-based circuits. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dispersion of the refractive index of a samarium-doped Se{sup 95}Te{sup 5} chalcogenide glassy semiconductor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Atayeva, S. U., E-mail: seva-atayeva@mail.ru; Mekhtiyeva, S. I.; Isayev, A. I.

2015-07-15

The transmission spectrum of a Se{sup 95}Te{sup 5} chalcogenide glassy semiconductor doped with samarium (0.05, 0.1, 0.25, 0.5, and 1 at %) is studied; the Swanepoel method and the single-oscillator model are used to determine the oscillator energy E{sup 0}, dispersion energy E{sup d}, optical width of the band gap E{sup g}, and linear (n) and nonlinear (n{sup 2}) refractive indices. The changes in the values of these parameters as a result of doping are attributed to modification of the local structure and to a change in the concentration of defect states.

Absolute instability of polaron mode in semiconductor magnetoplasma

NASA Astrophysics Data System (ADS)

Paliwal, Ayushi; Dubey, Swati; Ghosh, S.

2018-01-01

Using coupled mode theory under hydrodynamic regime, a compact dispersion relation is derived for polaron mode in semiconductor magnetoplasma. The propagation and amplification characteristics of the wave are explored in detail. The analysis deals with the behaviour of anomalous threshold and amplification derived from dispersion relation, as function of external parameters like doping concentration and applied magnetic field. The results of this investigation are hoped to be useful in understanding electron-longitudinal optical phonon interplay in polar n-type semiconductor plasmas under the influence of coupled collective cyclotron excitations. The best results in terms of smaller threshold and higher gain of polaron mode could be achieved by choosing moderate doping concentration in the medium at higher magnetic field. For numerical appreciation of the results, relevant data of III-V n-GaAs compound semiconductor at 77 K is used. Present study provides a qualitative picture of polaron mode in magnetized n-type polar semiconductor medium duly shined by a CO2 laser.

Micro-Raman spectroscopy as a tool for the characterization of silicon carbide in power semiconductor material processing

NASA Astrophysics Data System (ADS)

De Biasio, M.; Kraft, M.; Schultz, M.; Goller, B.; Sternig, D.; Esteve, R.; Roesner, M.

2017-05-01

Silicon carbide (SiC) is a wide band-gap semi-conductor material that is used increasingly for high voltage power devices, since it has a higher breakdown field strength and better thermal conductivity than silicon. However, in particular its hardness makes wafer processing difficult and many standard semi-conductor processes have to be specially adapted. We measure the effects of (i) mechanical processing (i.e. grinding of the backside) and (ii) chemical and thermal processing (i.e. doping and annealing), using confocal microscopy to measure the surface roughness of ground wafers and micro-Raman spectroscopy to measure the stresses induced in the wafers by grinding. 4H-SiC wafers with different dopings were studied before and after annealing, using depth-resolved micro-Raman spectroscopy to observe how doping and annealing affect: i.) the damage and stresses induced on the crystalline structure of the samples and ii.) the concentration of free electrical carriers. Our results show that mechanical, chemical and thermal processing techniques have effects on this semiconductor material that can be observed and characterized using confocal microscopy and high resolution micro Raman spectroscopy.

Theoretical study of ozone adsorption on the surface of Fe, Co and Ni doped boron nitride nanosheets

NASA Astrophysics Data System (ADS)

Farmanzadeh, Davood; Askari Ardehjani, Nastaran

2018-06-01

In this work, the adsorption of ozone molecule on Fe, Co and Ni doped boron nitride nanosheets (BNNSs) were investigated using density functional theory. The most stable adsorption configurations, charge transfer and adsorption energy of ozone molecule on pure and doped BNNSs are calculated. It is shown that ozone molecule has no remarkable interaction with pure boron nitride nanosheet, it tends to be chemisorbed on Fe, Co and Ni doped BNNSs with adsorption energy in the range of -249.4 to -686.1 kJ/mol. In all configurations, the adsorption of ozone molecule generates a semiconductor by reducing Eg in the pure and Fe, Co and Ni doped boron nitride nanosheet. It shows that the conductance of BNNSs change over the adsorption of ozone molecule. The obtained results in this study can be used in developing BN-based sheets for ozone molecule removal.

Homogeneous 2D MoTe2 p-n Junctions and CMOS Inverters formed by Atomic-Layer-Deposition-Induced Doping.

PubMed

Lim, June Yeong; Pezeshki, Atiye; Oh, Sehoon; Kim, Jin Sung; Lee, Young Tack; Yu, Sanghyuck; Hwang, Do Kyung; Lee, Gwan-Hyoung; Choi, Hyoung Joon; Im, Seongil

2017-08-01

Recently, α-MoTe 2 , a 2D transition-metal dichalcogenide (TMD), has shown outstanding properties, aiming at future electronic devices. Such TMD structures without surface dangling bonds make the 2D α-MoTe 2 a more favorable candidate than conventional 3D Si on the scale of a few nanometers. The bandgap of thin α-MoTe 2 appears close to that of Si and is quite smaller than those of other typical TMD semiconductors. Even though there have been a few attempts to control the charge-carrier polarity of MoTe 2 , functional devices such as p-n junction or complementary metal-oxide-semiconductor (CMOS) inverters have not been reported. Here, we demonstrate a 2D CMOS inverter and p-n junction diode in a single α-MoTe 2 nanosheet by a straightforward selective doping technique. In a single α-MoTe 2 flake, an initially p-doped channel is selectively converted to an n-doped region with high electron mobility of 18 cm 2 V -1 s -1 by atomic-layer-deposition-induced H-doping. The ultrathin CMOS inverter exhibits a high DC voltage gain of 29, an AC gain of 18 at 1 kHz, and a low static power consumption of a few nanowatts. The results show a great potential of α-MoTe 2 for future electronic devices based on 2D semiconducting materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hall Effect Spintronics

DTIC Science & Technology

2014-01-01

ferromagnetic films with perpendicular anisotropy were examined, and finally, the magnetoresistance and Hall effect in Manganese- doped Germanium was...interest in ferromagnetic semiconductors. Germanium doped with Mn is particularly interesting Distribution A: Approved for public release...unavoidable, and doped films are strongly inhomogeneous with GexMny, metallic precipitates coexisting with Mn-rich regions and Mn dilute matrix

Doping of vanadium to nanocrystalline diamond films by hot filament chemical vapor deposition

PubMed Central

2012-01-01

Doping an impure element with a larger atomic volume into crystalline structure of buck crystals is normally blocked because the rigid crystalline structure could not tolerate a larger distortion. However, this difficulty may be weakened for nanocrystalline structures. Diamonds, as well as many semiconductors, have a difficulty in effective doping. Theoretical calculations carried out by DFT indicate that vanadium (V) is a dopant element for the n-type diamond semiconductor, and their several donor state levels are distributed between the conduction band and middle bandgap position in the V-doped band structure of diamond. Experimental investigation of doping vanadium into nanocrystalline diamond films (NDFs) was first attempted by hot filament chemical vapor deposition technique. Acetone/H2 gas mixtures and vanadium oxytripropoxide (VO(OCH2CH2CH3)3) solutions of acetone with V and C elemental ratios of 1:5,000, 1:2,000, and 1:1,000 were used as carbon and vanadium sources, respectively. The resistivity of the V-doped NDFs decreased two orders with the increasing V/C ratios. PMID:22873631

Cu doped diamond: Effect of charge state and defect aggregation on spin interactions in a 3d transition metal doped wide band-gap semiconductor

NASA Astrophysics Data System (ADS)

Benecha, E. M.; Lombardi, E. B.

2018-05-01

We present a first principles study of Cu in diamond using DFT+U electronic structure methods, by carefully considering the impact of co-doping, charge state, and Fermi level position on its stability, lattice location, spin states, and electronic properties. We show that the energetic stability and spin states of Cu are strongly dependent on the Fermi level position and the type of diamond co-doping, with Cu being energetically more favorable in n-type or p-type co-doped diamond compared to intrinsic diamond. Since Cu has been predicted to order magnetically in a number of other wide band-gap semiconductors, we have also evaluated this possibility for Cu doped diamond. We show that while Cu exhibits strong spin interactions at specific interatomic separations in diamond, a detailed consideration of the impact of Fermi level position and Cu aggregation precludes magnetic ordering, with Cu forming non-magnetic, antiferromagnetic, or paramagnetic clusters. These results have important implications in the understanding of the properties of transition metal dopants in diamond for device applications.

Madelung and Hubbard interactions in polaron band model of doped organic semiconductors

PubMed Central

Png, Rui-Qi; Ang, Mervin C.Y.; Teo, Meng-How; Choo, Kim-Kian; Tang, Cindy Guanyu; Belaineh, Dagmawi; Chua, Lay-Lay; Ho, Peter K.H.

2016-01-01

The standard polaron band model of doped organic semiconductors predicts that density-of-states shift into the π–π* gap to give a partially filled polaron band that pins the Fermi level. This picture neglects both Madelung and Hubbard interactions. Here we show using ultrahigh workfunction hole-doped model triarylamine–fluorene copolymers that Hubbard interaction strongly splits the singly-occupied molecular orbital from its empty counterpart, while Madelung (Coulomb) interactions with counter-anions and other carriers markedly shift energies of the frontier orbitals. These interactions lower the singly-occupied molecular orbital band below the valence band edge and give rise to an empty low-lying counterpart band. The Fermi level, and hence workfunction, is determined by conjunction of the bottom edge of this empty band and the top edge of the valence band. Calculations are consistent with the observed Fermi-level downshift with counter-anion size and the observed dependence of workfunction on doping level in the strongly doped regime. PMID:27582355

Reconfiguring crystal and electronic structures of MoS 2 by substitutional doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suh, Joonki; Tan, Teck Leong; Zhao, Weijie

Doping of traditional semiconductors has enabled technological applications in modern electronics by tailoring their chemical, optical and electronic properties. However, substitutional doping in two-dimensional semiconductors is at a comparatively early stage, and the resultant effects are less explored. In this work, we report unusual effects of degenerate doping with Nb on structural, electronic and optical characteristics of MoS 2 crystals. The doping readily induces a structural transformation from naturally occurring 2H stacking to 3R stacking. Electronically, a strong interaction of the Nb impurity states with the host valence bands drastically and nonlinearly modifies the electronic band structure with the valencemore » band maximum of multilayer MoS 2 at the Γ point pushed upward by hybridization with the Nb states. Finally, when thinned down to monolayers, in stark contrast, such significant nonlinear effect vanishes, instead resulting in strong and broadband photoluminescence via the formation of exciton complexes tightly bound to neutral acceptors.« less

Reconfiguring crystal and electronic structures of MoS 2 by substitutional doping

DOE PAGES

Suh, Joonki; Tan, Teck Leong; Zhao, Weijie; ...

2018-01-15

Doping of traditional semiconductors has enabled technological applications in modern electronics by tailoring their chemical, optical and electronic properties. However, substitutional doping in two-dimensional semiconductors is at a comparatively early stage, and the resultant effects are less explored. In this work, we report unusual effects of degenerate doping with Nb on structural, electronic and optical characteristics of MoS 2 crystals. The doping readily induces a structural transformation from naturally occurring 2H stacking to 3R stacking. Electronically, a strong interaction of the Nb impurity states with the host valence bands drastically and nonlinearly modifies the electronic band structure with the valencemore » band maximum of multilayer MoS 2 at the Γ point pushed upward by hybridization with the Nb states. Finally, when thinned down to monolayers, in stark contrast, such significant nonlinear effect vanishes, instead resulting in strong and broadband photoluminescence via the formation of exciton complexes tightly bound to neutral acceptors.« less

Nanocrystal doped matrixes

DOEpatents

Parce, J. Wallace; Bernatis, Paul; Dubrow, Robert; Freeman, William P.; Gamoras, Joel; Kan, Shihai; Meisel, Andreas; Qian, Baixin; Whiteford, Jeffery A.; Ziebarth, Jonathan

2010-01-12

Matrixes doped with semiconductor nanocrystals are provided. In certain embodiments, the semiconductor nanocrystals have a size and composition such that they absorb or emit light at particular wavelengths. The nanocrystals can comprise ligands that allow for mixing with various matrix materials, including polymers, such that a minimal portion of light is scattered by the matrixes. The matrixes of the present invention can also be utilized in refractive index matching applications. In other embodiments, semiconductor nanocrystals are embedded within matrixes to form a nanocrystal density gradient, thereby creating an effective refractive index gradient. The matrixes of the present invention can also be used as filters and antireflective coatings on optical devices and as down-converting layers. Processes for producing matrixes comprising semiconductor nanocrystals are also provided. Nanostructures having high quantum efficiency, small size, and/or a narrow size distribution are also described, as are methods of producing indium phosphide nanostructures and core-shell nanostructures with Group II-VI shells.

Synthesis and Spectroscopy of Silver-Doped PbSe Quantum Dots

DOE PAGES

Kroupa, Daniel M.; Hughes, Barbara K.; Miller, Elisa M.; ...

2017-06-25

Electronic impurity doping of bulk semiconductors is an essential component of semiconductor science and technology. Yet there are only a handful of studies demonstrating control of electronic impurities in semiconductor nanocrystals. Here, we studied electronic impurity doping of colloidal PbSe quantum dots (QDs) using a postsynthetic cation exchange reaction in which Pb is exchanged for Ag. We found that varying the concentration of dopants exposed to the as-synthesized PbSe QDs controls the extent of exchange. The electronic impurity doped QDs exhibit the fundamental spectroscopic signatures associated with injecting a free charge carrier into a QD under equilibrium conditions, including amore » bleach of the first exciton transition and the appearance of a quantum-confined, low-energy intraband absorption feature. Photoelectron spectroscopy confirms that Ag acts as a p-type dopant for PbSe QDs and infrared spectroscopy is consistent with k • p calculations of the size-dependent intraband transition energy. We find that to bleach the first exciton transition by an average of 1 carrier per QD requires that approximately 10% of the Pb be replaced by Ag. Here, we hypothesize that the majority of incorporated Ag remains at the QD surface and does not interact with the core electronic states of the QD. Instead, the excess Ag at the surface promotes the incorporation of <1% Ag into the QD core where it causes p-type doping behavior.« less

Electronic Structure, Surface Doping, and Optical Response in Epitaxial WSe2 Thin Films.

PubMed

Zhang, Yi; Ugeda, Miguel M; Jin, Chenhao; Shi, Su-Fei; Bradley, Aaron J; Martín-Recio, Ana; Ryu, Hyejin; Kim, Jonghwan; Tang, Shujie; Kim, Yeongkwan; Zhou, Bo; Hwang, Choongyu; Chen, Yulin; Wang, Feng; Crommie, Michael F; Hussain, Zahid; Shen, Zhi-Xun; Mo, Sung-Kwan

2016-04-13

High quality WSe2 films have been grown on bilayer graphene (BLG) with layer-by-layer control of thickness using molecular beam epitaxy. The combination of angle-resolved photoemission, scanning tunneling microscopy/spectroscopy, and optical absorption measurements reveal the atomic and electronic structures evolution and optical response of WSe2/BLG. We observe that a bilayer of WSe2 is a direct bandgap semiconductor, when integrated in a BLG-based heterostructure, thus shifting the direct-indirect band gap crossover to trilayer WSe2. In the monolayer limit, WSe2 shows a spin-splitting of 475 meV in the valence band at the K point, the largest value observed among all the MX2 (M = Mo, W; X = S, Se) materials. The exciton binding energy of monolayer-WSe2/BLG is found to be 0.21 eV, a value that is orders of magnitude larger than that of conventional three-dimensional semiconductors, yet small as compared to other two-dimensional transition metal dichalcogennides (TMDCs) semiconductors. Finally, our finding regarding the overall modification of the electronic structure by an alkali metal surface electron doping opens a route to further control the electronic properties of TMDCs.

Electronic structure, surface doping, and optical response in epitaxial WSe 2 thin films

DOE PAGES

Zhang, Yi; Ugeda, Miguel M.; Jin, Chenhao; ...

2016-03-14

High quality WSe 2 films have been grown on bilayer graphene (BLG) with layer-by-layer control of thickness using molecular beam epitaxy. The combination of angle-resolved photoemission, scanning tunneling microscopy/spectroscopy, and optical absorption measurements reveal the atomic and electronic structures evolution and optical response of WSe 2/BLG. We observe that a bilayer of WSe 2 is a direct bandgap semiconductor, when integrated in a BLG-based heterostructure, thus shifting the direct–indirect band gap crossover to trilayer WSe 2. In the monolayer limit, WSe 2 shows a spin-splitting of 475 meV in the valence band at the K point, the largest value observedmore » among all the MX 2 (M = Mo, W; X = S, Se) materials. The exciton binding energy of monolayer-WSe 2/BLG is found to be 0.21 eV, a value that is orders of magnitude larger than that of conventional three-dimensional semiconductors, yet small as compared to other two-dimensional transition metal dichalcogennides (TMDCs) semiconductors. Lastly, our finding regarding the overall modification of the electronic structure by an alkali metal surface electron doping opens a route to further control the electronic properties of TMDCs.« less

Ex situ n+ doping of GeSn alloys via non-equilibrium processing

NASA Astrophysics Data System (ADS)

Prucnal, S.; Berencén, Y.; Wang, M.; Rebohle, L.; Böttger, R.; Fischer, I. A.; Augel, L.; Oehme, M.; Schulze, J.; Voelskow, M.; Helm, M.; Skorupa, W.; Zhou, S.

2018-06-01

Full integration of Ge-based alloys like GeSn with complementary-metal-oxide-semiconductor technology would require the fabrication of p- and n-type doped regions for both planar and tri-dimensional device architectures which is challenging using in situ doping techniques. In this work, we report on the influence of ex situ doping on the structural, electrical and optical properties of GeSn alloys. n-type doping is realized by P implantation into GeSn alloy layers grown by molecular beam epitaxy (MBE) followed by flash lamp annealing. We show that effective carrier concentration of up to 1 × 1019 cm‑3 can be achieved without affecting the Sn distribution. Sn segregation at the surface accompanied with an Sn diffusion towards the crystalline/amorphous GeSn interface is found at P fluences higher than 3 × 1015 cm‑2 and electron concentration of about 4 × 1019 cm‑3. The optical and structural properties of ion-implanted GeSn layers are comparable with the in situ doped MBE grown layers.

The effect of doping on low temperature growth of high quality GaAs nanowires on polycrystalline films

PubMed Central

DeJarld, Matt; Teran, Alan; Luengo-Kovac, Marta; Yan, Lifan; Moon, Eun Seong; Beck, Sara; Guillen, Cristina; Sih, Vanessa; Phillips, Jamie; Milunchick, Joanna Mirecki

2016-01-01

The increasing demand for miniature autonomous sensors requires low cost integration methods, but to date, material limitations have prevented the direct growth of optically active III-V materials on CMOS devices. We report on the deposition of GaAs nanowires on polycrystalline conductive films to allow for direct integration of optoelectronic devices on dissimilar materials. Undoped, Si-doped, and Be-doped nanowires were grown at Ts=400°C on oxide (indium tin oxide) and metallic (platinum and titanium) films. Be-doping is shown to significantly reduce the nanowire diameter and improve the nanowire aspect ratio to 50:1. Photoluminescence measurements of Be-doped nanowires are 1–2 orders of magnitude stronger than undoped and Si-doped nanowires and have a thermal activation energy of 14meV, which is comparable to nanowires grown on crystalline substrates. Electrical measurements confirm that the metal-semiconductor junction is Ohmic. These results demonstrate the feasibility of integrating nanowire-based optoelectronic devices directly on CMOS chips. PMID:27834310

Anisotropic strain relaxation of Si-doped metamorphic InAlAs graded buffers on InP

NASA Astrophysics Data System (ADS)

Gu, Yi; Zhang, Yonggang; Chen, Xingyou; Ma, Yingjie; Zheng, Yuanliao; Du, Ben; Zhang, Jian

2017-09-01

The effects of Si doping on the strain relaxation of InP-based metamorphic In x Al1-x As graded buffers have been investigated. The highly Si-doped sample shows an increased ridge period along the [1 1 0] direction in the cross-hatch morphology measured by atomic force microscope. X-ray diffraction reciprocal space mapping measurements reveal that the high Si-doping induced incomplete relaxation as well as inhomogeneous residual strain along the [1 -1 0] direction, which was also observed in micro-Raman measurements. The anisotropic strain relaxation is attributed to the Si-doping enhanced anisotropy of misfit dislocations along the orthogonal directions. The α-misfit dislocations along the [1 -1 0] direction are further delayed to generate in highly Si-doped InAlAs buffer, while the β-misfit dislocations along the [1 1 0] direction are not. These results supply useful suggestions on the design and demonstration of semiconductor metamorphic devices.

Chemical Vapor Deposition Growth of Degenerate p-Type Mo-Doped ReS2 Films and Their Homojunction.

PubMed

Qin, Jing-Kai; Shao, Wen-Zhu; Xu, Cheng-Yan; Li, Yang; Ren, Dan-Dan; Song, Xiao-Guo; Zhen, Liang

2017-05-10

Substitutional doping of transition metal dichalcogenide two-dimensional materials has proven to be effective in tuning their intrinsic properties, such as band gap, transport characteristics, and magnetism. In this study, we realized substitutional doping of monolayer rhenium disulfide (ReS 2 ) with Mo via chemical vapor deposition. Scanning transmission electron microscopy demonstrated that Mo atoms are successfully doped into ReS 2 by substitutionally replacing Re atoms in the lattice. Electrical measurements revealed the degenerate p-type semiconductor behavior of Mo-doped ReS 2 field effect transistors, in agreement with density functional theory calculations. The p-n diode device based on a doped ReS 2 and ReS 2 homojunction exhibited gate-tunable current rectification behaviors, and the maximum rectification ratio could reach up to 150 at V d = -2/+2 V. The successful synthesis of p-type ReS 2 in this study could largely promote its application in novel electronic and optoelectronic devices.

Primary research efforts on exploring the commercial possibilities of thin film growth and materials purification in space

NASA Technical Reports Server (NTRS)

1989-01-01

The progress made on research programs in the 1987 to 1988 year is reported. The research is aimed at producing thin film semiconductors and superconductor materials in space. Sophisticated vacuum chambers and equipment were attained for the epitaxial thin film growth of semiconductors, metals and superconductors. In order to grow the best possible epitaxial films at the lowest possible temperatures on earth, materials are being isoelectronically doped during growth. It was found that isoelectrically doped film shows the highest mobility in comparison with films grown at optimal temperatures. Success was also attained in growing epitaxial films of InSb on sapphire which show promise for infrared sensitive devices in the III-V semiconductor system.

Buffer Layer Doping Concentration Measurement Using VT-VSUB Characteristics of GaN HEMT with p-GaN Substrate Layer

NASA Astrophysics Data System (ADS)

Hu, Cheng-Yu; Nakatani, Katsutoshi; Kawai, Hiroji; Ao, Jin-Ping; Ohno, Yasuo

To improve the high voltage performance of AlGaN/GaN heterojunction field effect transistors (HFETs), we have fabricated AlGaN/GaN HFETs with p-GaN epi-layer on sapphire substrate with an ohmic contact to the p-GaN (p-sub HFET). Substrate bias dependent threshold voltage variation (VT-VSUB) was used to directly determine the doping concentration profile in the buffer layer. This VT-VSUB method was developed from Si MOSFET. For HFETs, the insulator is formed by epitaxially grown and heterogeneous semiconductor layer while for Si MOSFETs the insulator is amorphous SiO2. Except that HFETs have higher channel mobility due to the epitaxial insulator/semiconductor interface, HFETs and Si MOSFETs are basically the same in the respect of device physics. Based on these considerations, the feasibility of this VT-VSUB method for AlGaN/GaN HFETs was discussed. In the end, the buffer layer doping concentration was measured to be 2 × 1017cm-3, p-type, which is well consistent with the Mg concentration obtained from secondary ion mass spectroscopy (SIMS) measurement.

Tris(2-(1H-pyrazol-1-yl)pyridine)cobalt(III) as p-type dopant for organic semiconductors and its application in highly efficient solid-state dye-sensitized solar cells.

PubMed

Burschka, Julian; Dualeh, Amalie; Kessler, Florian; Baranoff, Etienne; Cevey-Ha, Ngoc-Lê; Yi, Chenyi; Nazeeruddin, Mohammad K; Grätzel, Michael

2011-11-16

Chemical doping is an important strategy to alter the charge-transport properties of both molecular and polymeric organic semiconductors that find widespread application in organic electronic devices. We report on the use of a new class of Co(III) complexes as p-type dopants for triarylamine-based hole conductors such as spiro-MeOTAD and their application in solid-state dye-sensitized solar cells (ssDSCs). We show that the proposed compounds fulfill the requirements for this application and that the discussed strategy is promising for tuning the conductivity of spiro-MeOTAD in ssDSCs, without having to rely on the commonly employed photo-doping. By using a recently developed high molar extinction coefficient organic D-π-A sensitizer and p-doped spiro-MeOTAD as hole conductor, we achieved a record power conversion efficiency of 7.2%, measured under standard solar conditions (AM1.5G, 100 mW cm(-2)). We expect these promising new dopants to find widespread applications in organic electronics in general and photovoltaics in particular.

Near-thermal limit gating in heavily doped III-V semiconductor nanowires using polymer electrolytes

NASA Astrophysics Data System (ADS)

Ullah, A. R.; Carrad, D. J.; Krogstrup, P.; Nygârd, J.; Micolich, A. P.

2018-02-01

Doping is a common route to reducing nanowire transistor on-resistance but it has limits. A high doping level gives significant loss in gate performance and ultimately complete gate failure. We show that electrolyte gating remains effective even when the Be doping in our GaAs nanowires is so high that traditional metal-oxide gates fail. In this regime we obtain a combination of subthreshold swing and contact resistance that surpasses the best existing p -type nanowire metal-oxide semiconductor field-effect transistors (MOSFETs). Our subthreshold swing of 75 mV/dec is within 25 % of the room-temperature thermal limit and comparable with n -InP and n -GaAs nanowire MOSFETs. Our results open a new path to extending the performance and application of nanowire transistors, and motivate further work on improved solid electrolytes for nanoscale device applications.

Spin Hall Effect in Doped Semiconductor Structures

NASA Astrophysics Data System (ADS)

Tse, Wang-Kong; Das Sarma, Sankar

2006-03-01

We present a microscopic theory of the extrinsic spin Hall effect based on the diagrammatic perturbation theory. Side-jump (SJ) and skew-scattering (SS) contributions are explicitly taken into account to calculate the spin Hall conductivity, and we show their effects scale as σxy^SJ/σxy^SS ˜(/τ)/ɛF, where τ being the transport relaxation time. Motivated by recent experimental work we apply our theory to n-doped and p-doped 3D and 2D GaAs structures, obtaining analytical formulas for the SJ and SS contributions. Moreover, the ratio of the spin Hall conductivity to longitudinal conductivity is found as σs/σc˜10-3-10-4, in reasonable agreement with the recent experimental results of Kato et al. [Science 306, 1910 (2004)] in n-doped 3D GaAs system.

A phenomenological model for systematization and prediction of doping limits in II{endash}VI and I{endash}III{endash}VI{sub 2} compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, S.B.; Wei, S.; Zunger, A.

1998-03-01

Semiconductors differ widely in their ability to be doped. As their band gap increases, it is usually possible to dope them either n or p type, but not both. This asymmetry is documented here, and explained phenomenologically in terms of the {open_quotes}doping pinning rule.{close_quotes} {copyright} {ital 1998 American Institute of Physics.}

Phosphorus doping a semiconductor particle

DOEpatents

Stevens, G.D.; Reynolds, J.S.

1999-07-20

A method of phosphorus doping a semiconductor particle using ammonium phosphate is disclosed. A p-doped silicon sphere is mixed with a diluted solution of ammonium phosphate having a predetermined concentration. These spheres are dried with the phosphorus then being diffused into the sphere to create either a shallow or deep p-n junction. A good PSG glass layer is formed on the surface of the sphere during the diffusion process. A subsequent segregation anneal process is utilized to strip metal impurities from near the p-n junction into the glass layer. A subsequent HF strip procedure is then utilized to removed the PSG layer. Ammonium phosphate is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirement. 1 fig.

Phosphorous doping a semiconductor particle

DOEpatents

Stevens, Gary Don; Reynolds, Jeffrey Scott

1999-07-20

A method (10) of phosphorus doping a semiconductor particle using ammonium phosphate. A p-doped silicon sphere is mixed with a diluted solution of ammonium phosphate having a predetermined concentration. These spheres are dried (16, 18), with the phosphorus then being diffused (20) into the sphere to create either a shallow or deep p-n junction. A good PSG glass layer is formed on the surface of the sphere during the diffusion process. A subsequent segregation anneal process is utilized to strip metal impurities from near the p-n junction into the glass layer. A subsequent HF strip procedure is then utilized to removed the PSG layer. Ammonium phosphate is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirement.

High-performance all-printed amorphous oxide FETs and logics with electronically compatible electrode/ channel interface.

PubMed

Sharma, Bhupendra Kumar; Stoesser, Anna; Mondal, Sandeep Kumar; Garlapati, Suresh K; Fawey, Mohammed H; Chakravadhanula, Venkata Sai Kiran; Kruk, Robert; Hahn, Horst; Dasgupta, Subho

2018-06-12

Oxide semiconductors typically show superior device performance compared to amorphous silicon or organic counterparts, especially, when they are physical vapor deposited. However, it is not easy to reproduce identical device characteristics when the oxide field-effect transistors (FETs) are solution-processed/ printed; the level of complexity further intensifies with the need to print the passive elements as well. Here, we developed a protocol for designing the most electronically compatible electrode/ channel interface based on the judicious material selection. Exploiting this newly developed fabrication schemes, we are now able to demonstrate high-performance all-printed FETs and logic circuits using amorphous indium-gallium-zinc oxide (a-IGZO) semiconductor, indium tin oxide (ITO) as electrodes and composite solid polymer electrolyte as the gate insulator. Interestingly, all-printed FETs demonstrate an optimal electrical performance in terms of threshold voltages and device mobility and may very well be compared with devices fabricated using sputtered ITO electrodes. This observation originates from the selection of electrode/ channel materials from the same transparent semiconductor oxide family, resulting in the formation of In-Sn-Zn-O (ITZO) based diffused a-IGZO/ ITO interface that controls doping density while ensuring high electrical performance. Compressive spectroscopic studies reveal that Sn doping mediated excellent band alignment of IGZO with ITO electrodes is responsible for the excellent device performance observed. All-printed n-MOS based logic circuits have also been demonstrated towards new-generation portable electronics.

Origin of spin polarization in an edge boron doped zigzag graphene nanoribbon: a potential spin filter.

PubMed

Chakrabarty, Soubhik; Wasey, A H M Abdul; Thapa, Ranjit; Das, G P

2018-08-24

To realize a graphene based spintronic device, the prime challenge is to control the electronic structure of edges. In this work we find the origin of the spin filtering property in edge boron doped zigzag graphene nanoribbons (ZGNRs) and provide a guide to preparing a graphene based next-generation spin filter based device. Here, we unveil the role of orbitals (p-electron) to tune the electronic, magnetic and transport properties of edge B doped ZGNRs. When all the edge carbon atoms at one of the edges of ZGNRs are replaced by B (100% edge B doping), the system undergoes a semiconductor to metal transition. The role of passivation of the edge with single/double atomic hydrogen on the electronic properties and its relation with the p-electron is correlated in-depth. 50% edge B doped ZGNRs (50% of the edge C atoms at one of the edges are replaced by B) also show half-metallicity when the doped edge is left unpassivated. The half-metallic systems show 100% spin filtering efficiency for a wide range of bias voltages. Zero-bias transmission function of the other configurations shows asymmetric behavior for the up and down spin channels, thereby indicating their possible application potential in nano-spintronics.

A first-principles study of impurity effects on monolayer MoS2: bandgap dominated by donor impurities

NASA Astrophysics Data System (ADS)

Zhang, Hua; Zhou, Wenzhe; Yang, Zhixiong; Wu, Shoujian; Ouyang, Fangping; Xu, Hui

2017-12-01

Based on the first principles calculation, the electrical properties and optical properties of monolayer molybdenum disulfide (MoS2) substitutionally doped by the VB and VIIB transition metal atoms (V, Nb, Ta, Mn, Tc, Re) were investigated. It is found that n-type doping or p-type doping tunes the Fermi level into the conduction band or the valence band respectively, leading to the degenerate semiconductor, while the compensatorily doped systems where the number of valence electrons is not alerted remain direct band gap ranging from 0.958 eV to 1.414 eV. According to the analysis on densities of states, the LUMO orbitals of donor impurities play the crucial role in band gap tuning. Hence, the band gap and optical properties of doped MoS2 are dominated by the species of the donor. Due to the reduction of the band gap, doped MoS2 have a lower threshold energy of photon absorption and an enhanced absorption in near infrared region. These results provide a significant guidance for the design of new 2D optoelectronic materials based on transition metal disulfide.

Electrolytic photodissociation of chemical compounds by iron oxide electrodes

DOEpatents

Somorjai, Gabor A.; Leygraf, Christofer H.

1984-01-01

Chemical compounds can be dissociated by contacting the same with a p/n type semi-conductor diode having visible light as its sole source of energy. The diode consists of low cost, readily available materials, specifically polycrystalline iron oxide doped with silicon in the case of the n-type semi-conductor electrode, and polycrystalline iron oxide doped with magnesium in the case of the p-type electrode. So long as the light source has an energy greater than 2.2 electron volts, no added energy source is needed to achieve dissociation.

Electrolytic photodissociation of chemical compounds by iron oxide photochemical diodes

DOEpatents

Somorjai, Gabor A.; Leygraf, Christofer H.

1985-01-01

Chemical compounds can be dissociated by contacting the same with a p/n type semi-conductor photochemical diode having visible light as its sole source of energy. The photochemical diode consists of low cost, readily available materials, specifically polycrystalline iron oxide doped with silicon in the case of the n-type semi-conductor electrode, and polycrystalline iron oxide doped with magnesium in the case of the p-type electrode. So long as the light source has an energy greater than 2.2 electron volts, no added energy source is needed to achieve dissociation.

Dual ohmic contact to N- and P-type silicon carbide

NASA Technical Reports Server (NTRS)

Okojie, Robert S. (Inventor)

2013-01-01

Simultaneous formation of electrical ohmic contacts to silicon carbide (SiC) semiconductor having donor and acceptor impurities (n- and p-type doping, respectively) is disclosed. The innovation provides for ohmic contacts formed on SiC layers having n- and p-doping at one process step during the fabrication of the semiconductor device. Further, the innovation provides a non-discriminatory, universal ohmic contact to both n- and p-type SiC, enhancing reliability of the specific contact resistivity when operated at temperatures in excess of 600.degree. C.

Optically switched graphene/4H-SiC junction bipolar transistor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandrashekhar, MVS; Sudarshan, Tangali S.; Omar, Sabih U.

A bi-polar device is provided, along with methods of making the same. The bi-polar device can include a semiconductor substrate doped with a first dopant, a semiconductor layer on the first surface of the semiconductor substrate, and a Schottky barrier layer on the semiconductor layer. The method of forming a bi-polar device can include: forming a semiconductor layer on a first surface of a semiconductor substrate, where the semiconductor substrate comprises a first dopant and where the semiconductor layer comprises a second dopant that has an opposite polarity than the first dopant; and forming a Schottky barrier layer on amore » first portion of the semiconductor layer while leaving a second portion of the semiconductor layer exposed.« less

A new approximation of Fermi-Dirac integrals of order 1/2 for degenerate semiconductor devices

NASA Astrophysics Data System (ADS)

AlQurashi, Ahmed; Selvakumar, C. R.

2018-06-01

There had been tremendous growth in the field of Integrated circuits (ICs) in the past fifty years. Scaling laws mandated both lateral and vertical dimensions to be reduced and a steady increase in doping densities. Most of the modern semiconductor devices have invariably heavily doped regions where Fermi-Dirac Integrals are required. Several attempts have been devoted to developing analytical approximations for Fermi-Dirac Integrals since numerical computations of Fermi-Dirac Integrals are difficult to use in semiconductor devices, although there are several highly accurate tabulated functions available. Most of these analytical expressions are not sufficiently suitable to be employed in semiconductor device applications due to their poor accuracy, the requirement of complicated calculations, and difficulties in differentiating and integrating. A new approximation has been developed for the Fermi-Dirac integrals of the order 1/2 by using Prony's method and discussed in this paper. The approximation is accurate enough (Mean Absolute Error (MAE) = 0.38%) and easy enough to be used in semiconductor device equations. The new approximation of Fermi-Dirac Integrals is applied to a more generalized Einstein Relation which is an important relation in semiconductor devices.

Highly reproducible alkali metal doping system for organic crystals through enhanced diffusion of alkali metal by secondary thermal activation.

PubMed

Lee, Jinho; Park, Chibeom; Song, Intek; Koo, Jin Young; Yoon, Taekyung; Kim, Jun Sung; Choi, Hee Cheul

2018-05-16

In this paper, we report an efficient alkali metal doping system for organic single crystals. Our system employs an enhanced diffusion method for the introduction of alkali metal into organic single crystals by controlling the sample temperature to induce secondary thermal activation. Using this system, we achieved intercalation of potassium into picene single crystals with closed packed crystal structures. Using optical microscopy and Raman spectroscopy, we confirmed that the resulting samples were uniformly doped and became K 2 picene single crystal, while only parts of the crystal are doped and transformed into K 2 picene without secondary thermal activation. Moreover, using a customized electrical measurement system, the insulator-to-semiconductor transition of picene single crystals upon doping was confirmed by in situ electrical conductivity and ex situ temperature-dependent resistivity measurements. X-ray diffraction studies showed that potassium atoms were intercalated between molecular layers of picene, and doped samples did not show any KH- nor KOH-related peaks, indicating that picene molecules are retained without structural decomposition. During recent decades, tremendous efforts have been exerted to develop high-performance organic semiconductors and superconductors, whereas as little attention has been devoted to doped organic crystals. Our method will enable efficient alkali metal doping of organic crystals and will be a resource for future systematic studies on the electrical property changes of these organic crystals upon doping.

Features of the band structure and conduction mechanisms of n-HfNiSn semiconductor heavily Lu-doped

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romaka, V. A., E-mail: vromaka@polynet.lviv.ua; Rogl, P.; Romaka, V. V.

2015-03-15

The crystal and electronic structures, energy, kinetic, and magnetic characteristics of n-HfNiSn semiconductor heavily doped with a Lu acceptor impurity in the ranges T = 80–400 K and N{sub A}{sup Lu} ≈ 1.9 × 10{sup 20}−1.9 × 10{sup 21} cm{sup −3} (x = 0.01–0.10) at H ≤ 10 kG is studied. The nature of the structural-defect generation mechanism leading to changes in the band gap and the degree of semiconductor compensation is determined. Its essence is the simultaneous reduction and elimination of donor-type structural defects due to the displacement of ∼1% of Ni atoms from the Hf (4a) site, themore » generation of acceptor-type structural defects by substituting Ni atoms with Lu atoms at the 4c site, and the generation of donor-type defects such as vacancies at the Sn (4b) site. The results of calculations of the electronic structure of Hf{sub 1−x}Lu{sub x}NiSn are in agreement with experimental data. The results are discussed within the model of a heavily doped and compensated Shklovskii-Efros semiconductor.« less

Interface Energetics and Chemical Doping of Organic Electronic Materials

NASA Astrophysics Data System (ADS)

Kahn, Antoine

2014-03-01

The energetics of organic semiconductors and their interfaces are central to the performance of organic thin film devices. The relative positions of charge transport states across the many interfaces of multi-layer OLEDs, OPV cells and OFETs determine in great part the efficiency and lifetime of these devices. New experiments are presented here, that look in detail at the position of these transport states and associated gap states and electronic traps that tail into the energy gap of organic molecular (e.g. pentacene) or polymer (P3HT, PBDTTT-C) semiconductors, and which directly affect carrier mobility in these materials. Disorder, sometime caused by simple exposure to an inert gas, impurities and defects are at the origin of these electronic gap states. Recent efforts in chemical doping in organic semiconductors aimed at mitigating the impact of electronic gap states are described. An overview of the reducing or oxidizing power of several n- and p-type dopants for vacuum- or solution-processed films, and their effect on the electronic structure and conductivity of both vacuum- and solution-processed organic semiconductor films is given. Finally, the filling (compensation) of active gap states via doping is investigated on the electron-transport materials C60 and P(NDI2OD-T2) , and the hole-transport polymer PBDTTT-C.

