Bipolar molecular composites: a new class of high-electron-mobility organic solids

NASA Astrophysics Data System (ADS)

Lin, Liang-Bih; Jenekhe, Samson A.; Borsenberger, Paul M.

1997-10-01

We describe high electron mobility in organic solids in the form of bipolar molecular composites of N,N'-bis(1,2-dimethylpropyl)-1,4,5,8-naphthalenetetracarboxylic diimide (NTDI) and tri-p-tolylaniine (TTA). The electron mobility in the NTDI/TTA composites is ~2 x 10 cm2/Vs, which is a factor of 4 to 6 higher than in pure NTDI and isone of the highest values reported for disordered organic solids. The field and temperature dependencies of the charge mobility can be described using the disorder formalism due to Bassler and co-workers, which provides an estimation of the energy width σ of the hopping site manifold. Analysis of the data gave σ=0.081 and 0.060 eV for the electron and hole mobilities in a NTDI/TTA composite of 0.5510.45 molar ratio. The energetic disorder for electron transport in the bipolar composites is substantially lower than for pure NTDI, which is 0.093 eV. The results suggest that the observed enhancement arises from a substantial reduction of energetic disorder in the electron transport manifold of the bipolar composites. The reduction of energetic disorder may be due to intermolecular charge transfer between NTDI and TTA. Such a charge transfer could stabilize the electron transport manifold by better charge delocalization, and consequently, less energetic disorder. Another possible reason for the observed enhanced electron mobility is the reduction of NTDI dimers that can act as carrier traps by the presence of TTA molecules in the bipolar composites. These results also suggest that bipolar composites represent a promising new class of high electron mobility organic solids.

Rylene and related diimides for organic electronics.

PubMed

Zhan, Xiaowei; Facchetti, Antonio; Barlow, Stephen; Marks, Tobin J; Ratner, Mark A; Wasielewski, Michael R; Marder, Seth R

2011-01-11

Organic electron-transporting materials are essential for the fabrication of organic p-n junctions, photovoltaic cells, n-channel field-effect transistors, and complementary logic circuits. Rylene diimides are a robust, versatile class of polycyclic aromatic electron-transport materials with excellent thermal and oxidative stability, high electron affinities, and, in many cases, high electron mobilities; they are, therefore, promising candidates for a variety of organic electronics applications. In this review, recent developments in the area of high-electron-mobility diimides based on rylenes and related aromatic cores, particularly perylene- and naphthalene-diimide-based small molecules and polymers, for application in high-performance organic field-effect transistors and photovoltaic cells are summarized and analyzed.

Electron mobility on the surface of liquid Helium: influence of surface level atoms and depopulation of lowest subbands

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

Grigoriev, P. D., E-mail: grigorev@itp.ac.ru; Dyugaev, A. M.; Lebedeva, E. V.

2008-02-15

The temperature dependence of electron mobility is examined. We calculate the contribution to the electron scattering rate from the surface level atoms (SLAs), proposed in [10]. This contribution is substantial at low temperatures T < 0.5, when the He vapor concentration is exponentially small. We also study the effect of depopulation of the lowest energy subband, which leads to an increase in the electron mobility at high temperature. The results explain certain long-standing discrepancies between the existing theory and experiment on electron mobility on the surface of liquid helium.

Electron mobility enhancement in metalorganic-vapor-phase-epitaxy-grown InAlN high-electron-mobility transistors by control of surface morphology of spacer layer

NASA Astrophysics Data System (ADS)

Yamada, Atsushi; Ishiguro, Tetsuro; Kotani, Junji; Nakamura, Norikazu

2018-01-01

We demonstrated low-sheet-resistance metalorganic-vapor-phase-epitaxy-grown InAlN high-electron-mobility transistors using AlGaN spacers with excellent surface morphology. We systematically investigated the effects of AlGaN spacer growth conditions on surface morphology and electron mobility. We found that the surface morphology of InAlN barriers depends on that of AlGaN spacers. Ga desorption from AlGaN spacers was suppressed by increasing the trimethylaluminum (TMA) supply rate, resulting in the small surface roughnesses of InAlN barriers and AlGaN spacers. Moreover, we found that an increase in the NH3 supply rate also improved the surface morphologies of InAlN barriers and AlGaN spacers as long as the TMA supply rate was high enough to suppress the degradation of GaN channels. Finally, we realized a low sheet resistance of 185.5 Ω/sq with a high electron mobility of 1210 cm2 V-1 s-1 by improving the surface morphologies of AlGaN spacers and InAlN barriers.

Indium antimonide quantum well structures for electronic device applications

NASA Astrophysics Data System (ADS)

Edirisooriya, Madhavie

The electron effective mass is smaller in InSb than in any other III-V semiconductor. Since the electron mobility depends inversely on the effective mass, InSb-based devices are attractive for field effect transistors, magnetic field sensors, ballistic transport devices, and other applications where the performance depends on a high mobility or a long mean free path. In addition, electrons in InSb have a large g-factor and strong spin orbit coupling, which makes them well suited for certain spin transport devices. The first n-channel InSb high electron mobility transistor (HEMT) was produced in 2005 with a power-delay product superior to HEMTs with a channel made from any other III-V semiconductor. The high electron mobility in the InSb quantum-well channel increases the switching speed and lowers the required supply voltage. This dissertation focuses on several materials challenges that can further increase the appeal of InSb quantum wells for transistors and other electronic device applications. First, the electron mobility in InSb quantum wells, which is the highest for any semiconductor quantum well, can be further increased by reducing scattering by crystal defects. InSb-based heteroepitaxy is usually performed on semi-insulating GaAs (001) substrates due to the lack of a lattice matched semi-insulating substrate. The 14.6% mismatch between the lattice parameters of GaAs and InSb results in the formation of structural defects such as threading dislocations and microtwins which degrade the electrical and optical properties of InSb-based devices. Chapter 1 reviews the methods and procedures for growing InSb-based heterostructures by molecular beam epitaxy. Chapters 2 and 3 introduce techniques for minimizing the crystalline defects in InSb-based structures grown on GaAs substrates. Chapter 2 discusses a method of reducing threading dislocations by incorporating AlyIn1-ySb interlayers in an AlxIn1-xSb buffer layer and the reduction of microtwin defects by growth on GaAs substrates that are oriented 2° away from the [011] direction. Chapter 3 discusses designing InSb QW layer structures that are strain balanced. By applying these defect-reducing techniques, the electron mobility in InSb quantum wells at room temperature was significantly increased. For complementary logic technology, p-channel transistors with high mobility are equally as important as n-channel transistors. However, achieving a high hole mobility in III-V semiconductors is challenging. A controlled introduction of strain in the quantum-well material is an effective technique for enhancing the hole mobility beyond its value in bulk material. The strain reduces the hole effective mass by splitting the heavy hole and light hole valence bands. Chapter 4 discusses a successful attempt to realize p-type InSb quantum well structures. The biaxial strain applied via a relaxed metamorphic buffer resulted in a significantly higher room-temperature hole mobility and a record high low-temperature hole mobility. To demonstrate the usefulness of high mobility in a device structure, magnetoresistive devices were fabricated from remotely doped InSb QWs. Such devices have numerous practical applications such as position and speed sensors and as read heads in magnetic storage systems. In a magnetoresistive device composed of a series of shorted Hall bars, the magnetoresistance is proportional to the electron mobility squared for small magnetic fields. Hence, the high electron mobility in InSb QWs makes them highly preferable for geometrical magnetoresistors. Chapter 5 reports the fabrication and characterization of InSb quantum-well magnetoresistors. The excellent transport properties of the InSb QWs resulted in high room-temperature sensitivity to applied magnetic fields. Finally, Chapter 6 provides the conclusions obtained during this research effort, and makes suggestions for future work.

Design rules for charge-transport efficient host materials for phosphorescent organic light-emitting diodes.

PubMed

May, Falk; Al-Helwi, Mustapha; Baumeier, Björn; Kowalsky, Wolfgang; Fuchs, Evelyn; Lennartz, Christian; Andrienko, Denis

2012-08-22

The use of blue phosphorescent emitters in organic light-emitting diodes (OLEDs) imposes demanding requirements on a host material. Among these are large triplet energies, the alignment of levels with respect to the emitter, the ability to form and sustain amorphous order, material processability, and an adequate charge carrier mobility. A possible design strategy is to choose a π-conjugated core with a high triplet level and to fulfill the other requirements by using suitable substituents. Bulky substituents, however, induce large spatial separations between conjugated cores, can substantially reduce intermolecular electronic couplings, and decrease the charge mobility of the host. In this work we analyze charge transport in amorphous 2,8-bis(triphenylsilyl)dibenzofuran, an electron-transporting material synthesized to serve as a host in deep-blue OLEDs. We show that mesomeric effects delocalize the frontier orbitals over the substituents recovering strong electronic couplings and lowering reorganization energies, especially for electrons, while keeping energetic disorder small. Admittance spectroscopy measurements reveal that the material has indeed a high electron mobility and a small Poole-Frenkel slope, supporting our conclusions. By linking electronic structure, molecular packing, and mobility, we provide a pathway to the rational design of hosts with high charge mobilities.

Large thermoelectric power factor from crystal symmetry-protected non-bonding orbital in half-Heuslers.