Semiconductor-to-metal transition in rutile TiO 2 induced by tensile strain

DOE PAGES

Benson, Eric E.; Miller, Elisa M.; Nanayakkara, Sanjini U.; ...

2017-02-10

Here, we report the first observation of a reversible, degenerate doping of titanium dioxide with strain, which is referred to as a semiconductor-to-metal transition. Application of tensile strain to a ~50 nm film of rutile TiO 2 thermally grown on a superelastic nitinol (NiTi intermetallic) substrate causes reversible degenerate doping as evidenced by electrochemistry, X-ray photoelectron spectroscopy (XPS), and conducting atomic force microscopy (CAFM). Cyclic voltammetry and impedance measurements show behavior characteristic of a highly doped n-type semiconductor for unstrained TiO 2 transitioning to metallic behavior under tensile strain. The transition reverses when strain is removed. Valence band XPS spectramore » show that samples strained to 5% exhibit metallic-like intensity near the Fermi level. Strain also induces a distinct transition in CAFM current-voltage curves from rectifying (typical of an n-type semiconductor) to ohmic (metal-like) behavior. We propose that strain raises the energy distribution of oxygen vacancies ( n-type dopants) near the conduction band and causes an increase in carrier concentration. As the carrier concentration is increased, the width of the depletion region is reduced, which then permits electron tunneling through the space charge barrier resulting in the observed metallic behavior.« less

Method and apparatus for use of III-nitride wide bandgap semiconductors in optical communications

DOEpatents

Hui, Rongqing [Lenexa, KS; Jiang, Hong-Xing [Manhattan, KS; Lin, Jing-Yu [Manhattan, KS

2008-03-18

The present disclosure relates to the use of III-nitride wide bandgap semiconductor materials for optical communications. In one embodiment, an optical device includes an optical waveguide device fabricated using a III-nitride semiconductor material. The III-nitride semiconductor material provides for an electrically controllable refractive index. The optical waveguide device provides for high speed optical communications in an infrared wavelength region. In one embodiment, an optical amplifier is provided using optical coatings at the facet ends of a waveguide formed of erbium-doped III-nitride semiconductor materials.

Optical Properties of the Organic Semiconductor Polyacetylene.

NASA Astrophysics Data System (ADS)

Feldblum, Avinoam Y.

Polyacetylene is the prototype conducting organic polymer. In its pristine form, it exhibits physical properties closely resembling those of a conventional inorganic semiconductor. When chemically or electrochemically doped, the polymer undergoes a semiconductor-metal transition. The nature of lightly doped polyacetylene, prior to the metallic transition, is not well understood. In addition, there still remain questions as to the nature of the pristine film itself. In this thesis, optical absorption experiments were performed in order to gain a clearer understanding of the electronic structure of polyacetylene. To attain this understanding, opto-electrochemical spectroscopy (OES), a new technique combining optical measurements with in situ electrochemical doping was developed. Optical absorption measurements were performed on cis-(CH)(,x) in order to examine doping induced isomerization. When doped to metallic levels followed by compensation or undoping, cis-(CH)(,x) isomerizes to trans-(CH)(,x). Using OES, one finds that with light doping, the main contribution to the midgap transition comes from the small trans content in the film. Electrochemical cycling shows isomerization beginning below y = 0.01 and repeated cycling to different concentrations indicate that the total isomerization depends on the value of the highest dopant level. These results suggest that upon light doping, the trans-(CH)(,x) dopes first, followed by enough cis-(CH)(,x) isomerizing to accomodate the injected charge. A quantitative study of the effects of doping on the absorption coefficient of trans-(CH)(,x) was carried out using OES. Upon doping, the interband absorption uniformly decreases over an extremely wide range. A strong absorbtion appeared at mid-gap; its oscillator strength increasing linearly with dopant concentration. A weak shoulder is observed on the interband edge which grows at low concentrations and then decreases to zero by 4%. These results agree with the predictions of the soliton model--the midgap absorption is identified as a soliton level and the shoulder as a transition between localized polaron levels. The pressure dependence of the photoabsorption of cis- and trans-(CH)(,x) has been measured. In both cases the bandedge shifted to a lower energy, and the value of the peak absorption coefficient decreased. These results suggest that the observed bandwidth is due primarily to the transverse transfer integral.

Compensation of native donor doping in ScN: Carrier concentration control and p-type ScN

NASA Astrophysics Data System (ADS)

Saha, Bivas; Garbrecht, Magnus; Perez-Taborda, Jaime A.; Fawey, Mohammed H.; Koh, Yee Rui; Shakouri, Ali; Martin-Gonzalez, Marisol; Hultman, Lars; Sands, Timothy D.

2017-06-01

Scandium nitride (ScN) is an emerging indirect bandgap rocksalt semiconductor that has attracted significant attention in recent years for its potential applications in thermoelectric energy conversion devices, as a semiconducting component in epitaxial metal/semiconductor superlattices and as a substrate material for high quality GaN growth. Due to the presence of oxygen impurities and native defects such as nitrogen vacancies, sputter-deposited ScN thin-films are highly degenerate n-type semiconductors with carrier concentrations in the (1-6) × 1020 cm-3 range. In this letter, we show that magnesium nitride (MgxNy) acts as an efficient hole dopant in ScN and reduces the n-type carrier concentration, turning ScN into a p-type semiconductor at high doping levels. Employing a combination of high-resolution X-ray diffraction, transmission electron microscopy, and room temperature optical and temperature dependent electrical measurements, we demonstrate that p-type Sc1-xMgxN thin-film alloys (a) are substitutional solid solutions without MgxNy precipitation, phase segregation, or secondary phase formation within the studied compositional region, (b) exhibit a maximum hole-concentration of 2.2 × 1020 cm-3 and a hole mobility of 21 cm2/Vs, (c) do not show any defect states inside the direct gap of ScN, thus retaining their basic electronic structure, and (d) exhibit alloy scattering dominating hole conduction at high temperatures. These results demonstrate MgxNy doped p-type ScN and compare well with our previous reports on p-type ScN with manganese nitride (MnxNy) doping.

Graphene/CdTe heterostructure solar cell and its enhancement with photo-induced doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Shisheng, E-mail: shishenglin@zju.edu.cn; Chen, Hongsheng; State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027

2015-11-09

We report a type of solar cell based on graphene/CdTe Schottky heterostructure, which can be improved by surface engineering as graphene is atomic thin. By coating a layer of ultrathin CdSe quantum dots onto graphene/CdTe heterostructure, the power conversion efficiency is increased from 2.08% to 3.10%. Photo-induced doping is mainly accounted for this enhancement, as evidenced by field effect transport, Raman, photoluminescence, and quantum efficiency measurements. This work demonstrates a feasible way of improving the performance of graphene/semiconductor heterostructure solar cells by combining one dimensional with two dimensional materials.

Planar varactor frequency multiplier devices with blocking barrier

NASA Technical Reports Server (NTRS)

Lieneweg, Udo (Inventor); Frerking, Margaret A. (Inventor); Maserjian, Joseph (Inventor)

1994-01-01

The invention relates to planar varactor frequency multiplier devices with a heterojunction blocking barrier for near millimeter wave radiation of moderate power from a fundamental input wave. The space charge limitation of the submillimeter frequency multiplier devices of the BIN(sup +) type is overcome by a diode structure comprising an n(sup +) doped layer of semiconductor material functioning as a low resistance back contact, a layer of semiconductor material with n-type doping functioning as a drift region grown on the back contact layer, a delta doping sheet forming a positive charge at the interface of the drift region layer with a barrier layer, and a surface metal contact. The layers thus formed on an n(sup +) doped layer may be divided into two isolated back-to-back BNN(sup +) diodes by separately depositing two surface metal contacts. By repeating the sequence of the drift region layer and the barrier layer with the delta doping sheet at the interfaces between the drift and barrier layers, a plurality of stacked diodes is formed. The novelty of the invention resides in providing n-type semiconductor material for the drift region in a GaAs/AlGaAs structure, and in stacking a plurality of such BNN(sup +) diodes stacked for greater output power with and connected back-to-back with the n(sup +) GaAs layer as an internal back contact and separate metal contact over an AlGaAs barrier layer on top of each stack.

All-semiconductor metamaterial-based optical circuit board at the microscale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Min, Li; Huang, Lirong, E-mail: lrhuang@hust.edu.cn

2015-07-07

The newly introduced metamaterial-based optical circuit, an analogue of electronic circuit, is becoming a forefront topic in the fields of electronics, optics, plasmonics, and metamaterials. However, metals, as the commonly used plasmonic elements in an optical circuit, suffer from large losses at the visible and infrared wavelengths. We propose here a low-loss, all-semiconductor metamaterial-based optical circuit board at the microscale by using interleaved intrinsic GaAs and doped GaAs, and present the detailed design process for various lumped optical circuit elements, including lumped optical inductors, optical capacitors, optical conductors, and optical insulators. By properly combining these optical circuit elements and arrangingmore » anisotropic optical connectors, we obtain a subwavelength optical filter, which can always hold band-stop filtering function for various polarization states of the incident electromagnetic wave. All-semiconductor optical circuits may provide a new opportunity in developing low-power and ultrafast components and devices for optical information processing.« less

Excitonic pathway to photoinduced magnetism in colloidal nanocrystals with nonmagnetic dopants

NASA Astrophysics Data System (ADS)

Pinchetti, Valerio; Di, Qiumei; Lorenzon, Monica; Camellini, Andrea; Fasoli, Mauro; Zavelani-Rossi, Margherita; Meinardi, Francesco; Zhang, Jiatao; Crooker, Scott A.; Brovelli, Sergio

2018-02-01

Electronic doping of colloidal semiconductor nanostructures holds promise for future device concepts in optoelectronic and spin-based technologies. Ag+ is an emerging electronic dopant in iii-v and ii-vi nanostructures, introducing intragap electronic states optically coupled to the host conduction band. With its full 4d shell Ag+ is nonmagnetic, and the dopant-related luminescence is ascribed to decay of the conduction-band electron following transfer of the photoexcited hole to Ag+. This optical activation process and the associated modification of the electronic configuration of Ag+ remain unclear. Here, we trace a comprehensive picture of the excitonic process in Ag-doped CdSe nanocrystals and demonstrate that, in contrast to expectations, capture of the photohole leads to conversion of Ag+ to paramagnetic Ag2+. The process of exciton recombination is thus inextricably tied to photoinduced magnetism. Accordingly, we observe strong optically activated magnetism and diluted magnetic semiconductor behaviour, demonstrating that optically switchable magnetic nanomaterials can be obtained by exploiting excitonic processes involving nonmagnetic impurities.

Enhanced Ferromagnetism in Nanoscale GaN:Mn Wires Grown on GaN Ridges.

PubMed

Cheng, Ji; Jiang, Shengxiang; Zhang, Yan; Yang, Zhijian; Wang, Cunda; Yu, Tongjun; Zhang, Guoyi

2017-05-02

The problem of weak magnetism has hindered the application of magnetic semiconductors since their invention, and on the other hand, the magnetic mechanism of GaN-based magnetic semiconductors has been the focus of long-standing debate. In this work, nanoscale GaN:Mn wires were grown on the top of GaN ridges by metalorganic chemical vapor deposition (MOCVD), and the superconducting quantum interference device (SQUID) magnetometer shows that its ferromagnetism is greatly enhanced. Secondary ion mass spectrometry (SIMS) and energy dispersive spectroscopy (EDS) reveal an obvious increase of Mn composition in the nanowire part, and transmission electron microscopy (TEM) and EDS mapping results further indicate the correlation between the abundant stacking faults (SFs) and high Mn doping. When further combined with the micro-Raman results, the magnetism in GaN:Mn might be related not only to Mn concentration, but also to some kinds of built-in defects introduced together with the Mn doping or the SFs.

Semiconductor saturable absorber mirror passively Q-switched 2.97 μm fluoride fiber laser

NASA Astrophysics Data System (ADS)

Li, Jianfeng; Luo, Hongyu; He, Yulian; Liu, Yong; Luo, Binbin; Sun, Zhongyuan; Zhang, Lin; Turitsyn, Sergei K.

2014-05-01

A diode-cladding-pumped mid-infrared passively Q-switched Ho3+-doped fluoride fiber laser using a reverse designed broad band semiconductor saturable mirror (SESAM) was demonstrated. Nonlinear reflectivity of the SESAM was measured using an in-house Yb3+-doped mode-locked fiber laser at 1062 nm. Stable pulse train was produced at a slope efficient of 12.1% with respect to the launched pump power. Maximum pulse energy of 6.65 μJ with a pulse width of 1.68 μs and signal to noise ratio (SNR) of ~50 dB was achieved at a repetition rate of 47.6 kHz and center wavelength of 2.971 μm. To the best of our knowledge, this is the first 3 μm region SESAM based Q-switched fiber laser with the highest average power and pulse energy, as well as the longest wavelength from mid-infrared passively Q-switched fluoride fiber lasers.

Semiconductor saturable absorber mirror passively Q-switched 2.97 μm fluoride fiber laser

NASA Astrophysics Data System (ADS)

Li, J. F.; Luo, H. Y.; He, Y. L.; Liu, Y.; Zhang, L.; Zhou, K. M.; Rozhin, A. G.; Turistyn, S. K.

2014-06-01

A diode-cladding-pumped mid-infrared passively Q-switched Ho3+-doped fluoride fiber laser using a reverse designed broad band semiconductor saturable mirror (SESAM) was demonstrated. Nonlinear reflectivity of the SESAM was measured using an in-house Yb3+-doped mode-locked fiber laser at 1062 nm. Stable pulse train was produced at a slope efficient of 12.1% with respect to the launched pump power. Maximum pulse energy of 6.65 µJ with a pulse width of 1.68 µs and signal-to-noise ratio (SNR) of ~50 dB was achieved at a repetition rate of 47.6 kHz and center wavelength of 2.971 µm. To the best of our knowledge, this is the first 3 µm region SESAM-based Q-switched fiber laser with the highest average power and pulse energy, as well as the longest wavelength from mid-infrared passively Q-switched fluoride fiber lasers.

Cadmium-free junction fabrication process for CuInSe.sub.2 thin film solar cells

DOEpatents

Ramanathan, Kannan V.; Contreras, Miguel A.; Bhattacharya, Raghu N.; Keane, James; Noufi, Rommel

1999-01-01

The present invention provides an economical, simple, dry and controllable semiconductor layer junction forming process to make cadmium free high efficiency photovoltaic cells having a first layer comprised primarily of copper indium diselenide having a thin doped copper indium diselenide n-type region, generated by thermal diffusion with a group II(b) element such as zinc, and a halide, such as chlorine, and a second layer comprised of a conventional zinc oxide bilayer. A photovoltaic device according the present invention includes a first thin film layer of semiconductor material formed primarily from copper indium diselenide. Doping of the copper indium diselenide with zinc chloride is accomplished using either a zinc chloride solution or a solid zinc chloride material. Thermal diffusion of zinc chloride into the copper indium diselenide upper region creates the thin n-type copper indium diselenide surface. A second thin film layer of semiconductor material comprising zinc oxide is then applied in two layers. The first layer comprises a thin layer of high resistivity zinc oxide. The second relatively thick layer of zinc oxide is doped to exhibit low resistivity.

Understanding and control of bipolar self-doping in copper nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fioretti, Angela N., E-mail: afiorett@mines.edu, E-mail: riy.zakutayev@nrel.gov; Tamboli, Adele C.; Caskey, Christopher M.

2016-05-14

Semiconductor materials that can be doped both n-type and p-type are desirable for diode-based applications and transistor technology. Copper nitride (Cu{sub 3}N) is a metastable semiconductor with a solar-relevant bandgap that has been reported to exhibit bipolar doping behavior. However, deeper understanding and better control of the mechanism behind this behavior in Cu{sub 3}N is currently lacking in the literature. In this work, we use combinatorial growth with a temperature gradient to demonstrate both conduction types of phase-pure, sputter-deposited Cu{sub 3}N thin films. Room temperature Hall effect and Seebeck effect measurements show n-type Cu{sub 3}N with 10{sup 17} electrons/cm{sup 3}more » for low growth temperature (≈35 °C) and p-type with 10{sup 15} holes/cm{sup 3}–10{sup 16} holes/cm{sup 3} for elevated growth temperatures (50 °C–120 °C). Mobility for both types of Cu{sub 3}N was ≈0.1 cm{sup 2}/Vs–1 cm{sup 2}/Vs. Additionally, temperature-dependent Hall effect measurements indicate that ionized defects are an important scattering mechanism in p-type films. By combining X-ray absorption spectroscopy and first-principles defect theory, we determined that V{sub Cu} defects form preferentially in p-type Cu{sub 3}N, while Cu{sub i} defects form preferentially in n-type Cu{sub 3}N, suggesting that Cu{sub 3}N is a compensated semiconductor with conductivity type resulting from a balance between donor and acceptor defects. Based on these theoretical and experimental results, we propose a kinetic defect formation mechanism for bipolar doping in Cu{sub 3}N that is also supported by positron annihilation experiments. Overall, the results of this work highlight the importance of kinetic processes in the defect physics of metastable materials and provide a framework that can be applied when considering the properties of such materials in general.« less

Colloidal inorganic nanocrystals: Nucleation, growth and biological applications

NASA Astrophysics Data System (ADS)

Lynch, Jared James

Colloidal inorganic nanocrystals are a class of material whose size ranges from a few nanometers to a hundred nanometers in dimension. These nanocrystals have size dependent properties that differ significantly from the bulk material counterparts. Due to their unique physical properties colloidal inorganic nanocrystals have several promising applications in a diverse range of areas, such as biomedical diagnosis, catalysis, plasmonics, high-density data storage and solar energy conversion. This dissertation presents the study of the formation of iron oxide nanocrystals under the influence of solvent and Ar gas bubbles, the phase transfer of metal oxide nanocrystals into water using inorganic ions, and the doping of semiconductor CdS/ZnS core/shell nanocrystals with copper and silver ions. First, the formation of iron oxide nanocrystals is investigated in the presence of boiling solvent or Ar bubbles. Using a non-injection based synthesis method, the thermal decomposition of iron oleate was studied under various reaction conditions, and the role of the bubbles on the nucleation and growth of iron oxide nanocrystals was determined. Kinetics studies were used to elucidate how latent heat transfer from the bubbles allows for "active monomers" to form preferentially from exothermic reactions taking place during nucleation. General insights into colloidal inorganic nanocrystal formation are discussed. Second, a non-injection based synthesis for CdS/ZnS core/shell nanocrystals is used to make high quality semiconductor particles which are intentionally doped with Cu or Ag ions. The Ag ions effect on the optical properties of the CdS/ZnS nanocrystals is investigated. The absorption and fluorescence of the samples is measured as a function of time and temperature. Proposed mechanisms for the observations are given and thoroughly discussed. Comparisons between previous results for Cu doped CdS/ZnS nanocrystals are also made to further understand how doping of semiconductor nanocrystals can be realized. Finally, a novel phase transfer process is demonstrated using inorganic salts, such as sodium arsenite, to make water soluble metal oxide nanocrystals. The water soluble iron oxide nanocrystals are fully characterized by several complementary techniques and then used in cellular studies. The arsenite-coated iron oxide composite nanocrystals (AICN) are shown to be effective cancer therapy agents.

Hypervalent surface interactions for colloidal stability and doping of silicon nanocrystals

PubMed Central

Wheeler, Lance M.; Neale, Nathan R.; Chen, Ting; Kortshagen, Uwe R.

2013-01-01

Colloidal semiconductor nanocrystals have attracted attention for cost-effective, solution-based deposition of quantum-confined thin films for optoelectronics. However, two significant challenges must be addressed before practical nanocrystal-based devices can be realized. The first is coping with the ligands that terminate the nanocrystal surfaces. Though ligands provide the colloidal stability needed to cast thin films from solution, these ligands dramatically hinder charge carrier transport in the resulting film. Second, after a conductive film is achieved, doping has proven difficult for further control of the optoelectronic properties of the film. Here we report the ability to confront both of these challenges by exploiting the ability of silicon to engage in hypervalent interactions with hard donor molecules. For the first time, we demonstrate the significant potential of applying the interaction to the nanocrystal surface. In this study, hypervalent interactions are shown to provide colloidal stability as well as doping of silicon nanocrystals. PMID:23893292

Bipolar doping and band-gap anomalies in delafossite transparent conductive oxides.

PubMed

Nie, Xiliang; Wei, Su-Huai; Zhang, S B

2002-02-11

Doping wide-gap materials p type is highly desirable but often difficult. This makes the recent discovery of p-type delafossite oxides, CuM(III)O2, very attractive. The CuM(III)O2 also show unique and unexplained physical properties: Increasing band gap from M(III) = Al,Ga, to In, not seen in conventional semiconductors. The largest gap CuInO2 can be mysteriously doped both n and p type but not the smaller gaps CuAlO2 and CuGaO2. Here, we show that both properties are results of a large disparity between the fundamental gap and the apparent optical gap, a finding that could lead to a breakthrough in the study of bipolarly dopable wide-gap semiconductor oxides.

High gain photoconductive semiconductor switch having tailored doping profile zones

DOEpatents

Baca, Albert G.; Loubriel, Guillermo M.; Mar, Alan; Zutavern, Fred J; Hjalmarson, Harold P.; Allerman, Andrew A.; Zipperian, Thomas E.; O'Malley, Martin W.; Helgeson, Wesley D.; Denison, Gary J.; Brown, Darwin J.; Sullivan, Charles T.; Hou, Hong Q.

2001-01-01

A photoconductive semiconductor switch with tailored doping profile zones beneath and extending laterally from the electrical contacts to the device. The zones are of sufficient depth and lateral extent to isolate the contacts from damage caused by the high current filaments that are created in the device when it is turned on. The zones may be formed by etching depressions into the substrate, then conducting epitaxial regrowth in the depressions with material of the desired doping profile. They may be formed by surface epitaxy. They may also be formed by deep diffusion processes. The zones act to reduce the energy density at the contacts by suppressing collective impact ionization and formation of filaments near the contact and by reducing current intensity at the contact through enhanced current spreading within the zones.

SEMICONDUCTOR PHYSICS Dose-rate dependence of optically stimulated luminescence signal

NASA Astrophysics Data System (ADS)

Pingqiang, Wei; Zhaoyang, Chen; Yanwei, Fan; Yurun, Sun; Yun, Zhao

2010-10-01

Optically stimulated luminescence (OSL) is the luminescence emitted from a semiconductor during its exposure to light. The OSL intensity is a function of the total dose absorbed by the sample. The dose-rate dependence of the OSL signal of the semiconductor CaS doped Ce and Sm was studied by numerical simulation and experiments. Based on a one-trap/one-center model, the whole OSL process was represented by a series of differential equations. The dose-rate properties of the materials were acquired theoretically by solving the equations. Good coherence was achieved between numerical simulation and experiments, both of which showed that the OSL signal was independent of dose rate. This result validates that when using OSL as a dosimetry technique, the dose-rate effect can be neglected.

Weak doping dependence of the antiferromagnetic coupling between nearest-neighbor Mn2 + spins in (Ba1 -xKx) (Zn1-yMny) 2As2

NASA Astrophysics Data System (ADS)

Surmach, M. A.; Chen, B. J.; Deng, Z.; Jin, C. Q.; Glasbrenner, J. K.; Mazin, I. I.; Ivanov, A.; Inosov, D. S.

2018-03-01

Dilute magnetic semiconductors (DMS) are nonmagnetic semiconductors doped with magnetic transition metals. The recently discovered DMS material (Ba1 -xKx) (Zn1-yMny) 2As2 offers a unique and versatile control of the Curie temperature TC by decoupling the spin (Mn2 +, S =5 /2 ) and charge (K+) doping in different crystallographic layers. In an attempt to describe from first-principles calculations the role of hole doping in stabilizing ferromagnetic order, it was recently suggested that the antiferromagnetic exchange coupling J between the nearest-neighbor Mn ions would experience a nearly twofold suppression upon doping 20% of holes by potassium substitution. At the same time, further-neighbor interactions become increasingly ferromagnetic upon doping, leading to a rapid increase of TC. Using inelastic neutron scattering, we have observed a localized magnetic excitation at about 13 meV associated with the destruction of the nearest-neighbor Mn-Mn singlet ground state. Hole doping results in a notable broadening of this peak, evidencing significant particle-hole damping, but with only a minor change in the peak position. We argue that this unexpected result can be explained by a combined effect of superexchange and double-exchange interactions.

Study of Sn and Mg doping effects on TiO2/Ge stack structure by combinatorial synthesis

NASA Astrophysics Data System (ADS)

Nagata, Takahiro; Suzuki, Yoshihisa; Yamashita, Yoshiyuki; Ogura, Atsushi; Chikyow, Toyohiro

2018-04-01

The effects of Sn and Mg doping of a TiO2 film on a Ge substrate were investigated to improve leakage current properties and Ge diffusion into the TiO2 film. For systematic analysis, dopant-composition-spread TiO2 samples with dopant concentrations of up to 20.0 at. % were fabricated by RF sputtering and a combinatorial method. X-ray photoelectron spectroscopy revealed that the instability of Mg doping of TiO2 at dopant concentrations above 10.5 at. %. Both Sn and Mg dopants reduced Ge diffusion into TiO2. Sn doping enhanced the crystallization of the rutile phase, which is a high-dielectric-constant phase, although the Mg-doped TiO2 film indicated an amorphous structure. Sn-doping indicated systematic leakage current reduction with increasing dopant concentration. Doping at Sn concentrations higher than 16.8 at. % improved the leakage properties (˜10-7 A/cm2 at -3.0 V) and capacitance-voltage properties of metal-insulator-semiconductor (MIS) operation. The Sn doping of TiO2 may be useful for interface control and as a dielectric material for Ge-based MIS capacitors.

Effect of Nitrogen Doping Level on the Performance of N-Doped Carbon Quantum Dot/TiO2 Composites for Photocatalytic Hydrogen Evolution.

PubMed

Shi, Run; Li, Zi; Yu, Huijun; Shang, Lu; Zhou, Chao; Waterhouse, Geoffrey I N; Wu, Li-Zhu; Zhang, Tierui

2017-11-23

Carbon quantum dots (CQDs) have attracted widespread interest for photocatalytic applications, owing to their low cost and excellent electron donor/acceptor properties. However, their advancement as visible-light photosensitizers in CQDs/semiconductor nanocomposites is currently impaired by their poor quantum yields (QYs). Herein, we describe the successful fabrication of a series of nitrogen-doped CQDs (NCDs) with N/C atomic ratios ranging from 0.14-0.30. NCDs with the highest N-doping level afforded a remarkable external QY of 66.8 % at 360 nm, and outstanding electron transfer properties and photosensitization efficiencies when physically adsorbed on P25 TiO 2 . A NCDs/P25-TiO 2 hybrid demonstrated excellent performance for hydrogen evolution in aqueous methanol under both UV and visible-light illumination relative to pristine P25 TiO 2 . Controlled nitrogen doping of CQDs therefore represents a very effective strategy for optimizing the performance of CQDs/semiconductor hybrid photocatalysts. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analysis of Photoluminescence Thermal Quenching: Guidance for the Design of Highly Effective p-type Doping of Nitrides

PubMed Central

Liu, Zhiqiang; Huang, Yang; Yi, Xiaoyan; Fu, Binglei; Yuan, Guodong; Wang, Junxi; Li, Jinmin; Zhang, Yong

2016-01-01

A contact-free diagnostic technique for examining position of the impurity energy level of p-type dopants in nitride semiconductors was proposed based on photoluminescence thermal quenching. The Mg ionization energy was extracted by the phenomenological rate-equation model we developed. The diagnostic technique and analysis model reported here are priorities for the design of highly effective p-doping of nitrides and could also be used to explain the abnormal and seldom analyzed low characteristic temperature T0 (about 100 K) of thermal quenching in p-type nitrides systems. An In-Mg co-doped GaN system is given as an example to prove the validity of our methods. Furthermore, a hole concentration as high as 1.94 × 1018 cm−3 was achieved through In-Mg co-doping, which is nearly one order of magnitude higher than typically obtained in our lab. PMID:27550805

Analysis of Photoluminescence Thermal Quenching: Guidance for the Design of Highly Effective p-type Doping of Nitrides.

PubMed

Liu, Zhiqiang; Huang, Yang; Yi, Xiaoyan; Fu, Binglei; Yuan, Guodong; Wang, Junxi; Li, Jinmin; Zhang, Yong

2016-08-23

A contact-free diagnostic technique for examining position of the impurity energy level of p-type dopants in nitride semiconductors was proposed based on photoluminescence thermal quenching. The Mg ionization energy was extracted by the phenomenological rate-equation model we developed. The diagnostic technique and analysis model reported here are priorities for the design of highly effective p-doping of nitrides and could also be used to explain the abnormal and seldom analyzed low characteristic temperature T0 (about 100 K) of thermal quenching in p-type nitrides systems. An In-Mg co-doped GaN system is given as an example to prove the validity of our methods. Furthermore, a hole concentration as high as 1.94 × 10(18) cm(-3) was achieved through In-Mg co-doping, which is nearly one order of magnitude higher than typically obtained in our lab.

Analysis of Photoluminescence Thermal Quenching: Guidance for the Design of Highly Effective p-type Doping of Nitrides

NASA Astrophysics Data System (ADS)

Liu, Zhiqiang; Huang, Yang; Yi, Xiaoyan; Fu, Binglei; Yuan, Guodong; Wang, Junxi; Li, Jinmin; Zhang, Yong

2016-08-01

A contact-free diagnostic technique for examining position of the impurity energy level of p-type dopants in nitride semiconductors was proposed based on photoluminescence thermal quenching. The Mg ionization energy was extracted by the phenomenological rate-equation model we developed. The diagnostic technique and analysis model reported here are priorities for the design of highly effective p-doping of nitrides and could also be used to explain the abnormal and seldom analyzed low characteristic temperature T0 (about 100 K) of thermal quenching in p-type nitrides systems. An In-Mg co-doped GaN system is given as an example to prove the validity of our methods. Furthermore, a hole concentration as high as 1.94 × 1018 cm-3 was achieved through In-Mg co-doping, which is nearly one order of magnitude higher than typically obtained in our lab.

Multi-color Long Wavelength Infrared Detectors Based On III-V Semiconductors

DTIC Science & Technology

2010-07-30

both interband and intersubband transitions that form the basis of may optoelectronic devices. The research performed under this grant made it...based on interband and intersubband transitions in InAs and InGaAs QDs as a means for room temperature, multi-color photodetection in the visible...AM1.5 standard solar simulator. DOPING EFFECT ON INTERBAND AND INTERSUBBAND MULTICOLOR INFRARED PHOTODETECTORS: First, many samples and devices

Observation of hole hopping via dopant in MoOx-doped organic semiconductors: Mechanism analysis and application for high performance organic light-emitting devices

NASA Astrophysics Data System (ADS)

Qiao, Xianfeng; Chen, Jiangshan; Li, Xinglin; Ma, Dongge

2010-05-01

Conduction mechanism in molybdenum trioxide (MoOx)-doped hole- and electron-type organic semiconductors is investigated. The used hole-transporting materials are N ,N'-diphenyl-N ,N'-bis(1-naphthylphenyl)-1, 1'-biphen4, 4'-diamine, 4',4″-tri(N-carbazolyl)triphenylamine, 4, 4'-N,N-dicarbazole-biphenyl, and pentacene and the used electron-transporting material is (8-quinolinolato) aluminum (Alq3). It can be seen that the hole conductivity is significantly enhanced upon MoOx doping, and more importantly, dominant hole current could be realized in a typical electron-transport material Alq3 by doping MoOx. Hence, high efficiency organic light-emitting devices can also be achieved even using MoOx-doped Alq3 film as hole transporting layer. The mechanism investigation indicates that the MoOx plays an important role in the hole transport. It is showed that the MoOx serves as the hole hopping sites, whereas the used organic materials serve as the transport medium and determine the magnitude of transport current. Furthermore, it is found that doping MoOx into the organic materials also reduces the energy and position disorders of the doped organic films, which are well demonstrated by the study on transport characteristics of the doped films at various temperatures.

Surface Passivation by Quantum Exclusion Using Multiple Layers

NASA Technical Reports Server (NTRS)

Hoenk, Michael E. (Inventor)

2013-01-01

A semiconductor device has a multilayer doping to provide improved passivation by quantum exclusion. The multilayer doping includes a plurality M of doped layers, where M is an integer greater than 1. The dopant sheet densities in the M doped layers need not be the same, but in principle can be selected to be the same sheet densities or to be different sheet densities. M-1 interleaved layers provided between the M doped layers are not deliberately doped (also referred to as "undoped layers"). Structures with M=2, M=3 and M=4 have been demonstrated and exhibit improved passivation.

PULSION® HP: Tunable, High Productivity Plasma Doping

NASA Astrophysics Data System (ADS)

Felch, S. B.; Torregrosa, F.; Etienne, H.; Spiegel, Y.; Roux, L.; Turnbaugh, D.

2011-01-01

Plasma doping has been explored for many implant applications for over two decades and is now being used in semiconductor manufacturing for two applications: DRAM polysilicon counter-doping and contact doping. The PULSION HP is a new plasma doping tool developed by Ion Beam Services for high-volume production that enables customer control of the dominant mechanism—deposition, implant, or etch. The key features of this tool are a proprietary, remote RF plasma source that enables a high density plasma with low chamber pressure, resulting in a wide process space, and special chamber and wafer electrode designs that optimize doping uniformity.

Process Control in Production-Worthy Plasma Doping Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winder, Edmund J.; Fang Ziwei; Arevalo, Edwin

2006-11-13

As the semiconductor industry continues to scale devices of smaller dimensions and improved performance, many ion implantation processes require lower energy and higher doses. Achieving these high doses (in some cases {approx}1x1016 ions/cm2) at low energies (<3 keV) while maintaining throughput is increasingly challenging for traditional beamline implant tools because of space-charge effects that limit achievable beam density at low energies. Plasma doping is recognized as a technology which can overcome this problem. In this paper, we highlight the technology available to achieve process control for all implant parameters associated with modem semiconductor manufacturing.

Large n- and p-type thermoelectric power factors from doped semiconducting single-walled carbon nanotube thin films

DOE PAGES

MacLeod, Bradley A.; Stanton, Noah J.; Gould, Isaac E.; ...

2017-09-08

Lightweight, robust, and flexible single-walled carbon nanotube (SWCNT) materials can be processed inexpensively using solution-based techniques, similar to other organic semiconductors. In contrast to many semiconducting polymers, semiconducting SWCNTs (s-SWCNTs) represent unique one-dimensional organic semiconductors with chemical and physical properties that facilitate equivalent transport of electrons and holes. These factors have driven increasing attention to employing s-SWCNTs for electronic and energy harvesting applications, including thermoelectric (TE) generators. Here we demonstrate a combination of ink chemistry, solid-state polymer removal, and charge-transfer doping strategies that enable unprecedented n-type and p-type TE power factors, in the range of 700 μW m –1 Kmore » –2 at 298 K for the same solution-processed highly enriched thin films containing 100% s-SWCNTs. We also demonstrate that the thermal conductivity appears to decrease with decreasing s-SWCNT diameter, leading to a peak material zT ≈ 0.12 for s-SWCNTs with diameters in the range of 1.0 nm. Here, our results indicate that the TE performance of s-SWCNT-only material systems is approaching that of traditional inorganic semiconductors, paving the way for these materials to be used as the primary components for efficient, all-organic TE generators.« less

UV/ozone assisted local graphene (p)/ZnO(n) heterojunctions as a nanodiode rectifier

NASA Astrophysics Data System (ADS)

Sahatiya, Parikshit; Badhulika, Sushmee

2016-07-01

Here we report the fabrication of a novel graphene/ZnO nanodiode by UV/ozone assisted oxidation of graphene and demonstrate its application as a half-wave rectifier to generate DC voltage. The method involves the use of electrospinning for one-step in situ synthesis and alignment of single Gr/ZnO nanocomposite across metal electrodes. On subsequent UV illumination, graphene oxidizes, which induces p type doping and ZnO being an n type semiconductor, thus resulting in the formation of a nanodiode. The as-fabricated device shows strong non-linear current-voltage characteristic similar to that of conventional semiconductor p-n junction diodes. Excellent rectifying behavior with a rectification ratio of ~103 was observed and the nanodiodes were found to exhibit long-term repeatability in their performance. Ideality factor and barrier height, as calculated by the thermionic emission model, were found to be 1.6 and 0.504 eV respectively. Due to the fact that diodes are the basic building blocks in the electronics and semiconductor industry, the successful fabrication of these nanodiodes based on UV assisted p type doping of graphene indicates that this approach can be used for developing highly scalable and efficient components for nanoelectronics, such as rectifiers and logic gates that find applications in numerous fields.

Structural and electrical properties of Si- and Ti-doped Cu{sub 2}SnSe{sub 3} bulks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wubet, Walelign; Kuo, Dong-Hau, E-mail: dhkuo@mail.ntust.edu.tw

2015-07-15

Silicon-doped (Cu{sub 2}(Sn{sub 1−x}Si{sub x})Se{sub 3} and titanium-doped (Cu{sub 2}(Sn{sub 1−x}Ti{sub x})Se{sub 3} at x=0, 0.05, 0.1, 0.15, and 0.2 were prepared at 550 °C for 2 h with soluble sintering aids of volatile Sb{sub 2}S{sub 3} and Te. Defect chemistry was studied by measuring structural and electrical properties of Si-doped and Ti-doped Cu{sub 2}SnSe{sub 3} (CTSe) as a function of dopant concentration. Si-doped CTSe pellets show p-type at x=0 and 0.05 and n-type at x=0.1, 0.15, and 0.2, whereas Ti-doped CTSe pellets show p-type at x=0, 0.05 and 0.1 and n-type at x=0.15 and 0.2. The lowest hole concentrationmore » of 3.6×10{sup 17} cm{sup −3} and the highest mobility of 1525 cm{sup 2} V{sup −1} s{sup −1} were obtained for the Si-doped (Cu{sub 2}(Sn{sub 1−x}Si{sub x})Se{sub 3} bulks at x=0.1 (10% Si), while they were 3.1×10{sup 17} cm{sup −3} and 813 cm{sup 2} V{sup −1} s{sup −1} for the Ti-doped CTSe bulks at x=0.15 (15% Ti), as compared to 1.1×10{sup 18} cm{sup −3} and 209 cm{sup 2} V{sup −1} s{sup −1} for undoped one. The explanations based upon antisite defects of Si-to-Sn, Ti-to-Sn, Cu-to-Sn, and Sn-to-Cu for the changes in electrical property were declared. The study in bulk Si-doped and Ti-doped CTSe is based upon defect state and is consistent and supported by the data of electrical property and lattice parameter. - Graphical abstract: Cu{sub 2}SnSe{sub 3} (CTSe) semiconductor is interesting because of its adjustable electrical properties by extrinsic doping. Si and Ti doping in CTSe leads to high carrier mobility above 800 cm{sup 2} V{sup −1} s{sup −1}. - Highlights: • Cu{sub 2}SnSe{sub 3} (CTSe) is an interesting semiconductor because of its adjustable electrical properties. • Cu(In,Ga)Se{sub 2}, on the contrary, is difficult to change its electrical properties. • Si and Ti doping can change p-CTSe to n-CTSe. • The lowest electron concentration in doped CTSe had the highest mobility above 800 cm{sup 2} V{sup −1} s{sup −1}. • The defects of Si-to-Sn, Ti-to-Sn, Cu-to-Sn, and Sn-to-Cu in Si- and Ti-doped CTSe were proposed.« less

Junction-based field emission structure for field emission display

DOEpatents

Dinh, Long N.; Balooch, Mehdi; McLean, II, William; Schildbach, Marcus A.

2002-01-01

A junction-based field emission display, wherein the junctions are formed by depositing a semiconducting or dielectric, low work function, negative electron affinity (NEA) silicon-based compound film (SBCF) onto a metal or n-type semiconductor substrate. The SBCF can be doped to become a p-type semiconductor. A small forward bias voltage is applied across the junction so that electron transport is from the substrate into the SBCF region. Upon entering into this NEA region, many electrons are released into the vacuum level above the SBCF surface and accelerated toward a positively biased phosphor screen anode, hence lighting up the phosphor screen for display. To turn off, simply switch off the applied potential across the SBCF/substrate. May be used for field emission flat panel displays.

Nonequilibrium-Plasma-Synthesized ZnO Nanocrystals with Plasmon Resonance Tunable via Al Doping and Quantum Confinement.

PubMed

Greenberg, Benjamin L; Ganguly, Shreyashi; Held, Jacob T; Kramer, Nicolaas J; Mkhoyan, K Andre; Aydil, Eray S; Kortshagen, Uwe R

2015-12-09

Metal oxide semiconductor nanocrystals (NCs) exhibit localized surface plasmon resonances (LSPRs) tunable within the infrared (IR) region of the electromagnetic spectrum by vacancy or impurity doping. Although a variety of these NCs have been produced using colloidal synthesis methods, incorporation and activation of dopants in the liquid phase has often been challenging. Herein, using Al-doped ZnO (AZO) NCs as an example, we demonstrate the potential of nonthermal plasma synthesis as an alternative strategy for the production of doped metal oxide NCs. Exploiting unique, thoroughly nonequilibrium synthesis conditions, we obtain NCs in which dopants are not segregated to the NC surfaces and local doping levels are high near the NC centers. Thus, we achieve overall doping levels as high as 2 × 10(20) cm(-3) in NCs with diameters ranging from 12.6 to 3.6 nm, and for the first time experimentally demonstrate a clear quantum confinement blue shift of the LSPR energy in vacancy- and impurity-doped semiconductor NCs. We propose that doping of central cores and heavy doping of small NCs are achievable via nonthermal plasma synthesis, because chemical potential differences between dopant and host atoms-which hinder dopant incorporation in colloidal synthesis-are irrelevant when NC nucleation and growth proceed via irreversible interactions among highly reactive gas-phase ions and radicals and ligand-free NC surfaces. We explore how the distinctive nucleation and growth kinetics occurring in the plasma influences dopant distribution and activation, defect structure, and impurity phase formation.

Plasmonic-Electronic Transduction

DTIC Science & Technology

2012-01-31

including metal silicides (Pt-, Pd-, Ni-, W- silicides ), semimetals (Sb, Bi, graphite), doped-semiconductors (Si, CuInSe), and conducting polymers... silicides and doped silicon,” J. W. Cleary, R. E. Peale, D. J. Shelton, G. D. Boreman, C. W. Smith, M. Ishigami, R. Soref, A. Drehman, W.R. Buchwald

A primary exploration to quasi-two-dimensional rare-earth ferromagnetic particles: holmium-doped MoS2 sheet as room-temperature magnetic semiconductor

NASA Astrophysics Data System (ADS)

Chen, Xi; Lin, Zheng-Zhe

2018-05-01

Recently, two-dimensional materials and nanoparticles with robust ferromagnetism are even of great interest to explore basic physics in nanoscale spintronics. More importantly, room-temperature magnetic semiconducting materials with high Curie temperature is essential for developing next-generation spintronic and quantum computing devices. Here, we develop a theoretical model on the basis of density functional theory calculations and the Ruderman-Kittel-Kasuya-Yoshida theory to predict the thermal stability of two-dimensional magnetic materials. Compared with other rare-earth (dysprosium (Dy) and erbium (Er)) and 3 d (copper (Cu)) impurities, holmium-doped (Ho-doped) single-layer 1H-MoS2 is proposed as promising semiconductor with robust magnetism. The calculations at the level of hybrid HSE06 functional predict a Curie temperature much higher than room temperature. Ho-doped MoS2 sheet possesses fully spin-polarized valence and conduction bands, which is a prerequisite for flexible spintronic applications.

Accurate calculation of field and carrier distributions in doped semiconductors

NASA Astrophysics Data System (ADS)

Yang, Wenji; Tang, Jianping; Yu, Hongchun; Wang, Yanguo

2012-06-01

We use the numerical squeezing algorithm(NSA) combined with the shooting method to accurately calculate the built-in fields and carrier distributions in doped silicon films (SFs) in the micron and sub-micron thickness range and results are presented in graphical form for variety of doping profiles under different boundary conditions. As a complementary approach, we also present the methods and the results of the inverse problem (IVP) - finding out the doping profile in the SFs for given field distribution. The solution of the IVP provides us the approach to arbitrarily design field distribution in SFs - which is very important for low dimensional (LD) systems and device designing. Further more, the solution of the IVP is both direct and much easy for all the one-, two-, and three-dimensional semiconductor systems. With current efforts focused on the LD physics, knowing of the field and carrier distribution details in the LD systems will facilitate further researches on other aspects and hence the current work provides a platform for those researches.

(Sr{sub 1-x}Na{sub x})(Cd{sub 1-x}Mn{sub x}){sub 2}As{sub 2}: A new charge and spin doping decoupled diluted magnetic semiconductors with CaAl{sub 2}Si{sub 2}-type structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Bijuan; Deng, Zheng; Li, Wenmin

2016-08-28

We report the synthesis and characterization of a new bulk diluted ferromagnetic semiconductor via Na and Mn co-doping in SrCd{sub 2}As{sub 2} with a hexagonal CaAl{sub 2}Si{sub 2}-type structure. Together with carrier doping via (Sr,Na) substitution, spin doping via (Cd,Mn) substitution results in ferromagnetic order with Curie temperature of T{sub C} up to 13 K. Negative magnetoresistance is assigned to weak localization at low temperatures, where the magnetization of samples becomes saturated. The hexagonal structure of (Sr{sub 1−x}Na{sub x})(Cd{sub 1−x}Mn{sub x}){sub 2}As{sub 2} can be acted as a promising candidate for spin manipulations owing to its relatively small coercive field ofmore » less than 24 Oe.« less

Nonlinear Elasticity of Doped Semiconductors

DTIC Science & Technology

2017-02-01

experimental data from the Stanford University group. The obtained results show that the goal of the project has been reached. MSU has full...length extension modes in n-doped silicon (Si) microelectromechanical (MEMS) resonators and have started a comparison with the experimental data from...coupling to shear strain modes. • Tested the theory against the existing in the literature experimental data on the effect of doping on the speed of

Conjugated-Backbone Effect of Organic Small Molecules for n-Type Thermoelectric Materials with ZT over 0.2.

PubMed

Huang, Dazhen; Yao, Huiying; Cui, Yutao; Zou, Ye; Zhang, Fengjiao; Wang, Chao; Shen, Hongguang; Jin, Wenlong; Zhu, Jia; Diao, Ying; Xu, Wei; Di, Chong-An; Zhu, Daoben

2017-09-20

Conjugated backbones play a fundamental role in determining the electronic properties of organic semiconductors. On the basis of two solution-processable dihydropyrrolo[3,4-c]pyrrole-1,4-diylidenebis(thieno[3,2-b]thiophene) derivatives with aromatic and quinoid structures, we have carried out a systematic study of the relationship between the conjugated-backbone structure and the thermoelectric properties. In particular, a combination of UV-vis-NIR spectra, photoemission spectroscopy, and doping optimization are utilized to probe the interplay between energy levels, chemical doping, and thermoelectric performance. We found that a moderate change in the conjugated backbone leads to varied doping mechanisms and contributes to dramatic changes in the thermoelectric performance. Notably, the chemically doped A-DCV-DPPTT, a small molecule with aromatic structure, exhibits an electrical conductivity of 5.3 S cm -1 and a high power factor (PF 373 K ) up to 236 μW m -1 K -2 , which is 50 times higher than that of Q-DCM-DPPTT with a quinoid structure. More importantly, the low thermal conductivity enables A-DCV-DPPTT to possess a figure of merit (ZT) of 0.23 ± 0.03, which is the highest value reported to date for thermoelectric materials based on organic small molecules. These results demonstrate that the modulation of the conjugated backbone represents a powerful strategy for tuning the electronic structure and mobility of organic semiconductors toward a maximum thermoelectric performance.

Spin Hall Effect in Doped Semiconductor Structures

NASA Astrophysics Data System (ADS)

Tse, Wang-Kong; Das Sarma, S.

2006-02-01

In this Letter we present a microscopic theory of the extrinsic spin Hall effect based on the diagrammatic perturbation theory. Side-jump and skew-scattering contributions are explicitly taken into account to calculate the spin Hall conductivity, and we show that their effects scale as σxySJ/σxySS˜(ℏ/τ)/ɛF, with τ being the transport relaxation time. Motivated by recent experimental work we apply our theory to n- and p-doped 3D and 2D GaAs structures, obtaining σs/σc˜10-3-10-4, where σs(c) is the spin Hall (charge) conductivity, which is in reasonable agreement with the recent experimental results of Kato et al. [Science 306, 1910 (2004)]SCIEAS0036-807510.1126/science.1105514 in n-doped 3D GaAs system.

Metal-Semiconductor Nanocomposites for High Efficiency Thermoelectric Power Generation

DTIC Science & Technology

2013-12-07

standard III–V compound semiconductor processing techniques with terbium- doped InGaAs of high terbium concentration, Journal of Vacuum Science...even lower the required temperature for strong covalent bonding. We performed the oxide bonding for this substrate transfer task (see Figure 16 for...appropriate controls for assessing ErSb:InGaSb and other nanocomposites of p-type III-V compound semiconductors and their alloys. UCSC group calculated

High Thermoelectric Power Factor of a Diketopyrrolopyrrole-Based Low Bandgap Polymer via Finely Tuned Doping Engineering

PubMed Central

Jung, In Hwan; Hong, Cheon Taek; Lee, Un-Hak; Kang, Young Hun; Jang, Kwang-Suk; Cho, Song Yun

2017-01-01

We studied the thermoelectric properties of a diketopyrrolopyrrole-based semiconductor (PDPP3T) via a precisely tuned doping process using Iron (III) chloride. In particular, the doping states of PDPP3T film were linearly controlled depending on the dopant concentration. The outstanding Seebeck coefficient of PDPP3T assisted the excellent power factors (PFs) over 200 μW m−1K−2 at the broad range of doping concentration (3–8 mM) and the maximum PF reached up to 276 μW m−1K−2, which is much higher than that of poly(3-hexylthiophene), 56 μW m−1K−2. The high-mobility of PDPP3T was beneficial to enhance the electrical conductivity and the low level of total dopant volume was important to maintain high Seebeck coefficients. In addition, the low bandgap PDPP3T polymer effiectively shifted its absorption into near infra-red area and became more colorless after doping, which is great advantage to realize transparent electronic devices. Our results give importance guidance to develop thermoelectric semiconducting polymers and we suggest that the use of low bandgap and high-mobility polymers, and the accurate control of the doping levels are key factors for obtaining the high thermoelectric PF. PMID:28317929

Gas-Sensing Devices Based on Zn-Doped NiO Two-Dimensional Grainy Films with Fast Response and Recovery for Ammonia Molecule Detection

NASA Astrophysics Data System (ADS)

Wang, Jian; Wei, Xiaowei; Wangyang, Peihua

2015-12-01

Zn-doped NiO two-dimensional grainy films on glass substrates are shown to be an ammonia-sensing material with excellent comprehensive performance, which could real-time detect and monitor ammonia (NH3) in the surrounding environment. The morphology and structure analysis indicated that the as-fabricated semiconductor films were composed of particles with diameters ranging from 80 to 160 nm, and each particle was composed of small crystalline grain with a narrow size about 20 nm, which was the face-centered cubic single crystal structure. X-ray diffraction peaks shifted toward lower angle, and the size of the lattice increased compared with undoped NiO, which demonstrated that zinc ions have been successfully doped into the NiO host structure. Simultaneously, we systematically investigated the gas-sensing properties of the Zn-doped NiO sensors for NH3 detection at room temperature. The sensor based on doped NiO sensing films gave four to nine times faster response and four to six times faster recovery speeds than those of sensor with undoped NiO films, which is important for the NiO sensor practical applications. Moreover, we found that the doped NiO sensors owned outstanding selectivity toward ammonia.

A simplified approach to the band gap correction of defect formation energies: Al, Ga, and In-doped ZnO

NASA Astrophysics Data System (ADS)

Saniz, R.; Xu, Y.; Matsubara, M.; Amini, M. N.; Dixit, H.; Lamoen, D.; Partoens, B.

2013-01-01

The calculation of defect levels in semiconductors within a density functional theory approach suffers greatly from the band gap problem. We propose a band gap correction scheme that is based on the separation of energy differences in electron addition and relaxation energies. We show that it can predict defect levels with a reasonable accuracy, particularly in the case of defects with conduction band character, and yet is simple and computationally economical. We apply this method to ZnO doped with group III elements (Al, Ga, In). As expected from experiment, the results indicate that Zn substitutional doping is preferred over interstitial doping in Al, Ga, and In-doped ZnO, under both zinc-rich and oxygen-rich conditions. Further, all three dopants act as shallow donors, with the +1 charge state having the most advantageous formation energy. Also, doping effects on the electronic structure of ZnO are sufficiently mild so as to affect little the fundamental band gap and lowest conduction bands dispersion, which secures their n-type transparent conducting behavior. A comparison with the extrapolation method based on LDA+U calculations and with the Heyd-Scuseria-Ernzerhof hybrid functional (HSE) shows the reliability of the proposed scheme in predicting the thermodynamic transition levels in shallow donor systems.

Atomic-scale investigations of current and future devices: from nitride-based transistors to quantum computing

NASA Astrophysics Data System (ADS)

Gordon, Luke

Our era is defined by its technology, and our future is dependent on its continued evolution. Over the past few decades, we have witnessed the expansion of advanced technology into all walks of life and all industries, driven by the exponential increase in the speed and power of semiconductor-based devices. However, as the length scale of devices reaches the atomic scale, a deep understanding of atomistic theory and its application is increasingly crucial. In order to illustrate the power of an atomistic approach to understanding devices, we will present results and conclusions from three interlinked projects: n-type doping of III-nitride semiconductors, defects for quantum computing, and macroscopic simulations of devices. First, we will study effective n-type doping of III-nitride semiconductors and their alloys, and analyze the barriers to effective n-type doping of III-nitrides and their alloys. In particular, we will study the formation of DX centers, and predict alloy composition onsets for various III-nitride alloys. In addition, we will perform a comprehensive study of alternative dopants, and provide potential alternative dopants to improve n-type conductivity in AlN and wide-band-gap nitride alloys. Next, we will discuss how atomic-scale defects can act as a curse for the development of quantum computers by contributing to decoherence at an atomic scale, specifically investigating the effect of two-level state defects (TLS) systems in alumina as a source of decoherence in superconducting qubits based on Josephson junctions; and also as a blessing, by allowing the identification of wholly new qubits in different materials, specifically showing calculations on defects in SiC for quantum computing applications. Finally, we will provide examples of recent calculations we have performed for devices using macrosopic device simulations, largely in conjunction with first-principles calculations. Specifically, we will discuss the power of using a multi-scale approach to accurately model oxide and nitride-based heterostructures, and thereby illustrate our ability to predict device performance on scales unreachable using a purely first-principles approach.

Notes on the plasma resonance peak employed to determine doping in SiC

DOE PAGES

Engelbrecht, J. A. A.; van Rooyen, I. J.; Henry, A.; ...

2015-07-23

In this study, the doping level of a semiconductor material can be determined using the plasma resonance frequency to obtain the carrier concentration associated with doping. This paper provides an overview of the procedure for the three most common polytypes of SiC. Results for 3C-SiC are presented and discussed. In phosphorus doped samples analysed, it is submitted that the 2nd plasma resonance cannot be detected due to high values of the free carrier damping constant γ.

Work function characterization of solution-processed cobalt silicide

DOE PAGES

Ullah, Syed Shihab; Robinson, Matt; Hoey, Justin; ...

2012-05-08

Cobalt silicide thin films were prepared by spin-coating Si6H12-based inks onto various substrates followed by a thermal treatment. The work function of the solution processed Co-Si was determined by both capacitance-voltage (C-V) measurements of metal-oxide-semiconductor (MOS) structures as well as by ultraviolet photoelectron spectroscopy (UPS). The UPS-derived work function was 4.80 eV for a Co-Si film on Si (100) while C-V of MOS structures yielded a work function of 4.36 eV where the metal was solution-processed Co-Si, the oxide was SiO2 and the semiconductor was a B-doped Si wafer.

Silicon carbide novel optical sensor for combustion systems and nuclear reactors

NASA Astrophysics Data System (ADS)

Lim, Geunsik; Kar, Aravinda

2014-09-01

Crystalline silicon carbide is a wide bandgap semiconductor material with excellent optical properties, chemical inertness, radiation hardness and high mechanical strength at high temperatures. It is an excellent material platform for sensor applications in harsh environments such as combustion systems and nuclear reactors. A laser doping technique is used to fabricate SiC sensors for different combustion gases such as CO2, CO, NO and NO2. The sensor operates based on the principle of semiconductor optics, producing optical signal in contrast to conventional electrical sensors that produces electrical signal. The sensor response is measured with a low power He-Ne or diode laser.

Better Ohmic Contacts For InP Semiconductor Devices

NASA Technical Reports Server (NTRS)

Weizer, Victor G.; Fatemi, Navid S.

1995-01-01

Four design modifications enable fabrication of improved ohmic contacts on InP-based semiconductor devices. First modification consists of insertion of layer of gold phosphide between n-doped InP and metal or other overlayer of contact material. Second, includes first modification plus use of particular metal overlayer to achieve very low contact resistivities. Third, also involves deposition of Au(2)P(3) interlayer; in addition, refractory metal (W or Ta) deposited to form contact overlayer. In fourth, contact layer of Auln alloy deposited directly on InP. Improved contacts exhibit low electrical resistances and fabricated without exposing devices to destructive predeposition or postdeposition treatments.

High electron doping to a wide band gap semiconductor 12CaO•7Al2O3 thin film

NASA Astrophysics Data System (ADS)

Miyakawa, Masashi; Hirano, Masahiro; Kamiya, Toshio; Hosono, Hideo

2007-04-01

High-density electrons (˜1.9×1021cm-3) were doped into a polycrystalline film of a wide band gap (˜7eV) semiconductor 12CaO•7Al2O3 (C12A7) by an in situ postdeposition reduction treatment using an oxygen-deficient C12A7 overlayer. The resultant film exhibits metallic conduction with a Hall mobility of ˜2.5cm2V-1s-1 and a conductivity of ˜800Scm-1. Optical analyses indicate that most of the doped electrons behave as free carriers with an effective mass of 0.82me and the estimated in-grain mobility is 5.2cm2V-1s-1, which agrees reasonably with the value obtained for high-quality single crystals.

Superconductivity in compensated and uncompensated semiconductors.

PubMed

Yanase, Youichi; Yorozu, Naoyuki

2008-12-01

We investigate the localization and superconductivity in heavily doped semiconductors. The crossover from the superconductivity in the host band to that in the impurity band is described on the basis of the disordered three-dimensional attractive Hubbard model for binary alloys. The microscopic inhomogeneity and the thermal superconducting fluctuation are taken into account using the self-consistent 1-loop order theory. The superconductor-insulator transition accompanies the crossover from the host band to the impurity band. We point out an enhancement of the critical temperature T c around the crossover. Further localization of electron wave functions leads to the localization of Cooper pairs and induces the pseudogap. We find that both the doping compensation by additional donors and the carrier increase by additional acceptors suppress the superconductivity. A theoretical interpretation is proposed for the superconductivity in the boron-doped diamond, SiC, and Si.

Superconductivity in compensated and uncompensated semiconductors

PubMed Central

Yanase, Youichi; Yorozu, Naoyuki

2008-01-01

We investigate the localization and superconductivity in heavily doped semiconductors. The crossover from the superconductivity in the host band to that in the impurity band is described on the basis of the disordered three-dimensional attractive Hubbard model for binary alloys. The microscopic inhomogeneity and the thermal superconducting fluctuation are taken into account using the self-consistent 1-loop order theory. The superconductor-insulator transition accompanies the crossover from the host band to the impurity band. We point out an enhancement of the critical temperature Tc around the crossover. Further localization of electron wave functions leads to the localization of Cooper pairs and induces the pseudogap. We find that both the doping compensation by additional donors and the carrier increase by additional acceptors suppress the superconductivity. A theoretical interpretation is proposed for the superconductivity in the boron-doped diamond, SiC, and Si. PMID:27878018

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kroupa, Daniel M.; Hughes, Barbara K.; Miller, Elisa M.

Electronic impurity doping of bulk semiconductors is an essential component of semiconductor science and technology. Yet there are only a handful of studies demonstrating control of electronic impurities in semiconductor nanocrystals. Here, we studied electronic impurity doping of colloidal PbSe quantum dots (QDs) using a postsynthetic cation exchange reaction in which Pb is exchanged for Ag. We found that varying the concentration of dopants exposed to the as-synthesized PbSe QDs controls the extent of exchange. The electronic impurity doped QDs exhibit the fundamental spectroscopic signatures associated with injecting a free charge carrier into a QD under equilibrium conditions, including amore » bleach of the first exciton transition and the appearance of a quantum-confined, low-energy intraband absorption feature. Photoelectron spectroscopy confirms that Ag acts as a p-type dopant for PbSe QDs and infrared spectroscopy is consistent with k • p calculations of the size-dependent intraband transition energy. We find that to bleach the first exciton transition by an average of 1 carrier per QD requires that approximately 10% of the Pb be replaced by Ag. Here, we hypothesize that the majority of incorporated Ag remains at the QD surface and does not interact with the core electronic states of the QD. Instead, the excess Ag at the surface promotes the incorporation of <1% Ag into the QD core where it causes p-type doping behavior.« less

Controlling the Photocorrosion of Zinc Sulfide Nanoparticles in Water by Doping with Chloride and Cobalt Ions.

PubMed

Weide, Philipp; Schulz, Katharina; Kaluza, Stefan; Rohe, Markus; Beranek, Radim; Muhler, Martin

2016-12-06

Photodegradation under UV light irradiation is a major drawback in photocatalytic applications of sulfide semiconductors. ZnS nanoparticles were doped with very low amounts of chloride or cobalt ions in the ppm range and codoped with chloride and cobalt ions during their synthesis by precipitation in aqueous solution followed by calcination. The high-temperature wurtzite phase annealed at 800 °C had a high susceptibility to UV irradiation in water, while the low-temperature zincblende phase annealed at 400 °C was found to be stable. Chlorine doping increased the rate of photocorrosion in water, whereas cobalt doping led to a stabilization of the ZnS nanoparticles. Based on photochemical and spectroscopic investigations applying UV/vis, X-ray photoelectron, and photoluminescence spectroscopy, the increased susceptibility of Cl-doped ZnS is ascribed to a higher number of surface point defects, whereas the stabilization by Co 2+ is caused by additional recombination pathways for the charge carriers in the bulk, thus avoiding photocorrosion processes at the surface. Additional doping of Cl-doped ZnS with cobalt ions was found to counteract the detrimental effect of the chloride ions efficiently.

Interfacial characteristics and leakage current transfer mechanisms in organometal trihalide perovskite gate-controlled devices via doping of PCBM

NASA Astrophysics Data System (ADS)

Wang, Yucheng; Zhang, Yuming; Liu, Yintao; Pang, Tiqiang; Hu, Ziyang; Zhu, Yuejin; Luan, Suzhen; Jia, Renxu

2017-11-01

Two types of perovskite (with and without doping of PCBM) based metal-oxide-semiconductor (MOS) gate-controlled devices were fabricated and characterized. The study of the interfacial characteristics and charge transfer mechanisms by doping of PCBM were analyzed by material and electrical measurements. Doping of PCBM does not affect the size and crystallinity of perovskite films, but has an impact on carrier extraction in perovskite MOS devices. The electrical hysteresis observed in capacitance-voltage and current-voltage measurements can be alleviated by doping of PCBM. Experimental results demonstrate that extremely low trap densities are found for the perovskite device without doping, while the doped sample leads to higher density of interface state. Three mechanisms including Ohm’s law, trap-filled-limit (TFL) emission, and child’s law were used to analyze possible charge transfer mechanisms. Ohm’s law mechanism is well suitable for charge transfer of both the perovskite MOS devices under light condition at large voltage, while TFL emission well addresses the behavior of charge transfer under dark at small voltage. This change of charge transfer mechanism is attributed to the impact of the ion drift within perovskites.

Electroluminescence from metal-oxide-semiconductor devices with erbium-doped CeO{sub 2} films on silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lv, Chunyan; Department of Chemistry, Huzhou University, Zhejiang, Huzhou 313000; Zhu, Chen

2015-04-06

We report on erbium (Er)-related electroluminescence (EL) in the visible and near-infrared (NIR) from metal-oxide-semiconductor (MOS) devices with Er-doped CeO{sub 2} (CeO{sub 2}:Er) films on silicon. The onset voltage of such EL under either forward or reverse bias is smaller than 10 V. Moreover, the EL quenching can be avoidable for the CeO{sub 2}:Er-based MOS devices. Analysis on the current-voltage characteristic of the device indicates that the electron transportation at the EL-enabling voltages under either forward or reverse bias is dominated by trap-assisted tunneling mechanism. Namely, electrons in n{sup +}-Si/ITO can tunnel into the conduction band of CeO{sub 2} host viamore » defect states at sufficiently high forward/reverse bias voltages. Then, a fraction of such electrons are accelerated by electric field to become hot electrons, which impact-excite the Er{sup 3+} ions, thus leading to characteristic emissions. It is believed that this work has laid the foundation for developing viable silicon-based emitters using CeO{sub 2}:Er films.« less

Metal-nonmetal oscillations in doped blue phosphorene: a first-principles study

NASA Astrophysics Data System (ADS)

Li, Hui; Zhang, Liwei; Cai, Xiaolin; Li, Xiaohua; Wang, Baoji; Yu, Weiyang; Zhao, Ruiqi

2018-05-01

Based on density functional theory (DFT), we have systematically investigated the geometry structure and electronic properties of group IIIA, IVA, VA, and VIA atoms doped blue phosphorene, such as B‑, C‑, N‑, O‑, Al‑, Si- and S-doped blue phosphorene systems. We find that the electronic properties of blue phosphorene are drastically modified by the number of valence electrons in dopant atoms. An intriguing general rule of metal-nonmetal oscillations have been obtained that the dopant atoms from even group, such as IVA and VIA, lead to metal properties, while dopant atoms from odd group, such as IIIA and VA, give rise to semiconductor properties, which is different from traditional n or p doping effect in bulk case. This even–odd oscillating behavior is attributed to the peculiar bonding characteristics of blue phosphorene and the strong hybridization of sp orbitals between dopants and blue phosphorene. Then the underlying mechanism has been investigated with the electronic filling analysis. These results pave an intriguing way to tune the transport properties of electronic and photoelectronic devices based on blue phosphorene.

Modulation-Doped SrTiO3/SrTi1-xZrxO3 Heterostructures

NASA Astrophysics Data System (ADS)

Kajdos, Adam Paul

Two-dimensional electron gases (2DEGs) in SrTiO3 have attracted considerable attention for exhibiting a variety of interesting physical phenomena, such as superconductivity and magnetism. So far, most of the literature has focused on interfaces between nonpolar SrTiO3 and polar perovskite oxides (e.g. LaAlO3 or rare-earth titanates), where high carrier density 2DEGs (˜3 x 1014 cm-2) are generated by polar discontinuity. Modulation doping is an alternative approach to generating a 2DEG that has been explored extensively in III-V semiconductors but has not heretofore been explored in complex oxides. This approach involves interfacing an undoped semiconductor with a doped semiconductor whose conduction band edge lies at a higher energy, which results in electrons diffusing into the undoped semiconductor transport channel, where scattering from ionized dopants is minimized. Realizing a high-mobility modulation-doped structure with a SrTiO3 transport channel therefore requires both the optimization of the transport channel by minimizing native defects as well as the development of a perovskite oxide which has a suitable band offset with SrTiO3 and can be electron-doped. The growth of high electron mobility SrTiO3 as a suitable transport channel material was previously demonstrated using the hybrid molecular beam epitaxy (MBE) approach, where Sr is delivered via a solid source and Ti is delivered using a metal-organic precursor, titanium (IV) tetra-isopropoxide (TTIP). Expanding on this, in-situ reflection high-energy electron diffraction (RHEED) is used to track the surface and resulting film cation stoichiometry of homoepitaxial SrTiO3 (001) thin films grown by hybrid MBE. It is shown that films with lattice parameters identical to bulk single-crystal substrates within the detection limit of high-resolution X-ray diffraction (XRD) measurements exhibit an evolution in surface reconstruction with increasing TTIP beam-equivalent pressure. The change in the observed surface reconstruction from (1x1) to (2x1) to c(4x4) is correlated with a change from mixed SrO/TiO2 to pure TiO2 surface termination. It is argued that optimal cation stoichiometry is achieved for growth conditions within the XRD-defined growth window that result in a c(4x4) surface lattice. The development of a doped perovskite oxide semiconductor with a suitable conduction band offset is then discussed as the next necessary step towards realizing modulation-doped heterostructures. The SrTixZr1-x O3 solid solution is investigated for this purpose, with a focus on optimizing cation stoichiometry to allow for controlled doping. In particular, the hybrid MBE growth of SrTixZr1-xO3 thin films is explored using a metal-organic precursor for Zr, zirconium tert-butoxide (ZTB). The successful generation of 2DEGs by modulation doping of SrTiO3 is then demonstrated in SrTiO3/La:SrTi0.95Zr0.05O 3 heterostructures, and the electronic structure is studied by Shubnikov-de Haas analysis using multiple-subband models.

Functionalization of graphene by size and doping control and its optoelectronic applications

NASA Astrophysics Data System (ADS)

Tang, Libin; Ji, Rongbin; Tian, Pin; Kong, Jincheng; Xiang, Jinzhong

2017-02-01

Graphene has received intensive attention in recent years because of the special physical and chemical properties. However, up to now graphene has not been widely used in optoelectronic fields yet, which is mainly caused by its semimetal properties. Therefore, changing its properties from semimetal to semiconductor is becoming a focal point. Recently, aiming at tuning the energy band of graphene, we have carried out systematic studies on the preparations of graphene based materials and devices, the CVD growth techniques of monolayer and double layer graphenes have been developed, the large-area doped graphene films have been fabricated to tune the structure-related optical and electrical properties. A novel graphene oxide (GO) preparation method namely "Tang-Lau method" has been invented, the graphene quantum dots growths by microwave assisted hydrothermal method and "Soft-Template method" have been developed, the Cl, S and K doped graphene quantum dots preparations by hydrothermal methods have also been invented. Systematic investigations have been carried out for the effect of preparation parameters on the properties of graphene based materials, the effects of size, doping elements on the energy level of graphene based materials have been explored and discussed. Based on the semiconducting graphene based materials, some novel room temperature photodetectors covering detection wavebands from UV, Vis and NIR have been designed and fabricated.

Superparamagnetic behavior of Fe-doped SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Hachisu, M.; Onuma, K.; Kondo, T.; Miike, K.; Miyasaka, T.; Mori, K.; Ichiyanagi, Y.

2014-02-01

SnO2 is an n-type semiconductor with a wide band gap of 3.62 eV, and SnO2 nanoparticles doped with magnetic ions are expected to realized new diluted magnetic semiconductors (DMSs). Realizing ferromagnetism at room temperature is important for spintronics device applications, and it is interesting that the magnetic properties of these DMS systems can be varied significantly by modifying the preparation methods or conditions. In this study, the magnetic properties of Fe-doped (3% and 5%) SnO2 nanoparticles, prepared using our novel chemical preparation method and encapsulated in amorphous SiO2, were investigated. The particle size (1.8-16.9 nm) and crystal phase were controlled by the annealing temperature. X-ray diffraction confirmed a rutile SnO2 single-phase structure for samples annealed at 1073-1373 K, and the composition was confirmed using X-ray fluorescence analysis. SQUID magnetometer measurements revealed superparamagnetic behavior of the 5%-Fe-doped sample at room temperature, although SnO2 is known to be diamagnetic. Magnetization curves at 5 K indicated that the 3%-Fe-doped has a larger magnetization than that of the 5%-Fe-doped sample. We conclude that the magnetization of the 5%-Fe-doped sample decreased at 5 K due to the superexchange interaction between the antiferromagnetic coupling in the nanoparticle system.

Cobalt-doped ZnO nanocrystals: quantum confinement and surface effects from ab initio methods.

PubMed

Schoenhalz, Aline L; Dalpian, Gustavo M

2013-10-14

Cobalt-doped ZnO nanocrystals were studied through ab initio methods based on the Density Functional Theory. Both quantum confinement and surface effects were explicitly taken into account. When only quantum confinement effects are considered, Co atoms interact through a superexchange mechanism, stabilizing an antiferromagnetic ground state. Usually, this is the case for high quality nanoparticles with perfect surface saturation. When the surfaces were considered, a strong hybridization between the Co atoms and surfaces was observed, strongly changing their electronic and magnetic properties. Our results indicated that the surfaces might qualitatively change the properties of impurities in semiconductor nanocrystals.

Lateral and Vertical Organic Transistors

NASA Astrophysics Data System (ADS)

Al-Shadeedi, Akram

An extensive study has been performed to provide a better understanding of the operation principles of doped organic field-effect transistors (OFETs), organic p-i-n diodes, Schottky diodes, and organic permeable base transistors (OPBTs). This has been accomplished by a combination of electrical and structural characterization of these devices. The discussion of doped OFETs focuses on the shift of the threshold voltage due to increased doping concentrations and the generation and transport of minority charge carriers. Doping of pentacene OFETs is achieved by co-evaporation of pentacene with the n-dopant W2(hpp)4. It is found that pentacene thin film are efficiently doped and that a conductivity in the range of 2.6 x 10-6 S cm-1 for 1 wt% to 2.5 x 10-4 S cm-1 for 16 wt% is reached. It is shown that n-doped OFET consisting of an n-doped channel and n-doped contacts are ambipolar. This behavior is surprising, as n-doping the contacts should suppress direct injection of minority charge carriers (holes). It was proposed that minority charge carrier injection and hence the ambipolar characteristic of n-doped OFETs can be explained by Zener tunneling inside the intrinsic pentacene layer underneath the drain electrode. It is shown that the electric field in this layer is indeed in the range of the breakdown field of pentacene based p-i-n Zener homodiodes. Doping the channel has a profound influence on the onset voltage of minority (hole) conduction. The onset voltage can be shifted by lightly n-doping the channel. The shift of onset voltage can be explained by two mechanisms: first, due to a larger voltage that has to be applied to the gate in order to fully deplete the n-doped layer. Second, it can be attributed to an increase in hole trapping by inactive dopants. Moreover, it has been shown that the threshold voltage of majority (electron) conduction is shifted by an increase in the doping concentration, and that the ambipolar OFETs can be turned into unipolar OFETs at high doping concentrations. In subsequent chapters, the working mechanisms of OPBTs are discussed. OPBTs consist of two Schottky diodes (top and bottom diode), and the charge transport in these C60-based Schottky diodes is studied first. Two transport regimes can be distinguished in forward direction - injection limited currents (ILCs) and space charge limited currents (SCLCs). It is found that the current increases exponentially with applied voltage in the ILC regime and depends quadratically on the applied voltage in the SCLC regime. Furthermore, it is observed that the forward and backward currents of the Schottky diode are increased by decreasing the C60 layer thickness, increasing the active area, and increasing the temperature. Furthermore, in order to reach a high performance, various treatments have been applied. Air exposure, a variation of the thickness of the top electrode, as well as annealing of the diodes are used to optimize the diodes. OPBTs are processed by using the semiconductor C60 due its high charge carrier mobility and good film-forming properties. Again, the working mechanism of OPBTs is studied by electrical characterization (base-sweep measurements and output characteristics). To achieve a high performance of OPBTs, various treatments and techniques have been applied. The annealing of the OPBTs after fabrication changes the morphology of the base electrode. Thus, openings (pinholes) are formed in the base electrode, which enables a high current transfer from the upper to lower semiconductor layer. The formation of openings is proved by analyzing SEM and TEM image of the base electrode. Adding a doped layer at the emitter is another process to optimize the OPBTs. The doped layer ensures a high charge carrier injection at the emitter, leading to a high transmission and current gain. Furthermore, it has been observed that the ON/OFF ratio and transconductance of OPBTs increases by decreasing their active area. A very high transconductance gm of 37 S/cm2 is reached, which has the potential to boost the switching speed of organic transistors to 5 MHz. Furthermore, it is shown that the base electrode thickness is an essential parameter for OPBTs. The current gain beta decreases by increasing thickness of base electrode, whereas the ON/OFF ratio increases for thicker base electrodes.

Defect Characterization in Semiconductors with Positron Annihilation Spectroscopy

NASA Astrophysics Data System (ADS)

Tuomisto, Filip

Positron annihilation spectroscopy is an experimental technique that allows the selective detection of vacancy defects in semiconductors, providing a means to both identify and quantify them. This chapter gives an introduction to the principles of the positron annihilation techniques and then discusses the physics of some interesting observations on vacancy defects related to growth and doping of semiconductors. Illustrative examples are selected from studies performed in silicon, III-nitrides, and ZnO.

A p-Type Zinc-Based Metal-Organic Framework.

PubMed

Shang, Congcong; Gautier, Romain; Jiang, Tengfei; Faulques, Eric; Latouche, Camille; Paris, Michael; Cario, Laurent; Bujoli-Doeuff, Martine; Jobic, Stéphane

2017-06-05

An original concept for the property tuning of semiconductors is demonstrated by the synthesis of a p-type zinc oxide (ZnO)-like metal-organic framework (MOF), (ZnC 2 O 3 H 2 ) n , which can be regarded as a possible alternative for ZnO, a natural n-type semiconductor. When small oxygen-rich organic linkers are introduced to the Zn-O system, oxygen vacancies and a deep valence-band maximum, the two obstacles for generating p-type behavior in ZnO, are restrained and raised, respectively. Further studies of this material on the doping and photoluminescence behaviors confirm its resemblance to metal oxides (MOs). This result answers the challenges of generating p-type behavior in an n-type-like system. This concept reveals that a new category of hybrid materials, with an embedded continuous metal-oxygen network, lies between the MOs and MOFs. It provides concrete support for the development of p-type hybrid semiconductors in the near future and, more importantly, the enrichment of tuning possibilities in inorganic semiconductors.

Semiconductor Nonlinear Dynamics Study by Broadband Terahertz Spectroscopy

NASA Astrophysics Data System (ADS)

Ho, I.-Chen

Semiconductor nonlinearity in the terahertz (THz) frequency range has been attracting considerable attention due to the recent development of high-power semiconductor-based nanodevices. However, the underlying physics concerning carrier dynamics in the presence of high-field THz transients is still obscure. This thesis introduces an ultrafast, time-resolved THz pump/THz probe approach to the study of semiconductor properties in the nonlinear regime. The carrier dynamics regarding two mechanisms, intervalley scattering and impact ionization, is observed for doped InAs on a sub-picosecond time scale. In addition, polaron modulation driven by intense THz pulses is experimentally and theoretically investigated. The observed polaron dynamics verifies the interaction between energetic electrons and a phonon field. In contrast to previous work which reports optical phonon responses, acoustic phonon modulations are addressed in this study. A further understanding of the intense field interacting with solid materials will accelerate the development of semiconductor devices. This thesis starts with the design and performance of a table-top THz spectrometer which has the advantages of ultra-broad bandwidth (one order higher bandwidth compared to a conventional ZnTe sensor) and high electric field strength (>100 kV/cm). Unlike the conventional THz time-domain spectroscopy, the spectrometer integrates a novel THz air-biased-coherent-detection (THz-ABCD) technique and utilizes selected gases as THz emitters and sensors. In comparison with commonly used electro-optic (EO) crystals or photoconductive (PC) dipole antennas, the gases have the benefits of no phonon absorption as existing in EO crystals and no carrier life time limitation as observed in PC dipole antennas. The newly development THz-ABCD spectrometer with a strong THz field strength capability provides a platform for various research topics especially on the nonlinear carrier dynamics of semiconductors. Two mechanisms, electron intervalley scattering and impact ionization of InAs crystals, are observed under the excitation of intense THz field on a sub-picosecond time scale. These two competing mechanisms are demonstrated by changing the impurity doping type of the semiconductors and varying the strength of the THz field. Another investigation of nonlinear carrier dynamics is the observation of coherent polaron oscillation in n-doped semiconductors excited by intense THz pulses. Through modulations of surface reflection with a THz pump/THz probe technique, this work experimentally verifies the interaction between energetic electrons and a phonon field, which has been theoretically predicted by previous publications, and shows that this interaction applies for the acoustic phonon modes. Usually, two transverse acoustic (2TA) phonon responses are inactive in infrared measurement, while they are detectable in second-order Raman spectroscopy. The study of polaron dynamics, with nonlinear THz spectroscopy (in the far-infrared range), provides a unique method to diagnose the overtones of 2TA phonon responses of semiconductors, and therefore incorporates the abilities of both infrared and Raman spectroscopy. This work presents a new milestone in wave-matter interaction and seeks to benefit the industrial applications in high power, small scale devices.

Passively Q-switched dual-wavelength thulium-doped fiber laser based on a multimode interference filter and a semiconductor saturable absorber

NASA Astrophysics Data System (ADS)

Wang, M.; Huang, Y. J.; Ruan, S. C.