PubMed

Zhou, Jiawei; Zhu, Hangtian; Liu, Te-Huan; Song, Qichen; He, Ran; Mao, Jun; Liu, Zihang; Ren, Wuyang; Liao, Bolin; Singh, David J; Ren, Zhifeng; Chen, Gang

2018-04-30

Modern society relies on high charge mobility for efficient energy production and fast information technologies. The power factor of a material-the combination of electrical conductivity and Seebeck coefficient-measures its ability to extract electrical power from temperature differences. Recent advancements in thermoelectric materials have achieved enhanced Seebeck coefficient by manipulating the electronic band structure. However, this approach generally applies at relatively low conductivities, preventing the realization of exceptionally high-power factors. In contrast, half-Heusler semiconductors have been shown to break through that barrier in a way that could not be explained. Here, we show that symmetry-protected orbital interactions can steer electron-acoustic phonon interactions towards high mobility. This high-mobility regime enables large power factors in half-Heuslers, well above the maximum measured values. We anticipate that our understanding will spark new routes to search for better thermoelectric materials, and to discover high electron mobility semiconductors for electronic and photonic applications.

Direct measurement of cyclotron coherence times of high-mobility two-dimensional electron gases.

PubMed

Wang, X; Hilton, D J; Reno, J L; Mittleman, D M; Kono, J

2010-06-07

We have observed long-lived (approximately 30 ps) coherent oscillations of charge carriers due to cyclotron resonance (CR) in high-mobility two-dimensional electrons in GaAs in perpendicular magnetic fields using time-domain terahertz spectroscopy. The observed coherent oscillations were fitted well by sinusoids with exponentially-decaying amplitudes, through which we were able to provide direct and precise measures for the decay times and oscillation frequencies simultaneously. This method thus overcomes the CR saturation effect, which is known to prevent determination of true CR linewidths in high-mobility electron systems using Fourier-transform infrared spectroscopy.

Achieving high field-effect mobility in amorphous indium-gallium-zinc oxide by capping a strong reduction layer.

PubMed

Zan, Hsiao-Wen; Yeh, Chun-Cheng; Meng, Hsin-Fei; Tsai, Chuang-Chuang; Chen, Liang-Hao

2012-07-10

An effective approach to reduce defects and increase electron mobility in a-IGZO thin-film transistors (a-IGZO TFTs) is introduced. A strong reduction layer, calcium, is capped onto the back interface of a-IGZO TFT. After calcium capping, the effective electron mobility of a-IGZO TFT increases from 12 cm(2) V(-1) s(-1) to 160 cm(2) V(-1) s(-1). This high mobility is a new record, which implies that the proposed defect reduction effect is key to improve electron transport in oxide semiconductor materials. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced mobility in vertically scaled N-polar high-electron-mobility transistors using GaN/InGaN composite channels

NASA Astrophysics Data System (ADS)

Li, Haoran; Wienecke, Steven; Romanczyk, Brian; Ahmadi, Elaheh; Guidry, Matthew; Zheng, Xun; Keller, Stacia; Mishra, Umesh K.

2018-02-01

A GaN/InGaN composite channel design for vertically scaled N-polar high-electron-mobility transistor (HEMT) structures is proposed and demonstrated by metal-organic chemical vapor deposition. In a conventional N-polar HEMT structure, as the channel thickness (tch) decreases, the sheet charge density (ns) decreases, the electric field in the channel increases, and the centroid of the two-dimensional electron gas (2DEG) moves towards the back-barrier/channel interface, resulting in stronger scattering and lower electron mobility (μ). In this study, a thin InGaN layer was introduced in-between the channel and the AlGaN cap to increase the 2DEG density and reduce the electric field in the channel and therefore increase the electron mobility. The dependence of μ on the InGaN thickness (tInGaN) and the indium composition (xIn) was investigated for different channel thicknesses. With optimized tInGaN and xIn, significant improvements in electron mobility were observed. For a 6 nm channel HEMT structure, the electron mobility increased from 606 to 1141 cm2/(V.s) when the 6 nm thick pure GaN channel was replaced by the 4 nm GaN/2 nm In0.1Ga0.9N composite channel.

Theoretical prediction of high carrier mobility in single-walled black phosphorus nanotubes

NASA Astrophysics Data System (ADS)

Li, Q. F.; Wang, H. F.; Yang, C. H.; Li, Q. Q.; Rao, W. F.

2018-05-01

One-dimensional semiconductors are promising materials for high-performance nanoscale devices. Using the first-principles calculations combined with deformation potential approximation, we study the electronic structures and carrier transport properties of black phosphorus nanotubes (BPNTs). It is found that both armchair and zigzag BPNTs with diameter 13.5-18.5 Å are direct bandgap semiconductors. At a similar diameter, the carrier mobility of zigzag BPNT is one order of magnitude larger than that of armchair BPNT. For armchair BPNTs, the electron mobility is about 90.70-155.33 cm2 V-1 s-1 at room temperature, which is about three times of its hole counterpart. For zigzag BPNTs, the maximum mobility can reach 2.87 ×103 cm2 V-1 s-1. Furthermore, the electronic properties can be effectively tuned by the strain. For zigzag (0,13) nanotube, there is a direct-to-indirect band gap transition at a tensile strain of about 6%. Moreover, the electron mobility is boosted sharply by one order of magnitude by applying the compressive or tensile strain. The electron mobility increases to 14.05 ×103 cm2 V-1 s-1 at a tensile strain of 9%. Our calculations highlight the tunable electronic properties and superior carrier mobility of BPNTs that are promising for interesting applications in future nano-electronic devices.

Low Temperature Photoluminescence (PL) from High Electron Mobility Transistors (HEMTs)

DTIC Science & Technology

2015-03-01

Photoluminescence Form InxAl1-xN Films Deposited by Plasma-Assisted Molecular Beam Epitaxy ,” Submitted to Applied Physics Letters, July 2014. 8 LIST OF...TECHNICAL REPORT RDMR-WD-14-55 LOW TEMPERATURE PHOTOLUMINESCENCE (PL) FROM HIGH ELECTRON MOBILITY TRANSISTORS ( HEMTS ...Mobility Transistors ( HEMTs ) 5. FUNDING NUMBERS 6. AUTHOR(S) Adam T. Roberts and Henry O. Everitt 7. PERFORMING ORGANIZATION NAME(S

Ultra-low noise high electron mobility transistors for high-impedance and low-frequency deep cryogenic readout electronics

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

Dong, Q.; Liang, Y. X.; Ferry, D.

2014-07-07

We report on the results obtained from specially designed high electron mobility transistors at 4.2 K: the gate leakage current can be limited lower than 1 aA, and the equivalent input noise-voltage and noise-current at 1 Hz can reach 6.3 nV/Hz{sup 1∕2} and 20 aA/Hz{sup 1∕2}, respectively. These results open the way to realize high performance low-frequency readout electronics under very low-temperature conditions.

High Thermoelectric Power Factor of High-Mobility 2D Electron Gas.

PubMed

Ohta, Hiromichi; Kim, Sung Wng; Kaneki, Shota; Yamamoto, Atsushi; Hashizume, Tamotsu

2018-01-01

Thermoelectric conversion is an energy harvesting technology that directly converts waste heat from various sources into electricity by the Seebeck effect of thermoelectric materials with a large thermopower ( S ), high electrical conductivity (σ), and low thermal conductivity (κ). State-of-the-art nanostructuring techniques that significantly reduce κ have realized high-performance thermoelectric materials with a figure of merit ( ZT = S 2 ∙σ∙ T ∙κ -1 ) between 1.5 and 2. Although the power factor (PF = S 2 ∙σ) must also be enhanced to further improve ZT , the maximum PF remains near 1.5-4 mW m -1 K -2 due to the well-known trade-off relationship between S and σ. At a maximized PF, σ is much lower than the ideal value since impurity doping suppresses the carrier mobility. A metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) structure on an AlGaN/GaN heterostructure is prepared. Applying a gate electric field to the MOS-HEMT simultaneously modulates S and σ of the high-mobility electron gas from -490 µV K -1 and ≈10 -1 S cm -1 to -90 µV K -1 and ≈10 4 S cm -1 , while maintaining a high carrier mobility (≈1500 cm 2 V -1 s -1 ). The maximized PF of the high-mobility electron gas is ≈9 mW m -1 K -2 , which is a two- to sixfold increase compared to state-of-the-art practical thermoelectric materials.

High Electron Mobility and Insights into Temperature-Dependent Scattering Mechanisms in InAsSb Nanowires.

PubMed

Boland, Jessica L; Amaduzzi, Francesca; Sterzl, Sabrina; Potts, Heidi; Herz, Laura M; Fontcuberta I Morral, Anna; Johnston, Michael B

2018-06-13

InAsSb nanowires are promising elements for thermoelectric devices, infrared photodetectors, high-speed transistors, as well as thermophotovoltaic cells. By changing the Sb alloy fraction the mid-infrared bandgap energy and thermal conductivity may be tuned for specific device applications. Using both terahertz and Raman noncontact probes, we show that Sb alloying increases the electron mobility in the nanowires by over a factor of 3 from InAs to InAs 0.65 Sb 0.35 . We also extract the temperature-dependent electron mobility via both terahertz and Raman spectroscopy, and we report the highest electron mobilities for InAs 0.65 Sb 0.35 nanowires to date, exceeding 16,000 cm 2 V -1 s -1 at 10 K.

Two-dimensional superconductivity induced by high-mobility carrier doping in LaTiO3/SrTiO3 hetero-structures

NASA Astrophysics Data System (ADS)

Biscaras, Johan; Hurand, S.; Palma, C.; Lesueur, J.; Bergeal, N.; Leboeuf, D.; Proust, C.; Rastogi, A.; Budhani, R. C.