2018-04-01

In this paper, we have demonstrated a theta cavity passively Q-switched dual-wavelength fiber laser based on a multimode interference filter and a semiconductor saturable absorber. Relying on the properties of the fiber theta cavity, the laser can operate unidirectionally without an optical isolator. A semiconductor saturable absorber played the role of passive Q-switch while a section of single-mode-multimode-single-mode fiber structure served as an multimode interference filter and was used for selecting the lasing wavelengths. By suitably manipulating the polarization controller, stable dual-wavelength Q-switched operation was obtained at ~1946.8 nm and ~1983.8 nm with maximum output power and minimum pulse duration of ~47 mW and ~762.5 ns, respectively. The pulse repetition rate can be tuned from ~20.2 kHz to ~79.7 kHz by increasing the pump power from ~2.12 W to ~5.4 W.

Wide-band-gap, alkaline-earth-oxide semiconductor and devices utilizing same

DOEpatents

Abraham, Marvin M.; Chen, Yok; Kernohan, Robert H.

1981-01-01

This invention relates to novel and comparatively inexpensive semiconductor devices utilizing semiconducting alkaline-earth-oxide crystals doped with alkali metal. The semiconducting crystals are produced by a simple and relatively inexpensive process. As a specific example, a high-purity lithium-doped MgO crystal is grown by conventional techniques. The crystal then is heated in an oxygen-containing atmosphere to form many [Li].degree. defects therein, and the resulting defect-rich hot crystal is promptly quenched to render the defects stable at room temperature and temperatures well above the same. Quenching can be effected conveniently by contacting the hot crystal with room-temperature air.

Features of the band structure and conduction mechanisms of n-HfNiSn heavily doped with Y

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romaka, V. A., E-mail: vromaka@polynet.lviv.ua; Rogl, P.; Romaka, V. V.

The crystalline and electronic structures, energy, kinetic, and magnetic characteristics of n-HfNiSn semiconductor heavily doped with Y acceptor impurity are studied in the ranges: T = 80–400 K, N{sub A}{sup Y} ≈ 1.9 × 10{sup 20}–5.7 × 10{sup 21} cm{sup –3} (x = 0.01–0.30), and H ≤ 10 kG. The nature of the mechanism of structural defect generation is determined, which leads to a change in the band gap and the degree of semiconductor compensation, the essence of which is the simultaneous reduction and elimination of structural donor-type defects as a result of the displacement of ~1% of Ni atomsmore » from the Hf (4a) site, and the generation of structural acceptor-type defects by substituting Hf atoms with Y atoms at the 4a site. The results of calculations of the electronic structure of Hf{sub 1–x}Y{sub x}NiSn are in agreement with the experimental data. The discussion is performed within the Shklovskii–Efros model of a heavily doped and compensated semiconductor.« less

First-principles study of the effects of Silicon doping on the Schottky barrier of TiSi2/Si interfaces

NASA Astrophysics Data System (ADS)

Wang, Han; Silva, Eduardo; West, Damien; Sun, Yiyang; Restrepo, Oscar; Zhang, Shengbai; Kota, Murali

As scaling of semiconductor devices is pursued in order to improve power efficiency, quantum effects due to the reduced dimensions on devices have become dominant factors in power, performance, and area scaling. In particular, source/drain contact resistance has become a limiting factor in the overall device power efficiency and performance. As a consequence, techniques such as heavy doping of source and drain have been explored to reduce the contact resistance, thereby shrinking the width of depletion region and lowering the Schottky barrier height. In this work, we study the relation between doping in Silicon and the Schottky barrier of a TiSi2/Si interface with first-principles calculation. Virtual Crystal Approximation (VCA) is used to calculate the average potential of the interface with varying doping concentration, while the I-V curve for the corresponding interface is calculated with a generalized one-dimensional transfer matrix method. The relation between substitutional and interstitial Boron and Phosphorus dopant near the interface, and their effect on tuning the Schottky barrier is studied. These studies provide insight to the type of doping and the effect of dopant segregation to optimize metal-semiconductor interface resistance.

Low-temperature magnetotransport of the narrow-gap semiconductor FeSb2

NASA Astrophysics Data System (ADS)

Takahashi, H.; Okazaki, R.; Yasui, Y.; Terasaki, I.

2011-11-01

We present a study of the magnetoresistance and Hall effect in the narrow-gap semiconductor FeSb2 at low temperatures. Both the electrical and Hall resistivities show unusual magnetic field dependence in the low-temperature range where a large Seebeck coefficient was observed. By applying a two-carrier model, we find that the carrier concentration decreases from 1 down to 10-4 ppm/unit cell and the mobility increases from 2000 to 28 000 cm2/Vs with decreasing temperature from 30 down to 4 K. At lower temperatures, the magnetoresistive behavior drastically changes and a negative magnetoresistance is observed at 3 K. These low-temperature behaviors are reminiscent of the low-temperature magnetotransport observed in doped semiconductors such as As-doped Ge, which is well described by a weak-localization picture. We argue a detailed electronic structure in FeSb2 inferred from our observations.

Characteristics of Superjunction Lateral-Double-Diffusion Metal Oxide Semiconductor Field Effect Transistor and Degradation after Electrical Stress

NASA Astrophysics Data System (ADS)

Lin, Jyh‑Ling; Lin, Ming‑Jang; Lin, Li‑Jheng

2006-04-01

The superjunction lateral double diffusion metal oxide semiconductor field effect has recently received considerable attention. Introducing heavily doped p-type strips to the n-type drift region increases the horizontal depletion capability. Consequently, the doping concentration of the drift region is higher and the conduction resistance is lower than those of conventional lateral-double-diffusion metal oxide semiconductor field effect transistors (LDMOSFETs). These characteristics may increase breakdown voltage (\\mathit{BV}) and reduce specific on-resistance (Ron,sp). In this study, we focus on the electrical characteristics of conventional LDMOSFETs on silicon bulk, silicon-on-insulator (SOI) LDMOSFETs and superjunction LDMOSFETs after bias stress. Additionally, the \\mathit{BV} and Ron,sp of superjunction LDMOSFETs with different N/P drift region widths and different dosages are discussed. Simulation tools, including two-dimensional (2-D) TSPREM-4/MEDICI and three-dimensional (3-D) DAVINCI, were employed to determine the device characteristics.

Betavoltaic Battery Conversion Efficiency Improvement Based on Interlayer Structures

NASA Astrophysics Data System (ADS)

Li, Da-Rang; Jiang, Lan; Yin, Jian-Hua; Tan, Yuan-Yuan; Lin, Nai

2012-07-01

Significant differences among the doping densities of PN junctions in semiconductors cause lattice mismatch and lattice defects that increase the recombination current of betavoltaic batteries. This extensively decreases the open circuit voltage and the short current, which results in low conversion efficiency. This study proposes P+PINN+-structure based betavoltaic batteries by adding an interlayer to typical PIN structures to improve conversion efficiency. Numerical simulations are conducted for the energy deposition of beta particles along the thickness direction in semiconductors. Based on this, 63Ni-radiation GaAs batteries with PIN and P+PINN+ structures are designed and fabricated to experimentally verify the proposed design. It turns out that the conversion efficiency of the betavoltaic battery with the proposed P+PINN+ structure is about 1.45 times higher than that with the traditional PIN structure.

The interplay of shape and crystalline anisotropies in plasmonic semiconductor nanocrystals

DOE PAGES

Kim, Jongwook; Agrawal, Ankit; Krieg, Franziska; ...

2016-05-16

Doped semiconductor nanocrystals are an emerging class of materials hosting localized surface plasmon resonance (LSPR) over a wide optical range. Studies so far have focused on tuning LSPR frequency by controlling the dopant and carrier concentrations in diverse semiconductor materials. However, the influence of anisotropic nanocrystal shape and of intrinsic crystal structure on LSPR remain poorly explored. Here, we illustrate how these two factors collaborate to determine LSPR characteristics in hexagonal cesium-doped tungsten oxide nanocrystals. The effect of shape anisotropy is systematically analyzed via synthetic control of nanocrystal aspect ratio (AR), from disks to nanorods. We demonstrate the dominant influencemore » of crystalline anisotropy, which uniquely causes strong LSPR band-splitting into two distinct peaks with comparable intensities. Modeling typically used to rationalize particle shape effects is refined by taking into account the anisotropic dielectric function due to crystalline anisotropy, thus fully accounting for the AR-dependent evolution of multiband LSPR spectra. Furthermore, this new insight into LSPR of semiconductor nanocrystals provides a novel strategy for an exquisite tuning of LSPR line shape.« less

A Designed Room Temperature Multilayered Magnetic Semiconductor

NASA Astrophysics Data System (ADS)

Bouma, Dinah Simone; Charilaou, Michalis; Bordel, Catherine; Duchin, Ryan; Barriga, Alexander; Farmer, Adam; Hellman, Frances; Materials Science Division, Lawrence Berkeley National Lab Team

2015-03-01

A room temperature magnetic semiconductor has been designed and fabricated by using an epitaxial antiferromagnet (NiO) grown in the (111) orientation, which gives surface uncompensated magnetism for an odd number of planes, layered with the lightly doped semiconductor Al-doped ZnO (AZO). Magnetization and Hall effect measurements of multilayers of NiO and AZO are presented for varying thickness of each. The magnetic properties vary as a function of the number of Ni planes in each NiO layer; an odd number of Ni planes yields on each NiO layer an uncompensated moment which is RKKY-coupled to the moments on adjacent NiO layers via the carriers in the AZO. This RKKY coupling oscillates with the AZO layer thickness, and it disappears entirely in samples where the AZO is replaced with undoped ZnO. The anomalous Hall effect data indicate that the carriers in the AZO are spin-polarized according to the direction of the applied field at both low temperature and room temperature. NiO/AZO multilayers are therefore a promising candidate for spintronic applications demanding a room-temperature semiconductor.

Defect Tolerant Semiconductors for Solar Energy Conversion.

PubMed

Zakutayev, Andriy; Caskey, Christopher M; Fioretti, Angela N; Ginley, David S; Vidal, Julien; Stevanovic, Vladan; Tea, Eric; Lany, Stephan

2014-04-03

Defect tolerance is the tendency of a semiconductor to keep its properties despite the presence of crystallographic defects. Scientific understanding of the origin of defect tolerance is currently missing. Here we show that semiconductors with antibonding states at the top of the valence band are likely to be tolerant to defects. Theoretical calculations demonstrate that Cu3N with antibonding valence band maximum has shallow intrinsic defects and no surface states, in contrast to GaN with bonding valence band maximum. Experimental measurements indicate shallow native donors and acceptors in Cu3N thin films, leading to 10(16)-10(17) cm(-3) doping with either electrons or holes depending on the growth conditions. The experimentally measured bipolar doping and the solar-matched optical absorption onset (1.4 eV) make Cu3N a promising candidate absorber for photovoltaic and photoelectrochemical solar cells, despite the calculated indirect fundamental band gap (1.0 eV). These conclusions can be extended to other materials with antibonding character of the valence band, defining a class of defect-tolerant semiconductors for solar energy conversion applications.

Direct measurement of the effective infrared dielectric response of a highly doped semiconductor metamaterial.

PubMed

Al Mohtar, Abeer; Kazan, Michel; Taliercio, Thierry; Cerutti, Laurent; Blaize, Sylvain; Bruyant, Aurélien

2017-03-24

We have investigated the effective dielectric response of a subwavelength grating made of highly doped semiconductors (HDS) excited in reflection, using numerical simulations and spectroscopic measurement. The studied system can exhibit strong localized surface resonances and has, therefore, a great potential for surface-enhanced infrared absorption (SEIRA) spectroscopy application. It consists of a highly doped InAsSb grating deposited on lattice-matched GaSb. The numerical analysis demonstrated that the resonance frequencies can be inferred from the dielectric function of an equivalent homogeneous slab by accounting for the complex reflectivity of the composite layer. Fourier transform infrared reflectivity (FTIR) measurements, analyzed with the Kramers-Kronig conversion technique, were used to deduce the effective response in reflection of the investigated system. From the knowledge of this phenomenological dielectric function, transversal and longitudinal energy-loss functions were extracted and attributed to transverse and longitudinal resonance modes frequencies.

Advances in imaging and quantification of electrical properties at the nanoscale using Scanning Microwave Impedance Microscopy (sMIM)

NASA Astrophysics Data System (ADS)

Friedman, Stuart; Stanke, Fred; Yang, Yongliang; Amster, Oskar

Scanning Microwave Impedance Microscopy (sMIM) is a mode for Atomic Force Microscopy (AFM) enabling imaging of unique contrast mechanisms and measurement of local permittivity and conductivity at the 10's of nm length scale. sMIM has been applied to a variety of systems including nanotubes, nanowires, 2D materials, photovoltaics and semiconductor devices. Early results were largely semi-quantitative. This talk will focus on techniques for extracting quantitative physical parameters such as permittivity, conductivity, doping concentrations and thin film properties from sMIM data. Particular attention will be paid to non-linear materials where sMIM has been used to acquire nano-scale capacitance-voltage curves. These curves can be used to identify the dopant type (n vs p) and doping level in doped semiconductors, both bulk samples and devices. Supported in part by DOE-SBIR DE-SC0009856.

Photoactivated and patternable charge transport materials and their use in organic light-emitting devices

NASA Astrophysics Data System (ADS)

Liu, Jie; Lewis, Larry N.; Duggal, Anil R.

2007-06-01

Organic light-emitting devices (OLEDs) usually employ at least one organic semiconductor layer that acts as a hole-injection material. The prototypical example is a conjugated polymer such as poly(3,4-ethylenedioxythiophene) heavily p doped with polystyrene sulfonic acid. Here, the authors describe a chemical doping strategy for hole injection material formulation that enables spatial patterning of the material conductivity through optical activation. The strategy utilizes an organic photoacid generator (PAG) dispersed in a polymeric organic semiconductor host. Upon UV irradiation, the PAG decomposes and generates a strong protonic acid that subsequently p dopes the host. The authors demonstrate an OLED made with such a light-activated hole-injection material and show that arbitrary emission patterning can be accomplished. This approach may provide a simple, low cost path toward specialty lighting and signage applications for OLED technology.

Effect of Ga doping and point defect on magnetism of ZnO

NASA Astrophysics Data System (ADS)

Hou, Qingyu; Zhao, Chunwang; Jia, Xiaofang; Qu, Lingfeng

2017-02-01

The combined influence mechanism of Ga doping and Zn vacancy or O vacancy on magnetism of ZnO is studied using the first-principle calculation. The coexistence of Ga doping and Zn vacancy can achieve a Curie temperature higher than room temperature and the Ga doped ZnO system is a p-type diluted degenerate semiconductor with metalized ferromagnetism. The magnetism of the doping system of Ga doping and Zn vacancy is mainly contributed by double-exchange interaction through the holes of Zn vacancy taking carrier as medium. However, the system of Ga doping and O vacancy is non-magnetic. In the coexistence of Ga doping and Zn vacancy or O vacancy, a close relative distance between doping and vacancy will reduce the formation energy of the doping system but increase the easiness of doping and vacancy, as well as enhance the stability of the doping system.

Thermal emitter comprising near-zero permittivity materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luk, Ting S.; Campione, Salvatore; Sinclair, Michael B.

A novel thermal source comprising a semiconductor hyperbolic metamaterial provides control of the emission spectrum and the angular emission pattern. These properties arise because of epsilon-near-zero conditions in the semiconductor hyperbolic metamaterial. In particular, the thermal emission is dominated by the epsilon-near-zero effect in the doped quantum wells composing the semiconductor hyperbolic metamaterial. Furthermore, different properties are observed for s and p polarizations, following the characteristics of the strong anisotropy of hyperbolic metamaterials.

Isoelectronic co-doping

DOEpatents

Mascarenhas, Angelo

2004-11-09

Isoelectronic co-doping of semiconductor compounds and alloys with deep acceptors and deep donors is used to decrease bandgap, to increase concentration of the dopant constituents in the resulting alloys, and to increase carrier mobilities lifetimes. Group III-V compounds and alloys, such as GaAs and GaP, are isoelectronically co-doped with, for example, N and Bi, to customize solar cells, thermal voltaic cells, light emitting diodes, photodetectors, and lasers on GaP, InP, GaAs, Ge, and Si substrates. Isoelectronically co-doped Group II-VI compounds and alloys are also included.

Current Modulation of a Heterojunction Structure by an Ultra-Thin Graphene Base Electrode.

PubMed

Alvarado Chavarin, Carlos; Strobel, Carsten; Kitzmann, Julia; Di Bartolomeo, Antonio; Lukosius, Mindaugas; Albert, Matthias; Bartha, Johann Wolfgang; Wenger, Christian

2018-02-27

Graphene has been proposed as the current controlling element of vertical transport in heterojunction transistors, as it could potentially achieve high operation frequencies due to its metallic character and 2D nature. Simulations of graphene acting as a thermionic barrier between the transport of two semiconductor layers have shown cut-off frequencies larger than 1 THz. Furthermore, the use of n-doped amorphous silicon, (n)-a-Si:H, as the semiconductor for this approach could enable flexible electronics with high cutoff frequencies. In this work, we fabricated a vertical structure on a rigid substrate where graphene is embedded between two differently doped (n)-a-Si:H layers deposited by very high frequency (140 MHz) plasma-enhanced chemical vapor deposition. The operation of this heterojunction structure is investigated by the two diode-like interfaces by means of temperature dependent current-voltage characterization, followed by the electrical characterization in a three-terminal configuration. We demonstrate that the vertical current between the (n)-a-Si:H layers is successfully controlled by the ultra-thin graphene base voltage. While current saturation is yet to be achieved, a transconductance of ~230 μ S was obtained, demonstrating a moderate modulation of the collector-emitter current by the ultra-thin graphene base voltage. These results show promising progress towards the application of graphene base heterojunction transistors.

Switching Plasmons: Gold Nanorod-Copper Chalcogenide Core-Shell Nanoparticle Clusters with Selectable Metal/Semiconductor NIR Plasmon Resonances.

PubMed

Muhammed, Madathumpady Abubaker Habeeb; Döblinger, Markus; Rodríguez-Fernández, Jessica

2015-09-16

Exerting control over the near-infrared (NIR) plasmonic response of nanosized metals and semiconductors can facilitate access to unexplored phenomena and applications. Here we combine electrostatic self-assembly and Cd(2+)/Cu(+) cation exchange to obtain an anisotropic core-shell nanoparticle cluster (NPC) whose optical properties stem from two dissimilar plasmonic materials: a gold nanorod (AuNR) core and a copper selenide (Cu(2-x)Se, x ≥ 0) supraparticle shell. The spectral response of the AuNR@Cu2Se NPCs is governed by the transverse and longitudinal plasmon bands (LPB) of the anisotropic metallic core, since the Cu2Se shell is nonplasmonic. Under aerobic conditions the shell undergoes vacancy doping (x > 0), leading to the plasmon-rich NIR spectrum of the AuNR@Cu(2-x)Se NPCs. For low vacancy doping levels the NIR optical properties of the dually plasmonic NPCs are determined by the LPBs of the semiconductor shell (along its major longitudinal axis) and of the metal core. Conversely, for high vacancy doping levels their NIR optical response is dominated by the two most intense plasmon modes from the shell: the transverse (along the shortest transversal axis) and longitudinal (along the major longitudinal axis) modes. The optical properties of the NPCs can be reversibly switched back to a purely metallic plasmonic character upon reversible conversion of AuNR@Cu(2-x)Se into AuNR@Cu2Se. Such well-defined nanosized colloidal assemblies feature the unique ability of holding an all-metallic, a metallic/semiconductor, or an all-semiconductor plasmonic response in the NIR. Therefore, they can serve as an ideal platform to evaluate the crosstalk between plasmonic metals and plasmonic semiconductors at the nanoscale. Furthermore, their versatility to display plasmon modes in the first, second, or both NIR windows is particularly advantageous for bioapplications, especially considering their strong absorbing and near-field enhancing properties.

Zinc Alloys for the Fabrication of Semiconductor Devices

NASA Technical Reports Server (NTRS)

Ryu, Yungryel; Lee, Tae S.

2009-01-01

ZnBeO and ZnCdSeO alloys have been disclosed as materials for the improvement in performance, function, and capability of semiconductor devices. The alloys can be used alone or in combination to form active photonic layers that can emit over a range of wavelength values. Materials with both larger and smaller band gaps would allow for the fabrication of semiconductor heterostructures that have increased function in the ultraviolet (UV) region of the spectrum. ZnO is a wide band-gap material possessing good radiation-resistance properties. It is desirable to modify the energy band gap of ZnO to smaller values than that for ZnO and to larger values than that for ZnO for use in semiconductor devices. A material with band gap energy larger than that of ZnO would allow for the emission at shorter wavelengths for LED (light emitting diode) and LD (laser diode) devices, while a material with band gap energy smaller than that of ZnO would allow for emission at longer wavelengths for LED and LD devices. The amount of Be in the ZnBeO alloy system can be varied to increase the energy bandgap of ZnO to values larger than that of ZnO. The amount of Cd and Se in the ZnCdSeO alloy system can be varied to decrease the energy band gap of ZnO to values smaller than that of ZnO. Each alloy formed can be undoped or can be p-type doped using selected dopant elements, or can be n-type doped using selected dopant elements. The layers and structures formed with both the ZnBeO and ZnCdSeO semiconductor alloys - including undoped, p-type-doped, and n-type-doped types - can be used for fabricating photonic and electronic semiconductor devices for use in photonic and electronic applications. These devices can be used in LEDs, LDs, FETs (field effect transistors), PN junctions, PIN junctions, Schottky barrier diodes, UV detectors and transmitters, and transistors and transparent transistors. They also can be used in applications for lightemitting display, backlighting for displays, UV and visible transmitters and detectors, high-frequency radar, biomedical imaging, chemical compound identification, molecular identification and structure, gas sensors, imaging systems, and for the fundamental studies of atoms, molecules, gases, vapors, and solids.

High current density 2D/3D MoS2/GaN Esaki tunnel diodes

NASA Astrophysics Data System (ADS)

Krishnamoorthy, Sriram; Lee, Edwin W.; Lee, Choong Hee; Zhang, Yuewei; McCulloch, William D.; Johnson, Jared M.; Hwang, Jinwoo; Wu, Yiying; Rajan, Siddharth

2016-10-01

The integration of two-dimensional materials such as transition metal dichalcogenides with bulk semiconductors offer interesting opportunities for 2D/3D heterojunction-based device structures without any constraints of lattice matching. By exploiting the favorable band alignment at the GaN/MoS2 heterojunction, an Esaki interband tunnel diode is demonstrated by transferring large area Nb-doped, p-type MoS2 onto heavily n-doped GaN. A peak current density of 446 A/cm2 with repeatable room temperature negative differential resistance, peak to valley current ratio of 1.2, and minimal hysteresis was measured in the MoS2/GaN non-epitaxial tunnel diode. A high current density of 1 kA/cm2 was measured in the Zener mode (reverse bias) at -1 V bias. The GaN/MoS2 tunnel junction was also modeled by treating MoS2 as a bulk semiconductor, and the electrostatics at the 2D/3D interface was found to be crucial in explaining the experimentally observed device characteristics.

Near-infrared strong coupling between metamaterials and epsilon-near-zero modes in degenerately doped semiconductor nanolayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campione, Salvatore; Wendt, Joel R.; Keeler, Gordon Arthur

Epsilon-near-zero (ENZ) modes provide a new path for tailoring light–matter interactions at the nanoscale. In this paper, we analyze a strongly coupled system at near-infrared frequencies comprising plasmonic metamaterial resonators and ENZ modes supported by degenerately doped semiconductor nanolayers. In strongly coupled systems that combine optical cavities and intersubband transitions, the polariton splitting (i.e., the ratio of Rabi frequency to bare cavity frequency) scales with the square root of the wavelength, thus favoring the long-wavelength regime. In contrast, we observe that the polariton splitting in ENZ/metamaterial resonator systems increases linearly with the thickness of the nanolayer supporting the ENZ modes.more » In this work, we employ an indium-tin-oxide nanolayer and observe a large experimental polariton splitting of approximately 30% in the near-infrared. As a result, this approach opens up many promising applications, including nonlinear optical components and tunable optical filters based on controlling the polariton splitting by adjusting the frequency of the ENZ mode.« less

Near-infrared strong coupling between metamaterials and epsilon-near-zero modes in degenerately doped semiconductor nanolayers

DOE PAGES

Campione, Salvatore; Wendt, Joel R.; Keeler, Gordon Arthur; ...

2016-01-14

Epsilon-near-zero (ENZ) modes provide a new path for tailoring light–matter interactions at the nanoscale. In this paper, we analyze a strongly coupled system at near-infrared frequencies comprising plasmonic metamaterial resonators and ENZ modes supported by degenerately doped semiconductor nanolayers. In strongly coupled systems that combine optical cavities and intersubband transitions, the polariton splitting (i.e., the ratio of Rabi frequency to bare cavity frequency) scales with the square root of the wavelength, thus favoring the long-wavelength regime. In contrast, we observe that the polariton splitting in ENZ/metamaterial resonator systems increases linearly with the thickness of the nanolayer supporting the ENZ modes.more » In this work, we employ an indium-tin-oxide nanolayer and observe a large experimental polariton splitting of approximately 30% in the near-infrared. As a result, this approach opens up many promising applications, including nonlinear optical components and tunable optical filters based on controlling the polariton splitting by adjusting the frequency of the ENZ mode.« less

Nitrogen plasma-treated multilayer graphene-based field effect transistor fabrication and electronic characteristics

NASA Astrophysics Data System (ADS)

Su, Wei-Jhih; Chang, Hsuan-Chen; Honda, Shin-ichi; Lin, Pao-Hung; Huang, Ying-Sheng; Lee, Kuei-Yi

2017-08-01

Chemical doping with hetero-atoms is an effective method used to change the characteristics of materials. Nitrogen doping technology plays a critical role in regulating the electronic properties of graphene. Nitrogen plasma treatment was used in this work to dope nitrogen atoms to modulate multilayer graphene electrical properties. The measured I-V multilayer graphene-base field-effect transistor characteristics (GFETs) showed a V-shaped transfer curve with the hole and electron region separated from the measured current-voltage (I-V) minimum. GFETs fabricated with multilayer graphene from chemical vapor deposition (CVD) exhibited p-type behavior because of oxygen adsorption. After using different nitrogen plasma treatment times, the minimum in I-V characteristic shifted into the negative gate voltage region with increased nitrogen concentration and the GFET channel became an n-type semiconductor. GFETs could be easily fabricated using this method with potential for various applications. The GFET transfer characteristics could be tuned precisely by adjusting the nitrogen plasma treatment time.

Improvement for the performance of solar-blind photodetector based on β-Ga2O3 thin films by doping Zn

NASA Astrophysics Data System (ADS)

Zhao, Xiaolong; Wu, Zhenping; Zhi, Yusong; An, Yuehua; Cui, Wei; Li, Linghong; Tang, Weihua

2017-03-01

Highly oriented (\\bar{2} 0 1 ) Ga2-x Zn x O3 thin films with different doping concentrations were grown on (0 0 0 1) sapphire substrates by laser molecular beam epitaxy technology. The expansion of lattice and the shrinkage of band gap with increasing doping level confirms the chemical substitution of Zn2+ ions into the Ga2O3 crystal lattice. The emission intensity of blue-violet emission bands enhanced with the increase of (ZnGa)‧ under 254 nm ultraviolet excitation, and the maximum was obtained at x  =  0.8. A metal-semiconductor-metal structured solar-blind photodetector based on Ga2-x Zn x O3 (x  =  0, 0.8) was made, the increasing responsivity and diminishing relaxation time constants for β-Ga2-x Zn x O3 (x  =  0.8) photodetector were observed with 254 nm ultraviolet illumination.

AB INITIO Investigations of the Magnetism in Diluted Magnetic Semiconductor Fe-DOPED GaN

NASA Astrophysics Data System (ADS)

Cheng, Jie; Zhou, Jing; Xu, Wei; Dong, Peng

2014-01-01

In this paper, we present a first principle investigation on Fe-doped GaN with wurtzite and zinc-blend structure using full potential density functional calculations. Data point out that the magnetic behavior of Fe-doped GaN system is strongly dependent on Fe doping configurations. In agreement with the experimental reports, and independently by doping, antiferromagnetism occurs in the zinc-blend structure, while in the wurtzite structure ferromagnetism depends on the Fe doping configurations. Detailed analyses combined with density of state calculations support the assignment that the ferromagnetism is closely related to the impurity band at the origin of the hybridization of Fe 3d and N 2p states in the Fe-doped GaN of wurtzite phase.

Thermophysical Property Measurements of Molten Semiconductors in 1-g and Reduced-g Condition

NASA Technical Reports Server (NTRS)

Rhim, Won-Kyu

1999-01-01

Understanding and controlling the formation kinetics of varieties of crystal imperfections such as point defects, non uniform distribution of doping atoms, and impurity atoms in growing crystals are very important. Theoretical (numerical) modeling of the crystal growth process is an essential step to achieving these objectives. In order to obtain reliable modeling results, input parameters, i.e. various thermophysical parameters, must be accurate. The importance of accurate thermophysical properties of semiconductors in crystal growth cannot be overly emphasized. The total hemispherical emissivity, for instance, has a dramatic impact on the thermal environment. It determines the radiative emission from the surface of the melt which determines to a large extent the profile of the solidified crystal. In order to understand the convection and the turbulence in a melt, viscosity becomes an important parameter. The liquid surface tension determines the shape of the liquid-atmosphere interface near the solid-liquid-atmosphere triple point. Currently used values for these parameters are rather inaccurate, and this program intends to provide more reliable measurements of these thermophysical properties. Thus, the objective of this program is in the accurate measurements of various thermophysical properties which can be reliably used in the modeling of various crystal growth processes. In this program, thermophysical properties of molten semiconductors, such as Si, Ge, Si-Ge, and InSb will be measured as a function of temperature using the High Temperature Electrostatic Levitator at JPL. Each material will be doped by different kinds of impurities at various doping levels. Thermophysical properties which will be measured include: density, thermal expansion coefficient, surface tension, viscosity, specific heat, hemispherical total emissivity, and perhaps electrical and thermal conductivities. Many molten semiconductors are chemically reactive with crucibles. As a result, these dispersed impurities in the melts tend to substantially modify the properties of pure semiconductors. Sample levitation done in a vacuum clearly helps maintain the sample purity. However, in the 1-g environment, all gravity caused effects such as convection, sedimentation and buoyancy are still present in the sample. In addition, large forces needed to levitate a sample in the presence of the gravity can cause additional flows in the melt. The use of the High Temperature Electrostatic Levitator (HTESL) for the present research is a recent development and little is known about the flows induced by the electrostatic forces. In this ground base program, we will define the limits of HTESL technology as various thermophysical properties of molten semiconductors are measured.

Method of doping organic semiconductors

DOEpatents

Kloc, Christian Leo [Constance, DE; Ramirez, Arthur Penn [Summit, NJ; So, Woo-Young [New Providence, NJ

2012-02-28

A method includes the steps of forming a contiguous semiconducting region and heating the region. The semiconducting region includes polyaromatic molecules. The heating raises the semiconducting region to a temperature above room temperature. The heating is performed in the presence of a dopant gas and the absence of light to form a doped organic semiconducting region.

Mid-Gap States and Normal vs Inverted Bonding in Luminescent Cu+- and Ag+-Doped CdSe Nanocrystals.

PubMed

Nelson, Heidi D; Hinterding, Stijn O M; Fainblat, Rachel; Creutz, Sidney E; Li, Xiaosong; Gamelin, Daniel R

2017-05-10

Mid-gap luminescence in copper (Cu + )-doped semiconductor nanocrystals (NCs) involves recombination of delocalized conduction-band electrons with copper-localized holes. Silver (Ag + )-doped semiconductor NCs show similar mid-gap luminescence at slightly (∼0.3 eV) higher energy, suggesting a similar luminescence mechanism, but this suggestion appears inconsistent with the large difference between Ag + and Cu + ionization energies (∼1.5 eV), which should make hole trapping by Ag + highly unfavorable. Here, Ag + -doped CdSe NCs (Ag + :CdSe) are studied using time-resolved variable-temperature photoluminescence (PL) spectroscopy, magnetic circularly polarized luminescence (MCPL) spectroscopy, and time-dependent density functional theory (TD-DFT) to address this apparent paradox. In addition to confirming that Ag + :CdSe and Cu + :CdSe NCs display similar broad PL with large Stokes shifts, we demonstrate that both also show very similar temperature-dependent PL lifetimes and magneto-luminescence. Electronic-structure calculations further predict that both dopants generate similar localized mid-gap states. Despite these strong similarities, we conclude that these materials possess significantly different electronic structures. Specifically, whereas photogenerated holes in Cu + :CdSe NCs localize primarily in Cu(3d) orbitals, formally oxidizing Cu + to Cu 2+ , in Ag + :CdSe NCs they localize primarily in 4p orbitals of the four neighboring Se 2- ligands, and Ag + is not oxidized. This difference reflects a shift from "normal" to "inverted" bonding going from Cu + to Ag + . The spectroscopic similarities are explained by the fact that, in both materials, photogenerated holes are localized primarily within covalent [MSe 4 ] dopant clusters (M = Ag + , Cu + ). These findings reconcile the similar spectroscopies of Ag + - and Cu + -doped semiconductor NCs with the vastly different ionization potentials of their Ag + and Cu + dopants.

Strain-mediated electronic properties of pristine and Mn-doped GaN monolayers

NASA Astrophysics Data System (ADS)

Sharma, Venus; Srivastava, Sunita

2018-04-01

Graphene-like two-dimensional (2D) monolayer structures GaN has gained enormous amount of interest due to high thermal stability and inherent energy band gap for practical applications. First principles calculations are performed to investigate the electronic structure and strain-mediated electronic properties of pristine and Mn-doped GaN monolayer. Binding energy of Mn dopant at various adsorption site is found to be nearly same indicating these sites to be equally favorable for adsorption of foreign atom. Depending on the adsorption site, GaN monolayer can act as p-type or n-type magnetic semiconductor. The tensile strength of both pristine and doped GaN monolayer (∼24 GPa) at ultimate tensile strain of 34% is comparable with the tensile strength of graphene. The in-plane biaxial strain modulate the energy band gap of both pristine and doped-monolayer from direct to indirect gap semiconductor and finally retendered theme into metal at critical value of applied strain. These characteristics make GaN monolayer to be potential candidate for the future applications in tunable optoelectronics.

Magnetic phase change in Mn-doped ZnSnAs2 thin films depending on Mn concentration

NASA Astrophysics Data System (ADS)

Uchitomi, Naotaka; Hidaka, Shiro; Saito, Shin; Asubar, Joel T.; Toyota, Hideyuki

2018-04-01

The relationship between Mn concentration and Curie temperature (TC) is studied for Mn-doped ZnSnAs2 ferromagnetic semiconductors, epitaxially grown on InP substrates by molecular beam epitaxy. In the ferromagnetic phase, Mn distributions in a (Zn,Mn,Sn)As2 thin film with 7.2 cation percent (cat. %) Mn are investigated using three-dimensional atom probe tomography. The results indicate an inhomogeneous distribution which spreads to a relatively high Mn concentration of 9.0 at. % (at. %). In the paramagnetic phase, it is found that the paramagnetic to ferromagnetic transition takes place sharply with a TC of 334 K when the Mn doping concentration increases to about 4 cat. % Mn, which corresponds to a magnetic percolation threshold for ferromagnetism in (Zn,Mn,Sn)As2. An effective Curie temperature ⟨TC⟩ is considered to bridge the Curie temperatures obtained experimentally to those calculated theoretically in inhomogeneous magnetic semiconductors. The behavior of magnetism in Mn-doped ZnSnAs2 can be explained by three different phases within the present framework.

Novel diluted magnetic semiconductor materials based on zinc oxide

NASA Astrophysics Data System (ADS)

Chakraborti, Deepayan

The primary aim of this work was to develop a ZnO based diluted magnetic semiconductor (DMS) materials system which displays ferromagnetism above room temperature and to understand the origin of long-range ferromagnetic ordering in these systems. Recent developments in the field of spintronics (spin based electronics) have led to an extensive search for materials in which semiconducting properties can be integrated with magnetic properties to realize the objective of successful fabrication of spin-based devices. For these devices we require a high efficiency of spin current injection at room temperature. Diluted magnetic semiconductors (DMS) can serve this role, but they should not only display room temperature ferromagnetism (RTFM) but also be capable of generating spin polarized carriers. Transition metal doped ZnO has proved to be a potential candidate as a DMS showing RTFM. The origin of ferromagnetic ordering in ZnO is still under debate. However, the presence of magnetic secondary phases, composition fluctuations and nanoclusters could also explain the observation of ferromagnetism in the DMS samples. This encouraged us to investigate Cu-doped(+ spin in the 2+ valence state) ZnO system as a probable candidate exhibiting RTFM because neither metallic Cu nor its oxides (Cu2O or CuO) are ferromagnetic. The role of defects and free carriers on the ferromagnetic ordering of Cu-doped ZnO thin films was studied to ascertain the origin of ferromagnetism in this system. A novel non-equilibrium Pulsed Laser Deposition technique has been used to grow high quality epitaxial thin films of Cu:ZnO and (Co,Cu):ZnO on c-plane Sapphire by domain matching epitxay. Both the systems showed ferromagnetic ordering above 300K but Cu ions showed a much stronger ferromagnetic ordering than Co, especially at low concentrations (1-2%) of Cu where we realized near 100% polarization. But, the incorporation of Cu resulted in a 2-order of magnitude rise in the resistivity from 10-1 to 101 Ohm cm which can prove to be detrimental to the injection of polarized electrons. In order to decrease the resistivity and to understand the role of free carriers in mediating the ferromagnetic ordering, the Cu-doped ZnO films were co-doped with an n-type dopant like Al which increased the free carriers concentration by 3 orders of magnitude from 1017 to 1020 cm -3 without significantly altering the near 100% spin polarization in the Cu:ZnO system. This lack of correlation between free carrier concentration and the magnetic moment implied that a free carrier mediated exchange does not stabilize the long range ferromagnetic ordering. A reduction in the number of oxygen vacancies brought about by high temperature oxygen annealing had a large degrading effect on the ferromagnetism by reducing the total saturation magnetization by almost an order of magnitude. This strong dependence of magnetization on vacancy concentration and the corresponding weak relationship with free carriers pointed towards a defect mediated mechanism, such as a bound magnetic polaron mediated exchange as being responsible for stabilizing the ferromagnetic ordering in these systems. However, a BMP mechanism would not guarantee a strong coupling between the free carriers and the localized spins to produce spin-polarized current. To investigate this we have fabricated spin valve type device structures where a nonmagnetic ZnO layer was sandwiched between two ferromagnetic (Cu,Al):ZnO layers allowing us to study spin polarized carrier injection across the nonmagnetic semiconductor gap. Initial results have shown evidence of spin polarized carrier injection across the nonmagnetic semiconductor layer even at 300K. Hence, this work demonstrates that the (Cu,Al):ZnO system may become a viable solution for spin injection into spintronic devices.

Self-Assembled Formation of Well-Aligned Cu-Te Nano-Rods on Heavily Cu-Doped ZnTe Thin Films

NASA Astrophysics Data System (ADS)

Liang, Jing; Cheng, Man Kit; Lai, Ying Hoi; Wei, Guanglu; Yang, Sean Derman; Wang, Gan; Ho, Sut Kam; Tam, Kam Weng; Sou, Iam Keong

2016-11-01

Cu doping of ZnTe, which is an important semiconductor for various optoelectronic applications, has been successfully achieved previously by several techniques. However, besides its electrical transport characteristics, other physical and chemical properties of heavily Cu-doped ZnTe have not been reported. We found an interesting self-assembled formation of crystalline well-aligned Cu-Te nano-rods near the surface of heavily Cu-doped ZnTe thin films grown via the molecular beam epitaxy technique. A phenomenological growth model is presented based on the observed crystallographic morphology and measured chemical composition of the nano-rods using various imaging and chemical analysis techniques. When substitutional doping reaches its limit, the extra Cu atoms favor an up-migration toward the surface, leading to a one-dimensional surface modulation and formation of Cu-Te nano-rods, which explain unusual observations on the reflection high energy electron diffraction patterns and apparent resistivity of these thin films. This study provides an insight into some unexpected chemical reactions involved in the heavily Cu-doped ZnTe thin films, which may be applied to other material systems that contain a dopant having strong reactivity with the host matrix.

Self-compensation in arsenic doping of CdTe

DOE PAGES

Ablekim, Tursun; Swain, Santosh K.; Yin, Wan -Jian; ...

2017-07-04

Efficient p-type doping in CdTe has remained a critical challenge for decades, limiting the performance of CdTe-based semiconductor devices. Arsenic is a promising p-type dopant; however, reproducible doping with high concentration is difficult and carrier lifetime is low. We systematically studied defect structures in As-doped CdTe using high-purity single crystal wafers to investigate the mechanisms that limit p-type doping. Two As-doped CdTe with varying acceptor density and two undoped CdTe were grown in Cd-rich and Te-rich environments. The defect structures were investigated by thermoelectric-effect spectroscopy (TEES), and first-principles calculations were used for identifying and assigning the experimentally observed defects. Measurementsmore » revealed activation of As is very low in both As-doped samples with very short lifetimes indicating strong compensation and the presence of significant carrier trapping defects. Defect studies suggest two acceptors and one donor level were introduced by As doping with activation energies at ~88 meV, ~293 meV and ~377 meV. In particular, the peak shown at ~162 K in the TEES spectra is very prominent in both As-doped samples, indicating a signature of AX-center donors. In conclusion, the AX-centers are believed to be responsible for most of the compensation because of their low formation energy and very prominent peak intensity in TEES spectra.« less

Self-compensation in arsenic doping of CdTe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ablekim, Tursun; Swain, Santosh K.; Yin, Wan -Jian

Efficient p-type doping in CdTe has remained a critical challenge for decades, limiting the performance of CdTe-based semiconductor devices. Arsenic is a promising p-type dopant; however, reproducible doping with high concentration is difficult and carrier lifetime is low. We systematically studied defect structures in As-doped CdTe using high-purity single crystal wafers to investigate the mechanisms that limit p-type doping. Two As-doped CdTe with varying acceptor density and two undoped CdTe were grown in Cd-rich and Te-rich environments. The defect structures were investigated by thermoelectric-effect spectroscopy (TEES), and first-principles calculations were used for identifying and assigning the experimentally observed defects. Measurementsmore » revealed activation of As is very low in both As-doped samples with very short lifetimes indicating strong compensation and the presence of significant carrier trapping defects. Defect studies suggest two acceptors and one donor level were introduced by As doping with activation energies at ~88 meV, ~293 meV and ~377 meV. In particular, the peak shown at ~162 K in the TEES spectra is very prominent in both As-doped samples, indicating a signature of AX-center donors. In conclusion, the AX-centers are believed to be responsible for most of the compensation because of their low formation energy and very prominent peak intensity in TEES spectra.« less

Creating ligand-free silicon germanium alloy nanocrystal inks.

PubMed

Erogbogbo, Folarin; Liu, Tianhang; Ramadurai, Nithin; Tuccarione, Phillip; Lai, Larry; Swihart, Mark T; Prasad, Paras N

2011-10-25

Particle size is widely used to tune the electronic, optical, and catalytic properties of semiconductor nanocrystals. This contrasts with bulk semiconductors, where properties are tuned based on composition, either through doping or through band gap engineering of alloys. Ideally, one would like to control both size and composition of semiconductor nanocrystals. Here, we demonstrate production of silicon-germanium alloy nanoparticles by laser pyrolysis of silane and germane. We have used FTIR, TEM, XRD, EDX, SEM, and TOF-SIMS to conclusively determine their structure and composition. Moreover, we show that upon extended sonication in selected solvents, these bare nanocrystals can be stably dispersed without ligands, thereby providing the possibility of using them as an ink to make patterned films, free of organic surfactants, for device fabrication. The engineering of these SiGe alloy inks is an important step toward the low-cost fabrication of group IV nanocrystal optoelectronic, thermoelectric, and photovoltaic devices.

Infrared spectroscopy of organic semiconductors modified by self-assembled monolayers

NASA Astrophysics Data System (ADS)

Khatib, O.; Lee, B.; Podzorov, V.; Yuen, J.; Heeger, A. J.; Li, Z. Q.; di Ventra, M.; Basov, D. N.

2009-03-01

Recently, self-assembled monolayers (SAMs) were used to modify electronic surface properties of organic single crystals, leading to several orders of magnitude increase in the electrical conductivity^1. Motivated by this discovery, the same technique was applied to polymers. Here we present a thorough spectroscopic investigation of organic semiconductors based on poly(3-hexlthiophene) (P3HT) that have been treated with a fluorinated trichlorosilane SAM. Infrared spectroscopy offers access to details of charge injection, electrostatic doping, and the electronic structure that are not always available from transport measurements, which can be dominated by defects and contact effects. In polymer films, the SAM molecules penetrate into the bulk, leading to a rich spectrum of electronic excitations in the mid-infrared energy range. ^1 M. F. Calhoun, J. Sanchez, D. Olaya, M. E. Gershenson, V. Podzorov, Electronic functionalization of the surface of organic semiconductors with self-assembled monolayers, Nature Mater. 7, 84--89 (2008)

Plastic lab-on-a-chip for fluorescence excitation with integrated organic semiconductor lasers.

PubMed

Vannahme, Christoph; Klinkhammer, Sönke; Lemmer, Uli; Mappes, Timo

2011-04-25

Laser light excitation of fluorescent markers offers highly sensitive and specific analysis for bio-medical or chemical analysis. To profit from these advantages for applications in the field or at the point-of-care, a plastic lab-on-a-chip with integrated organic semiconductor lasers is presented here. First order distributed feedback lasers based on the organic semiconductor tris(8-hydroxyquinoline) aluminum (Alq3) doped with the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyril)-4H-pyrane (DCM), deep ultraviolet induced waveguides, and a nanostructured microfluidic channel are integrated into a poly(methyl methacrylate) (PMMA) substrate. A simple and parallel fabrication process is used comprising thermal imprint, DUV exposure, evaporation of the laser material, and sealing by thermal bonding. The excitation of two fluorescent marker model systems including labeled antibodies with light emitted by integrated lasers is demonstrated.

Fabricating porous silicon carbide

NASA Technical Reports Server (NTRS)

Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

1994-01-01

The formation of porous SiC occurs under electrochemical anodization. A sample of SiC is contacted electrically with nickel and placed into an electrochemical cell which cell includes a counter electrode and a reference electrode. The sample is encapsulated so that only a bare semiconductor surface is exposed. The electrochemical cell is filled with an HF electrolyte which dissolves the SiC electrochemically. A potential is applied to the semiconductor and UV light illuminates the surface of the semiconductor. By controlling the light intensity, the potential and the doping level, a porous layer is formed in the semiconductor and thus one produces porous SiC.

Fluorene-Based Two-Dimensional Covalent Organic Framework with Thermoelectric Properties through Doping.

PubMed

Wang, Liangying; Dong, Bin; Ge, Rile; Jiang, Fengxing; Xu, Jingkun

2017-03-01

Organic semiconductors have great potential as flexible thermoelectric materials. A fluorene-based covalent organic framework (FL-COF-1) was designed with the aim of creating an enhanced π-π interaction among the crystalline backbones. By the introduction of fluorene units into the frameworks, the FL-COF-1 had high thermal stability with a BET surface area over 1300 m 2 g -1 . The open frameworks were favorable for doping with iodine and followed with the improved charge carrier mobility. The compressed pellet of I 2 @FL-COF-1 exhibited a high Seebeck coefficient of 2450 μV K -1 and power factor of 0.063 μW m -1 K -2 at room temperature, giving the first example of COFs' potential application as thermoelectric materials.

Recent advances in enhanced luminescence upconversion of lanthanide-doped NaYF4 phosphors

NASA Astrophysics Data System (ADS)

Kumar, Deepak; Verma, Kartikey; Verma, Shefali; Chaudhary, Babulal; Som, Sudipta; Sharma, Vishal; Kumar, Vijay; Swart, Hendrik C.

2018-04-01

NaYF4 is regarded as the best upconversion (UC) matrix owing to its low phonon energy, more chemical stability, and a superior refractive index. This review reports on the various synthesis techniques of lanthanide-doped NaYF4 phosphors for UC application. The UC intensity depends on different properties of the matrix and those are discussed in detail. Plasmon-enhanced luminescence UC of the lanthanide-doped NaYF4 core-shells structure is discussed based on a literature survey. The present review provides the information about how the UC intensity can be enhanced. The idea about the UC is then deliberately used for versatile applications such as luminescent materials, display devices, biomedical imaging and different security appliances. In addition, the present review demonstrates the recent trends of NaYF4 UC materials in solar cell devices. The role of NaYF4 phosphor to eradicate the spectral variance among the incident solar spectrum, semiconductor as well as the sub-band gap nature of the semiconductor materials is also discussed in detail. Considering the fact that the research status on NaYF4 phosphor for photovoltaic application is now growing, the present review is therefore very important to the researchers. More importantly, this may promote more interesting research platforms to investigate the realistic use of UC nanophosphors as spectral converters for solar cells.

Electro-plasmonic 2 × 2 channel-routing switch arranged on a thin-Si-doped metal/insulator/semiconductor/metal structure.

PubMed

Moazzam, Mostafa Keshavarz; Kaatuzian, Hassan

2016-01-20

Plasmonics as a new field of chip-scale technology is the interesting substrate of this study to propose and numerically investigate a metal/insulator/semiconductor/metal (MISM)-structure 2×2 plasmonic routing switch. As a planar subwavelength arrangement, the presented design has two npn-doped side-coupled dual waveguides whose duty is to route the propagating surface plasmon polaritons through the device. Relying on the MISM structure, which has a MOS-like thin-film arrangement of typically 45 nm doped silicon covered by a layer of 8 nm thick HfO(2) gate insulator, the routing configuration is electrically addressed based on the carrier-induced plasma dispersion effects as an external electro-plasmonic switching control. Finite-element-method-conducted electromagnetic simulations are employed to evaluate the switch optical response at telecom wavelength of λ=1550  nm, due to which the balanced operation measure of extinction ratios larger than 10 dB and insertion losses of around -1.8  dB are obtained for both channels of CROSS and STRAIGHT. Compared with other photonic and plasmonic switching counterparts, this configuration, besides its potential for CMOS compatibility, can be utilized as a high-speed compact building block to sustain higher-speed, more miniaturized, and less consuming electro-optic routing/switching protocols toward complicated optical integrated circuits and systems.

A first-principles study of group IV and VI atoms doped blue phosphorene

NASA Astrophysics Data System (ADS)

Bai, Ruimin; Chen, Zheng; Gou, Manman; Zhang, Yixin

2018-02-01

Using first-principles calculations, we have systematically investigated the structural, electronic and magnetic properties of blue phosphorene doped by group IV and VI atoms, including C, Si, Ge, Sn, O, S, Se and Te. All the doped systems are energetically stable. Only C, Si, Ge and O-substituted systems show the characteristics of spin polarization and the magnetic moments are all 1.0 μB. Moreover, we found that C, Si, Ge and O doped systems are indirect bandgap semiconductors, while Sn, S, Se and Te doped systems present metallic property. These results show that blue phosphorene can be used prospectively in optoelectronic and spintronic devices.

First principles study of electronic and structural properties of single walled zigzag boron nitride nanotubes doped with the elements of group IV

NASA Astrophysics Data System (ADS)

Bahari, Ali; jalalinejad, Amir; Bagheri, Mosahhar; Amiri, Masoud

2017-11-01

In this paper, structural and electronic properties and stability of (10, 0) born nitride nanotube (BNNT) are considered within density functional theory by doping group IV elements of the periodic table. The HOMO-LUMO gap has been strongly modified and treated a dual manner by choosing B or N sites for dopant atoms. Formation energy calculation shows that B site doping is more stable than N site doping. Results also show that all dopants turn the pristine BNNT into a p-type semiconductor except for carbon-doped BNNT at B site.

Rietveld-refinement and optical study of the Fe doped ZnO thin film by RF magnetron sputtering

NASA Astrophysics Data System (ADS)

Kumar, Arun; Dhiman, Pooja; Singh, M.

2017-05-01

Fe Doped ZnO Dilute Magnetic Semiconductor thin film prepared by RF magnetron sputtering on glass substrate and Influence of 3% Fe-doping on structural and Optical properties has been studied. The Rietveld-refinement analysis shows that Fe doping has a significant effect on crystalline structure, grain size and strain in the thin film. Two dimensional and three-dimensional atom probe tomography of the thin film shows that Fe ions are randomly distributed which is supported by Xray Diffraction (XRD). Fe-doping is found to effectively modify the band gap energy up to 3.5 eV.

Carrier-induced ferromagnetism in half-metallic Co-doped ZnS-diluted magnetic semiconductor: a DFT study

NASA Astrophysics Data System (ADS)

Saikia, D.; Borah, J. P.

2018-03-01

Systematic experimental and theoretical calculations have been performed to investigate the origin of the carrier-induced ferromagnetism in the Co-doped ZnS-diluted magnetic semiconductors. The crystalline structure, morphology of the chemically synthesized Co-doped ZnS nanoparticles are evaluated using X-ray diffraction (XRD) and transmission electron microscopy (TEM) and obtained the average crystallite size in the range 5-8 nm. Fourier transform-infrared spectra reveal the characteristic Zn-S vibrations of cubic ZnS and also show the splitting of peaks with increasing Co concentration which indicates that the Co-doping level beyond 3% affects the structure of ZnS. The room temperature ferromagnetic behavior analyzed by M- H curve exhibited up to the doping level 5%, achieving due to the indirect ` p- d' exchange interactions between the localized ` d' spins of Co2+ ion and the free-delocalized carriers in the host lattice. The existence of the antiferromagnetic coupling is discernable beyond the 5% doping level, owing to the short-range super-exchange interactions between the characteristic ` d' spins of the Co2+ ions which minimize the ferromagnetic ordering. Band structure and density of states (DOS) calculations demonstrate the p- d hybridization mechanism in Co-doped ZnS system which is the main cause of realizing ferromagnetic ordering in the system and also shows the half-metallic characteristics with the combination of semiconducting and metallic nature in the spin-up and spin-down states, respectively.

PdO Doping Tunes Band-Gap Energy Levels as Well as Oxidative Stress Responses to a Co3O4p-Type Semiconductor in Cells and the Lung

PubMed Central

2014-01-01

We demonstrate through PdO doping that creation of heterojunctions on Co3O4 nanoparticles can quantitatively adjust band-gap and Fermi energy levels to study the impact of metal oxide nanoparticle semiconductor properties on cellular redox homeostasis and hazard potential. Flame spray pyrolysis (FSP) was used to synthesize a nanoparticle library in which the gradual increase in the PdO content (0–8.9%) allowed electron transfer from Co3O4 to PdO to align Fermi energy levels across the heterojunctions. This alignment was accompanied by free hole accumulation at the Co3O4 interface and production of hydroxyl radicals. Interestingly, there was no concomitant superoxide generation, which could reflect the hole dominance of a p-type semiconductor. Although the electron flux across the heterojunctions induced upward band bending, the Ec levels of the doped particles showed energy overlap with the biological redox potential (BRP). This allows electron capture from the redox couples that maintain the BRP from −4.12 to −4.84 eV, causing disruption of cellular redox homeostasis and induction of oxidative stress. PdO/Co3O4 nanoparticles showed significant increases in cytotoxicity at 25, 50, 100, and 200 μg/mL, which was enhanced incrementally by PdO doping in BEAS-2B and RAW 264.7 cells. Oxidative stress presented as a tiered cellular response involving superoxide generation, glutathione depletion, cytokine production, and cytotoxicity in epithelial and macrophage cell lines. A progressive series of acute pro-inflammatory effects could also be seen in the lungs of animals exposed to incremental PdO-doped particles. All considered, generation of a combinatorial PdO/Co3O4 nanoparticle library with incremental heterojunction density allowed us to demonstrate the integrated role of Ev, Ec, and Ef levels in the generation of oxidant injury and inflammation by the p-type semiconductor, Co3O4. PMID:24673286

PdO doping tunes band-gap energy levels as well as oxidative stress responses to a Co₃O₄ p-type semiconductor in cells and the lung.

PubMed

Zhang, Haiyuan; Pokhrel, Suman; Ji, Zhaoxia; Meng, Huan; Wang, Xiang; Lin, Sijie; Chang, Chong Hyun; Li, Linjiang; Li, Ruibin; Sun, Bingbing; Wang, Meiying; Liao, Yu-Pei; Liu, Rong; Xia, Tian; Mädler, Lutz; Nel, André E

2014-04-30

We demonstrate through PdO doping that creation of heterojunctions on Co3O4 nanoparticles can quantitatively adjust band-gap and Fermi energy levels to study the impact of metal oxide nanoparticle semiconductor properties on cellular redox homeostasis and hazard potential. Flame spray pyrolysis (FSP) was used to synthesize a nanoparticle library in which the gradual increase in the PdO content (0-8.9%) allowed electron transfer from Co3O4 to PdO to align Fermi energy levels across the heterojunctions. This alignment was accompanied by free hole accumulation at the Co3O4 interface and production of hydroxyl radicals. Interestingly, there was no concomitant superoxide generation, which could reflect the hole dominance of a p-type semiconductor. Although the electron flux across the heterojunctions induced upward band bending, the E(c) levels of the doped particles showed energy overlap with the biological redox potential (BRP). This allows electron capture from the redox couples that maintain the BRP from -4.12 to -4.84 eV, causing disruption of cellular redox homeostasis and induction of oxidative stress. PdO/Co3O4 nanoparticles showed significant increases in cytotoxicity at 25, 50, 100, and 200 μg/mL, which was enhanced incrementally by PdO doping in BEAS-2B and RAW 264.7 cells. Oxidative stress presented as a tiered cellular response involving superoxide generation, glutathione depletion, cytokine production, and cytotoxicity in epithelial and macrophage cell lines. A progressive series of acute pro-inflammatory effects could also be seen in the lungs of animals exposed to incremental PdO-doped particles. All considered, generation of a combinatorial PdO/Co3O4 nanoparticle library with incremental heterojunction density allowed us to demonstrate the integrated role of E(v), E(c), and E(f) levels in the generation of oxidant injury and inflammation by the p-type semiconductor, Co3O4.

Assessment of a Thermoelectric Vest through Physical and Mental Performance

DTIC Science & Technology

2012-04-01

system is a sandwich- type structure of doped bismuth telluride (Bi2Te3) soldered between two ceramic plates. Bi2Te3 acts as a semiconductor and after... doping , the material becomes an efficient TE. Variations in doping create P-N junctions throughout the TE. Figure 3 shows a schematic of a TE...Excalibur Sport Ergonometer was used to increase subject’s core body temperature. The Excalibur Sport is a multi-adjustable ergonometer and is

Superlattices and Semiconductor/Semiconductor Interfaces.

DTIC Science & Technology

1984-01-17

the electron effective ’J. N. Schulman and T. C. Mc"il AppI. Phys. Lett 34. 66311979). masse in the snuff band-gap alloys, suggesting reducedp- 3.P...et al. " have made DLTS measurements on n-type, , lead to the loss of electrically active indium through the for- indium doped CdTe films grown on BaF

Insights on semiconductor-metal transition in indium-doped zinc oxide from x-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry and x-ray diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saw, K. G., E-mail: kgsaw@usm.my; Aznan, N. M., E-mail: nanieaz1004@gmail.com; Yam, F. K., E-mail: yamfk@yahoo.com

2016-07-06

ZnO thin films doped with various amounts of In impurities were prepared by magnetron sputtering at a substrate temperature of 150°C. The shift in optical bandgap of the In-doped ZnO films is studied as a function of carrier concentration. Nominally doped ZnO films exhibit an increase in the measured optical band gap known as the Burstein-Moss effect. Dominant band gap narrowing is observed with increased doping. XPS and TOFSIMS analyses confirm that In is incorporated in the ZnO material. The In 3d peaks show that no metallic In is present as a result of heavy doping. The XRD phase analysismore » shows a preferential c-axis growth but a shift of the ZnO (002) peak to lower 2-theta values with increasing FWHM as the carrier concentration increases indicates the decline in the quality of crystallinity. An elongation of the c lattice constant is also observed and is likely to be caused by intersitital In as the amount of In dopants increases. The incorporation of In induces a semiconductor-metal transition between the carrier concentrations of 3.58 – 5.61×10{sup 19} cm{sup −3} and structural changes in the ZnO host material.« less

EPR and Ferromagnetism in Diluted Magnetic Semiconductor Quantum Wells

NASA Astrophysics Data System (ADS)

König, Jürgen; MacDonald, Allan H.

2003-08-01

Motivated by recent measurements of electron paramagnetic resonance spectra in modulation-doped CdMnTe quantum wells [

Conversion of type of quantum well structure

NASA Technical Reports Server (NTRS)

Ning, Cun-Zheng (Inventor)

2007-01-01

A method for converting a Type 2 quantum well semiconductor material to a Type 1 material. A second layer of undoped material is placed between first and third layers of selectively doped material, which are separated from the second layer by undoped layers having small widths. Doping profiles are chosen so that a first electrical potential increment across a first layer-second layer interface is equal to a first selected value and/or a second electrical potential increment across a second layer-third layer interface is equal to a second selected value. The semiconductor structure thus produced is useful as a laser material and as an incident light detector material in various wavelength regions, such as a mid-infrared region.

Conversion of Type of Quantum Well Structure

NASA Technical Reports Server (NTRS)

Ning, Cun-Zheng (Inventor)

2007-01-01

A method for converting a Type 2 quantum well semiconductor material to a Type 1 material. A second layer of undoped material is placed between first and third layers of selectively doped material, which are separated from the second layer by undoped layers having small widths. Doping profiles are chosen so that a first electrical potential increment across a first layer-second layer interface is equal to a first selected value and/or a second electrical potential increment across a second layer-third layer interface is equal to a second selected value. The semiconductor structure thus produced is useful as a laser material and as an incident light detector material in various wavelength regions, such as a mid-infrared region.

Thermovoltaic semiconductor device including a plasma filter

DOEpatents

Baldasaro, Paul F.

1999-01-01

A thermovoltaic energy conversion device and related method for converting thermal energy into an electrical potential. An interference filter is provided on a semiconductor thermovoltaic cell to pre-filter black body radiation. The semiconductor thermovoltaic cell includes a P/N junction supported on a substrate which converts incident thermal energy below the semiconductor junction band gap into electrical potential. The semiconductor substrate is doped to provide a plasma filter which reflects back energy having a wavelength which is above the band gap and which is ineffectively filtered by the interference filter, through the P/N junction to the source of radiation thereby avoiding parasitic absorption of the unusable portion of the thermal radiation energy.

The Effect of the Electron Tunneling on the Photoelectric Hot Electrons Generation in Metallic-Semiconductor Nanostructures

NASA Astrophysics Data System (ADS)

Elsharif, Asma M.

2018-01-01

Semiconductor photonic crystals (MSPhC) were used to convert solar energy into hot electrons. An experimental model was designed by using metallic semiconductor photonic crystals (MSPhC). The designed MSPhC is based on TiO2/Au schottky contact. The model has similar nanocavity structure for broad gold absorption, but the materials on top of the cavity were changed to a metal and a semiconductor in order to collect the hot electrons. Detailed design steps and characterization have shown a broadband sub-bandgap photoresponse at a wavelength of 590 nm. This is due to the surface plasmon absorption by the wafer-scale Au/TiO2 metallic-semiconductor photonic crystal. Analytical calculation of the hot electron transport from the Au thin layer to the TiO2 conduction band is discussed. This theoretical study is based on the quantum tunneling effect. The photo generation of the hot electrons was undertaken at different wavelengths in Au absorber followed by tunneling through a schottky barrier into a TiO2 collector. The presence of a tunnel current from the absorber to the collector under illumination, offers a method to extract carriers from a hot-electron distribution at few bias voltages is presented in this study. The effects of doping different concentrations of the semiconductor on the evolution of the current characteristics were also investigated and discussed. The electrical characteristics were found to be sensitive to any change in the thickness of the barrier.

Chemo-sensors development based on low-dimensional codoped Mn2O3-ZnO nanoparticles using flat-silver electrodes.

PubMed

Rahman, Mohammed M; Gruner, George; Al-Ghamdi, Mohammed Saad; Daous, Muhammed A; Khan, Sher Bahadar; Asiri, Abdullah M

2013-03-28

Semiconductor doped nanostructure materials have attained considerable attention owing to their electronic, opto-electronic, para-magnetic, photo-catalysis, electro-chemical, mechanical behaviors and their potential applications in different research areas. Doped nanomaterials might be a promising owing to their high-specific surface-area, low-resistances, high-catalytic activity, attractive electro-chemical and optical properties. Nanomaterials are also scientifically significant transition metal-doped nanostructure materials owing to their extraordinary mechanical, optical, electrical, electronic, thermal, and magnetic characteristics. Recently, it has gained significant interest in manganese oxide doped-semiconductor materials in order to develop their physico-chemical behaviors and extend their efficient applications. It has not only investigated the basic of magnetism, but also has huge potential in scientific features such as magnetic materials, bio- & chemi-sensors, photo-catalysts, and absorbent nanomaterials. The chemical sensor also displays the higher-sensitivity, reproducibility, long-term stability, and enhanced electrochemical responses. The calibration plot is linear (r2 = 0.977) over the 0.1 nM to 50.0 μM 4-nitrophenol concentration ranges. The sensitivity and detection limit is ~4.6667 μA cm-2 μM-1 and ~0.83 ± 0.2 nM (at a Signal-to-Noise-Ratio, SNR of 3) respectively. To best of our knowledge, this is the first report for detection of 4-nitrophenol chemical with doped Mn2O3-ZnO NPs using easy and reliable I-V technique in short response time. As for the doped nanostructures, NPs are introduced a route to a new generation of toxic chemo-sensors, but a premeditate effort has to be applied for doped Mn2O3-ZnO NPs to be taken comprehensively for large-scale applications, and to achieve higher-potential density with accessible to individual chemo-sensors. In this report, it is also discussed the prospective utilization of Mn2O3-ZnO NPs on the basis of carcinogenic chemical sensing, which could also be applied for the detection of hazardous chemicals in ecological, environmental, and health care fields.

Chemo-sensors development based on low-dimensional codoped Mn2O3-ZnO nanoparticles using flat-silver electrodes

PubMed Central

2013-01-01

Background Semiconductor doped nanostructure materials have attained considerable attention owing to their electronic, opto-electronic, para-magnetic, photo-catalysis, electro-chemical, mechanical behaviors and their potential applications in different research areas. Doped nanomaterials might be a promising owing to their high-specific surface-area, low-resistances, high-catalytic activity, attractive electro-chemical and optical properties. Nanomaterials are also scientifically significant transition metal-doped nanostructure materials owing to their extraordinary mechanical, optical, electrical, electronic, thermal, and magnetic characteristics. Recently, it has gained significant interest in manganese oxide doped-semiconductor materials in order to develop their physico-chemical behaviors and extend their efficient applications. It has not only investigated the basic of magnetism, but also has huge potential in scientific features such as magnetic materials, bio- & chemi-sensors, photo-catalysts, and absorbent nanomaterials. Results The chemical sensor also displays the higher-sensitivity, reproducibility, long-term stability, and enhanced electrochemical responses. The calibration plot is linear (r2 = 0.977) over the 0.1 nM to 50.0 μM 4-nitrophenol concentration ranges. The sensitivity and detection limit is ~4.6667 μA cm-2 μM-1 and ~0.83 ± 0.2 nM (at a Signal-to-Noise-Ratio, SNR of 3) respectively. To best of our knowledge, this is the first report for detection of 4-nitrophenol chemical with doped Mn2O3-ZnO NPs using easy and reliable I-V technique in short response time. Conclusions As for the doped nanostructures, NPs are introduced a route to a new generation of toxic chemo-sensors, but a premeditate effort has to be applied for doped Mn2O3-ZnO NPs to be taken comprehensively for large-scale applications, and to achieve higher-potential density with accessible to individual chemo-sensors. In this report, it is also discussed the prospective utilization of Mn2O3-ZnO NPs on the basis of carcinogenic chemical sensing, which could also be applied for the detection of hazardous chemicals in ecological, environmental, and health care fields. PMID:23537000

Intrinsic and extrinsic doping of ZnO and ZnO alloys

NASA Astrophysics Data System (ADS)

Ellmer, Klaus; Bikowski, André

2016-10-01

In this article the doping of the oxidic compound semiconductor ZnO is reviewed with special emphasis on n-type doping. ZnO naturally exhibits n-type conductivity, which is used in the application of highly doped n-type ZnO as a transparent electrode, for instance in thin film solar cells. For prospective application of ZnO in other electronic devices (LEDs, UV photodetectors or power devices) p-type doping is required, which has been reported only minimally. Highly n-type doped ZnO can be prepared by doping with the group IIIB elements B, Al, Ga, and In, which act as shallow donors according to the simple hydrogen-like substitutional donor model of Bethe (1942 Theory of the Boundary Layer of Crystal Rectifiers (Boston, MA: MIT Rad Lab.)). Group IIIA elements (Sc, Y, La etc) are also known to act as shallow donors in ZnO, similarly explainable by the shallow donor model of Bethe. Some reports showed that even group IVA (Ti, Zr, Hf) and IVB (Si, Ge) elements can be used to prepare highly doped ZnO films—which, however, can no longer be explained by the simple hydrogen-like substitutional donor model. More probably, these elements form defect complexes that act as shallow donors in ZnO. On the other hand, group V elements on oxygen lattice sites (N, P, As, and Sb), which were viewed for a long time as typical shallow acceptors, behave instead as deep acceptors, preventing high hole concentrations in ZnO at room temperature. Also, ‘self’-compensation, i.e. the formation of a large number of intrinsic donors at high acceptor concentrations seems to counteract the p-type doping of ZnO. At donor concentrations above about 1020 cm-3, the electrical activation of the dopant elements is often less than 100%, especially in polycrystalline thin films. Reasons for the electrical deactivation of the dopant atoms are (i) the formation of dopant-defect complexes, (ii) the compensation of the electrons by acceptors (Oi, VZn) or (iii) the formation of secondary phases, for instance Al2O3, Ga2O3 etc. The strong influence of the different deposition methods and annealing conditions on the doping of ZnO is discussed. This review shows that, though it is one of the best-investigated oxide compound semiconductors over many decades, understanding of the details of the doping properties and mechanisms of zinc oxide is still in its infancy. Based on this review, prospective research opportunities are devised.

High performance Si nanowire field-effect-transistors based on a CMOS inverter with tunable threshold voltage.

PubMed

Van, Ngoc Huynh; Lee, Jae-Hyun; Sohn, Jung Inn; Cha, Seung Nam; Whang, Dongmok; Kim, Jong Min; Kang, Dae Joon

2014-05-21

We successfully fabricated nanowire-based complementary metal-oxide semiconductor (NWCMOS) inverter devices by utilizing n- and p-type Si nanowire field-effect-transistors (NWFETs) via a low-temperature fabrication processing technique. We demonstrate that NWCMOS inverter devices can be operated at less than 1 V, a significantly lower voltage than that of typical thin-film based complementary metal-oxide semiconductor (CMOS) inverter devices. This low-voltage operation was accomplished by controlling the threshold voltage of the n-type Si NWFETs through effective management of the nanowire (NW) doping concentration, while realizing high voltage gain (>10) and ultra-low static power dissipation (≤3 pW) for high-performance digital inverter devices. This result offers a viable means of fabricating high-performance, low-operation voltage, and high-density digital logic circuits using a low-temperature fabrication processing technique suitable for next-generation flexible electronics.

Strong enhancement of emission efficiency in GaN light-emitting diodes by plasmon-coupled light amplification of graphene

NASA Astrophysics Data System (ADS)

Kim, Jong Min; Kim, Sung; Hwang, Sung Won; Kim, Chang Oh; Shin, Dong Hee; Kim, Ju Hwan; Jang, Chan Wook; Kang, Soo Seok; Hwang, Euyheon; Choi, Suk-Ho; El-Gohary, Sherif H.; Byun, Kyung Min

2018-02-01

Recently, we have demonstrated that excitation of plasmon-polaritons in a mechanically-derived graphene sheet on the top of a ZnO semiconductor considerably enhances its light emission efficiency. If this scheme is also applied to device structures, it is then expected that the energy efficiency of light-emitting diodes (LEDs) increases substantially and the commercial potential will be enormous. Here, we report that the plasmon-induced light coupling amplifies emitted light by ˜1.6 times in doped large-area chemical-vapor-deposition-grown graphene, which is useful for practical applications. This coupling behavior also appears in GaN-based LEDs. With AuCl3-doped graphene on Ga-doped ZnO films that is used as transparent conducting electrodes for the LEDs, the average electroluminescence intensity is 1.2-1.7 times enhanced depending on the injection current. The chemical doping of graphene may produce the inhomogeneity in charge densities (i.e., electron/hole puddles) or roughness, which can play a role as grating couplers, resulting in such strong plasmon-enhanced light amplification. Based on theoretical calculations, the plasmon-coupled behavior is rigorously explained and a method of controlling its resonance condition is proposed.

Experimental study on the 4H-SiC-based VDMOSFETs with lightly doped P-well field-limiting rings termination

NASA Astrophysics Data System (ADS)

He, Yan Jing; Lv, Hong Liang; Tang, Xiao Yan; Song, Qing Wen; Zhang, Yi Meng; Han, Chao; Zhang, Yi Men; Zhang, Yu Ming

2017-03-01

A lightly doped P-well field-limiting rings (FLRs) termination on 4H-SiC vertical double-implanted metal-oxide-semiconductor field-effect transistors (VDMOSFETs) has been investigated. Based on the simulation, the proposed termination applied to 4H-SiC VDMOSFET could achieve an almost same breakdown voltage (BV) and have the advantage of lower ion-implantation damage comparing with P+ FLRs termination. Meanwhile, this kind of termination also reduces the difficulty and consumption of fabrication process. 4H-SiC VDMOSFETs with lightly doped P-well (FLRs) termination have been fabricated on 10 μm thick epi-layer with nitrogen doping concentration of 6.2 × 1015 cm-3. The maximum breakdown voltage of the 4H-SiC VDMOSFETs has achieved as high as 1610 V at a current of 15 μA, which is very close to the simulated result of 1643 V and about 90% of the plane parallel breakdown voltage of 1780 V. It is considered that P-well FLRs termination is an effective, robust and process-tolerant termination structure suitable for 4H-SiC VDMOSFET.

Hg-Based Epitaxial Materials for Topological Insulators

DTIC Science & Technology

2014-07-01

Research Laboratory for investigation of properties. 15. SUBJECT TERMS EOARD, topological insulator , diluted magnetic ...topological superconductors and spintronics to quantum computation (e.g. see C.L.Kane and J.E.Moore "Topological Insulators " Physics World (2011) 24...tetradymite semiconductors Bi2Te3, Bi2Se3, and Sb2Te3 which form magnetically ordered insulators when doped with transition metal elements Cr or Fe (Rui Yu et

Chemically fixed p-n heterojunctions for polymer electronics by means of covalent B-F bond formation.

PubMed

Hoven, Corey V; Wang, Huiping; Elbing, Mark; Garner, Logan; Winkelhaus, Daniel; Bazan, Guillermo C

2010-03-01

Widely used solid-state devices fabricated with inorganic semiconductors, including light-emitting diodes and solar cells, derive much of their function from the p-n junction. Such junctions lead to diode characteristics and are attained when p-doped and n-doped materials come into contact with each other. Achieving bilayer p-n junctions with semiconducting polymers has been hindered by difficulties in the deposition of thin films with independent p-doped and n-doped layers. Here we report on how to achieve permanently fixed organic p-n heterojunctions by using a cationic conjugated polyelectrolyte with fluoride counteranions and an underlayer composed of a neutral conjugated polymer bearing anion-trapping functional groups. Application of a bias leads to charge injection and fluoride migration into the neutral layer, where irreversible covalent bond formation takes place. After the initial charging and doping, one obtains devices with no delay in the turn on of light-emitting electrochemical behaviour and excellent current rectification. Such devices highlight how mobile ions in organic media can open opportunities to realize device structures in ways that do not have analogies in the world of silicon and promise new opportunities for integrating organic materials within technologies now dominated by inorganic semiconductors.

Chemically fixed p-n heterojunctions for polymer electronics by means of covalent B-F bond formation

NASA Astrophysics Data System (ADS)

Hoven, Corey V.; Wang, Huiping; Elbing, Mark; Garner, Logan; Winkelhaus, Daniel; Bazan, Guillermo C.

2010-03-01

Widely used solid-state devices fabricated with inorganic semiconductors, including light-emitting diodes and solar cells, derive much of their function from the p-n junction. Such junctions lead to diode characteristics and are attained when p-doped and n-doped materials come into contact with each other. Achieving bilayer p-n junctions with semiconducting polymers has been hindered by difficulties in the deposition of thin films with independent p-doped and n-doped layers. Here we report on how to achieve permanently fixed organic p-n heterojunctions by using a cationic conjugated polyelectrolyte with fluoride counteranions and an underlayer composed of a neutral conjugated polymer bearing anion-trapping functional groups. Application of a bias leads to charge injection and fluoride migration into the neutral layer, where irreversible covalent bond formation takes place. After the initial charging and doping, one obtains devices with no delay in the turn on of light-emitting electrochemical behaviour and excellent current rectification. Such devices highlight how mobile ions in organic media can open opportunities to realize device structures in ways that do not have analogies in the world of silicon and promise new opportunities for integrating organic materials within technologies now dominated by inorganic semiconductors.

Sub-parts per million NO2 chemi-transistor sensors based on composite porous silicon/gold nanostructures prepared by metal-assisted etching.

PubMed

Sainato, Michela; Strambini, Lucanos Marsilio; Rella, Simona; Mazzotta, Elisabetta; Barillaro, Giuseppe

2015-04-08

Surface doping of nano/mesostructured materials with metal nanoparticles to promote and optimize chemi-transistor sensing performance represents the most advanced research trend in the field of solid-state chemical sensing. In spite of the promising results emerging from metal-doping of a number of nanostructured semiconductors, its applicability to silicon-based chemi-transistor sensors has been hindered so far by the difficulties in integrating the composite metal-silicon nanostructures using the complementary metal-oxide-semiconductor (CMOS) technology. Here we propose a facile and effective top-down method for the high-yield fabrication of chemi-transistor sensors making use of composite porous silicon/gold nanostructures (cSiAuNs) acting as sensing gate. In particular, we investigate the integration of cSiAuNs synthesized by metal-assisted etching (MAE), using gold nanoparticles (NPs) as catalyst, in solid-state junction-field-effect transistors (JFETs), aimed at the detection of NO2 down to 100 parts per billion (ppb). The chemi-transistor sensors, namely cSiAuJFETs, are CMOS compatible, operate at room temperature, and are reliable, sensitive, and fully recoverable for the detection of NO2 at concentrations between 100 and 500 ppb, up to 48 h of continuous operation.

An Optoelectronics Research Center

DTIC Science & Technology

2006-03-08

compared with a -2 mm wide slab, -200 nrn thick silicon (SOl) top-only-gate planar MOSFET with otherwise similar doping profiles, gate length and...acoustic phonons, impurity doping profile and surface roughness influences the transport process in the channel regions. The electron mobility in the...application areas including: nanoscale epitaxial growth for semiconductor heterostructures; nanofluidics for biological separations; nanomagnetics for

Conjugated ionomers for photovoltaic applications: electric field driven charge separation in organic photovoltaics. Final Technical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lonergan, Mark

Final technical report for Conjugated ionomers for photovoltaic applications, electric field driven charge separation in organic photovoltaics. The central goal of the work we completed was been to understand the photochemical and photovoltaic properties of ionically functionalized conjugated polymers (conjugated ionomers or polyelectrolytes) and energy conversion systems based on them. We primarily studied two classes of conjugated polymer interfaces that we developed based either upon undoped conjugated polymers with an asymmetry in ionic composition (the ionic junction) or doped conjugated polymers with an asymmetry in doping type (the p-n junction). The materials used for these studies have primarily been themore » polyacetylene ionomers. We completed a detailed study of p-n junctions with systematically varying dopant density, photochemical creation of doped junctions, and experimental and theoretical work on charge transport and injection in polyacetylene ionomers. We have also completed related work on the use of conjugated ionomers as interlayers that improve the efficiency or organic photovoltaic systems and studied several important aspects of the chemistry of ionically functionalized semiconductors, including mechanisms of so-called "anion-doping", the formation of charge transfer complexes with oxygen, and the synthesis of new polyfluorene polyelectrolytes. We also worked worked with the Haley group at the University of Oregon on new indenofluorene-based organic acceptors.« less

Gain and refractive index dynamics in p-doped InAs quantum dash semiconductor optical amplifiers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komolibus, Katarzyna; Tyndall National Institute, University College Cork, Cork T12 R5CP; Piwonski, Tomasz, E-mail: tomasz.piwonski@tyndall.ie

The ultrafast carrier dynamics in a p-doped dash-in-a-well structure at 1.5 μm is experimentally investigated. An analysis of the timescales related to carrier relaxation and escape processes as well as the “dynamical” linewidth enhancement factor is presented and compared with results obtained from similar un-doped materials. Intentional p-doping of the active region results in an enhancement of the intermediate timescale of the gain dynamics associated with phonon-assisted electron capture and a reduction of the α-factor due to increased differential gain.