2013-03-01

Transition metal oxides display a great variety of quantum electronic behaviors where correlations often play an important role. The achievement of high quality epitaxial interfaces involving such materials gives a unique opportunity to engineer artificial materials where new electronic orders take place. It has been shown recently that a two-dimensional electron gas 2DEG could form at the interface of two insulators such as LaAlO3 and SrTiO3, or LaTiO3 (a Mott insulator) and SrTiO3. We show that a superconducting two-dimensional electron gas is formed at the LaTiO3/SrTiO3 interface whose properties can be modulated by field effect using a metallic gate on the back of the substrate. The gas consists of two types of carriers : a majority of low-mobility carriers always present, and a few high-mobility ones that can be injected by electrostatic doping. The calculation of the electrons spatial distribution in the confinement potential shows that the high-mobility electrons responsible for superconductivity set at the edge of the gas whose extension can be tuned by field effect.

High-mobility ambipolar ZnO-graphene hybrid thin film transistors.

PubMed

Song, Wooseok; Kwon, Soon Yeol; Myung, Sung; Jung, Min Wook; Kim, Seong Jun; Min, Bok Ki; Kang, Min-A; Kim, Sung Ho; Lim, Jongsun; An, Ki-Seok

2014-02-11

In order to combine advantages of ZnO thin film transistors (TFTs) with a high on-off ratio and graphene TFTs with extremely high carrier mobility, we present a facile methodology for fabricating ZnO thin film/graphene hybrid two-dimensional TFTs. Hybrid TFTs exhibited ambipolar behavior, an outstanding electron mobility of 329.7 ± 16.9 cm(2)/V·s, and a high on-off ratio of 10(5). The ambipolar behavior of the ZnO/graphene hybrid TFT with high electron mobility could be due to the superimposed density of states involving the donor states in the bandgap of ZnO thin films and the linear dispersion of monolayer graphene. We further established an applicable circuit model for understanding the improvement in carrier mobility of ZnO/graphene hybrid TFTs.

Metals bioleaching from electronic waste by Chromobacterium violaceum and Pseudomonads sp.

PubMed

Pradhan, Jatindra Kumar; Kumar, Sudhir

2012-11-01

These days, electronic waste needs to be taken into consideration due to its materials content, but due to the heterogeneity of the metals present, reprocessing of electronic waste is quite limited. The bioleaching of metals from electronic waste was investigated by using cyanogenic bacterial strains (Chromobacterium violaceum, Pseudomonas aeruginosa and Pseudomonas fluorescens). A two-step bioleaching process was followed under cyanide-forming conditions for maximum metals mobilization. Both single and mixed cultures of cyanogenic bacteria were able to mobilize metals from electronic waste with different efficiencies. In all the flasks in which high metal mobilizations were observed, the consequent biomass productions were also high. Pseudomonas aeruginosa was applied in the bioleaching process for the first time and this achieved its bioleaching ability of mobilization of metals from electronic waste. Chromobacterium violaceum as a single culture and a mixture of C. violaceum and P. aeruginosa exhibited maximum metal mobilization. Chromobacterium violaceum was capable of leaching more than 79, 69, 46, 9 and 7% of Cu, Au, Zn, Fe and Ag, respectively at an electronic waste concentration of 1% w/v. Moreover, the mixture of C. violaceum and P. aeruginosa exhibited metals leaching of more than 83, 73, 49, 13 and 8% of total Cu, Au, Zn, Fe, and Ag, respectively. Precious metals were mobilized through bioleaching which might be considered as an industrial application for recycling of electronic waste in the near future.

Terahertz time-domain magnetospectroscopy of a high-mobility two-dimensional electron gas.

PubMed

Wang, Xiangfeng; Hilton, David J; Ren, Lei; Mittleman, Daniel M; Kono, Junichiro; Reno, John L

2007-07-01

We have observed cyclotron resonance in a high-mobility GaAs/AlGaAs two-dimensional electron gas by using the techniques of terahertz time-domain spectroscopy combined with magnetic fields. From this, we calculate the real and imaginary parts of the diagonal elements of the magnetoconductivity tensor, which in turn allows us to extract the concentration, effective mass, and scattering time of the electrons in the sample. We demonstrate the utility of ultrafast terahertz spectroscopy, which can recover the true linewidth of cyclotron resonance in a high-mobility (>10(6) cm(2)V(-1)s(-1)) sample without being affected by the saturation effect.

High-mobility ambipolar ZnO-graphene hybrid thin film transistors

PubMed Central

Song, Wooseok; Kwon, Soon Yeol; Myung, Sung; Jung, Min Wook; Kim, Seong Jun; Min, Bok Ki; Kang, Min-A; Kim, Sung Ho; Lim, Jongsun; An, Ki-Seok

2014-01-01

In order to combine advantages of ZnO thin film transistors (TFTs) with a high on-off ratio and graphene TFTs with extremely high carrier mobility, we present a facile methodology for fabricating ZnO thin film/graphene hybrid two-dimensional TFTs. Hybrid TFTs exhibited ambipolar behavior, an outstanding electron mobility of 329.7 ± 16.9 cm2/V·s, and a high on-off ratio of 105. The ambipolar behavior of the ZnO/graphene hybrid TFT with high electron mobility could be due to the superimposed density of states involving the donor states in the bandgap of ZnO thin films and the linear dispersion of monolayer graphene. We further established an applicable circuit model for understanding the improvement in carrier mobility of ZnO/graphene hybrid TFTs. PMID:24513629

High electron mobility and quantum oscillations in non-encapsulated ultrathin semiconducting Bi 2O 2Se

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

Wu, Jinxiong; Yuan, Hongtao; Meng, Mengmeng

Identifying new two-dimensional (2D) materials with both high carrier mobility and a large electronic band gap is critical for novel electronics and optoelectronics applications. Here, we demonstrated a new air-stable ultrahigh-mobility layered Bi 2O 2Se semiconductor with a large band gap of ~ 0.8 eV and a low effective mass of ~ 0.14 m 0. High-quality 2D Bi2O2Se crystals with a thickness down to a monolayer and a domain size greater than 200 μm were readily grown by chemical vapor deposition (CVD). Size-tunable band gap of Bi 2O 2Se was found to increase as thinning down to the monolayer duemore » to the quantum confinement effect. An ultrahigh Hall mobility of > 20,000 cm 2 V -1 s -1 was achieved in as-grown Bi 2O 2Se flakes at 1.9 K, which allows for the observation of Shubnikov–de Haas quantum oscillations. Top-gated field-effect transistors based on CVD-grown 2D Bi 2O 2Se crystals (down to bilayer) exhibited high Hall mobility (up to 450 cm 2 V -1 s -1), large current on/off ratios (>106) and near-ideal subthreshold swings (~65 mV/dec) at room temperature. Our results make the high-mobility 2D Bi 2O 2Se semiconductor a promising candidate for future high-speed and low-power electronic applications.« less

High electron mobility and quantum oscillations in non-encapsulated ultrathin semiconducting Bi 2O 2Se

DOE PAGES

Wu, Jinxiong; Yuan, Hongtao; Meng, Mengmeng; ...

2017-04-03

Identifying new two-dimensional (2D) materials with both high carrier mobility and a large electronic band gap is critical for novel electronics and optoelectronics applications. Here, we demonstrated a new air-stable ultrahigh-mobility layered Bi 2O 2Se semiconductor with a large band gap of ~ 0.8 eV and a low effective mass of ~ 0.14 m 0. High-quality 2D Bi2O2Se crystals with a thickness down to a monolayer and a domain size greater than 200 μm were readily grown by chemical vapor deposition (CVD). Size-tunable band gap of Bi 2O 2Se was found to increase as thinning down to the monolayer duemore » to the quantum confinement effect. An ultrahigh Hall mobility of > 20,000 cm 2 V -1 s -1 was achieved in as-grown Bi 2O 2Se flakes at 1.9 K, which allows for the observation of Shubnikov–de Haas quantum oscillations. Top-gated field-effect transistors based on CVD-grown 2D Bi 2O 2Se crystals (down to bilayer) exhibited high Hall mobility (up to 450 cm 2 V -1 s -1), large current on/off ratios (>106) and near-ideal subthreshold swings (~65 mV/dec) at room temperature. Our results make the high-mobility 2D Bi 2O 2Se semiconductor a promising candidate for future high-speed and low-power electronic applications.« less

Molecular gated-AlGaN/GaN high electron mobility transistor for pH detection.

PubMed

Ding, Xiangzhen; Yang, Shuai; Miao, Bin; Gu, Le; Gu, Zhiqi; Zhang, Jian; Wu, Baojun; Wang, Hong; Wu, Dongmin; Li, Jiadong

2018-04-18

A molecular gated-AlGaN/GaN high electron mobility transistor has been developed for pH detection. The sensing surface of the sensor was modified with 3-aminopropyltriethoxysilane to provide amphoteric amine groups, which would play the role of receptors for pH detection. On modification with 3-aminopropyltriethoxysilane, the transistor exhibits good chemical stability in hydrochloric acid solution and is sensitive for pH detection. Thus, our molecular gated-AlGaN/GaN high electron mobility transistor acheived good electrical performances such as chemical stability (remained stable in hydrochloric acid solution), good sensitivity (37.17 μA/pH) and low hysteresis. The results indicate a promising future for high-quality sensors for pH detection.

Phonon-electron coupling and tunneling effect on charge transport in organic semi-conductor crystals of Cn-BTBT.

PubMed

Zhou, Yecheng; Deng, Wei-Qiao; Zhang, Hao-Li

2016-09-14

Cn-[1]benzothieno[3,2-b][1]-benzothiophene (BTBT) crystals show very high hole mobilities in experiments. These high mobilities are beyond existing theory prediction. Here, we employed different quantum chemistry methods to investigate charge transfer in Cn-BTBT crystals and tried to find out the reasons for the underestimation in the theory. It was found that the hopping rate estimated by the Fermi Golden Rule is higher than that of the Marcus theory due to the high temperature approximation and failure at the classic limit. More importantly, molecular dynamics simulations revealed that the phonon induced fluctuation of electronic transfer integral is much larger than the average of the electronic transfer integral itself. Mobilities become higher if simulations implement the phonon-electron coupling. This conclusion indicates that the phonon-electron coupling promotes charge transfer in organic semi-conductors at room temperature.

Phonon-electron coupling and tunneling effect on charge transport in organic semi-conductor crystals of Cn-BTBT

NASA Astrophysics Data System (ADS)

Zhou, Yecheng; Deng, Wei-Qiao; Zhang, Hao-Li

2016-09-01

Cn-[1]benzothieno[3,2-b][1]-benzothiophene (BTBT) crystals show very high hole mobilities in experiments. These high mobilities are beyond existing theory prediction. Here, we employed different quantum chemistry methods to investigate charge transfer in Cn-BTBT crystals and tried to find out the reasons for the underestimation in the theory. It was found that the hopping rate estimated by the Fermi Golden Rule is higher than that of the Marcus theory due to the high temperature approximation and failure at the classic limit. More importantly, molecular dynamics simulations revealed that the phonon induced fluctuation of electronic transfer integral is much larger than the average of the electronic transfer integral itself. Mobilities become higher if simulations implement the phonon-electron coupling. This conclusion indicates that the phonon-electron coupling promotes charge transfer in organic semi-conductors at room temperature.

AlGaN/GaN high electron mobility transistor grown on GaN template substrate by molecule beam epitaxy system

NASA Astrophysics Data System (ADS)

Tsai, Jenn-Kai; Chen, Y. L.; Gau, M. H.; Pang, W. Y.; Hsu, Y. C.; Lo, Ikai; Hsieh, C. H.

2008-03-01

In this study, AlGaN/GaN high electron mobility transistor (HEMT) structure was grow on GaN template substrate radio frequency plasma assisted molecular beam epitaxy (MBE) equipped with an EPI UNI-Bulb nitrogen plasma source. The undoped GaN template substrate was grown on c-sapphire substrate by metal organic vapor phase epitaxy system (MOPVD). After growth of MOVPE and MBE, the samples are characterized by double crystal X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (SEM), atomic force microscopy (AFM), and Hall effect measurements. We found that the RMS roughness of template substrate play the major role in got the high value of mobility on AlGaN/GaN HEMT. When the roughness was lower than 0.77 nm in a 25 μm x 25 μm area, the mobility of HEMT at the temperature of 77 K was over 10000 cm^2/Vs.

A Mobile Learning Module for High School Fieldwork

ERIC Educational Resources Information Center

Hsu, Tzu-Yen; Chen, Che-Ming

2010-01-01

Although fieldwork is always cited as an important component of geographic education, there are many obstacles for executing high school fieldwork. Mobile electronic products are becoming popular and some schools are able to acquire these devices for mobile learning. This study attempts to provide a mobile-assisted means of guiding students…

The influence of surfaces on the transient terahertz conductivity and electron mobility of GaAs nanowires

NASA Astrophysics Data System (ADS)

Joyce, Hannah J.; Baig, Sarwat A.; Parkinson, Patrick; Davies, Christopher L.; Boland, Jessica L.; Tan, H. Hoe; Jagadish, Chennupati; Herz, Laura M.; Johnston, Michael B.

2017-06-01

Bare unpassivated GaAs nanowires feature relatively high electron mobilities (400-2100 cm2 V-1 s-1) and ultrashort charge carrier lifetimes (1-5 ps) at room temperature. These two properties are highly desirable for high speed optoelectronic devices, including photoreceivers, modulators and switches operating at microwave and terahertz frequencies. When engineering these GaAs nanowire-based devices, it is important to have a quantitative understanding of how the charge carrier mobility and lifetime can be tuned. Here we use optical-pump-terahertz-probe spectroscopy to quantify how mobility and lifetime depend on the nanowire surfaces and on carrier density in unpassivated GaAs nanowires. We also present two alternative frameworks for the analysis of nanowire photoconductivity: one based on plasmon resonance and the other based on Maxwell-Garnett effective medium theory with the nanowires modelled as prolate ellipsoids. We find the electron mobility decreases significantly with decreasing nanowire diameter, as charge carriers experience increased scattering at nanowire surfaces. Reducing the diameter from 50 nm to 30 nm degrades the electron mobility by up to 47%. Photoconductivity dynamics were dominated by trapping at saturable states existing at the nanowire surface, and the trapping rate was highest for the nanowires of narrowest diameter. The maximum surface recombination velocity, which occurs in the limit of all traps being empty, was calculated as 1.3  ×  106 cm s-1. We note that when selecting the optimum nanowire diameter for an ultrafast device, there is a trade-off between achieving a short lifetime and a high carrier mobility. To achieve high speed GaAs nanowire devices featuring the highest charge carrier mobilities and shortest lifetimes, we recommend operating the devices at low charge carrier densities.

Modeling of anomalous electron mobility in Hall thrusters

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

Koo, Justin W.; Boyd, Iain D.

Accurate modeling of the anomalous electron mobility is absolutely critical for successful simulation of Hall thrusters. In this work, existing computational models for the anomalous electron mobility are used to simulate the UM/AFRL P5 Hall thruster (a 5 kW laboratory model) in a two-dimensional axisymmetric hybrid particle-in-cell Monte Carlo collision code. Comparison to experimental results indicates that, while these computational models can be tuned to reproduce the correct thrust or discharge current, it is very difficult to match all integrated performance parameters (thrust, power, discharge current, etc.) simultaneously. Furthermore, multiple configurations of these computational models can produce reasonable integrated performancemore » parameters. A semiempirical electron mobility profile is constructed from a combination of internal experimental data and modeling assumptions. This semiempirical electron mobility profile is used in the code and results in more accurate simulation of both the integrated performance parameters and the mean potential profile of the thruster. Results indicate that the anomalous electron mobility, while absolutely necessary in the near-field region, provides a substantially smaller contribution to the total electron mobility in the high Hall current region near the thruster exit plane.« less

Temperature dependence of ballistic mobility in a metamorphic InGaAs/InAlAs high electron mobility transistor

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

Lee, Jongkyong; Gang, Suhyun; Jo, Yongcheol

We have investigated the temperature dependence of ballistic mobility in a 100 nm-long InGaAs/InAlAs metamorphic high-electron-mobility transistor designed for millimeter-wavelength RF applications. To extract the temperature dependence of quasi-ballistic mobility, our experiment involves measurements of the effective mobility in the low-bias linear region of the transistor and of the collision-dominated Hall mobility using a gated Hall bar of the same epitaxial structure. The data measured from the experiment are consistent with that of modeled ballistic mobility based on ballistic transport theory. These results advance the understanding of ballistic transport in various transistors with a nano-scale channel length that is comparable tomore » the carrier's mean free path in the channel.« less

Suppressed carrier density for the patterned high mobility two-dimensional electron gas at γ-Al2O3/SrTiO3 heterointerfaces

NASA Astrophysics Data System (ADS)

Niu, Wei; Gan, Yulin; Zhang, Yu; Valbjørn Christensen, Dennis; von Soosten, Merlin; Wang, Xuefeng; Xu, Yongbing; Zhang, Rong; Pryds, Nini; Chen, Yunzhong

2017-07-01

The two-dimensional electron gas (2DEG) at the non-isostructural interface between spinel γ-Al2O3 and perovskite SrTiO3 is featured by a record electron mobility among complex oxide interfaces in addition to a high carrier density up to the order of 1015 cm-2. Herein, we report on the patterning of 2DEG at the γ-Al2O3/SrTiO3 interface grown at 650 °C by pulsed laser deposition using a hard mask of LaMnO3. The patterned 2DEG exhibits a critical thickness of 2 unit cells of γ-Al2O3 for the occurrence of interface conductivity, similar to the unpatterned sample. However, its maximum carrier density is found to be approximately 3 × 1013 cm-2, much lower than that of the unpatterned sample (˜1015 cm-2). Remarkably, a high electron mobility of approximately 3600 cm2 V-1 s-1 was obtained at low temperatures for the patterned 2DEG at a carrier density of ˜7 × 1012 cm-2, which exhibits clear Shubnikov-de Haas quantum oscillations. The patterned high-mobility 2DEG at the γ-Al2O3/SrTiO3 interface paves the way for the design and application of spinel/perovskite interfaces for high-mobility all-oxide electronic devices.

High-Efficiency Nonfullerene Polymer Solar Cell Enabling by Integration of Film-Morphology Optimization, Donor Selection, and Interfacial Engineering.

PubMed

Zhang, Xin; Li, Weiping; Yao, Jiannian; Zhan, Chuanlang

2016-06-22

Carrier mobility is a vital factor determining the electrical performance of organic solar cells. In this paper we report that a high-efficiency nonfullerene organic solar cell (NF-OSC) with a power conversion efficiency of 6.94 ± 0.27% was obtained by optimizing the hole and electron transportations via following judicious selection of polymer donor and engineering of film-morphology and cathode interlayers: (1) a combination of solvent annealing and solvent vapor annealing optimizes the film morphology and hence both hole and electron mobilities, leading to a trade-off of fill factor and short-circuit current density (Jsc); (2) the judicious selection of polymer donor affords a higher hole and electron mobility, giving a higher Jsc; and (3) engineering the cathode interlayer affords a higher electron mobility, which leads to a significant increase in electrical current generation and ultimately the power conversion efficiency (PCE).