Development and Electrochemical Investigations of an EIS- (Electrolyte-Insulator-Semiconductor) based Biosensor for Cyanide Detection

PubMed Central

Turek, Monika; Ketterer, Lothar; Claβen, Melanie; Berndt, Heinz K.; Elbers, Gereon; Krüger, Peter; Keusgen, Michael; Schöning, Michael J.

2007-01-01

A cyanide biosensor based on a pH-sensitive p-doped electrolyte-insulator-semiconductor (EIS) structure with an immobilised enzyme (cyanidase) is realised at the laboratory scale. The immobilisation of the cyanidase is performed in two distinct steps: first, the covalent coupling of cyanidase to an N-hydroxysuccinimide- (NHS) activated Sepharose™ gel and then, the physical entrapment of NHS-activated Sepharose™ with the immobilised cyanidase in a dialysis membrane onto the EIS structure. The immobilisation of the cyanidase to the NHS-activated Sepharose™ is studied by means of gel electrophoresis measurements and investigations using an ammonia- (NH3) selective electrode. For the electrochemical characterisation of the cyanide biosensor, capacitance/voltage and constant capacitance measurements, respectively, have been carried out. A differential measurement procedure is presented to evaluate the cyanide concentration-dependent biosensor signals.

Hydrogen Gas Sensors Based on Semiconductor Oxide Nanostructures

PubMed Central

Gu, Haoshuang; Wang, Zhao; Hu, Yongming

2012-01-01

Recently, the hydrogen gas sensing properties of semiconductor oxide (SMO) nanostructures have been widely investigated. In this article, we provide a comprehensive review of the research progress in the last five years concerning hydrogen gas sensors based on SMO thin film and one-dimensional (1D) nanostructures. The hydrogen sensing mechanism of SMO nanostructures and some critical issues are discussed. Doping, noble metal-decoration, heterojunctions and size reduction have been investigated and proved to be effective methods for improving the sensing performance of SMO thin films and 1D nanostructures. The effect on the hydrogen response of SMO thin films and 1D nanostructures of grain boundary and crystal orientation, as well as the sensor architecture, including electrode size and nanojunctions have also been studied. Finally, we also discuss some challenges for the future applications of SMO nanostructured hydrogen sensors. PMID:22778599

Hybrid Co-deposition of Mixed-Valent Molybdenum-Germanium Oxides (MoxGeyOz): A Route to Tunable Optical Transmission (Postprint)

DTIC Science & Technology

2015-08-05

to increased doping levels in indirect semiconductors [84]. The slope, and magnitude of the transmission curves continue to decrease alongside UL...periodically aluminium- doped zinc oxide thin films, Thin Solid Films 519 (2011) 2280–2286. [2] T. Minami, H. Nanto, S. Takata, Highly conductive and...transparent aluminum doped zinc oxide thin films prepared by RF magnetron sputtering, Jpn. J. Appl. Phys. 23 (1984) L280. [3] T. Minami, Present status of

Doped Organic Transistors.

PubMed

Lüssem, Björn; Keum, Chang-Min; Kasemann, Daniel; Naab, Ben; Bao, Zhenan; Leo, Karl

2016-11-23

Organic field-effect transistors hold the promise of enabling low-cost and flexible electronics. Following its success in organic optoelectronics, the organic doping technology is also used increasingly in organic field-effect transistors. Doping not only increases device performance, but it also provides a way to fine-control the transistor behavior, to develop new transistor concepts, and even improve the stability of organic transistors. This Review summarizes the latest progress made in the understanding of the doping technology and its application to organic transistors. It presents the most successful doping models and an overview of the wide variety of materials used as dopants. Further, the influence of doping on charge transport in the most relevant polycrystalline organic semiconductors is reviewed, and a concise overview on the influence of doping on transistor behavior and performance is given. In particular, recent progress in the understanding of contact doping and channel doping is summarized.

Fundamental studies of graphene/graphite and graphene-based Schottky photovoltaic devices

NASA Astrophysics Data System (ADS)

Miao, Xiaochang

In the carbon allotropes family, graphene is one of the most versatile members and has been extensively studied since 2004. The goal of this dissertation is not only to investigate the novel fundamental science of graphene and its three-dimensional sibling, graphite, but also to explore graphene's promising potential in modern electronic and optoelectronic devices. The first two chapters provide a concise introduction to the fundamental solid state physics of graphene (as well as graphite) and the physics at the metal/semiconductor interfaces. In the third chapter, we demonstrate the formation of Schottky junctions at the interfaces of graphene (semimetal) and various inorganic semiconductors that play dominating roles in today's semiconductor technology, such as Si, SiC, GaAs and GaN. As shown from their current-voltage (I -V) and capacitance-voltage (C-V) characteristics, the interface physics can be well described within the framework of the Schottky-Mott model. The results are also well consist with that from our previous studies on graphite based Schottky diodes. In the fourth chapter, as an extension of graphene based Schottky work, we investigate the photovoltaic (PV) effect of graphene/Si junctions after chemically doped with an organic polymer (TFSA). The power conversion efficiency of the solar cell improves from 1.9% to 8.6% after TFSA doping, which is the record in all graphene based PVs. The I -V, C-V and external quantum efficiency measurements suggest 12 that such a significant enhancement in the device performance can be attributed to a doping-induced decrease in the series resistance and a simultaneous increase in the built-in potential. In the fifth chapter, we investigate for the first time the effect of uniaxial strains on magneto-transport properties of graphene. We find that low-temperature weak localization effect in monolayer graphene is gradually suppressed under increasing strains, which is due to a strain-induced decreased intervalley-scattering rate. In chapter 6, we study the high vacuum thermal annealing effect on an unconventional ferromagnetism (FM) in highly oriented pyrolytic graphite (HOPG). The FM diminishes and eventually disappears in annealed samples accompanied by improved electrical transport properties and crystallinity. Our results indicate that the FM is mainly coming from the lattice imperfections.

Interface designed MoS2/GaAs heterostructure solar cell with sandwich stacked hexagonal boron nitride

PubMed Central

Lin, Shisheng; Li, Xiaoqiang; Wang, Peng; Xu, Zhijuan; Zhang, Shengjiao; Zhong, Huikai; Wu, Zhiqian; Xu, Wenli; Chen, Hongsheng

2015-01-01

MoS2 is a layered two-dimensional semiconductor with a direct band gap of 1.8 eV. The MoS2/bulk semiconductor system offers a new platform for solar cell device design. Different from the conventional bulk p-n junctions, in the MoS2/bulk semiconductor heterostructure, static charge transfer shifts the Fermi level of MoS2 toward that of bulk semiconductor, lowering the barrier height of the formed junction. Herein, we introduce hexagonal boron nitride (h-BN) into MoS2/GaAs heterostructure to suppress the static charge transfer, and the obtained MoS2/h-BN/GaAs solar cell exhibits an improved power conversion efficiency of 5.42%. More importantly, the sandwiched h-BN makes the Fermi level tuning of MoS2 more effective. By employing chemical doping and electrical gating into the solar cell device, PCE of 9.03% is achieved, which is the highest among all the reported monolayer transition metal dichalcogenide based solar cells. PMID:26458358

Properties of Semiconductors: Synthesis of Oriented ZnO for Photoelectrochemistry and Photoremediation

ERIC Educational Resources Information Center

Koenig, Emma; Jacobs, Ari; Lisensky, George

2017-01-01

Semiconductors are an important class of materials; preparing ZnO nanorods allows semiconducting properties to be easily observed. The week before lab, groups of four students take 15 min to setup two fluorine-doped tin oxide glass (FTO) slides in a zinc nitrate and hexamethylenetetramine solution stored at 90°C until the next lab. Hexagonal ZnO…

Method of fabricating n-type and p-type microcrystalline semiconductor alloy material including band gap widening elements

DOEpatents

Guha, Subhendu; Ovshinsky, Stanford R.

1990-02-02

A method of fabricating doped microcrystalline semiconductor alloy material which includes a band gap widening element through a glow discharge deposition process by subjecting a precursor mixture which includes a diluent gas to an a.c. glow discharge in the absence of a magnetic field of sufficient strength to induce electron cyclotron resonance.

Platinum nanoparticles on gallium nitride surfaces: effect of semiconductor doping on nanoparticle reactivity.

PubMed

Schäfer, Susanne; Wyrzgol, Sonja A; Caterino, Roberta; Jentys, Andreas; Schoell, Sebastian J; Hävecker, Michael; Knop-Gericke, Axel; Lercher, Johannes A; Sharp, Ian D; Stutzmann, Martin

2012-08-01

Platinum nanoparticles supported on n- and p-type gallium nitride (GaN) are investigated as novel hybrid systems for the electronic control of catalytic activity via electronic interactions with the semiconductor support. In situ oxidation and reduction were studied with high pressure photoemission spectroscopy. The experiments revealed that the underlying wide-band-gap semiconductor has a large influence on the chemical composition and oxygen affinity of supported nanoparticles under X-ray irradiation. For as-deposited Pt cuboctahedra supported on n-type GaN, a higher fraction of oxidized surface atoms was observed compared to cuboctahedral particles supported on p-type GaN. Under an oxygen atmosphere, immediate oxidation was recorded for nanoparticles on n-type GaN, whereas little oxidation was observed for nanoparticles on p-type GaN. Together, these results indicate that changes in the Pt chemical state under X-ray irradiation depend on the type of GaN doping. The strong interaction between the nanoparticles and the support is consistent with charge transfer of X-ray photogenerated free carriers at the semiconductor-nanoparticle interface and suggests that GaN is a promising wide-band-gap support material for photocatalysis and electronic control of catalysis.

Regulation of depletion layer width in Pb(Zr,Ti)O3/Nb:SrTiO3 heterostructures

NASA Astrophysics Data System (ADS)

Bai, Yu; Jie Wang, Zhan; Cui, Jian Zhong; Zhang, Zhi Dong

2018-05-01

Improving the tunability of depletion layer width (DLW) in ferroelectric/semiconductor heterostructures is important for the performance of some devices. In this work, 200-nm-thick Pb(Zr0.4Ti0.6)O3 (PZT) films were deposited on different Nb-doped SrTiO3 (NSTO) substrates, and the tunability of DLW at PZT/NSTO interfaces were studied. Our results showed that the maximum tunability of the DLW was achieved at the NSTO substrate with 0.5 wt% Nb. On the basis of the modified capacitance model and the ferroelectric semiconductor theory, we suggest that the tunability of the DLW in PZT/NSTO heterostructures can be attributed to a delicate balance of the depletion layer charge and the ferroelectric polarization charge. Therefore, the performance of some devices related to the tunability of DLW in ferroelectric/semiconductor heterostructures can be improved by modulating the doping concentration in semiconducting electrode materials.

CMOS-based carbon nanotube pass-transistor logic integrated circuits

PubMed Central

Ding, Li; Zhang, Zhiyong; Liang, Shibo; Pei, Tian; Wang, Sheng; Li, Yan; Zhou, Weiwei; Liu, Jie; Peng, Lian-Mao

2012-01-01

Field-effect transistors based on carbon nanotubes have been shown to be faster and less energy consuming than their silicon counterparts. However, ensuring these advantages are maintained for integrated circuits is a challenge. Here we demonstrate that a significant reduction in the use of field-effect transistors can be achieved by constructing carbon nanotube-based integrated circuits based on a pass-transistor logic configuration, rather than a complementary metal-oxide semiconductor configuration. Logic gates are constructed on individual carbon nanotubes via a doping-free approach and with a single power supply at voltages as low as 0.4 V. The pass-transistor logic configurarion provides a significant simplification of the carbon nanotube-based circuit design, a higher potential circuit speed and a significant reduction in power consumption. In particular, a full adder, which requires a total of 28 field-effect transistors to construct in the usual complementary metal-oxide semiconductor circuit, uses only three pairs of n- and p-field-effect transistors in the pass-transistor logic configuration. PMID:22334080

Method for formation of thin film transistors on plastic substrates

DOEpatents

Carey, Paul G.; Smith, Patrick M.; Sigmon, Thomas W.; Aceves, Randy C.

1998-10-06

A process for formation of thin film transistors (TFTs) on plastic substrates replaces standard thin film transistor fabrication techniques, and uses sufficiently lower processing temperatures so that inexpensive plastic substrates may be used in place of standard glass, quartz, and silicon wafer-based substrates. The process relies on techniques for depositing semiconductors, dielectrics, and metals at low temperatures; crystallizing and doping semiconductor layers in the TFT with a pulsed energy source; and creating top-gate self-aligned as well as back-gate TFT structures. The process enables the fabrication of amorphous and polycrystalline channel silicon TFTs at temperatures sufficiently low to prevent damage to plastic substrates. The process has use in large area low cost electronics, such as flat panel displays and portable electronics.

Application of CaCu3Ti4O12 based quadruple perovskites as a promising candidate for optoelectronic devices

NASA Astrophysics Data System (ADS)

Pal, Kamalesh; Jana, Rajkumar; Dey, Arka; Ray, Partha P.; Seikh, Md Motin; Gayen, Arup

2018-05-01

We report the synthesis of nanosized (40-50 nm) CaCu3-xMnxTi4-xMnxO12 (x = 0, 0.5 and 1) quadruple perovskite (QP) semiconductor via a modified combustion method for use as Schottky barrier diode (SBD) at the Al/QP junction. The fabricated SBD is analysed on the basis of thermionic emission theory to observe its quality and some important diode parameters. For insight analysis of charge transport mechanism through metal-semiconductor junction, theory of space charge limited currents is applied and discussed in the light of parameters like carrier concentration, mobility-lifetime product and diffusion length. The Mn-doped exhibit better device performance compared to parent material.

Novel engineered compound semiconductor heterostructures for advanced electronics applications

NASA Astrophysics Data System (ADS)

Stillman, Gregory E.; Holonyak, Nick, Jr.; Coleman, James J.

1992-06-01

To provide the technology base that will enable SDIO capitalization on the performance advantages offered through novel engineered multiple-lavered compound semiconductor structures, this project has focussed on three specific areas: (1) carbon doping of AlGaAs/GaAs and InP/InGaAs materials for reliable high frequency heterojunction bipolar transistors; (2) impurity induced layer disordering and the environmental degradation of AlxGal-xAs-GaAs quantum-well heterostructures and the native oxide stabilization of AlxGal-xAs-GaAs quantum well heterostructure lasers; and (3) non-planar and strained-layer quantum well heterostructure lasers and laser arrays. The accomplishments in this three year research are reported in fifty-six publications and the abstracts included in this report.

Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Brebrick, R. F.; Burger, A.; Dudley, M.; Matyi, R.; Ramachandran, N.; Sha, Yi-Gao; Volz, M.; Shih, Hung-Dah

1999-01-01

Complete and systematic ground-based experimental and theoretical analyses on the Physical Vapor Transport (PVT) of ZnSe and related ternary compound semiconductors have been performed. The analyses included thermodynamics, mass flux, heat treatment of starting material, crystal growth, partial pressure measurements, optical interferometry, chemical analyses, photoluminescence, microscopy, x-ray diffraction and topography as well as theoretical, analytical and numerical analyses. The experimental results showed the influence of gravity orientation on the characteristics of: (1) the morphology of the as-grown crystals as well as the as-grown surface morphology of ZnSe and Cr doped ZnSe crystals; (2) the distribution of impurities and defects in ZnSe grown crystals; and (3) the axial segregation in ZnSeTe grown crystals.

Effects of hydrogen on acceptor activation in ternary nitride semiconductors

DOE PAGES

Fioretti, Angela N.; Stokes, Adam; Young, Matthew R.; ...

2017-02-09

Doping control is necessary to unlock the scientific and technological potential of many materials, including ternary II-IV-nitride semiconductors, which are closely related to binary GaN. In particular, ZnSnN 2 has been reported to have degenerate doping density, despite bandgap energies that are well suited for solar energy conversion. Here, we show that annealing Zn-rich Zn 1+xSn 1-xN 2 grown with added hydrogen reduces its free electron density by orders of magnitude, down to 4 x 10 16 cm -3. This experimental observation can be explained by hydrogen passivation of acceptors in Zn 1+xSn 1-xN 2 during growth, lowering the drivingmore » force for unintentional donor formation. Lastly, these results indicate that the doping control principles used in GaN can be translated to ZnSnN 2, suggesting that other strategies used in binary III-Vs can be applied to accelerate the technological development of ternary II-IV-N 2 materials.« less

Effect of solvents on optical band gap of silicon-doped graphene oxide

NASA Astrophysics Data System (ADS)

Tul Ain, Qura; Al-Modlej, Abeer; Alshammari, Abeer; Naeem Anjum, Muhammad

2018-03-01

The objective of this study was to determine the influence on the optical band gap when the same amount of silicon-doped graphene oxide was dissolved in three different solvents namely, distilled water, benzene, and dichloroethane. Ultraviolet-visible spectroscopy was used to analyse the optical properties of the solutions. Among all these solutions distilled water containing silicon-doped graphene oxide has the smallest optical band gap of 2.9 eV and is considered a semiconductor. Other solutions are not considered as semiconductors as they have optical band gaps greater than 4 eV. It was observed that there is an increase in the value of optical band gap of distilled water, benzene, and dichloroethane solutions indicating a rise in the insulating behaviour. In this experiment, graphene oxide was synthesised from graphite powder by modified Hummer’s method and was then doped with silicon. Synthesis and doping of graphene oxide were confirmed by various characterization techniques. Fourier transmission infrared spectroscopy was used for identification of surface functional groups. X-ray diffraction was carried out to confirm the formation of crystalline graphene oxide and silicon doped graphene oxide. In x-ray diffraction pattern, shifting of intensity peak from a 2θ value of 26.5° to 10° confirmed the synthesis of graphene oxide and various intensity peaks at different values of 2θ confirmed doping of graphene oxide with silicon. Scanning electron microscopy images indicated that graphene oxide sheets were decorated with spherical silicon nanoparticles. Energy dispersive x-ray spectroscopy showed that silicon doped graphene oxide powder contained 63.36% carbon, 34.05% oxygen, and 2.6% silicon.

Optical Absorption in Degenerately Doped Semiconductors: Mott Transition or Mahan Excitons?

NASA Astrophysics Data System (ADS)

Schleife, André; Rödl, Claudia; Fuchs, Frank; Hannewald, Karsten; Bechstedt, Friedhelm

2011-12-01

Electron doping turns semiconductors conductive even when they have wide fundamental band gaps. The degenerate electron gas in the lowest conduction-band states, e.g., of a transparent conducting oxide, drastically modifies the Coulomb interaction between the electrons and, hence, the optical properties close to the absorption edge. We describe these effects by developing an ab initio technique which captures also the Pauli blocking and the Fermi-edge singularity at the optical-absorption onset, that occur in addition to quasiparticle and excitonic effects. We answer the question whether free carriers induce an excitonic Mott transition or trigger the evolution of Wannier-Mott excitons into Mahan excitons. The prototypical n-type zinc oxide is studied as an example.

μSR investigation of a new diluted magnetic semiconductor Li(Zn,Mn,Cu)As with Mn and Cu codoping at the same Zn sites

NASA Astrophysics Data System (ADS)

Guo, S. L.; Zhao, Y.; Man, H. Y.; Ding, C.; Gong, X.; Zhi, G. X.; Fu, L. C.; Gu, Y. L.; Frandsen, B. A.; Liu, L.; Cheung, S. C.; Munsie, T. J.; Wilson, M. N.; Cai, Y. P.; Luke, G. M.; Uemura, Y. J.; Ning, F. L.

2016-09-01

We report the successful synthesis and characterization of a new type I-II-V bulk form diluted magnetic semiconductor (DMS) Li(Zn,Mn,Cu)As, in which charge and spin doping are decoupled via (Cu,Zn) and (Mn,Zn) substitution at the same Zn sites. Ferromagnetic transition temperature up to  ˜33 K has been observed with a coercive field  ˜40 Oe for the 12.5% doping level. μSR measurements confirmed that the magnetic volume fraction reaches nearly 100% at 2 K, and the mechanism responsible for the ferromagnetic interaction in this system is the same as other bulk form DMSs.

Evaluation of structural and optical properties of Ce3+ ions doped (PVA/PVP) composite films for new organic semiconductors

NASA Astrophysics Data System (ADS)

Ali, F. M.; Kershi, R. M.; Sayed, M. A.; AbouDeif, Y. M.

2018-06-01

Polymer blend films based on Polyvinyl alcohol (PVA)/Poly(vinylpyrrolidone) (PVP) doped with different concentration of cerium ions [(PVA/PVP)-x wt.% Ce3+] (x = 3%, 5%, 10% and 15%) were prepared by the conventional solution casting technique. The characteristics of the prepared polymer composite films were studied using X-ray diffraction (XRD), FT-IR and UV-Vis. spectroscopy. The XRD patterns of the investigated samples revealed a clear reduction on the structural parameters such as crystallinity degree and cluster size D of the doped PVA/PVP blend films compared with the virgin one whereas there is no big difference in the d spacing of the product composite films. Significant changes in FT-IR spectra are observed which reveal an interactions between the cerium ions and PVA/PVP blends. The absorption spectra in the ultraviolet-visible region showed a wide red shift in the fundamental absorption edge of (PVA/PVP)-x wt. % Ce3+ composites. The optical gap Eg gradually decreased from 4.54 eV for the undoped PVA/PVP film to 3.10 eV by increasing Ce3+ ions content. The optical dispersion parameters have been analyzed according to Wemple-Didomenico single oscillator model. The dispersion energy Ed, the single oscillator energy Eo, the average inter-band oscillator wavelength λo and the static refractive index no are strongly affected by cerium ions doping. Cerium ions incorporation in PVA/PVP blend films leads to a significant increase in the refractive index and decrease in the optical gap. These results are likely of great important in varieties of applications including polymer waveguides, organic semiconductors, polymer solar cells and optoelectronics devices.

TCNQ molecular semiconductor of the Cu(II)TAAB macrocycle: Optical and electrical properties.

PubMed

Sánchez Vergara, M E; Salcedo, R; Molina, Bertha; Carrera-Téllez, R; Álvarez-Bada, J R; Hernández-García, A; Gómez-Vidales, V

2018-07-05

The present study reports the doping of a semiconducting molecular material through the formation of hydrogen bonds between the macrocycle Cu(II)(TAAB) and the electronic acceptor TCNQ. According to density functional theory (DFT) calculations and electron paramagnetic resonance (EPR) analysis, the doped compound has the shape of a distorted square pyramid, with four nitrogen atoms in the equatorial position and the apical oxygen atom from the water ligands. These water molecules can generate strong hydrogen bonds with TCNQ and the TAAB metallic complex. Thin films of copper molecular material were obtained through high vacuum evaporation and were structurally characterized by IR spectroscopy, EPR and scanning electron microscopy (SEM). Additionally, the absorption coefficient (α) and photon energy (hν) were calculated from UV-vis spectroscopy and used to determine the optical activation energy in each film, from which its semiconducting behavior was established. An important aspect to consider is that the presence of hydrogen bonds is essential to establish the semiconducting nature of these species; this chemical behavior, as well as the resulting electronic mobility, have been studied by DFT theoretical calculations, which reinforce the experimental conclusion of a relationship between Cu(II)TAAB and TCNQ moieties generated by a weak bond. Finally, I-V characteristics have been obtained from a glass/ITO/doped molecular semiconductor/Ag device using Ag and ITO electrodes. Results for the copper-based device show that, at low voltages, the conduction process is of an ohmic nature while, at higher voltages, space-charge-limited current (SCLC) is found. It is highly probable that the doping effect in TCNQ favors electronic transport due to the formation of conduction channels caused by dopant-favored anisotropy. Copyright © 2018 Elsevier B.V. All rights reserved.

Doping Optimization for High Efficiency in Semiconductor Diode Lasers and Amplifiers

DTIC Science & Technology

2016-03-01

resistance 20 mΩ Ith Threshold current 350 mA Using this partial Taylor expansion in (32), the solution for the doping magnitude is C ≈ √ (2/L) I qAV0...2014. [3] M. Kanskar, T. Earles , T. Goodnough, E. Stiers, D. Botez, and L. J. Mawst, “High power conversion efficiency Al-free diode lasers for pumping

A statistical model of a metallic inclusion in semiconducting media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shikin, V. B., E-mail: shikin@issp.ac.ru

The properties of an isolated multicharged atom embedded into a semiconducting medium are discussed. The analysis generalizes the results of the known Thomas–Fermi theory for a multicharged (Z ≫ 1) atom in vacuum when it is immersed into an electron–hole gas of finite temperature. The Thomas–Fermi–Debye (TFD) atom problem is directly related to the properties of donors in low-doped semiconductors and is alternative in its conclusions to the ideal scenario of dissociation of donors. In the existing ideal statistics, an individual donor under infinitely low doping is completely ionized (a charged center does not hold its neutralizing counter-ions). A Thomas–Fermi–Debyemore » atom (briefly, a TFD donor) remains a neutral formation that holds its screening “coat” even for infinitely low doping level, i.e., in the region of n{sub d}λ{sub 0}{sup 3} ≪ 1, where n{sub d} is the concentration of the doping impurity and λ{sub 0} is the Debye length with the parameters of intrinsic semiconductor. Various observed consequences in the behavior of a TFD donor are discussed that allow one to judge the reality of the implications of the TFD donor model.« less

EDITORIAL: Focus on Dilute Magnetic Semiconductors FOCUS ON DILUTE MAGNETIC SEMICONDUCTORS

NASA Astrophysics Data System (ADS)

Chambers, Scott A.; Gallagher, Bryan

2008-05-01

This focus issue of New Journal of Physics is devoted to the materials science of dilute magnetic semiconductors (DMS). A DMS is traditionally defined as a diamagnetic semiconductor doped with a few to several atomic per cent of some transition metal with unpaired d electrons. Several kinds of dopant-dopant interactions can in principle couple the dopant spins leading to a ferromagnetic ground state in a dilute magnetic system. These include superexchange, which occurs principally in oxides and only between dopants with one intervening oxygen, and double exchange, in which dopants of different formal charges exchange an electron. In both of these mechanisms, the ferromagnetic alignment is not critically dependent on free carriers in the host semiconductor because exchange occurs via bonds. A third mechanism, discovered in the last few years, involves electrons associated with lattice defects that can apparently couple dopant spins. This mechanism is not well understood. Finally, the most desirable mechanism is carrier-mediated exchange interaction in which the dopant spins are coupled by itinerant electrons or holes in the host semiconductor. This mechanism introduces a fundamental link between magnetic and electrical transport properties and offers the possibility of new spintronic functionalities. In particular electrical gate control of ferromagnetism and the use of spin polarized currents to carry signals for analog and digital applications. The spin light emitting diode is a prototypical device of this kind that has been extensively used to characterize the extent of spin polarization in the active light emitting semiconductor heterostructure. The prototypical carrier mediated ferromagnetic DMS is Mn-doped GaAs. This and closely related narrow gap III-V materials have been very extensively studied. Their properties are generally quite well understood and they have led to important insights into fundamental properties of ferromagnetic systems with strong spin-orbit coupling. They have also led to the demonstration of a wide range of novel phenomena including some, like tunneling anisotropic magnetoresistance, which have subsequently been achieved in metal ferromagnetic systems. However despite considerable effort over many years the maximum Curie point achieved in (Ga,Mn)As is still less than 200 K. So unless some major new breakthrough is achieved these materials are unlikely to be of use for practical spin electronics technologies. In 2000, Dietl et al [1] published a seminal paper in which mean field theory was used to predict which of the common diamagnetic semiconductors would exhibit a Curie point above ambient if doped with 5 at.% Mn and a hole concentration of 3.5 × 1020 cm-3. Of the many host semiconductors simulated, only ZnO and GaN were predicted to exhibit a critical temperature in excess of 300 K. Since 2000, high-Tc DMS research has proliferated in both experimental and theoretical arenas. Many papers have been published containing claims of new DMS materials based largely on limited film growth, powder diffraction, and magnetometry. In these papers, a film which exhibits a hysteretic SQUID or VSM loop at 300 K and phase purity with only the host semiconductor detected by XRD are often claimed to be true ferromagnetic DMSs. Many of these papers are flawed because the criteria for a well-defined DMS are much more extensive. These include: (i) a random dopant distribution, (ii) a well-known and preferably unique charge state and preferentially a unique local structural environment for the dopant, (iii) a demonstrated coupling of the dopant spin to the host band structure, leading to spin polarization of the majority carriers, and (iv) a rational dependence of the saturation magnetization and Curie point on the magnetic dopant and carrier concentrations. Implicit in this list is that trivial causes of ferromagnetism, such as magnetic contamination and magnetic secondary phase formation, are eliminated. Yet, in many papers, the authors have not carried out the necessary control experiments and materials characterization to convincingly eliminate these possibilities. The former includes the growth of films without the magnetic dopant and the associated demonstration of the absence of ferromagnetism. Magnetic secondary phase formation is particularly problematic because in order to inject enough magnetic dopant to generate appreciable magnetization and spin polarization, one must often exceed the solid solubility of the dopant in the host. If the dopant is itself ferromagnetic in its elemental state, or if unintended magnetic products nucleate, spurious ferromagnetism will occur. Moreover, it is often a major analysis challenge to detect secondary phases when they consist of only a few per cent of the dopant; element specific spectroscopies such as x-ray absorption have been invaluable in this task. Powder diffraction is not sufficiently sensitive for this level of analysis. Against this backdrop, this focus issue of New Journal of Physics now appears. The editors' principal goal in soliciting papers has been to encourage investigators to submit work in which the necessary experiments have been done to allow the material to be adequately characterized. This collection contains a mix of experimental and theoretical papers, and many different types of materials are covered. This focus issue thus constitutes a snapshot in time of a fast-moving and fascinating field of materials physics. Reference [1] Dietl T, Ohno H, Matsukura F, Cibert J and Ferrand D 2000 Science 287 1019 Focus on Dilute Magnetic Semiconductors Contents Lithographically and electrically controlled strain effects on anisotropic magnetoresistance in (Ga,Mn)As E De Ranieri, A W Rushforth, K Výborný, U Rana, E Ahmad, R P Campion, C T Foxon, B L Gallagher, A C Irvine, J Wunderlich and T Jungwirth Structure and magnetism of cobalt-doped ZnO thin films M Ivill, S J Pearton, S Rawal, L Leu, P Sadik, R Das, A F Hebard, M Chisholm, J D Budai and D P Norton Role of charge carriers for ferromagnetism in cobalt-doped rutile TiO2 T Fukumura, H Toyosaki, K Ueno, M Nakano and M Kawasaki Ab-initio study of exchange constants and electronic structure in diluted magnetic group-IV semiconductors Silvia Picozzi and Marjana Ležaić Phase coherent transport in (Ga,Mn)As D Neumaier, K Wagner, U Wurstbauer, M Reinwald, W Wegscheider and D Weiss Hydrogen interstitials-mediated ferromagnetism in MnxGe1-x magnetic semiconductors Xin-Xin Yao, Shi-Shen Yan, Shu-Jun Hu, Xue-Ling Lin, Chong Han, Yan-Xue Chen, Guo-Lei Liu and Liang-Mo Mei Electronic structures of magnetic semiconductors FeCr2Se4 and Fe0.5Cu0.5Cr2Se4 B I Min, Seung Su Baik, H C Choi, S K Kwon and J-S Kang Investigation of pure and Co2+-doped ZnO quantum dot electronic structures using the density functional theory: choosing the right functional Ekaterina Badaeva, Yong Feng, Daniel R Gamelin and Xiaosong Li Magnetic properties of sol-gel-derived doped ZnO as a potential ferromagnetic semiconductor: a synchrotron-based study N R S Farley, K W Edmonds, A A Freeman, G van der Laan, C R Staddon, D H Gregory and B L Gallagher Local electronic structure of Cr in the II-VI diluted ferromagnetic semiconductor Zn1-xCrxTe M Kobayashi, Y Ishida, J I Hwang, G S Song, A Fujimori, C S Yang, L Lee, H-J Lin, D J Huang, C T Chen, Y Takeda, K Terai, S-I Fujimori, T Okane, Y Saitoh, H Yamagami, K Kobayashi, A Tanaka, H Saito and K Ando Lack of ferromagnetism in n-type cobalt-doped ZnO epitaxial thin films T C Kaspar, T Droubay, S M Heald, P Nachimuthu, C M Wang, V Shutthanandan, C A Johnson, D R Gamelin and S A Chambers XMCD studies on Co and Li doped ZnO magnetic semiconductors Thomas Tietze, Milan Gacic, Gisela Schütz, Gerhard Jakob, Sebastian Brück and Eberhard Goering Ferromagnetic semiconductors and the role of disorder B W Wessels An extensive comparison of anisotropies in MBE grown (Ga,Mn)As material C Gould, S Mark, K Pappert, R G Dengel, J Wenisch, R P Campion, A W Rushforth, D Chiba, Z Li, X Liu, W Van Roy, H Ohno, J K Furdyna, B Gallagher, K Brunner, G Schmidt and L W Molenkamp Local structural, magnetic and magneto-optical properties of Mn-doped SiC films prepared on a 3C-SiC(001) wafer Wenhong Wang, Fumiyoshi Takano, Hironori Ofuchi and Hiro Akinaga Effects of proton irradiation on the magnetic properties of GaGdN and GaCrN J K Hite, K K Allums, G T Thaler, C R Abernathy, S J Pearton, R M Frazier, R Dwivedi, R Wilkins and J M Zavada

Hall and Seebeck measurements estimate the thickness of a (buried) carrier system: Identifying interface electrons in In-doped SnO{sub 2} films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Papadogianni, Alexandra; Bierwagen, Oliver; White, Mark E.

2015-12-21

We propose a simple method based on the combination of Hall and Seebeck measurements to estimate the thickness of a carrier system within a semiconductor film. As an example, this method can distinguish “bulk” carriers, with homogeneous depth distribution, from “sheet” carriers, that are accumulated within a thin layer. The thickness of the carrier system is calculated as the ratio of the integral sheet carrier concentration, extracted from Hall measurements, to the volume carrier concentration, derived from the measured Seebeck coefficient of the same sample. For rutile SnO{sub 2}, the necessary relation of Seebeck coefficient to volume electron concentration inmore » the range of 3 × 10{sup 17} to 3 × 10{sup 20 }cm{sup −3} has been experimentally obtained from a set of single crystalline thin films doped with varying Sb-doping concentrations and unintentionally doped bulk samples, and is given as a “calibration curve.” Using this calibration curve, our method demonstrates the presence of interface electrons in homogeneously deep-acceptor (In) doped SnO{sub 2} films on sapphire substrates.« less

Lapped substrate for enhanced backsurface reflectivity in a thermophotovoltaic energy conversion system

DOEpatents

Baldasaro, Paul F; Brown, Edward J; Charache, Greg W; DePoy, David M

2000-01-01

A method for fabricating a thermophotovoltaic energy conversion cell including a thin semiconductor wafer substrate (10) having a thickness (.beta.) calculated to decrease the free carrier absorption on a heavily doped substrate; wherein the top surface of the semiconductor wafer substrate is provided with a thermophotovoltaic device (11), a metallized grid (12) and optionally an antireflective (AR) overcoating; and, the bottom surface (10') of the semiconductor wafer substrate (10) is provided with a highly reflecting coating which may comprise a metal coating (14) or a combined dielectric/metal coating (17).

Lapped substrate for enhanced backsurface reflectivity in a thermophotovoltaic energy conversion system

DOEpatents

Baldasaro, Paul F; Brown, Edward J; Charache, Greg W; DePoy, David M

2000-09-05

A method for fabricating a thermophotovoltaic energy conversion cell including a thin semiconductor wafer substrate (10) having a thickness (.beta.) calculated to decrease the free carrier absorption on a heavily doped substrate; wherein the top surface of the semiconductor wafer substrate is provided with a thermophotovoltaic device (11), a metallized grid (12) and optionally an antireflective (AR) overcoating; and, the bottom surface (10') of the semiconductor wafer substrate (10) is provided with a highly reflecting coating which may comprise a metal coating (14) or a combined dielectric/metal coating (17).

Fluorine doping: a feasible solution to enhancing the conductivity of high-resistance wide bandgap Mg0.51Zn0.49O active components

NASA Astrophysics Data System (ADS)

Liu, Lishu; Mei, Zengxia; Hou, Yaonan; Liang, Huili; Azarov, Alexander; Venkatachalapathy, Vishnukanthan; Kuznetsov, Andrej; Du, Xiaolong

2015-10-01

N-type doping of high-resistance wide bandgap semiconductors, wurtzite high-Mg-content MgxZn1-xO for instance, has always been a fundamental application-motivated research issue. Herein, we report a solution to enhancing the conductivity of high-resistance Mg0.51Zn0.49O active components, which has been reliably achieved by fluorine doping via radio-frequency plasma assisted molecular beam epitaxial growth. Fluorine dopants were demonstrated to be effective donors in Mg0.51Zn0.49O single crystal film having a solar-blind 4.43 eV bandgap, with an average concentration of 1.0 × 1019 F/cm3.The dramatically increased carrier concentration (2.85 × 1017 cm-3 vs ~1014 cm-3) and decreased resistivity (129 Ω · cm vs ~106 Ω cm) indicate that the electrical properties of semi-insulating Mg0.51Zn0.49O film can be delicately regulated by F doping. Interestingly, two donor levels (17 meV and 74 meV) associated with F were revealed by temperature-dependent Hall measurements. A Schottky type metal-semiconductor-metal ultraviolet photodetector manifests a remarkably enhanced photocurrent, two orders of magnitude higher than that of the undoped counterpart. The responsivity is greatly enhanced from 0.34 mA/W to 52 mA/W under 10 V bias. The detectivity increases from 1.89 × 109 cm Hz1/2/W to 3.58 × 1010 cm Hz1/2/W under 10 V bias at room temperature.These results exhibit F doping serves as a promising pathway for improving the performance of high-Mg-content MgxZn1-xO-based devices.

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

PubMed Central

Hazut, Ori; Agarwala, Arunava; Subramani, Thangavel; Waichman, Sharon; Yerushalmi, Roie

2013-01-01

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra shallow and sharp doping profiles at the nanometer scale. In MLCD process the dopant source is a monolayer containing dopant atoms. In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquid-solid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station. PMID:24326774

Theoretical analysis of nBn infrared photodetectors

NASA Astrophysics Data System (ADS)

Ting, David Z.; Soibel, Alexander; Khoshakhlagh, Arezou; Gunapala, Sarath D.

2017-09-01

The depletion and surface leakage dark current suppression properties of unipolar barrier device architectures such as the nBn have been highly beneficial for III-V semiconductor-based infrared detectors. Using a one-dimensional drift-diffusion model, we theoretically examine the effects of contact doping, minority carrier lifetime, and absorber doping on the dark current characteristics of nBn detectors to explore some basic aspects of their operation. We found that in a properly designed nBn detector with highly doped excluding contacts the minority carriers are extracted to nonequilibrium levels under reverse bias in the same manner as the high operating temperature (HOT) detector structure. Longer absorber Shockley-Read-Hall (SRH) lifetimes result in lower diffusion and depletion dark currents. Higher absorber doping can also lead to lower diffusion and depletion dark currents, but the benefit should be weighted against the possibility of reduced diffusion length due to shortened SRH lifetime. We also briefly examined nBn structures with unintended minority carrier blocking barriers due to excessive n-doping in the unipolar electron barrier, or due to a positive valence band offset between the barrier and the absorber. Both types of hole blocking structures lead to higher turn-on bias, although barrier n-doping could help suppress depletion dark current.

Effect of Si-doping on InAs nanowire transport and morphology

NASA Astrophysics Data System (ADS)

Wirths, S.; Weis, K.; Winden, A.; Sladek, K.; Volk, C.; Alagha, S.; Weirich, T. E.; von der Ahe, M.; Hardtdegen, H.; Lüth, H.; Demarina, N.; Grützmacher, D.; Schäpers, Th.

2011-09-01

The effect of Si-doping on the morphology, structure, and transport properties of nanowires was investigated. The nanowires were deposited by selective-area metal organic vapor phase epitaxy in an N2 ambient. It is observed that doping systematically affects the nanowire morphology but not the structure of the nanowires. However, the transport properties of the wires are greatly affected. Room-temperature four-terminal measurements show that with an increasing dopant supply the conductivity monotonously increases. For the highest doping level the conductivity is higher by a factor of 25 compared to only intrinsically doped reference nanowires. By means of back-gate field-effect transistor measurements it was confirmed that the doping results in an increased carrier concentration. Temperature dependent resistance measurements reveal, for lower doping concentrations, a thermally activated semiconductor-type increase of the conductivity. In contrast, the nanowires with the highest doping concentration show a metal-type decrease of the resistivity with decreasing temperature.

Spectroscopy of Charge Carriers and Traps in Field-Doped Single Crystal Organic Semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Xiaoyang

2014-12-10

The proposed research aims to achieve quantitative, molecular level understanding of charge carriers and traps in field-doped crystalline organic semiconductors via in situ linear and nonlinear optical spectroscopy, in conjunction with transport measurements and molecular/crystal engineering. Organic semiconductors are emerging as viable materials for low-cost electronics and optoelectronics, such as organic photovoltaics (OPV), organic field effect transistors (OFETs), and organic light emitting diodes (OLEDs). Despite extensive studies spanning many decades, a clear understanding of the nature of charge carriers in organic semiconductors is still lacking. It is generally appreciated that polaron formation and charge carrier trapping are two hallmarks associatedmore » with electrical transport in organic semiconductors; the former results from the low dielectric constants and weak intermolecular electronic overlap while the latter can be attributed to the prevalence of structural disorder. These properties have lead to the common observation of low charge carrier mobilities, e.g., in the range of 10-5 - 10-3 cm2/Vs, particularly at low carrier concentrations. However, there is also growing evidence that charge carrier mobility approaching those of inorganic semiconductors and metals can exist in some crystalline organic semiconductors, such as pentacene, tetracene and rubrene. A particularly striking example is single crystal rubrene (Figure 1), in which hole mobilities well above 10 cm2/Vs have been observed in OFETs operating at room temperature. Temperature dependent transport and spectroscopic measurements both revealed evidence of free carriers in rubrene. Outstanding questions are: what are the structural features and physical properties that make rubrene so unique? How do we establish fundamental design principles for the development of other organic semiconductors of high mobility? These questions are critically important but not comprehensive, as the nature of charge carriers is known to evolve as the carrier concentration increases, due to the presence of intrinsic disorder in organic semiconductors. Thus, a complementary question is: how does the nature of charge transport change as a function of carrier concentration?« less

a Study of Oxygen Precipitation in Heavily Doped Silicon.

NASA Astrophysics Data System (ADS)

Graupner, Robert Kurt

Gettering of impurities with oxygen precipitates is widely used during the fabrication of semiconductors to improve the performance and yield of the devices. Since the effectiveness of the gettering process is largely dependent on the initial interstitial oxygen concentration, accurate measurements of this parameter are of considerable importance. Measurements of interstitial oxygen following thermal cycles are required for development of semiconductor fabrication processes and for research into the mechanisms of oxygen precipitate nucleation and growth. Efforts by industrial associations have led to the development of standard procedures for the measurement of interstitial oxygen in wafers. However practical oxygen measurements often do not satisfy the requirements of such standard procedures. An additional difficulty arises when the silicon wafer has a low resitivity (high dopant concentration). In such cases the infrared light used for the measurement is severely attenuated by the electrons of holes introduced by the dopant. Since such wafers are the substrates used for the production of widely used epitaxial wafers, this measurement problem is economically important. Alternative methods such as Secondary Ion Mass Spectroscopy or Gas Fusion Analysis have been developed to measure oxygen in these cases. However, neither of these methods is capable of distinguishing interstitial oxygen from precipitated oxygen as required for precipitation studies. In addition to the commercial interest in heavily doped silicon substrates, they are also of interest for research into the role of point defects in nucleation and precipitation processes. Despite considerable research effort, there is still disagreement concerning the type of point defect and its role in semiconductor processes. Studies of changes in the interstitial oxygen concentration of heavily doped and lightly doped silicon wafers could help clarify the role of point defects in oxygen nucleation and precipitation processes. This could lead to more effective control and use of oxygen precipitation for gettering. One of the principal purposes of this thesis is the extension of the infrared interstitial oxygen measurement technique to situations outside the measurement capacities of the standard technique. These situations include silicon slices exhibiting interfering precipitate absorption bands and heavily doped n-type silicon wafers. A new method is presented for correcting for the effect of multiple reflections in silicon wafers with optically rough surfaces. The technique for the measurement of interstitial oxygen in heavily doped n-type wafers is then used to perform a comparative study of oxygen precipitation in heavily antimony doped (.035 ohm-cm) silicon and lightly doped p-type silicon. A model is presented to quantitatively explain the observed suppression of defect formation in heavily doped n-type wafers.

Defects and properties of cadmium oxide based transparent conductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Kin Man, E-mail: kinmanyu@cityu.edu.hk; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720; Detert, D. M.

Transparent conductors play an increasingly important role in a number of semiconductor technologies. This paper reports on the defects and properties of Cadmium Oxide, a transparent conducting oxide which can be potentially used for full spectrum photovoltaics. We carried out a systematic investigation on the effects of defects in CdO thin films undoped and intentionally doped with In and Ga under different deposition and annealing conditions. We found that at low growth temperatures (<200 °C), sputter deposition tends to trap both oxygen vacancies and compensating defects in the CdO film resulting in materials with high electron concentration of ∼2 × 10{sup 20}/cm{sup 3}more » and mobility in the range of 40–100 cm{sup 2}/V s. Thermal annealing experiments in different ambients revealed that the dominating defects in sputtered CdO films are oxygen vacancies. Oxygen rich CdO films grown by sputtering with increasing O{sub 2} partial pressure in the sputter gas mixture results in films with resistivity from ∼4 × 10{sup −4} to >1 Ω cm due to incorporation of excess O in the form of O-related acceptor defects, likely to be O interstitials. Intentional doping with In and Ga donors leads to an increase of both the electron concentration and the mobility. With proper doping CdO films with electron concentration of more than 10{sup 21 }cm{sup −3} and electron mobility higher than 120 cm{sup 2}/V s can be achieved. Thermal annealing of doped CdO films in N{sub 2} ambient can further improve the electrical properties by removing native acceptors and improving film crystallinity. Furthermore, the unique doping behavior and electrical properties of CdO were explored via simulations based on the amphoteric defect model. A comparison of the calculations and experimental results show that the formation energy of native donors and acceptors at the Fermi stabilization energy is ∼1 eV and that the mobility of sputtered deposited CdO is limited by a background acceptor concentration of ∼5–6 × 10{sup 20}/cm{sup 3}. The calculations offer an insight into understanding of the effects of defects on electrical properties of undoped and doped CdO and offer a potential to use similar methods to analyze doping and defect properties of other semiconductor materials.« less

High Efficiency InP Solar Cells from Low Toxicity Tertiarybutylphosphine

NASA Technical Reports Server (NTRS)

Hoffman, Richard W., Jr.; Fatemi, Navid S.; Wilt, David M.; Jenkins, Phillip P.; Brinker, David J.; Scheiman, David A.

1994-01-01

Large scale manufacture of phosphide based semiconductor devices by organo-metallic vapor phase epitaxy (OMVPE) typically requires the use of highly toxic phosphine. Advancements in phosphine substitutes have identified tertiarybutylphosphine (TBP) as an excellent precursor for OMVPE of InP. High quality undoped and doped InP films were grown using TBP and trimethylindium. Impurity doped InP films were achieved utilizing diethylzinc and silane for p and n type respectively. 16 percent efficient solar cells under air mass zero, one sun intensity were demonstrated with Voc of 871 mV and fill factor of 82.6 percent. It was shown that TBP could replace phosphine, without adversely affecting device quality, in OMVPE deposition of InP thus significantly reducing toxic gas exposure risk.

p-n Heterojunction of doped graphene films obtained by pyrolysis of biomass precursors.

PubMed

Latorre-Sánchez, Marcos; Primo, Ana; Atienzar, Pedro; Forneli, Amparo; García, Hermenegildo

2015-02-25

Nitrogen-doped graphene [(N)G] obtained by pyrolysis at 900 °C of nanometric chitosan films exhibits a Hall effect characteristic of n-type semiconductors. In contrast, boron-doped graphene [(B)G] obtained by pyrolysis of borate ester of alginate behaves as a p-type semiconductor based also on the Hall effect. A p-n heterojunction of (B)G-(N)G films is built by stepwise coating of a quartz plate using a mask. The heterojunction is created by the partial overlapping of the (B)G-(N)G films. Upon irradiation with a xenon lamp of aqueous solutions of H(2) PtCl(6) and MnCl(2) in contact with the heterojunction, preferential electron migration from (B)G to (N)G with preferential location of positive holes on (B)G is established by observation in scanning electron microscopy of the formation of Pt nanoparticles (NP) on (N)G and MnO(2) NP on (B)G. The benefits of the heterojunction with respect to the devices having one individual component as a consequence of the electron migration through the p-n heterojunction are illustrated by measuring the photocurrent in the (B)G-(N)G heterojunction (180% current enhancement with respect to the dark current) and compared it to the photocurrent of the individual (B)G (15% enhancement) and (N)G (55% enhancement) components. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Design of Highly Selective Gas Sensors via Physicochemical Modification of Oxide Nanowires: Overview

PubMed Central

Woo, Hyung-Sik; Na, Chan Woong; Lee, Jong-Heun

2016-01-01

Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW) networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and thus have been applied in the field of gas sensors over the years. In particular, n-type NWs such as SnO2, ZnO, and In2O3 are widely studied because of their simple synthetic preparation and high gas response. However, due to their usually high responses to C2H5OH and NO2, the selective detection of other harmful and toxic gases using oxide NWs remains a challenging issue. Various strategies—such as doping/loading of noble metals, decorating/doping of catalytic metal oxides, and the formation of core–shell structures—have been explored to enhance gas selectivity and sensitivity, and are discussed herein. Additional methods such as the transformation of n-type into p-type NWs and the formation of catalyst-doped hierarchical structures by branch growth have also proven to be promising for the enhancement of gas selectivity. Accordingly, the physicochemical modification of oxide NWs via various methods provides new strategies to achieve the selective detection of a specific gas, and after further investigations, this approach could pave a new way in the field of NW-based semiconductor-type gas sensors. PMID:27657076

Au doping effects on electrical and optical properties of vanadium dioxides

NASA Astrophysics Data System (ADS)

Zhu, YaBin; He, Fan; Na, Jie

2012-03-01

Vanadium dioxides were fabricated on normal glass substrates using reactive radio frequency (RF) magnetron sputtering. The oxygen flow volume and annealed temperatures as growth parameters are systematically investigated. The electrical and optical properties of VO2 and Au:VO2 thin films with different growth conditions are discussed. The semiconductor-metal phase transition temperature decreased by ˜10°C for the sample with Au doping compared to the sample without Au doping. However, the optical transmittance of Au:VO2 thin films is much lower than that of bare VO2. These results show that Au doping has a marked effect on the electrical and optical properties.

Design and simulation of GaN based Schottky betavoltaic nuclear micro-battery.

PubMed

San, Haisheng; Yao, Shulin; Wang, Xiang; Cheng, Zaijun; Chen, Xuyuan

2013-10-01

The current paper presents a theoretical analysis of Ni-63 nuclear micro-battery based on a wide-band gap semiconductor GaN thin-film covered with thin Ni/Au films to form Schottky barrier for carrier separation. The total energy deposition in GaN was calculated using Monte Carlo methods by taking into account the full beta spectral energy, which provided an optimal design on Schottky barrier width. The calculated results show that an 8 μm thick Schottky barrier can collect about 95% of the incident beta particle energy. Considering the actual limitations of current GaN growth technique, a Fe-doped compensation technique by MOCVD method can be used to realize the n-type GaN with a carrier concentration of 1×10(15) cm(-3), by which a GaN based Schottky betavoltaic micro-battery can achieve an energy conversion efficiency of 2.25% based on the theoretical calculations of semiconductor device physics. Copyright © 2013 Elsevier Ltd. All rights reserved.

High-Power Growth-Robust InGaAs/InAlAs Terahertz Quantum Cascade Lasers

PubMed Central

2017-01-01

We report on high-power terahertz quantum cascade lasers based on low effective electron mass InGaAs/InAlAs semiconductor heterostructures with excellent reproducibility. Growth-related asymmetries in the form of interface roughness and dopant migration play a crucial role in this material system. These bias polarity dependent phenomena are studied using a nominally symmetric active region resulting in a preferential electron transport in the growth direction. A structure based on a three-well optical phonon depletion scheme was optimized for this bias direction. Depending on the sheet doping density, the performance of this structure shows a trade-off between high maximum operating temperature and high output power. While the highest operating temperature of 155 K is observed for a moderate sheet doping density of 2 × 1010 cm–2, the highest peak output power of 151 mW is found for 7.3 × 1010 cm–2. Furthermore, by abutting a hyperhemispherical GaAs lens to a device with the highest doping level a record output power of 587 mW is achieved for double-metal waveguide structures. PMID:28470028

High-Power Growth-Robust InGaAs/InAlAs Terahertz Quantum Cascade Lasers.

PubMed

Deutsch, Christoph; Kainz, Martin Alexander; Krall, Michael; Brandstetter, Martin; Bachmann, Dominic; Schönhuber, Sebastian; Detz, Hermann; Zederbauer, Tobias; MacFarland, Donald; Andrews, Aaron Maxwell; Schrenk, Werner; Beck, Mattias; Ohtani, Keita; Faist, Jérôme; Strasser, Gottfried; Unterrainer, Karl

2017-04-19

We report on high-power terahertz quantum cascade lasers based on low effective electron mass InGaAs/InAlAs semiconductor heterostructures with excellent reproducibility. Growth-related asymmetries in the form of interface roughness and dopant migration play a crucial role in this material system. These bias polarity dependent phenomena are studied using a nominally symmetric active region resulting in a preferential electron transport in the growth direction. A structure based on a three-well optical phonon depletion scheme was optimized for this bias direction. Depending on the sheet doping density, the performance of this structure shows a trade-off between high maximum operating temperature and high output power. While the highest operating temperature of 155 K is observed for a moderate sheet doping density of 2 × 10 10 cm -2 , the highest peak output power of 151 mW is found for 7.3 × 10 10 cm -2 . Furthermore, by abutting a hyperhemispherical GaAs lens to a device with the highest doping level a record output power of 587 mW is achieved for double-metal waveguide structures.

Strong Depletion in Hybrid Perovskite p-n Junctions Induced by Local Electronic Doping.

PubMed

Ou, Qingdong; Zhang, Yupeng; Wang, Ziyu; Yuwono, Jodie A; Wang, Rongbin; Dai, Zhigao; Li, Wei; Zheng, Changxi; Xu, Zai-Quan; Qi, Xiang; Duhm, Steffen; Medhekar, Nikhil V; Zhang, Han; Bao, Qiaoliang

2018-04-01

A semiconductor p-n junction typically has a doping-induced carrier depletion region, where the doping level positively correlates with the built-in potential and negatively correlates with the depletion layer width. In conventional bulk and atomically thin junctions, this correlation challenges the synergy of the internal field and its spatial extent in carrier generation/transport. Organic-inorganic hybrid perovskites, a class of crystalline ionic semiconductors, are promising alternatives because of their direct badgap, long diffusion length, and large dielectric constant. Here, strong depletion in a lateral p-n junction induced by local electronic doping at the surface of individual CH 3 NH 3 PbI 3 perovskite nanosheets is reported. Unlike conventional surface doping with a weak van der Waals adsorption, covalent bonding and hydrogen bonding between a MoO 3 dopant and the perovskite are theoretically predicted and experimentally verified. The strong hybridization-induced electronic coupling leads to an enhanced built-in electric field. The large electric permittivity arising from the ionic polarizability further contributes to the formation of an unusually broad depletion region up to 10 µm in the junction. Under visible optical excitation without electrical bias, the lateral diode demonstrates unprecedented photovoltaic conversion with an external quantum efficiency of 3.93% and a photodetection responsivity of 1.42 A W -1 . © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Accurate potential drop sheet resistance measurements of laser-doped areas in semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heinrich, Martin, E-mail: mh.seris@gmail.com; NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore 117456; Kluska, Sven

2014-10-07

It is investigated how potential drop sheet resistance measurements of areas formed by laser-assisted doping in crystalline Si wafers are affected by typically occurring experimental factors like sample size, inhomogeneities, surface roughness, or coatings. Measurements are obtained with a collinear four point probe setup and a modified transfer length measurement setup to measure sheet resistances of laser-doped lines. Inhomogeneities in doping depth are observed from scanning electron microscope images and electron beam induced current measurements. It is observed that influences from sample size, inhomogeneities, surface roughness, and coatings can be neglected if certain preconditions are met. Guidelines are given onmore » how to obtain accurate potential drop sheet resistance measurements on laser-doped regions.« less

Fast and slow light property improvement in erbium-doped amplifier

NASA Astrophysics Data System (ADS)

Peng, P. C.; Wu, F. K.; Kao, W. C.; Chen, J.; Lin, C. T.; Chi, S.

2013-01-01

This work experimentally demonstrates improvement of the fast light property in erbium-doped amplifiers at room temperature. The difference between the signal power and the pump power associated with bending loss is used to control the signal power at the different positions of the erbium-doped fiber (EDF) to improve the fast light property. Periodic bending of the EDF increases the time advance of the probe signal by over 288%. Additionally, this concept also could improve the fast light property using coherent population oscillations in semiconductor optical amplifiers.

Semiconductor tunnel junction with enhancement layer

DOEpatents

Klem, John F.; Zolper, John C.

1997-01-01

The incorporation of a pseudomorphic GaAsSb layer in a runnel diode structure affords a new degree of freedom in designing runnel junctions for p-n junction device interconnects. Previously only doping levels could be varied to control the tunneling properties. This invention uses the valence band alignment band of the GaAsSb with respect to the surrounding materials to greatly relax the doping requirements for tunneling.

Giant Dirac point shift of graphene phototransistors by doped silicon substrate current

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shimatani, Masaaki; Ogawa, Shinpei, E-mail: Ogawa.Shimpei@eb.MitsubishiElectric.co.jp; Fujisawa, Daisuke

2016-03-15

Graphene is a promising new material for photodetectors due to its excellent optical properties and high-speed response. However, graphene-based phototransistors have low responsivity due to the weak light absorption of graphene. We have observed a giant Dirac point shift upon white light illumination in graphene-based phototransistors with n-doped Si substrates, but not those with p-doped substrates. The source-drain current and substrate current were investigated with and without illumination for both p-type and n-type Si substrates. The decay time of the drain-source current indicates that the Si substrate, SiO{sub 2} layer, and metal electrode comprise a metal-oxide-semiconductor (MOS) capacitor due tomore » the presence of defects at the interface between the Si substrate and SiO{sub 2} layer. The difference in the diffusion time of the intrinsic major carriers (electrons) and the photogenerated electron-hole pairs to the depletion layer delays the application of the gate voltage to the graphene channel. Therefore, the giant Dirac point shift is attributed to the n-type Si substrate current. This phenomenon can be exploited to realize high-performance graphene-based phototransistors.« less

Defect-Rich Dopant-Free ZrO2 Nanostructures with Superior Dilute Ferromagnetic Semiconductor Properties.

PubMed

Rahman, Md Anisur; Rout, S; Thomas, Joseph P; McGillivray, Donald; Leung, Kam Tong

2016-09-14

Control of the spin degree of freedom of an electron has brought about a new era in spin-based applications, particularly spin-based electronics, with the potential to outperform the traditional charge-based semiconductor technology for data storage and information processing. However, the realization of functional spin-based devices for information processing remains elusive due to several fundamental challenges such as the low Curie temperature of group III-V and II-VI semiconductors (<200 K), and the low spin-injection efficiencies of existing III-V, II-VI, and transparent conductive oxide semiconductors in a multilayer device structure, which are caused by precipitation and migration of dopants from the host layer to the adjacent layers. Here, we use catalyst-assisted pulsed laser deposition to grow, for the first time, oxygen vacancy defect-rich, dopant-free ZrO2 nanostructures with high TC (700 K) and high magnetization (5.9 emu/g). The observed magnetization is significantly greater than both doped and defect-rich transparent conductive oxide nanomaterials reported to date. We also provide the first experimental evidence that it is the amounts and types of oxygen vacancy defects in, and not the phase of ZrO2 that control the ferromagnetic order in undoped ZrO2 nanostructures. To explain the origin of ferromagnetism in these ZrO2 nanostructures, we hypothesize a new defect-induced bound polaron model, which is generally applicable to other defect-rich, dopant-free transparent conductive oxide nanostructures. These results provide new insights into magnetic ordering in undoped dilute ferromagnetic semiconductor oxides and contribute to the design of exotic magnetic and novel multifunctional materials.

Role of Morphological Structure, Doping, and Coating of Different Materials in the Sensing Characteristics of Humidity Sensors

PubMed Central

Tripathy, Ashis; Pramanik, Sumit; Cho, Jongman; Santhosh, Jayasree; Osman, Noor Azuan Abu

2014-01-01

The humidity sensing characteristics of different sensing materials are important properties in order to monitor different products or events in a wide range of industrial sectors, research and development laboratories as well as daily life. The primary aim of this study is to compare the sensing characteristics, including impedance or resistance, capacitance, hysteresis, recovery and response times, and stability with respect to relative humidity, frequency, and temperature, of different materials. Various materials, including ceramics, semiconductors, and polymers, used for sensing relative humidity have been reviewed. Correlations of the different electrical characteristics of different doped sensor materials as the most unique feature of a material have been noted. The electrical properties of different sensor materials are found to change significantly with the morphological changes, doping concentration of different materials and film thickness of the substrate. Various applications and scopes are pointed out in the review article. We extensively reviewed almost all main kinds of relative humidity sensors and how their electrical characteristics vary with different doping concentrations, film thickness and basic sensing materials. Based on statistical tests, the zinc oxide-based sensing material is best for humidity sensor design since it shows extremely low hysteresis loss, minimum response and recovery times and excellent stability. PMID:25256110

Bare and boron-doped cubic silicon carbide nanowires for electrochemical detection of nitrite sensitively

PubMed Central

Yang, Tao; Zhang, Liqin; Hou, Xinmei; Chen, Junhong; Chou, Kuo-Chih

2016-01-01

Fabrication of eletrochemical sensors based on wide bandgap compound semiconductors has attracted increasing interest in recent years. Here we report for the first time electrochemical nitrite sensors based on cubic silicon carbide (SiC) nanowires (NWs) with smooth surface and boron-doped cubic SiC NWs with fin-like structure. Multiple techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) were used to characterize SiC and boron-doped SiC NWs. As for the electrochemical behavior of both SiC NWs electrode, the cyclic voltammetric results show that both SiC electrodes exhibit wide potential window and excellent electrocatalytic activity toward nitrite oxidation. Differential pulse voltammetry (DPV) determination reveals that there exists a good linear relationship between the oxidation peak current and the concentration in the range of 50–15000 μmoL L−1 (cubic SiC NWs) and 5–8000 μmoL L−1 (B-doped cubic SiC NWs) with the detection limitation of 5 and 0.5 μmoL L−1 respectively. Compared with previously reported results, both as-prepared nitrite sensors exhibit wider linear response range with comparable high sensitivity, high stability and reproducibility. PMID:27109361

Modulation of electronic transport properties in armchair phosphorene nanoribbons by doping and edge passivation.

PubMed

Guo, Caixia; Wang, Tianxing; Xia, Congxin; Liu, Yufang

2017-10-09

The electronic structures and transport properties of group IV atoms (C, Si, Ge)-doped armchair phosphorene nanoribbons (APNRs) are investigated using first-principles calculations, considering different edge passivation. The results show that the C, Si, Ge dopants can induce the transition occur from semiconductor to metal in the APNRs. The negative differential resistance (NDR) behavior in the doped APNR system is robust with respect to the doping concentration and edge passivation type. However, their current peak positions and peak-to-valley ratio (PVR) values are correlated with doping concentration and edge passivation type. In particular, for the C, Si-doped APNRs, the low bias NDR behavior with the PVR (10 5 -10 8 ) can be observed when doping concentration is low in the APNRs with the F and H edge passivation. These results may play an important role for the fabrication of future low power consumption nano-electronic devices.

Effects of Eu doping and O vacancy on the magnetic and optical properties of ZnO

NASA Astrophysics Data System (ADS)

Ling-Feng, Qu; Qing-Yu, Hou; Xiao-Fang, Jia; Zhen-Chao, Xu; Chun-Wang, Zhao

2018-02-01

We calculated the electronic structure and optical properties of Eu mono-doped ZnO systems with or without O vacancy. We also determined the relative energy of ferromagnetic and antiferromagnetic orders of Eu-double-doped ZnO systems. The double-doped systems possess high Curie temperature and achieve room temperature ferromagnetism. The magnetism in the Eu mono-doped system without O vacancy is caused by the -Eu3+-O2--Eu3+- bound magnetopolaron (BMP) model. The magnetism of Eu mono-doped ZnO systems with O vacancy is more stable than that without O vacancy, and such magnetism is attributed to the -Eu3+-VO++-Eu3+- BMP model. The absorption spectrum for mono-doped systems is red shifted, and this finding confirms that Eu-mono-doped ZnO is a candidate photocatalyst for various applications. Therefore, Eu-double-doped ZnO can be practically used as an unambiguous diluted magnetic semiconductor.

Doped bottom-contact organic field-effect transistors

NASA Astrophysics Data System (ADS)

Liu, Shiyi; Billig, Paul; Al-Shadeedi, Akram; Kaphle, Vikash; Lüssem, Björn

2018-07-01

The influence of doping on doped bottom-gate bottom-contact organic field-effect transistors (OFETs) is discussed. It is shown that the inclusion of a doped layer at the dielectric/organic semiconductor layer leads to a significant reduction in the contact resistances and a fine control of the threshold voltage. Through varying the thickness of the doped layer, a linear shift of threshold voltage V T from ‑3.1 to ‑0.22 V is observed for increasing thickness of doped layer. Meanwhile, the contact resistance at the source and drain electrode is reduced from 138.8 MΩ at V GS = ‑10 V for 3 nm to 0.3 MΩ for 7 nm thick doped layers. Furthermore, an increase of charge mobility is observed for increasing thickness of doped layer. Overall, it is shown that doping can minimize injection barriers in bottom-contact OFETs with channel lengths in the micro-meter regime, which has the potential to increase the performance of this technology further.

Charge Carriers Modulate the Bonding of Semiconductor Nanoparticle Dopants As Revealed by Time-Resolved X-ray Spectroscopy

DOE PAGES

Hassan, Asra; Zhang, Xiaoyi; Liu, Xiaohan; ...

2017-08-28

Understanding the electronic structure of doped semiconductors is essential to realize advancements in electronics and in the rational design of nanoscale devices. Here, we report the results of time-resolved X-ray absorption studies on copper-doped cadmium sulfide nanoparticles that provide an explicit description of the electronic dynamics of the dopants. The interaction of a dopant ion and an excess charge carrier is unambiguously observed via monitoring the oxidation state. The experimental data combined with DFT calculations demonstrate that dopant bonding to the host matrix is modulated by its interaction with charge carriers. Additionally, the transient photoluminescence and the kinetics of dopantmore » oxidation reveal the presence of two types of surface-bound ions that create mid-gap states.« less

A theoretical study of heterojunction and graded band gap type solar cells

NASA Technical Reports Server (NTRS)

Sutherland, J. E.; Hauser, J. R.

1977-01-01

A computer program was designed for the analysis of variable composition solar cells and applied to several proposed solar cell structures using appropriate semiconductor materials. The program simulates solar cells made of a ternary alloy of two binary semiconductors with an arbitrary composition profile, and an abrupt or Gaussian doping profile of polarity n-on-p or p-on-n with arbitrary doping levels. Once the device structure is specified, the program numerically solves a complete set of differential equations and calculates electrostatic potential, quasi-Fermi levels, carrier concentrations and current densities, total current density and efficiency as functions of terminal voltage and position within the cell. These results are then recorded by computer in tabulated or plotted form for interpretation by the user.

Optimal doping control of magnetic semiconductors via subsurfactant epitaxy.

PubMed

Zeng, Changgan; Zhang, Zhenyu; van Benthem, Klaus; Chisholm, Matthew F; Weitering, Hanno H

2008-02-15

"Subsurfactant epitaxy" is established as a conceptually new approach for introducing manganese as a magnetic dopant into germanium. A kinetic pathway is devised in which the subsurface interstitial sites on Ge(100) are first selectively populated with Mn, while lateral diffusion and clustering on or underneath the surface are effectively suppressed. Subsequent Ge deposition as a capping layer produces a novel surfactantlike phenomenon as the interstitial Mn atoms float towards newly defined subsurface sites at the growth front. Furthermore, the Mn atoms that failed to float upwards are uniformly distributed within the Ge capping layer. The resulting doping levels of order 0.25 at. % would normally be considered too low for ferromagnetic ordering, but the Curie temperature exceeds room temperature by a comfortable margin. Subsurfactant epitaxy thus enables superior dopant control in magnetic semiconductors.

Charge Carriers Modulate the Bonding of Semiconductor Nanoparticle Dopants As Revealed by Time-Resolved X-ray Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassan, Asra; Zhang, Xiaoyi; Liu, Xiaohan

Understanding the electronic structure of doped semiconductors is essential to realize advancements in electronics and in the rational design of nanoscale devices. Here, we report the results of time-resolved X-ray absorption studies on copper-doped cadmium sulfide nanoparticles that provide an explicit description of the electronic dynamics of the dopants. The interaction of a dopant ion and an excess charge carrier is unambiguously observed via monitoring the oxidation state. The experimental data combined with DFT calculations demonstrate that dopant bonding to the host matrix is modulated by its interaction with charge carriers. Additionally, the transient photoluminescence and the kinetics of dopantmore » oxidation reveal the presence of two types of surface-bound ions that create mid-gap states.« less

Carbon nanotube polymer composites for photonic devices

NASA Astrophysics Data System (ADS)

Scardaci, V.; Rozhin, A. G.; Hennrich, F.; Milne, W. I.; Ferrari, A. C.

2007-03-01

We report the fabrication of high optical quality single wall carbon nanotube polyvinyl alcohol composites and their application in nanotube based photonic devices. These show a broad absorption of semiconductor tubes centred at ∼1.55 μm, the spectral range of interest for optical communications. The films are used as mode-lockers in an erbium doped fibre laser, achieving ∼700 fs mode-locked pulses. Raman spectroscopy shows no damage after a long time continuous laser operation.

Systematic approach on the fabrication of Co doped ZnO semiconducting nanoparticles by mixture of fuel approach for Antibacterial applications

NASA Astrophysics Data System (ADS)

Rajendar, V.; Dayakar, T.; Shobhan, K.; Srikanth, I.; Venkateswara Rao, K.

2014-11-01

Zinc oxide (ZnO) is a wide band gap semiconductor (3.2 eV) with a high exciton binding energy (60 meV), where it has wide applications in advanced spintronic devices. The theoretical prediction of room temperature ferromagnetism and also antibacterial activity will be possible through the investigation of diluted magnetic semiconductors (DMS), such as transition metal doped ZnO, especially Cobalt doped ZnO. The aim of the work is the synthesis of Cobalt (Co) doped ZnO nanopowders were prepared Zn1-xCoxO (0 ⩽ x ⩾ 0.09) nanopowders from Sol-Gel auto combustion method have been synthesized with precursors such as Zinc and Cobalt nitrates with the assistance Ammonium acetate & Urea as fuel by increasing the cobalt concentration in zinc oxide and their structural, morphological, optical, Thermal, magnetic and antibacterial properties were studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Transmission Electron microscope (TEM), UV-visible spectroscopy, thermo gravimetric/differential thermal analysis (TG/DTA) and vibrating sample magneto meter (VSM). From the antibacterial studies, against gram positive Bacillus subtilis bacteria is most abundant bacteria in soil and indoor atmosphere, which affects the stored spintronic devices so that the devices should be made with antibacterial activity of DMS like Co doped ZnO. In this article is found that ZnO:Co nanopowders with higher Co doping level (0.07 and 0.09 wt%) exhibit good antibacterial efficiency. The magnetization curves obtained using vibrating sample magnetometer (VSM) show a sign of strong room temperature ferromagnetic behavior when the Co doping level is 0.05 wt% and a weak room temperature ferromagnetic behavior Co doping level is below 0.07 wt%, and also they found to exhibit antiferromagnetic and paramagnetic properties, when the Co doping levels are 0.07 and 0.09 wt%, respectively, to enhance and increase the special magnetic and antibacterial property for sophisticated devices for the sustainable technologies.

Organic semiconductor crystals.

PubMed

Wang, Chengliang; Dong, Huanli; Jiang, Lang; Hu, Wenping

2018-01-22

Organic semiconductors have attracted a lot of attention since the discovery of highly doped conductive polymers, due to the potential application in field-effect transistors (OFETs), light-emitting diodes (OLEDs) and photovoltaic cells (OPVs). Single crystals of organic semiconductors are particularly intriguing because they are free of grain boundaries and have long-range periodic order as well as minimal traps and defects. Hence, organic semiconductor crystals provide a powerful tool for revealing the intrinsic properties, examining the structure-property relationships, demonstrating the important factors for high performance devices and uncovering fundamental physics in organic semiconductors. This review provides a comprehensive overview of the molecular packing, morphology and charge transport features of organic semiconductor crystals, the control of crystallization for achieving high quality crystals and the device physics in the three main applications. We hope that this comprehensive summary can give a clear picture of the state-of-art status and guide future work in this area.

Photon detector configured to employ the Gunn effect and method of use

DOEpatents

Cich, Michael J

2015-03-17

Embodiments disclosed herein relate to photon detectors configured to employ the Gunn effect for detecting high-energy photons (e.g., x-rays and gamma rays) and methods of use. In an embodiment, a photon detector for detecting high-energy photons is disclosed. The photon detector includes a p-i-n semiconductor diode having a p-type semiconductor region, an n-type semiconductor region, and a compensated i-region disposed between the p-type semiconductor region and the n-type semiconductor region. The compensated i-region and has a width of about 100 .mu.m to about 400 .mu.m and is configured to exhibit the Gunn effect when the p-i-n semiconductor diode is forward biased a sufficient amount. The compensated i-region is doped to include a free carrier concentration of less than about 10.sup.10 cm.sup.-3.

Reversible and Precisely Controllable p/n-Type Doping of MoTe2 Transistors through Electrothermal Doping.

PubMed

Chang, Yuan-Ming; Yang, Shih-Hsien; Lin, Che-Yi; Chen, Chang-Hung; Lien, Chen-Hsin; Jian, Wen-Bin; Ueno, Keiji; Suen, Yuen-Wuu; Tsukagoshi, Kazuhito; Lin, Yen-Fu

2018-03-01

Precisely controllable and reversible p/n-type electronic doping of molybdenum ditelluride (MoTe 2 ) transistors is achieved by electrothermal doping (E-doping) processes. E-doping includes electrothermal annealing induced by an electric field in a vacuum chamber, which results in electron (n-type) doping and exposure to air, which induces hole (p-type) doping. The doping arises from the interaction between oxygen molecules or water vapor and defects of tellurium at the MoTe 2 surface, and allows the accurate manipulation of p/n-type electrical doping of MoTe 2 transistors. Because no dopant or special gas is used in the E-doping processes of MoTe 2 , E-doping is a simple and efficient method. Moreover, through exact manipulation of p/n-type doping of MoTe 2 transistors, quasi-complementary metal oxide semiconductor adaptive logic circuits, such as an inverter, not or gate, and not and gate, are successfully fabricated. The simple method, E-doping, adopted in obtaining p/n-type doping of MoTe 2 transistors undoubtedly has provided an approach to create the electronic devices with desired performance. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Morphological Effect of Doping Environment on Silicon Nanowires Grown by Plasma-Assisted Chemical Vapor Deposition

NASA Astrophysics Data System (ADS)

Lohn, Andrew J.; Cormia, Robert D.; Fryauf, David M.; Zhang, Junce; Norris, Kate J.; Kobayashi, Nobuhiko P.

2012-11-01

Physical properties of semiconductor nanowires are tied intimately to their specific morphologies such as length and diameter. We studied the growth of silicon nanowires and found their lengths and diameters to vary over orders of magnitude in different doping environments. In all cases we examined, doping resulted in increased diameters. In addition, boron doping was found to accelerate volume growth rate while arsenic and antimony both appeared to slow it down. We further studied the formation of the native oxides that cover the nanowires. X-ray photoelectron spectroscopy indicated that properties of the native oxides are also dependent on doping environment and correlated to doping-dependent shifts in apparent binding energy of the Si 2p3/2 peak illustrating that the electronic contribution is the dominant mechanism for the oxide growth.

The investigation of Ce doped ZnO crystal: The electronic, optical and magnetic properties

NASA Astrophysics Data System (ADS)

Wen, Jun-Qing; Zhang, Jian-Min; Qiu, Ze-Gang; Yang, Xu; Li, Zhi-Qin

2018-04-01

The electronic, optical and magnetic properties of Ce doped ZnO crystal have been studied by using first principles method. The research of formation energies show that Ce doped ZnO is energetically stable, and the formation energies reduce from 6.25% to 12.5% for Ce molar percentage. The energy band is still direct band gap after Ce doped, and band gap increases with the increase of Cesbnd Ce distance. The Fermi level moves upward into conduction band and the DOS moves to lower energy with the increase of Ce concentration, which showing the properties of n-type semiconductor. The calculated optical properties imply that Ce doped causes a red-shift of absorption peaks, and enhances the absorption of the visible light. The transition from ferromagnetic to antiferromagnetic has been found in Ce doped ZnO.

Fabrication and characterization of novel transparent conducting oxide N-CNT doped ZnO for photovoltaic applications

NASA Astrophysics Data System (ADS)

Benyounes, Anas; Abbas, Naseem; Hammi, Maryama; Ziat, Younes; Slassi, Amine; Zahra, Nida

2018-02-01

The present research reports on the electrical and optical properties of N-CNT doped with ZnO, which is considered as wurtzite transparent and conducting oxide semiconductor structure. The thin films of N-doped carbon nanotubes/ZnO were prepared using sol-gel method, then we carried out investigations in optical and electrical point of view to extract their usefulness in photovoltaic applications. For this purpose, ZnO films were doped by several ratios of carbon nanotubes and N-doped carbon nanotubes. The electrical studies were performed over these two kinds of doped ZnO films, the electrical conductivity has found to be more important for ZnO films filled with N-CNTs. This finding is pretty explained by the electronic conduction hold by nitrogen as charge carriers within carbon nanotubes.

Method for formation of thin film transistors on plastic substrates

DOEpatents

Carey, P.G.; Smith, P.M.; Sigmon, T.W.; Aceves, R.C.

1998-10-06

A process for formation of thin film transistors (TFTs) on plastic substrates replaces standard thin film transistor fabrication techniques, and uses sufficiently lower processing temperatures so that inexpensive plastic substrates may be used in place of standard glass, quartz, and silicon wafer-based substrates. The process relies on techniques for depositing semiconductors, dielectrics, and metals at low temperatures; crystallizing and doping semiconductor layers in the TFT with a pulsed energy source; and creating top-gate self-aligned as well as back-gate TFT structures. The process enables the fabrication of amorphous and polycrystalline channel silicon TFTs at temperatures sufficiently low to prevent damage to plastic substrates. The process has use in large area low cost electronics, such as flat panel displays and portable electronics. 5 figs.

Fabrication and characterization of active nanostructures

NASA Astrophysics Data System (ADS)

Opondo, Noah F.

Three different nanostructure active devices have been designed, fabricated and characterized. Junctionless transistors based on highly-doped silicon nanowires fabricated using a bottom-up fabrication approach are first discussed. The fabrication avoids the ion implantation step since silicon nanowires are doped in-situ during growth. Germanium junctionless transistors fabricated with a top down approach starting from a germanium on insulator substrate and using a gate stack of high-k dielectrics and GeO2 are also presented. The levels and origin of low-frequency noise in junctionless transistor devices fabricated from silicon nanowires and also from GeOI devices are reported. Low-frequency noise is an indicator of the quality of the material, hence its characterization can reveal the quality and perhaps reliability of fabricated transistors. A novel method based on low-frequency noise measurement to envisage trap density in the semiconductor bandgap near the semiconductor/oxide interface of nanoscale silicon junctionless transistors (JLTs) is presented. Low-frequency noise characterization of JLTs biased in saturation is conducted at different gate biases. The noise spectrum indicates either a Lorentzian or 1/f. A simple analysis of the low-frequency noise data leads to the density of traps and their energy within the semiconductor bandgap. The level of noise in silicon JLT devices is lower than reported values on transistors fabricated using a top-down approach. This noise level can be significantly improved by improving the quality of dielectric and the channel interface. A micro-vacuum electron device based on silicon field emitters for cold cathode emission is also presented. The presented work utilizes vertical Si nanowires fabricated by means of self-assembly, standard lithography and etching techniques as field emitters in this dissertation. To obtain a high nanowire density, hence a high current density, a simple and inexpensive Langmuir Blodgett technique to deposit silica nanoparticles as a mask to etch Si is adopted. Fabrication and characterization of a metal-gated microtriode with a high current density and low operating voltage are presented.