Room-temperature mobility above 2200 cm{sup 2}/V·s of two-dimensional electron gas in a sharp-interface AlGaN/GaN heterostructure

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

Chen, Jr-Tai, E-mail: jrche@ifm.liu.se; Persson, Ingemar; Nilsson, Daniel

A high mobility of 2250 cm{sup 2}/V·s of a two-dimensional electron gas (2DEG) in a metalorganic chemical vapor deposition-grown AlGaN/GaN heterostructure was demonstrated. The mobility enhancement was a result of better electron confinement due to a sharp AlGaN/GaN interface, as confirmed by scanning transmission electron microscopy analysis, not owing to the formation of a traditional thin AlN exclusion layer. Moreover, we found that the electron mobility in the sharp-interface heterostructures can sustain above 2000 cm{sup 2}/V·s for a wide range of 2DEG densities. Finally, it is promising that the sharp-interface AlGaN/GaN heterostructure would enable low contact resistance fabrication, less impurity-related scattering, andmore » trapping than the AlGaN/AlN/GaN heterostructure, as the high-impurity-contained AlN is removed.« less

Proceedings of the AFOSR Special Conference on Prime-Power for High Energy Space Systems, Norfolk, Virginia, 22-25 February 1982. Volume 2

DTIC Science & Technology

1982-02-25

However, because the mobility of the ions is much smaller than the mobility of the electrons (for cesium i = 1/500 Me), and because of ion...space applications of this high temperature in- sulation. Use of glass-alumina insulation for motors in mobile applications would reduce cooling...present and/or mobile only during irradiation. VII-7-7 WS 710 01AS$ AesowRpIOr MEA8IJRtED MOt AN FTER L5 MvV ELECTRON NtADIATION Fig. 7 -- Growth of

Field-induced strain degradation of AlGaN/GaN high electron mobility transistors on a nanometer scale

NASA Astrophysics Data System (ADS)

Lin, Chung-Han; Doutt, D. R.; Mishra, U. K.; Merz, T. A.; Brillson, L. J.

2010-11-01

Nanoscale Kelvin probe force microscopy and depth-resolved cathodoluminescence spectroscopy reveal an electronic defect evolution inside operating AlGaN/GaN high electron mobility transistors with degradation under electric-field-induced stress. Off-state electrical stress results in micron-scale areas within the extrinsic drain expanding and decreasing in electric potential, midgap defects increasing by orders-of-magnitude at the AlGaN layer, and local Fermi levels lowering as gate-drain voltages increase above a characteristic stress threshold. The pronounced onset of defect formation, Fermi level movement, and transistor degradation at the threshold gate-drain voltage of J. A. del Alamo and J. Joh [Microelectron. Reliab. 49, 1200 (2009)] is consistent with crystal deformation and supports the inverse piezoelectric model of high electron mobility transistor degradation.

Electrical properties and subband occupancy at the (La ,Sr ) (Al ,Ta ) O3/SrTi O3 interface

NASA Astrophysics Data System (ADS)

Han, K.; Huang, Z.; Zeng, S. W.; Yang, M.; Li, C. J.; Zhou, W. X.; Wang, X. Renshaw; Venkatesan, T.; Coey, J. M. D.; Goiran, M.; Escoffier, W.; Ariando

2017-06-01

The quasi-two-dimensional electron gas at oxide interfaces provides a platform for investigating quantum phenomena in strongly correlated electronic systems. Here, we study the transport properties at the high-mobility (L a0.3S r0.7 ) (A l0.65T a0.35 ) O3/SrTi O3 interface. Before oxygen annealing, the as-grown interface exhibits a high electron density and electron occupancy of two subbands: higher-mobility electrons (μ1≈104c m2V-1s-1 at 2 K) occupy the lower-energy 3 dxy subband, while lower-mobility electrons (μ1≈103c m2V-1s-1 at 2 K) propagate in the higher-energy 3 dxz /yz -dominated subband. After removing oxygen vacancies by annealing in oxygen, only a single type of 3 dxy electrons remain at the annealed interface, showing tunable Shubnikov-de Haas oscillations below 9 T at 2 K and an effective mass of 0.7 me . By contrast, no oscillation is observed at the as-grown interface even when electron mobility is increased to 50 000 c m2V-1s-1 by gating voltage. Our results reveal the important roles of both carrier mobility and subband occupancy in tuning the quantum transport at oxide interfaces.

First-principles studies of electron transport in Ga2O3

NASA Astrophysics Data System (ADS)

Kang, Youngho; Krishnaswamy, Karthik; Peelaers, Hartwin; van de Walle, Chris G.

Ga2O3 is a wide-gap semiconductor with a monoclinic crystal structure and a band gap of 4.8 eV. Its high carrier mobility and large band gap have attracted a lot of attention for use in high power electronics and transparent conductors. Despite its potential for adoption in these applications, an understanding of its carrier transport properties is still lacking. In this study we use first-principles calculations to analyze and compute the electron scattering rates in Ga2O3. Scattering due to ionized impurities and polar longitudinal-optical (LO) phonon is taken into account. We find that the electron mobility is nearly isotropic, despite the low-symmetry monoclinic structure of Ga2O3. At low carrier densities ( 1017 cm-3), the mobility is limited by LO phonon scattering. Scattering by ionized impurities becomes increasingly important at higher carrier densities. This type of scattering is enhanced when compensating native point defects are present; in particular, gallium vacancies, which are triply negatively charged, can have a strong effect on mobility. These effects explain the downturn in mobility observed in experiments at high carrier densities. This work was supported by ARO and NSF.

A study on the electron transport properties of ZnON semiconductors with respect to the relative anion content

PubMed Central

Park, Jozeph; Kim, Yang Soo; Ok, Kyung-Chul; Park, Yun Chang; Kim, Hyun You; Park, Jin-Seong; Kim, Hyun-Suk

2016-01-01

High-mobility zinc oxynitride (ZnON) semiconductors were grown by RF sputtering using a Zn metal target in a plasma mixture of Ar, N2, and O2 gas. The RF power and the O2 to N2 gas flow rates were systematically adjusted to prepare a set of ZnON films with different relative anion contents. The carrier density was found to be greatly affected by the anion composition, while the electron mobility is determined by a fairly complex mechanism. First-principles calculations indicate that excess vacant nitrogen sites (VN) in N-rich ZnON disrupt the local electron conduction paths, which may be restored by having oxygen anions inserted therein. The latter are anticipated to enhance the electron mobility, and the exact process parameters that induce such a phenomenon can only be found experimentally. Contour plots of the Hall mobility and carrier density with respect to the RF power and O2 to N2 gas flow rate ratio indicate the existence of an optimum region where maximum electron mobility is obtained. Using ZnON films grown under the optimum conditions, the fabrication of high-performance devices with field-effect mobility values exceeding 120 cm2/Vs is demonstrated based on simple reactive RF sputtering methods. PMID:27098656

Improvement of electron mobility in La:BaSnO{sub 3} thin films by insertion of an atomically flat insulating (Sr,Ba)SnO{sub 3} buffer layer

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

Shiogai, Junichi, E-mail: junichi.shiogai@imr.tohoku.ac.jp; Nishihara, Kazuki; Sato, Kazuhisa

One perovskite oxide, ASnO{sub 3} (A = Sr, Ba), is a candidate for use as a transparent conductive oxide with high electron mobility in single crystalline form. However, the electron mobility of films grown on SrTiO{sub 3} substrates does not reach the bulk value, probably because of dislocation scattering that originates from the large lattice mismatch. This study investigates the effect of insertion of bilayer BaSnO{sub 3} / (Sr,Ba)SnO{sub 3} for buffering this large lattice mismatch between La:BaSnO{sub 3} and SrTiO{sub 3} substrate. The insertion of 200-nm-thick BaSnO{sub 3} on (Sr,Ba)SnO{sub 3} bilayer buffer structures reduces the number of dislocationsmore » and improves surface smoothness of the films after annealing as proved respectively by scanning transmission electron microscopy and atomic force microscopy. A systematic investigation of BaSnO{sub 3} buffer layer thickness dependence on Hall mobility of the electron transport in La:BaSnO{sub 3} shows that the highest obtained value of mobility is 78 cm{sup 2}V{sup −1}s{sup −1} because of its fewer dislocations. High electron mobility films based on perovskite BaSnO{sub 3} can provide a good platform for transparent-conducting-oxide electronic devices and for creation of fascinating perovskite heterostructures.« less

Tuning charge transport in pentacene thin-film transistors using the strain-induced electron-phonon coupling modification

NASA Astrophysics Data System (ADS)

Lin, Yow-Jon; Chang, Hsing-Cheng; Liu, Day-Shan

2015-03-01

Tuning charge transport in the bottom-contact pentacene-based organic thin-film transistors (OTFTs) using a MoO x capping layer that serves to the electron-phonon coupling modification is reported. For OTFTs with a MoO x front gate, the enhanced field-effect carrier mobility is investigated. The time domain data confirm the electron-trapping model. To understand the origin of a mobility enhancement, an analysis of the temperature-dependent Hall-effect characteristics is presented. Similarly, the Hall-effect carrier mobility was dramatically increased by capping a MoO x layer on the pentacene front surface. However, the carrier concentration is not affected. The Hall-effect carrier mobility exhibits strong temperature dependence, indicating the dominance of tunneling (hopping) at low (high) temperatures. A mobility enhancement is considered to come from the electron-phonon coupling modification that results from the contribution of long-lifetime electron trapping.

Development of Cryogenic Enhancement-Mode Pseudomorphic High-Electron-Mobility Transistor Amplifier

NASA Astrophysics Data System (ADS)

Hirata, T.; Okazaki, T.; Obara, K.; Yano, H.; Ishikawa, O.

2017-06-01

This paper reports the technical details of the development of a low-temperature amplifier for nuclear magnetic resonance measurements of superfluid {}^3He in very confined geometries. The amplifier consists of commercially available enhancement-mode pseudomorphic high-electron-mobility transistor devices and temperature-insensitive passive components with an operating frequency range of 0.2-6 MHz.

Electronic structures of superionic conductor Li3N

NASA Astrophysics Data System (ADS)

Aoki, Masaru; Ode, Yoshiyuki; Tsumuraya, Kazuo

2011-03-01

Lithium nitride is a superionic conductor with high Li conductivity. The compound has been studied extensively because of its potential utility as electrolyte in solid-state batteries. Though the mobility of the cations within the crystalline solid is high comparable to that of molten salts, the mechanism of the high mobility of the cations remains unsolved. To clarify the origin of the mobility we investigate the electronic states of the Li cations in the Li 3 N crystal with the first principles electronic structure analysis, focusing a correlation between the cations and the ionicities of the constituent atoms. We have found the existence of the covalent bonding between the Li atoms in the Li 3 N crystal in spite of the ionized states of the constituent atoms.

Modeling of high composition AlGaN channel high electron mobility transistors with large threshold voltage

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

Bajaj, Sanyam, E-mail: bajaj.10@osu.edu; Hung, Ting-Hsiang; Akyol, Fatih

2014-12-29

We report on the potential of high electron mobility transistors (HEMTs) consisting of high composition AlGaN channel and barrier layers for power switching applications. Detailed two-dimensional (2D) simulations show that threshold voltages in excess of 3 V can be achieved through the use of AlGaN channel layers. We also calculate the 2D electron gas mobility in AlGaN channel HEMTs and evaluate their power figures of merit as a function of device operating temperature and Al mole fraction in the channel. Our models show that power switching transistors with AlGaN channels would have comparable on-resistance to GaN-channel based transistors for the samemore » operation voltage. The modeling in this paper shows the potential of high composition AlGaN as a channel material for future high threshold enhancement mode transistors.« less

Thermal Analysis of AlGaN/GaN High-Electron-Mobility Transistor and Its RF Power Efficiency Optimization with Source-Bridged Field-Plate Structure.

PubMed

Kwak, Hyeon-Tak; Chang, Seung-Bo; Jung, Hyun-Gu; Kim, Hyun-Seok

2018-09-01

In this study, we consider the relationship between the temperature in a two-dimensional electron gas (2-DEG) channel layer and the RF characteristics of an AlGaN/GaN high-electron-mobility transistor by changing the geometrical structure of the field-plate. The final goal is to achieve a high power efficiency by decreasing the channel layer temperature. First, simulations were performed to compare and contrast the experimental data of a conventional T-gate head structure. Then, a source-bridged field-plate (SBFP) structure was used to obtain the lower junction temperature in the 2-DEG channel layer. The peak electric field intensity was reduced, and a decrease in channel temperature resulted in an increase in electron mobility. Furthermore, the gate-to-source capacitance was increased by the SBFP structure. However, under the large current flow condition, the SBFP structure had a lower maximum temperature than the basic T-gate head structure, which improved the device electron mobility. Eventually, an optimum position of the SBFP was used, which led to higher frequency responses and improved the breakdown voltages. Hence, the optimized SBFP structure can be a promising candidate for high-power RF devices.

High electron mobility and quantum oscillations in non-encapsulated ultrathin semiconducting Bi2O2Se

NASA Astrophysics Data System (ADS)

Wu, Jinxiong; Yuan, Hongtao; Meng, Mengmeng; Chen, Cheng; Sun, Yan; Chen, Zhuoyu; Dang, Wenhui; Tan, Congwei; Liu, Yujing; Yin, Jianbo; Zhou, Yubing; Huang, Shaoyun; Xu, H. Q.; Cui, Yi; Hwang, Harold Y.; Liu, Zhongfan; Chen, Yulin; Yan, Binghai; Peng, Hailin

2017-07-01

High-mobility semiconducting ultrathin films form the basis of modern electronics, and may lead to the scalable fabrication of highly performing devices. Because the ultrathin limit cannot be reached for traditional semiconductors, identifying new two-dimensional materials with both high carrier mobility and a large electronic bandgap is a pivotal goal of fundamental research. However, air-stable ultrathin semiconducting materials with superior performances remain elusive at present. Here, we report ultrathin films of non-encapsulated layered Bi2O2Se, grown by chemical vapour deposition, which demonstrate excellent air stability and high-mobility semiconducting behaviour. We observe bandgap values of ˜0.8 eV, which are strongly dependent on the film thickness due to quantum-confinement effects. An ultrahigh Hall mobility value of >20,000 cm2 V-1 s-1 is measured in as-grown Bi2O2Se nanoflakes at low temperatures. This value is comparable to what is observed in graphene grown by chemical vapour deposition and at the LaAlO3-SrTiO3 interface, making the detection of Shubnikov-de Haas quantum oscillations possible. Top-gated field-effect transistors based on Bi2O2Se crystals down to the bilayer limit exhibit high Hall mobility values (up to 450 cm2 V-1 s-1), large current on/off ratios (>106) and near-ideal subthreshold swing values (˜65 mV dec-1) at room temperature. Our results make Bi2O2Se a promising candidate for future high-speed and low-power electronic applications.

Role of dislocations and carrier concentration in limiting the electron mobility of InN films grown by plasma assisted molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Tangi, Malleswararao; De, Arpan; Shivaprasad, S. M.

2018-01-01

We report the molecular beam epitaxy growth of device quality InN films on GaN epilayer and nano-wall network (NWN) templates deposited on c-sapphire by varying the film thickness up to 1 μm. The careful experiments are directed towards obtaining high mobility InN layers having a low band gap with improved crystal quality. The dislocation density is quantified by using high resolution X-ray diffraction rocking curve broadening values of symmetric and asymmetric reflections, respectively. We observe that the dislocation density of the InN films grown on GaN NWN is less than that of the films grown on the GaN epilayer. This is attributed to the nanoepitaxial lateral overlayer growth (ELOG) process, where the presence of voids at the interface of InN/GaN NWN prevents the propagation of dislocation lines into the InN epilayers, thereby causing less defects in the overgrown InN films. Thus, this new adaptation of the nano-ELOG growth process enables us to prepare InN layers with high electron mobility. The obtained electron mobility of 2121 cm2/Vs for 1 μm thick InN/GaN NWN is comparable with the literature values of similar thickness InN films. Furthermore, in order to understand the reasons that limit electron mobility, the charge neutrality condition is employed to study the variation of electron mobility as a function of dislocation density and carrier concentration. Overall, this study provides a route to attaining improved crystal quality and electronic properties of InN films.

A study of electrically active traps in AlGaN/GaN high electron mobility transistor

NASA Astrophysics Data System (ADS)

Yang, Jie; Cui, Sharon; Ma, T. P.; Hung, Ting-Hsiang; Nath, Digbijoy; Krishnamoorthy, Sriram; Rajan, Siddharth

2013-10-01

We have studied electron conduction mechanisms and the associated roles of the electrically active traps in the AlGaN layer of an AlGaN/GaN high electron mobility transistor structure. By fitting the temperature dependent I-V (Current-Voltage) curves to the Frenkel-Poole theory, we have identified two discrete trap energy levels. Multiple traces of I-V measurements and constant-current injection experiment all confirm that the main role of the traps in the AlGaN layer is to enhance the current flowing through the AlGaN barrier by trap-assisted electron conduction without causing electron trapping.

Prediction of a mobile two-dimensional electron gas at the LaSc O3 /BaSn O3 (001) interface

NASA Astrophysics Data System (ADS)

Paudel, Tula R.; Tsymbal, Evgeny Y.

2017-12-01

Two-dimensional electron gases (2DEG) at oxide interfaces, such as LaAl O3 /SrTi O3 (001), have aroused significant interest due to their high carrier density (˜1014c m-2 ) and strong lateral confinement (˜1 nm). However, these 2DEGs are normally hosted by the weakly dispersive and degenerate d bands (e.g., Ti -3 d bands), which are strongly coupled to the lattice, causing mobility of such 2DEGs to be relatively low at room temperature (˜1 c m2/Vs ). Here, we propose using oxide host materials with the conduction bands formed from s electrons to increase carrier mobility and soften its temperature dependence. Using first-principles density functional theory calculations, we investigate LaSc O3 /BaSn O3 (001) heterostructure and as a model system, where the conduction band hosts the s -like carriers. We find that the polar discontinuity at this interface leads to electronic reconstruction resulting in the formation of the 2DEG at this interface. The conduction electrons reside in the highly dispersive Sn -5 s bands, which have a large band width and a low effective mass. The predicted 2DEG is expected to be highly mobile even at room temperature due to the reduced electron-phonon scattering via the inter-band scattering channel. A qualitatively similar behavior is predicted for a doped BaSn O3 , where a monolayer of BaO is replaced with LaO. We anticipate that the quantum phenomena associated with these 2DEGs to be more pronounced owing to the high mobility of the carriers.