Comparative assessment of erbium fiber ring lasers and reflective SOA linear lasers for fiber Bragg grating dynamic strain sensing.

PubMed

Wei, Heming; Krishnaswamy, Sridhar

2017-05-01

Fiber Bragg grating (FBG) dynamic strain sensors using both an erbium-based fiber ring laser configuration and a reflective semiconductor optical amplifier (RSOA)-based linear laser configuration are investigated theoretically and experimentally. Fiber laser models are first presented to analyze the output characteristics of both fiber laser configurations when the FBG sensor is subjected to dynamic strains at high frequencies. Due to differences in the transition times of erbium and the semiconductor (InP/InGaAsP), erbium-doped fiber amplifier (EDFA)- and RSOA-based fiber lasers exhibit different responses and regimes of stability when the FBG is subjected to dynamic strains. The responses of both systems are experimentally verified using an adaptive photorefractive two-wave mixing (TWM) spectral demodulation technique. The experimental results show that the RSOA-FBG fiber linear cavity laser is stable and can stably respond to dynamic strains at high frequencies. An example application using a multiplexed TWM interferometer to demodulate multiple FBG sensors is also discussed.

Semiconductor tunnel junction with enhancement layer

DOEpatents

Klem, J.F.; Zolper, J.C.

1997-10-21

The incorporation of a pseudomorphic GaAsSb layer in a runnel diode structure affords a new degree of freedom in designing runnel junctions for p-n junction device interconnects. Previously only doping levels could be varied to control the tunneling properties. This invention uses the valence band alignment band of the GaAsSb with respect to the surrounding materials to greatly relax the doping requirements for tunneling. 5 figs.

Polycrystalline silicon semiconducting material by nuclear transmutation doping

DOEpatents

Cleland, John W.; Westbrook, Russell D.; Wood, Richard F.; Young, Rosa T.

1978-01-01

A NTD semiconductor material comprising polycrystalline silicon having a mean grain size less than 1000 microns and containing phosphorus dispersed uniformly throughout the silicon rather than at the grain boundaries.

Dependence of the magnetic properties of the dilute magnetic semiconductor Zn1-xMnxO nanorods on their Mn doping levels

NASA Astrophysics Data System (ADS)

Thongjamroon, S.; Ding, J.; Herng, T. S.; Tang, I. M.; Thongmee, S.

2017-10-01

The effects of Mn doping on the ferromagnetic properties of the dilute magnetic semiconductor Zn1-xMnxO nanorods (NR's) having the nominal composit-ions x = 0, 0.01, 0.03, 0.04 and 0.05 grown by a low temperature hydrothermal method are studied. Energy dispersive X-ray (EDX) is used to determine the actual amounts of the elements in each NR's. X-ray diffraction, scanning electron microscopy, photoluminescence and vibrating sample magnetometer measurements are used to observe the effects of the Mn substitution on the properties of the doped ZnO and to relate the changes in the properties to changes in the defect content. It is observed that the saturation magnetization of the Mn ions in the wurtzite structure varies from 0.0210 μB/Mn2+ to 0.0234 μB/Mn2+ reaching a high of 0.0251 μB/Mn2+ as the Mn concentrations is varied from 0.9 to 7.36 atomic%. It is argued that the changes in the saturation magnetization are due to the competition between the direct Mn-Mn exchange interaction and the indirect Mn-O-Mn exchange interaction in the doped Mn ZnO NP's.

The n-type conduction of indium-doped Cu{sub 2}O thin films fabricated by direct current magnetron co-sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Xing-Min; Su, Xiao-Qiang; Ye, Fan, E-mail: yefan@szu.edu.cn

2015-08-24

Indium-doped Cu{sub 2}O thin films were fabricated on K9 glass substrates by direct current magnetron co-sputtering in an atmosphere of Ar and O{sub 2}. Metallic copper and indium disks were used as the targets. X-ray diffraction showed that the diffraction peaks could only be indexed to simple cubic Cu{sub 2}O, with no other phases detected. Indium atoms exist as In{sup 3+} in Cu{sub 2}O. Ultraviolet-visible spectroscopy showed that the transmittance of the samples was relatively high and that indium doping increased the optical band gaps. The Hall effect measurement showed that the samples were n-type semiconductors at room temperature. Themore » Seebeck effect test showed that the films were n-type semiconductors near or over room temperature (<400 K), changing to p-type at relatively high temperatures. The conduction by the samples in the temperature range of the n-type was due to thermal band conduction and the donor energy level was estimated to be 620.2–713.8 meV below the conduction band. The theoretical calculation showed that indium doping can raise the Fermi energy level of Cu{sub 2}O and, therefore, lead to n-type conduction.« less

Electrical transport and structural characterization of epitaxial monolayer MoS2 /n- and p-doped GaN vertical lattice-matched heterojunctions

NASA Astrophysics Data System (ADS)

Ruzmetov, D.; O'Regan, T.; Zhang, K.; Herzing, A.; Mazzoni, A.; Chin, M.; Huang, S.; Zhang, Z.; Burke, R.; Neupane, M.; Birdwell, Ag; Shah, P.; Crowne, F.; Kolmakov, A.; Leroy, B.; Robinson, J.; Davydov, A.; Ivanov, T.

We investigate vertical semiconductor junctions consisting of monolayer MoS2 that is epitaxially grown on n- and p-doped GaN crystals. Such a junction represents a building block for 2D/3D vertical semiconductor heterostructures. Epitaxial, lattice-matched growth of MoS2 on GaN is important to ensure high quality interfaces that are crucial for the efficient vertical transport. The MoS2/GaN junctions were characterized with cross-sectional and planar scanning transmission electron microscopy (STEM), scanning tunneling microscopy, and atomic force microscopy. The MoS2/GaN lattice mismatch is measured to be near 1% using STEM. The electrical transport in the out-of-plane direction across the MoS2/GaN junctions was measured using conductive atomic force microscopy and mechanical nano-probes inside a scanning electron microscope. Nano-disc metal contacts to MoS2 were fabricated by e-beam lithography and evaporation. The current-voltage curves of the vertical MoS2/GaN junctions exhibit rectification with opposite polarities for n-doped and p-doped GaN. The metal contact determines the general features of the current-voltage curves, and the MoS2 monolayer modifies the electrical transport across the contact/GaN interface.

Electron-plasmon and electron-phonon satellites in the angle-resolved photoelectron spectra of n -doped anatase TiO2

NASA Astrophysics Data System (ADS)

Caruso, Fabio; Verdi, Carla; Poncé, Samuel; Giustino, Feliciano

2018-04-01

We develop a first-principles approach based on many-body perturbation theory to investigate the effects of the interaction between electrons and carrier plasmons on the electronic properties of highly doped semiconductors and oxides. Through the evaluation of the electron self-energy, we account simultaneously for electron-plasmon and electron-phonon coupling in theoretical calculations of angle-resolved photoemission spectra, electron linewidths, and relaxation times. We apply this methodology to electron-doped anatase TiO2 as an illustrative example. The simulated spectra indicate that electron-plasmon coupling in TiO2 underpins the formation of satellites at energies comparable to those of polaronic spectral features. At variance with phonons, however, the energy of plasmons and their spectral fingerprints depends strongly on the carrier concentration, revealing a complex interplay between plasmon and phonon satellites. The electron-plasmon interaction accounts for approximately 40% of the total electron-boson interaction strength, and it is key to improve the agreement with measured quasiparticle spectra.

Conjugated ionic state and its distribution in perylene bisimide doped film: A characterization of Z-scanning in confocal Raman spectroscopy.

PubMed

Zhou, Xuehong; Zhang, Wenqiang; Wang, Cong; Zhou, Jiadong; Liu, Linlin; Xie, Zengqi; Ma, Yuguang

2018-04-27

Ion-doped states are significant for improving the performance in organic semiconductor-based devices, which require clear characterization to understand their relationship with conductivity and charge transporting mechanisms. In this paper, Raman spectroscopy is used to track the evolution of a dianion-anion-neutral mixture in a perylene bisimide (PBI)-doped film under air, with z-scanning carried out in the confocal mode. The precise distribution for the different states along the film depth is realized within 3.5 μm. The whole film is clearly divided into three regions: the ion-poor state, transition region and ion-rich state. The ion ratio and distribution are strongly related to the film conductivity and the onset voltage shift. Changes in the distribution of the ionic species during oxidation and electrode catalysis are clearly recorded by z-scanning, which is beneficial for understanding the charge transfer properties as well as the mechanism underlying working devices. Copyright © 2018 Elsevier B.V. All rights reserved.

The role of Mg dopant on the morphological, structural and optical properties of Mg doped zinc oxide grown through hydrothermal method

NASA Astrophysics Data System (ADS)

Susetyo, P.; Fauzia, V.; Sugihartono, I.

2017-04-01

ZnO nanorods is a low cost II-VI semiconductor compound with huge potential to be applied in optoelectronic devices i.e. light emitting diodes, solar cells, gas sensor, spintronic devices and lasers. In order to improve the electrical and optical properties, group II, III and IV elements were widely investigated as dopand elements on ZnO. In this work, magnesium (Mg) was doped into ZnO nanorods. Samples were prepared firstly by deposition of undoped ZnO seed layer on indium thin oxide coated glass substrates by ultrasonic spray pyrolysis method and then followed by the growth of ZnO nanorods doped by three different Mg concentrations by hydrothermal method. Based on the morphological, microstructural and optical characterizations results, it is concluded that the increase of magnesium concentration tends to reduce the diameter of ZnO nanorods, increases the bandgap energy and decreases the UV absorption the luminescence in UV and visible range.

n-type conversion of SnS by isovalent ion substitution: Geometrical doping as a new doping route

PubMed Central

Ran, Fan-Yong; Xiao, Zewen; Toda, Yoshitake; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

2015-01-01

Tin monosulfide (SnS) is a naturally p-type semiconductor with a layered crystal structure, but no reliable n-type SnS has been obtained by conventional aliovalent ion substitution. In this work, carrier polarity conversion to n-type was achieved by isovalent ion substitution for polycrystalline SnS thin films on glass substrates. Substituting Pb2+ for Sn2+ converted the majority carrier from hole to electron, and the free electron density ranged from 1012 to 1015 cm−3 with the largest electron mobility of 7.0 cm2/(Vs). The n-type conduction was confirmed further by the position of the Fermi level (EF) based on photoemission spectroscopy and electrical characteristics of pn heterojunctions. Density functional theory calculations reveal that the Pb substitution invokes a geometrical size effect that enlarges the interlayer distance and subsequently reduces the formation energies of Sn and Pb interstitials, which results in the electron doping. PMID:26020855

First-principles study of bandgap tuning in Ge1-xPbxSe

NASA Astrophysics Data System (ADS)

Lohani, Himanshu

2018-03-01

Narrow bandgap and its tuning are important aspects of materials for their technological applications. In this context group IV-VI semiconductors are one of the interesting candidates. In this paper, we explore the possibility of bandgap tuning in one of the family member of this family GeSe by using isoelectronic Pb doping. Our study is first-principles based electronic structure calculations of Ge1-xPbxSe. This study reveals that the Ge-p and Se-p states are strongly hybridized in GeSe and shows a gap in the DOS at Ef in GeSe. This gap reduces systematically with simultaneous enhancement of the states in the near Ef region as a function of Pb doping. This leads tuning of the indirect bandgap in GeSe via Pb doping. The results of the indirect bandgap decrement are consistent with the experimental findings. We propose a mechanism where the electrostatic effect of dopant Pb cation could be responsible for these changes in the electronic structure of GeSe.

Co-doped phosphorene: Enhanced sensitivity of CO gas sensing

NASA Astrophysics Data System (ADS)

Lei, S. Y.; Luan, S.; Yu, H.

2018-03-01

First-principle calculation was carried out to systematically investigate carbon monoxide (CO) adsorption on pristine and cobalt (Co)-doped phosphorenes (Co-bP). Whether or not CO is adsorped, pristine phosphorene is a direct-band-gap semiconductor. However, the bandgap of Co-bP experiences direct-to-indirect transition after CO molecule adsorption, which will affect optical absorption considerably, implying that Co doping can enhance the sensitivity of phosphorene as a CO gas sensor. Moreover, Co doping can improve an adsorption energy of CO to 1.31 eV, as compared with pristine phosphorene (0.12 eV), also indicating that Co-bP is energetically favorable for CO gas sensing.

Local structure analysis of diluted magnetic semiconductor Co and Al co-doped ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hyodo, K.; Morimoto, S.; Yamazaki, T.

2016-02-01

In this study, Co and Al ions co-doped ZnO nanoparticles (Zn(Al, Co)O NPs) were prepared by our original chemical preparation method. The obtained samples prepared by this method, were encapsulated in amorphous SiO{sub 2}. X-ray diffraction (XRD) results showed Zn(Al, Co)O NPs had a single-phase nature with hexagonal wurtzite structure. These particle sizes could be controlled to be approximately 30 nm. We investigate the effect that the increase in the carrier has on the magnetization by doping Al to Co-doped ZnO NPs. The local structures were qualitatively analyzed using X-ray absorption fine structure (XAFS) measurements.

Surface Morphology of Undoped and Doped ZnSe Films

NASA Technical Reports Server (NTRS)

George, T.; Hayes, M.; Chen, H.; Chattopadhyay, K.; Thomas E.; Morgan, S.; Burger, A.

1998-01-01

Rare-earth doped ions in polar II-VI semiconductors have recently played an important role in the optical properties of materials and devices. In this study, undoped ZnSe and erbium doped ZnSe films were grown by radio frequency (RF) magnetron sputtering method. Atomic Force Microscopy (AFM) was used together with optical microscopy and UV-Vis spectroscopy to characterize the films. Doped samples were found to have higher surface roughness and quite different surface morphology compared to that of undoped samples. The grown films generally show a relatively smooth and uniform surface indicating that they are of overall good quality. The impact of plasma etching on ZnSe:Er film examined under AFM is also discussed.

Optical Fiber Chemical Sensor with Sol-Gel Derived Refractive Material as Transducer for High Temperature Gas Sensing in Clean Coal Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shiquan Tao

2006-12-31

The chemistry of sol-gel derived silica and refractive metal oxide has been systematically studied. Sol-gel processes have been developed for preparing porous silica and semiconductor metal oxide materials. Micelle/reversed micelle techniques have been developed for preparing nanometer sized semiconductor metal oxides and noble metal particles. Techniques for doping metal ions, metal oxides and nanosized metal particles into porous sol-gel material have also been developed. Optical properties of sol-gel derived materials in ambient and high temperature gases have been studied by using fiber optic spectroscopic techniques, such as fiber optic ultraviolet/visible absorption spectrometry, fiber optic near infrared absorption spectrometry and fibermore » optic fluorescence spectrometry. Fiber optic spectrometric techniques have been developed for investigating the optical properties of these sol-gel derived materials prepared as porous optical fibers or as coatings on the surface of silica optical fibers. Optical and electron microscopic techniques have been used to observe the microstructure, such as pore size, pore shape, sensing agent distribution, of sol-gel derived material, as well as the size and morphology of nanometer metal particle doped in sol-gel derived porous silica, the nature of coating of sol-gel derived materials on silica optical fiber surface. In addition, the chemical reactions of metal ion, nanostructured semiconductor metal oxides and nanometer sized metal particles with gas components at room temperature and high temperatures have also been investigated with fiber optic spectrometric methods. Three classes of fiber optic sensors have been developed based on the thorough investigation of sol-gel chemistry and sol-gel derived materials. The first group of fiber optic sensors uses porous silica optical fibers doped with metal ions or metal oxide as transducers for sensing trace NH{sub 3} and H{sub 2}S in high temperature gas samples. The second group of fiber optic sensors uses sol-gel derived porous silica materials doped with nanometer particles of noble metals in the form of fiber or coating for sensing trace H{sub 2}, NH{sub 3} and HCl in gas samples at for applications ambient temperature. The third classes of fiber optic sensors use sol-gel derived semiconductor metal oxide coating on the surface of silica optical fiber as transducers for selectively sensing H{sub 2}, CH{sub 4} and CO at high temperature. In addition, optical fiber temperature sensors use the fluorescence signal of rare-earth metal ions doped porous silica optical fiber or the optical absorption signal of thermochromic metal oxide materials coated on the surface of silica optical fibers have also been developed for monitoring gas temperature of corrosive gas. Based on the results obtained from this project, the principle of fiber optic sensor techniques for monitoring matrix gas components as well as trace components of coal gasification derived syngas has been established. Prototype sensors for sensing trace ammonia and hydrogen sulfide in gasification derived syngas have been built up in our laboratory and have been tested using gas samples with matrix gas composition similar to that of gasification derived fuel gas. Test results illustrated the feasibility of these sensors for applications in IGCC processes.« less

Spin-dependent transport phenomena in organic semiconductors

NASA Astrophysics Data System (ADS)

Bergeson, Jeremy D.

Thin-film organic semiconductors transport can have an anomalously high sensitivity to low magnetic fields. Such a response is unexpected considering that thermal fluctuation energies are greater than the energy associated with the intrinsic spin of charge carriers at a modest magnetic field of 100 Oe by a factor of more than 104 at room temperature and is still greater by 102 even at liquid helium temperatures. Nevertheless, we report experimental characterization of (1) spin-dependent injection, detection and transport of spin-polarized current through organic semiconductors and (2) the influence of a magnetic field on the spin dynamics of recombination-limited transport. The first focus of this work was accomplished by fabricating basic spin-valve devices consisting of two magnetic layers spatially separated by a nonmagnetic organic semiconductor. The spin-valve effect is a change in electrical resistance due to the magnetizations of the magnetic layers changing from parallel to antiparallel alignment, or vice versa. The conductivities of the metallic contacts and that of the semiconductor differed by many orders of magnitude, which inhibited the injection of a spin-polarized current from the magnet into the nonmagnet. We successfully overcame the problem of conductivity mismatch by inserting ultra-thin tunnel barriers at the metal/semiconductor interfaces which aided in yielding a ˜20% spin-valve effect at liquid helium temperatures and the effect persisted up to 150 K. We built on this achievement by constructing spin valves where one of the metallic contacts was replaced by the organic-based magnetic semiconductor vanadium tetracyanoethylene (V[TCNE]2). At 10 K these devices produced the switching behavior of the spin-valve effect. The second focus of this work was the bulk magnetoresistance (MR) of small molecule, oligomer and polymer organic semiconductors in thin-film structures. At room temperature the resistance can change up to 8% at 100 Oe and 15% at 1000 Oe. Depending on parameters such as temperature, layer thickness, or applied voltage, the resistance of these materials may increase or decrease as a function of field. A model for this phenomenon, termed magnetoresistance by the interconversion of singlets and triplets (MIST), is developed to account for this anomalous behavior. This model predicts that increasing the spin-orbit coupling in the organic semiconductor should decrease the magnitude of the MR. In an experiment where the small molecule Alq3 was doped with phosphorescent sensitizers, to increase the spin-orbit coupling, the MR was observed to decrease by an order of magnitude or more, depending on the doping. In addition to low-magnetic-field effects, we show the experimental observation of high-field MR in devices with and without magnetic contacts. To the best of our knowledge, we are the first to report (1) a tunnel-barrier-assisted spin-valve effect into an organic semiconductor using partially polarized metallic magnetic electrodes and (2) an experimental characterization of the central impact of the hyperfine interaction and spin-orbit coupling on MR in organic semiconductors.

Nonlinear THz Plamonic Disk Resonators

NASA Astrophysics Data System (ADS)

Seren, Huseyin; Zhang, Jingdi; Keiser, George; Maddox, Scott; Fan, Kebin; Cao, Lingyue; Bank, Seth; Zhang, Xin; Averitt, Richard

2013-03-01

Particle surface plasmons (PPSs) at visible wavelengths continue to be actively investigated with the goal of nanoscale control of light. In contrast, terahertz (THz) surface plasmon experiments are at a nascent stage of investigation. Doped semiconductors with proper carrier density and mobility support THz PSPs. One approach is to utilize thick doped films etched into subwavelength disks. Given the ease of tuning the semiconductor carrier density, THz PSPs are tunable and exhibit interesting nonlinear THz plasmonic effects. We created THz PSP structures using MBE grown 2um thick InAs films with a doping concentration of 1e17cm-3 on 500um thick semi-insulating GaAs substrate. We patterned 40um diameter disks with a 60um period by reactive ion etching. Our THz time-domain measurements reveal a resonance at 1.1THz which agrees well with simulation results using a Drude model. A nonlinear response occurs at high THz electric field strengths (>50kV/cm). In particular, we observed a redshift and quenching of the resonance due to impact ionization which resulted in changes in the carrier density and effective mass due to inter-valley scattering.

Significantly enhanced visible light response in single TiO2 nanowire by nitrogen ion implantation

NASA Astrophysics Data System (ADS)

Wu, Pengcheng; Song, Xianyin; Si, Shuyao; Ke, Zunjian; Cheng, Li; Li, Wenqing; Xiao, Xiangheng; Jiang, Changzhong

2018-05-01

The metal-oxide semiconductor TiO2 shows enormous potential in the field of photoelectric detection; however, UV-light absorption only restricts its widespread application. It is considered that nitrogen doping can improve the visible light absorption of TiO2, but the effect of traditional chemical doping is far from being used for visible light detection. Herein, we dramatically broadened the absorption spectrum of the TiO2 nanowire (NW) by nitrogen ion implantation and apply the N-doped single TiO2 NW to visible light detection for the first time. Moreover, this novel strategy effectively modifies the surface states and thus regulates the height of Schottky barriers at the metal/semiconductor interface, which is crucial to realizing high responsivity and a fast response rate. Under the illumination of a laser with a wavelength of 457 nm, our fabricated photodetector exhibits favorable responsivity (8 A W-1) and a short response time (0.5 s). These results indicate that ion implantation is a promising method in exploring the visible light detection of TiO2.

Ion implantation in group III-nitride semiconductors: a tool for doping and defect studies

NASA Astrophysics Data System (ADS)

Zolper, J. C.

1997-06-01

Ion implantation is a flexible process technology for introducing an array of doping or compensating impurities into semiconductors. As the crystal quality of the group III-nitride materials continues to improve, ion implantation is playing an enabling role in exploring new dopant species and device structures. In this paper we review the recent developments in ion implantation processing of these materials with a particular emphasis on how this technology has brought new understanding to this materials system. In particular, the use of ion implantation to characterize impurity luminescence, doping, and compensation in III-nitride materials is reviewed. In addition, we address the nature of implantation induced damage in GaN which demonstrates a very strong resistance to amorphization while at the same time forming damage that is not easily removed by thermal annealing. Finally, we review the coupling of implantation with high temperature rapid thermal annealing to better understand the thermal stability of these materials and the redistribution properties of the common dopant (Si, O, Be, Mg, Ca, and Zn).

Electronic structure and p-type doping of ZnSnN2

NASA Astrophysics Data System (ADS)

Wang, Tianshi; Janotti, Anderson; Ni, Chaoying

ZnSnN2 is a promising solar-cell absorber material composed of earth abundant elements. Little is known about doping, defects, and how the valence and conduction bands in this material align with the bands in other semiconductors. Using density functional theory with the the Heyd-Scuseria-Ernzerhof hybrid functional (HSE06), we investigate the electronic structure of ZnSnN2, its band alignment to other semiconductors, such as GaN and ZnO, the possibility of p-type doping, and the possible causes of the observed unintentional n-type conductivity. We find that the position of the valence-band maximum of ZnSnN2 is 0.55 eV higher than that of GaN, yet the conduction-band minimum is close to that in ZnO. As possible p-type dopants, we explore Li, Na, and K substituting on the Zn site. Finally, we discuss the cause of unintentional n-type conductivity by analyzing the position of the conduction-band minimum with respect to that of GaN and ZnO.

Significantly enhanced visible light response in single TiO2 nanowire by nitrogen ion implantation.

PubMed

Wu, Pengcheng; Song, Xianyin; Si, Shuyao; Ke, Zunjian; Cheng, Li; Li, Wenqing; Xiao, Xiangheng; Jiang, Changzhong

2018-05-04

The metal-oxide semiconductor TiO 2 shows enormous potential in the field of photoelectric detection; however, UV-light absorption only restricts its widespread application. It is considered that nitrogen doping can improve the visible light absorption of TiO 2 , but the effect of traditional chemical doping is far from being used for visible light detection. Herein, we dramatically broadened the absorption spectrum of the TiO 2 nanowire (NW) by nitrogen ion implantation and apply the N-doped single TiO 2 NW to visible light detection for the first time. Moreover, this novel strategy effectively modifies the surface states and thus regulates the height of Schottky barriers at the metal/semiconductor interface, which is crucial to realizing high responsivity and a fast response rate. Under the illumination of a laser with a wavelength of 457 nm, our fabricated photodetector exhibits favorable responsivity (8 A W -1 ) and a short response time (0.5 s). These results indicate that ion implantation is a promising method in exploring the visible light detection of TiO 2 .

Exchange Enhancement of the Electron-Phonon Interaction: The Case of Weakly Doped Two-Dimensional Multivalley Semiconductors

NASA Astrophysics Data System (ADS)

Pamuk, Betül; Zoccante, Paolo; Baima, Jacopo; Mauri, Francesco; Calandra, Matteo

2018-04-01

The effect of the exchange interaction on the vibrational properties and on the electron-phonon coupling were investigated in several recent works. In most of the cases, exchange tends to enhance the electron-phonon interaction, although the motivations for such behaviour are not completely understood. Here we consider the class of weakly doped two-dimensional multivalley semiconductors and we demonstrate that a more global picture emerges. In particular we show that in these systems, at low enough doping, even a moderate electron-electron interaction enhances the response to any perturbation inducing a valley polarization. If the valley polarization is due to the electron-phonon coupling, the electron-electron interaction results in an enhancement of the superconducting critical temperature. We demonstrate the applicability of the theory by performing random phase approximation and first principles calculations in transition metal chloronitrides. We find that exchange is responsible for the enhancement of the superconducting critical temperature in LixZrNCl and that much larger Tcs could be obtained in intercalated HfNCl if the synthesis of cleaner samples could remove the Anderson insulating state competing with superconductivity.

Single-Crystal Growth of Cl-Doped n-Type SnS Using SnCl2 Self-Flux.

PubMed

Iguchi, Yuki; Inoue, Kazutoshi; Sugiyama, Taiki; Yanagi, Hiroshi

2018-06-05

SnS is a promising photovoltaic semiconductor owing to its suitable band gap energy and high optical absorption coefficient for highly efficient thin film solar cells. The most significant carnage is demonstration of n-type SnS. In this study, Cl-doped n-type single crystals were grown using SnCl 2 self-flux method. The obtained crystal was lamellar, with length and width of a few millimeters and thickness ranging between 28 and 39 μm. X-ray diffraction measurements revealed the single crystals had an orthorhombic unit cell. Since the ionic radii of S 2- and Cl - are similar, Cl doping did not result in substantial change in lattice parameter. All the elements were homogeneously distributed on a cleaved surface; the Sn/(S + Cl) ratio was 1.00. The crystal was an n-type degenerate semiconductor with a carrier concentration of ∼3 × 10 17 cm -3 . Hall mobility at 300 K was 252 cm 2 V -1 s -1 and reached 363 cm 2 V -1 s -1 at 142 K.

Semiconducting behavior of substitutionally doped bilayer graphene

NASA Astrophysics Data System (ADS)

Mousavi, Hamze; Khodadadi, Jabbar; Grabowski, Marek

2018-02-01

In the framework of the Green's functions approach, random tight-binding model and using the coherent potential approximation, electronic characteristics of the bilayer graphene are investigated by exploring various forms of substitutional doping of a single or both layers of the system by either boron and (or) nitrogen atoms. The results for displacement of the Fermi level resemble the behavior of acceptor or donor doping in a conventional semiconductor, dependent on the impurity type and concentration. The particular pattern of doping of just one layer with one impurity type is most efficient for opening a gap within the energy bands which could be tuned directly by impurity concentration. Doping both layers at the same time, each with one impurity type, leads to an anomaly whereby the gap decreases with increasing impurity concentration.

Manufacture of silicon-based devices having disordered sulfur-doped surface layers

DOEpatents

Carey, III; Edward, James [Newton, MA; Mazur, Eric [Concord, MA

2008-04-08

The present invention provides methods of fabricating a radiation-absorbing semiconductor wafer by irradiating at least one surface location of a silicon substrate, e.g., an n-doped crystalline silicon, by a plurality of temporally short laser pulses, e.g., femtosecond pulses, while exposing that location to a substance, e.g., SF.sub.6, having an electron-donating constituent so as to generate a substantially disordered surface layer (i.e., a microstructured layer) that incorporates a concentration of that electron-donating constituent, e.g., sulfur. The substrate is also annealed at an elevated temperature and for a duration selected to enhance the charge carrier density in the surface layer. For example, the substrate can be annealed at a temperature in a range of about 700 K to about 900 K.

Dispersion dependence of second-order refractive index and complex third-order optical susceptibility in oxide glasses

NASA Astrophysics Data System (ADS)

Abdel Wahab, F. A.; El-Diasty, Fouad; Abdel-Baki, Manal

2009-10-01

A method correlates Fresnel-based spectrophotometric measurements and Lorentz dispersion theory is presented to study the dispersion of nonlinear optical parameters in particularly oxide glasses in a very wide range of angular frequency. The second-order refractive index and third-order optical susceptibility of Cr-doped glasses are determined from linear refractive index. Furthermore, both real and imaginary components of the complex susceptibility are carried out. The study reveals the importance of determining the dispersion of nonlinear absorption (two-photon absorption coefficient) to find the maximum resonant and nonresonant susceptibilities of investigated glasses. The present method is applied on Cr-doped lithium aluminum silicate (LAS) glasses due to their semiconductor-like behavior and also to their application in laser industry.

Structural, electronic and magnetic properties of carbon doped boron nitride nanowire: Ab initio study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jalilian, Jaafar, E-mail: JaafarJalilian@gmail.com; Kanjouri, Faramarz, E-mail: kanjouri@khu.ac.ir

2016-11-15

Using spin-polarized density functional theory calculations, we demonstrated that carbon doped boron nitride nanowire (C-doped BNNW) has diverse electronic and magnetic properties depending on position of carbon atoms and their percentages. Our results show that only when one carbon atom is situated on the edge of the nanowire, C-doped BNNW is transformed into half-metal. The calculated electronic structure of the C-doped BNNW suggests that doping carbon can induce localized edge states around the Fermi level, and the interaction among localized edge states leads to semiconductor to half-metal transition. Overall, the bond reconstruction causes of appearance of different electronic behavior suchmore » as semiconducting, half-metallicity, nonmagnetic metallic, and ferromagnetic metallic characters. The formation energy of the system shows that when a C atom is doped on surface boron site, system is more stable than the other positions of carbon impurity. Our calculations show that C-doped BNNW may offer unique opportunities for developing nanoscale spintronic materials.« less

Localized Charges Control Exciton Energetics and Energy Dissipation in Doped Carbon Nanotubes.

PubMed

Eckstein, Klaus H; Hartleb, Holger; Achsnich, Melanie M; Schöppler, Friedrich; Hertel, Tobias

2017-10-24

Doping by chemical or physical means is key for the development of future semiconductor technologies. Ideally, charge carriers should be able to move freely in a homogeneous environment. Here, we report on evidence suggesting that excess carriers in electrochemically p-doped semiconducting single-wall carbon nanotubes (s-SWNTs) become localized, most likely due to poorly screened Coulomb interactions with counterions in the Helmholtz layer. A quantitative analysis of blue-shift, broadening, and asymmetry of the first exciton absorption band also reveals that doping leads to hard segmentation of s-SWNTs with intrinsic undoped segments being separated by randomly distributed charge puddles approximately 4 nm in width. Light absorption in these doped segments is associated with the formation of trions, spatially separated from neutral excitons. Acceleration of exciton decay in doped samples is governed by diffusive exciton transport to, and nonradiative decay at charge puddles within 3.2 ps in moderately doped s-SWNTs. The results suggest that conventional band-filling in s-SWNTs breaks down due to inhomogeneous electrochemical doping.

Carbon Doping of Compound Semiconductor Epitaxial Layers Grown by Metalorganic Chemical Vapor Deposition Using Carbon Tetrachloride.

NASA Astrophysics Data System (ADS)

Cunningham, Brian Thomas

1990-01-01

A dilute mixture of CCl_4 in high purity H_2 has been used as a carbon dopant source for rm Al_ {x}Ga_{1-x}As grown by low pressure metalorganic chemical vapor deposition (MOCVD). To understand the mechanism for carbon incorporation from CCl_4 doping and to provide experimental parameters for the growth of carbon doped device structures, the effects of various crystal growth parameters on CCl _4 doping have been studied, including growth temperature, growth rate, V/III ratio, Al composition, and CCl_4 flow rate. Although CCl _4 is an effective p-type dopant for MOCVD rm Al_{x}Ga_ {1-x}As, injection of CCl_4 into the reactor during growth of InP resulted in no change in the carrier concentration or carbon concentration. Abrupt, heavy carbon doping spikes in GaAs have been obtained using CCl_4 without a dopant memory effect. By annealing samples with carbon doping spikes grown within undoped, n-type, and p-type GaAs, the carbon diffusion coefficient in GaAs at 825 ^circC has been estimated and has been found to depend strongly on the GaAs background doping. Heavily carbon doped rm Al_{x}Ga _{1-x}As/GaAs superlattices have been found to be more stable against impurity induced layer disordering (IILD) than Mg or Zn doped superlattices, indicating that the low carbon diffusion coefficient limits the IILD process. Carbon doping has been used in the base region on an Npn AlGaAs/GaAs heterojunction bipolar transistor (HBT). Transistors with 3 x 10 μm self-aligned emitter fingers have been fabricated which exhibit a current gain cutoff frequency of f_ {rm t} = 26 GHz.

Correlation of Photocatalytic Activity with Band Structure of Low-dimensional Semiconductor Nanostructures

NASA Astrophysics Data System (ADS)

Meng, Fanke

Photocatalytic hydrogen generation by water splitting is a promising technique to produce clean and renewable solar fuel. The development of effective semiconductor photocatalysts to obtain efficient photocatalytic activity is the key objective. However, two critical reasons prevent wide applications of semiconductor photocatalysts: low light usage efficiency and high rates of charge recombination. In this dissertation, several low-dimensional semiconductors were synthesized with hydrothermal, hydrolysis, and chemical impregnation methods. The band structures of the low-dimensional semiconductor materials were engineered to overcome the above mentioned two shortcomings. In addition, the correlation between the photocatalytic activity of the low-dimensional semiconductor materials and their band structures were studied. First, we studied the effect of oxygen vacancies on the photocatalytic activity of one-dimensional anatase TiO2 nanobelts. Given that the oxygen vacancy plays a significant role in band structure and photocatalytic performance of semiconductors, oxygen vacancies were introduced into the anatase TiO2 nanobelts during reduction in H2 at high temperature. The oxygen vacancies of the TiO2 nanobelts boosted visible-light-responsive photocatalytic activity but weakened ultraviolet-light-responsive photocatalytic activity. As oxygen vacancies are commonly introduced by dopants, these results give insight into why doping is not always beneficial to the overall photocatalytic performance despite increases in absorption. Second, we improved the photocatalytic performance of two-dimensional lanthanum titanate (La2Ti2 O7) nanosheets, which are widely studied as an efficient photocatalyst due to the unique layered crystal structure. Nitrogen was doped into the La2Ti2O7 nanosheets and then Pt nanoparticles were loaded onto the La2Ti2O7 nanosheets. Doping nitrogen narrowed the band gap of the La2Ti 2O7 nanosheets by introducing a continuum of states by the valence band edge, unlike the mid-gap states introduced by oxygen vacancies, leading to an improvement in visible and UV photocatalysis. The Pt nanoparticles both enhanced separation of charge carriers and acted as reaction sites for hydrogen evolution. The photocatalytic hydrogen generation rate of the La 2Ti2O7 nanosheets was increased to ˜21 muM g-1 hr-1 from zero in visible light by nitrogen doping and Pt loading, showing the importance of the positioning of dopant energy levels within the band gap. Third, a hematite/reduced graphene oxide (alpha-Fe2 2O3/rGO) nanocomposite was synthesized by a hydrolysis method. The photocatalytic oxygen evolution rate of the hematite was increased from 387 to 752 muM g-1 hr-1 by incorporating rGO. Photoelectrochemical measurements showed that coupling the hematite nanoparticles with the rGO can greatly increase the photocurrent and reduce the charge recombination rate, overcoming the poor charge recombination characteristics of hematite and allowing its small band gap to be taken advantage of. Fourth, a Au/La 2Ti2O7/rGO heterostructure was synthesized to further enhance the photocatalytic hydrogen generation rate of the La 2Ti2O7 nanosheets. The enhanced performance of photocatalytic water splitting was due to plasmonic energy transfer, which resulted from the plasmonic Au nanoparticles on the La2Ti 2O7 nanosheets. This heterostructure showed doping, charge extraction, and plasmonics work synergistically. Fifth, nanoscale p-n junctions on the rGO were formed by depositing the p-type MoS 2 nanoplatelets onto the n-type nitrogen-doped rGO. The p-MoS2/n-rGO heterostructure had significant photocatalytic hydrogen generation activity under solar light irradiation. The enhanced charge generation and suppressed charge recombination due to the p-n junctions led to enhance solar hydrogen generation reaction while allowing replacement of the expensive Pt nanoparticles with an eco-friendly alternative. The research results in this dissertation are contributed to a better understanding of the relationship between the band structure tuning and photocatalytic activity of low-dimensional semiconductor nanostructures. The results lay out guidelines for the enhancement of large band gap semiconductors with poor solar utilization and small band gap semiconductors with poor charge recombination characteristics alike. Additionally, it is shown that the rare earth co-catalyst can be replaced with an earth friendly alternative, leading to a further increase in performance. The findings of this thesis can be used to guide photocatalyst selection and optimization for solar to hydrogen conversion.

Energy Level Alignment of N-Doping Fullerenes and Fullerene Derivatives Using Air-Stable Dopant.

PubMed

Bao, Qinye; Liu, Xianjie; Braun, Slawomir; Li, Yanqing; Tang, Jianxin; Duan, Chungang; Fahlman, Mats

2017-10-11

Doping has been proved to be one of the powerful technologies to achieve significant improvement in the performance of organic electronic devices. Herein, we systematically map out the interface properties of solution-processed air-stable n-type (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl) doping fullerenes and fullerene derivatives and establish a universal energy level alignment scheme for this class of n-doped system. At low doping levels at which the charge-transfer doping induces mainly bound charges, the energy level alignment of the n-doping organic semiconductor can be described by combining integer charger transfer-induced shifts with a so-called double-dipole step. At high doping levels, significant densities of free charges are generated and the charge flows between the organic film and the conducting electrodes equilibrating the Fermi level in a classic "depletion layer" scheme. Moreover, we demonstrate that the model holds for both n- and p-doping of π-backbone molecules and polymers. With the results, we provide wide guidance for identifying the application of the current organic n-type doping technology in organic electronics.

Doping process of p-type GaN nanowires: A first principle study

NASA Astrophysics Data System (ADS)

Xia, Sihao; Liu, Lei; Diao, Yu; Feng, Shu

2017-10-01

The process of p-type doping for GaN nanowires is investigated using calculations starting from first principles. The influence of different doping elements, sites, types, and concentrations is discussed. Results suggest that Mg is an optimal dopant when compared to Be and Zn due to its stronger stability, whereas Be atoms are more inclined to exist in the interspace of a nanowire. Interstitially-doped GaN nanowires show notable n-type conductivity, and thus, Be is not a suitable dopant, which is to be expected since systems with inner substitutional dopants are more favorable than those with surface substitutions. Both interstitial and substitutional doping affect the atomic structure near dopants and induce charge transfer between the dopants and adjacent atoms. By altering doping sites and concentrations, nanowire atomic structures remain nearly constant. Substitutional doping models show p-type conductivity, and Mg-doped nanowires with doping concentrations of 4% showing the strongest p-type conductivity. All doping configurations are direct bandgap semiconductors. This study is expected to direct the preparation of high-quality GaN nanowires.