High Mobility SiGe/Si Transistor Structures on Sapphire Substrates Using Ion Implantation

NASA Technical Reports Server (NTRS)

Alterovitz, S. A.; Mueller, C. H.; Croke, E. T.

2003-01-01

High mobility n-type SiGe/Si transistor structures have been fabricated on sapphire substrates by ion implanting phosphorus ions into strained 100 Angstrom thick silicon channels for the first time. The strained Si channels were sandwiched between Si(sub 0.7)Ge(sub 0.3) layers, which, in turn, were deposited on Si(sub 0.7)Ge(sub 0.3) virtual substrates and graded SiGe buffer layers. After the molecular beam epitaxy (MBE) film growth process was completed, ion thick silicon channels implantation and post-annealing were used to introduce donors. The phosphorous ions were preferentially located in the Si channel at a peak concentration of approximately 1x10(exp 18)/cu cm. Room temperature electron mobilities exceeding 750 sq cm/V-sec at carrier densities of 1x10(exp 12)/sq cm were measured. Electron concentration appears to be the key factor that determines mobility, with the highest mobility observed for electron densities in the 1 - 2x10(exp 12)/sq cm range.

Electron tunneling spectroscopy study of electrically active traps in AlGaN/GaN high electron mobility transistors

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

Yang, Jie, E-mail: jie.yang@yale.edu; Cui, Sharon; Ma, T. P.

2013-11-25

We investigate the energy levels of electron traps in AlGaN/GaN high electron mobility transistors by the use of electron tunneling spectroscopy. Detailed analysis of a typical spectrum, obtained in a wide gate bias range and with both bias polarities, suggests the existence of electron traps both in the bulk of AlGaN and at the AlGaN/GaN interface. The energy levels of the electron traps have been determined to lie within a 0.5 eV band below the conduction band minimum of AlGaN, and there is strong evidence suggesting that these traps contribute to Frenkel-Poole conduction through the AlGaN barrier.

25th anniversary article: key points for high-mobility organic field-effect transistors.

PubMed

Dong, Huanli; Fu, Xiaolong; Liu, Jie; Wang, Zongrui; Hu, Wenping

2013-11-20

Remarkable progress has been made in developing high performance organic field-effect transistors (OFETs) and the mobility of OFETs has been approaching the values of polycrystalline silicon, meeting the requirements of various electronic applications from electronic papers to integrated circuits. In this review, the key points for development of high mobility OFETs are highlighted from aspects of molecular engineering, process engineering and interface engineering. The importance of other factors, such as impurities and testing conditions is also addressed. Finally, the current challenges in this field for practical applications of OFETs are further discussed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electron transport properties of degenerate n-type GaN prepared by pulsed sputtering

NASA Astrophysics Data System (ADS)

Ueno, Kohei; Fudetani, Taiga; Arakawa, Yasuaki; Kobayashi, Atsushi; Ohta, Jitsuo; Fujioka, Hiroshi

2017-12-01

We report a systematic investigation of the transport properties of highly degenerate electrons in Ge-doped and Si-doped GaN epilayers prepared using the pulsed sputtering deposition (PSD) technique. Secondary-ion mass spectrometry and Hall-effect measurements revealed that the doping efficiency of PSD n-type GaN is close to unity at electron concentrations as high as 5.1 × 1020 cm-3. A record low resistivity for n-type GaN of 0.16 mΩ cm was achieved with an electron mobility of 100 cm2 V-1 s-1 at a carrier concentration of 3.9 × 1020 cm-3. We explain this unusually high electron mobility of PSD n-type GaN within the framework of conventional scattering theory by modifying a parameter related to nonparabolicity of the conduction band. The Ge-doped GaN films show a slightly lower electron mobility compared with Si-doped films with the same carrier concentrations, which is likely a consequence of the formation of a small number of compensation centers. The excellent electrical properties presented in this letter clearly demonstrate the striking advantages of the low-temperature PSD technique for growing high-quality and highly conductive n-type GaN.

High Thermoelectric Power Factor of High‐Mobility 2D Electron Gas

PubMed Central

Kim, Sung Wng; Kaneki, Shota; Yamamoto, Atsushi

2017-01-01

Abstract Thermoelectric conversion is an energy harvesting technology that directly converts waste heat from various sources into electricity by the Seebeck effect of thermoelectric materials with a large thermopower (S), high electrical conductivity (σ), and low thermal conductivity (κ). State‐of‐the‐art nanostructuring techniques that significantly reduce κ have realized high‐performance thermoelectric materials with a figure of merit (ZT = S 2∙σ∙T∙κ−1) between 1.5 and 2. Although the power factor (PF = S 2∙σ) must also be enhanced to further improve ZT, the maximum PF remains near 1.5–4 mW m−1 K−2 due to the well‐known trade‐off relationship between S and σ. At a maximized PF, σ is much lower than the ideal value since impurity doping suppresses the carrier mobility. A metal‐oxide‐semiconductor high electron mobility transistor (MOS‐HEMT) structure on an AlGaN/GaN heterostructure is prepared. Applying a gate electric field to the MOS‐HEMT simultaneously modulates S and σ of the high‐mobility electron gas from −490 µV K−1 and ≈10−1 S cm−1 to −90 µV K−1 and ≈104 S cm−1, while maintaining a high carrier mobility (≈1500 cm2 V−1 s−1). The maximized PF of the high‐mobility electron gas is ≈9 mW m−1 K−2, which is a two‐ to sixfold increase compared to state‐of‐the‐art practical thermoelectric materials. PMID:29375980

High Electron Mobility in SiGe/Si n-MODFET Structures on Sapphire Substrates

NASA Technical Reports Server (NTRS)

Mueller, Carl H.; Croke, Edward T.; Alterovitz, Samuel A.

2003-01-01

For the first time, SiGe/Si n-Modulation Doped Field Effect Transistors (n-MODFET) structures have been grown on sapphire substrates. Room temperature electron mobility value of 1271 square centimeters N-sec at an electron carrier density (n(sub e) = 1.33x10(exp 12) per square centimeter)) of 1.6 x 10(exp 12) per square centimeter was obtained. At 250 mK, the mobility increases to 13,313 square centimeters/V-sec (n(sub e)=1.33x10(exp 12) per square centimeter)) and Shubnikov-de Haas oscillations appear, showing excellent confinement of the two-dimensional electron gas.

High-Frequency, 6.2 Angstrom pN Heterojunction Diodes

DTIC Science & Technology

2012-01-01

this paper were grown by solid- source molecular beam epitaxy (MBE). Here, the use of a lower- case letter (p) for the narrow bandgap layer and upper...electron and hole mobilities. High electron mobil- ity transistors ( HEMTs ) fabricated from these materials have shown good operating characteristics [1,2...Furthermore, the first monolithic microwave integrated circuits (MMICs) fabricated using 6.1 Å based HEMTs have been demonstrated [3]. New mate- rials

Optical probing of the metal-to-insulator transition in a two-dimensional high-mobility electron gas

NASA Astrophysics Data System (ADS)

Dionigi, F.; Rossella, F.; Bellani, V.; Amado, M.; Diez, E.; Kowalik, K.; Biasiol, G.; Sorba, L.

2011-06-01

We study the quantum Hall liquid and the metal-insulator transition in a high-mobility two-dimensional electron gas, by means of photoluminescence and magnetotransport measurements. In the integer and fractional regime at ν>1/3, by analyzing the emission energy dispersion we probe the magneto-Coulomb screening and the hidden symmetry of the electron liquid. In the fractional regime above ν=1/3, the system undergoes metal-to-insulator transition, and in the insulating phase the dispersion becomes linear with evidence of an increased renormalized mass.

Superlattice structure modeling and simulation of High Electron Mobility Transistor for improved performance

NASA Astrophysics Data System (ADS)

Munusami, Ravindiran; Yakkala, Bhaskar Rao; Prabhakar, Shankar

2013-12-01

Magnetic tunnel junction were made by inserting the magnetic materials between the source, channel and the drain of the High Electron Mobility Transistor (HEMT) to enhance the performance. Material studio software package was used to design the superlattice layers. Different cases were analyzed to optimize the performance of the device by placing the magnetic material at different positions of the device. Simulation results based on conductivity reveals that the device has a very good electron transport due to the magnetic materials and will amplify very low frequency signals.

Mechanism behind the high thermoelectric power factor of SrTiO3 by calculating the transport coefficients

NASA Astrophysics Data System (ADS)

Shirai, Koun; Yamanaka, Kazunori

2013-02-01

The thermoelectric power factor of SrTiO3 is unusually high with respect to its mobility and band gap. Good thermoelectrics usually have high mobility and a narrow band gap, but such properties are not found in SrTiO3. We have determined the mechanism behind the high power factor by calculating the transport coefficients. The key to understanding the power factor is that different effective masses contribute to different transport phenomena. The discrepancy between the effective mass for the conductivity and the thermoelectric power showed that the conductivity and thermoelectric power are conveyed by electrons with different effective masses in the Brillouin zone. Light electrons were responsible for the high conductivity, whereas heavy electrons were responsible for the high thermoelectric power. The high carrier concentrations of more than 1020 cm-3 did not reduce the thermoelectric power of SrTiO3 above the classical limit. This indicates that the electrons carrying the thermoelectric power were not degenerate. This is achieved by a decrease in the Fermi energy and the contribution of the heavy electrons to the Seebeck coefficient. The strong dielectric screening also contributed to the high power factor. The Coulomb scattering by ionized impurities, which would usually reduce the carrier mobility, was effectively screened. These results clarify the mechanism behind the contribution of different types of electrons, and show that high thermoelectric power does not necessarily reduce conductivity. Our findings provide a new direction for the band engineering of thermoelectric materials.

Measurement of brightness temperature of two-dimensional electron gas in channel of a high electron mobility transistor at ultralow dissipation power

NASA Astrophysics Data System (ADS)

Korolev, A. M.; Shulga, V. M.; Turutanov, O. G.; Shnyrkov, V. I.

2016-07-01

A technically simple and physically clear method is suggested for direct measurement of the brightness temperature of two-dimensional electron gas (2DEG) in the channel of a high electron mobility transistor (HEMT). The usage of the method was demonstrated with the pseudomorphic HEMT as a specimen. The optimal HEMT dc regime, from the point of view of the "back action" problem, was found to belong to the unsaturated area of the static characteristics possibly corresponding to the ballistic electron transport mode. The proposed method is believed to be a convenient tool to explore the ballistic transport, electron diffusion, 2DEG properties and other electrophysical processes in heterostructures.

Nanocrystalline ZnON; High mobility and low band gap semiconductor material for high performance switch transistor and image sensor application

PubMed Central

Lee, Eunha; Benayad, Anass; Shin, Taeho; Lee, HyungIk; Ko, Dong-Su; Kim, Tae Sang; Son, Kyoung Seok; Ryu, Myungkwan; Jeon, Sanghun; Park, Gyeong-Su

2014-01-01

Interest in oxide semiconductors stems from benefits, primarily their ease of process, relatively high mobility (0.3–10 cm2/vs), and wide-bandgap. However, for practical future electronic devices, the channel mobility should be further increased over 50 cm2/vs and wide-bandgap is not suitable for photo/image sensor applications. The incorporation of nitrogen into ZnO semiconductor can be tailored to increase channel mobility, enhance the optical absorption for whole visible light and form uniform micro-structure, satisfying the desirable attributes essential for high performance transistor and visible light photo-sensors on large area platform. Here, we present electronic, optical and microstructural properties of ZnON, a composite of Zn3N2 and ZnO. Well-optimized ZnON material presents high mobility exceeding 100 cm2V−1s−1, the band-gap of 1.3 eV and nanocrystalline structure with multiphase. We found that mobility, microstructure, electronic structure, band-gap and trap properties of ZnON are varied with nitrogen concentration in ZnO. Accordingly, the performance of ZnON-based device can be adjustable to meet the requisite of both switch device and image-sensor potentials. These results demonstrate how device and material attributes of ZnON can be optimized for new device strategies in display technology and we expect the ZnON will be applicable to a wide range of imaging/display devices. PMID:24824778

Local 2D-2D tunneling in high mobility electron systems

NASA Astrophysics Data System (ADS)

Pelliccione, Matthew; Sciambi, Adam; Bartel, John; Goldhaber-Gordon, David; Pfeiffer, Loren; West, Ken; Lilly, Michael; Bank, Seth; Gossard, Arthur

2012-02-01

Many scanning probe techniques have been utilized in recent years to measure local properties of high mobility two-dimensional (2D) electron systems in GaAs. However, most techniques lack the ability to tunnel into the buried 2D system and measure local spectroscopic information. We report scanning gate measurements on a bilayer GaAs/AlGaAs heterostructure that allows for a local modulation of tunneling between two 2D electron layers. We call this technique Virtual Scanning Tunneling Microscopy (VSTM) [1,2] as the influence of the scanning gate is analogous to an STM tip, except at a GaAs/AlGaAs interface instead of a surface. We will discuss the spectroscopic capabilities of the technique, and show preliminary results of measurements on a high mobility 2D electron system.[1] A. Sciambi, M. Pelliccione et al., Appl. Phys. Lett. 97, 132103 (2010).[2] A. Sciambi, M. Pelliccione et al., Phys. Rev. B 84, 085301 (2011).

Mechanism of high-fluence proton induced electrical degradation in AlGaN/GaN high-electron-mobility transistors

NASA Astrophysics Data System (ADS)

Lei, Zhifeng; Guo, Hongxia; Tang, Minghua; Peng, Chao; Zhang, Zhangang; Huang, Yun; En, Yunfei

2018-07-01

The effects of displacement damage induced by 3 and 6 MeV protons in AlGaN/GaN high-electron-mobility transistors (HEMTs) are investigated. For the 6 MeV protons at a dose of 5 × 1014 cm‑2, a 12% decrease in saturation current, a 3.8% decrease in the peak transconductance, a 0.3 V positive shift of the threshold voltage, and a three-to fourfold decrease in reverse gate leakage current are observed compared with the pre-irradiation values. The main degradation mechanism is considered to be the generation of deep trap states in the band gap, which remove electrons and reduce the carrier mobility in a two-dimensional electron gas (2DEG). Both the carrier removal rate and negatively charged trap density can be extracted, which shows that about 3500 proton injections lead to one carrier removal. Proton fluence and energy are found to be two key parameters that affect the degradation characteristics of irradiated GaN HEMTs.

Molecular beam epitaxy growth of high electron mobility InAs/AlSb deep quantum well structure

NASA Astrophysics Data System (ADS)

Wang, Juan; Wang, Guo-Wei; Xu, Ying-Qiang; Xing, Jun-Liang; Xiang, Wei; Tang, Bao; Zhu, Yan; Ren, Zheng-Wei; He, Zhen-Hong; Niu, Zhi-Chuan

2013-07-01

InAs/AlSb deep quantum well (QW) structures with high electron mobility were grown by molecular beam epitaxy (MBE) on semi-insulating GaAs substrates. AlSb and Al0.75Ga0.25Sb buffer layers were grown to accommodate the lattice mismatch (7%) between the InAs/AlSb QW active region and GaAs substrate. Transmission electron microscopy shows abrupt interface and atomic force microscopy measurements display smooth surface morphology. Growth conditions of AlSb and Al0.75Ga0.25Sb buffer were optimized. Al0.75Ga0.25Sb is better than AlSb as a buffer layer as indicated. The sample with optimal Al0.75Ga0.25Sb buffer layer shows a smooth surface morphology with root-mean-square roughness of 6.67 Å. The electron mobility has reached as high as 27 000 cm2/Vs with a sheet density of 4.54 × 1011/cm2 at room temperature.

High Mobility Conjugated Polymers

DTIC Science & Technology

2007-10-20

will act as a trap for opposite charge carriers; the electron affinities were 4.0 eV (BBL) and 2.7 eV (PTHQx) and ionization potentials were 6.0 eV...transistors (OFETs), photovoltaic cells, and photodetectors, is limited primarily by the low charge carrier mobilities of current materials. To address this...showing a maximum mobility with hexyl. Fundamental insights into the structural factors that govern high mobility charge transport and recombination in

Electromechanical Displacement Detection With an On-Chip High Electron Mobility Transistor Amplifier

NASA Astrophysics Data System (ADS)

Oda, Yasuhiko; Onomitsu, Koji; Kometani, Reo; Warisawa, Shin-ichi; Ishihara, Sunao; Yamaguchi, Hiroshi

2011-06-01

We developed a highly sensitive displacement detection scheme for a GaAs-based electromechanical resonator using an integrated high electron mobility transistor (HEMT). Piezoelectric voltage generated by the vibration of the resonator is applied to the gate of the HEMT, resulting in the on-chip amplification of the signal voltage. This detection scheme achieves a displacement sensitivity of ˜9 pm·Hz-1/2, which is one of the highest among on-chip purely electrical displacement detection schemes at room temperature.

Low nonalloyed Ohmic contact resistance to nitride high electron mobility transistors using N-face growth

NASA Astrophysics Data System (ADS)

Wong, Man Hoi; Pei, Yi; Palacios, Tomás; Shen, Likun; Chakraborty, Arpan; McCarthy, Lee S.; Keller, Stacia; DenBaars, Steven P.; Speck, James S.; Mishra, Umesh K.

2007-12-01

Nonalloyed Ohmic contacts on Ga-face n+-GaN/AlGaN/GaN high electron mobility transistor (HEMT) structures typically have significant contact resistance to the two-dimensional electron gas (2DEG) due to the AlGaN barrier. By growing the HEMT structure inverted on the N-face, electrons from the contacts were able to access the 2DEG without going through an AlGaN layer. A low contact resistance of 0.16Ωmm and specific contact resistivity of 5.5×10-7Ωcm2 were achieved without contact annealing on the inverted HEMT structure.

Frequency quenching of microwave-induced resistance oscillations in a high-mobility two-dimensional electron gas

NASA Astrophysics Data System (ADS)

Studenikin, S. A.; Sachrajda, A. S.; Gupta, J. A.; Wasilewski, Z. R.; Fedorych, O. M.; Byszewski, M.; Maude, D. K.; Potemski, M.; Hilke, M.; West, K. W.; Pfeiffer, L. N.

2007-10-01

The frequency dependence of microwave-induced resistance oscillations (MIROs) has been studied experimentally in high-mobility electron GaAs/AlGaAs structures to explore the limits at which these oscillations can be observed. It is found that in dc transport experiments at frequencies above 120GHz , MIROs start to quench, while above 230GHz , they completely disappear. The results will need to be understood theoretically but are qualitatively discussed within a model in which forced electronic charge oscillations (plasmons) play an intermediate role in the interaction process between the radiation and the single-particle electron excitations between Landau levels.

Electrical transport, electrothermal transport, and effective electron mass in single-crystalline In2O3 films

NASA Astrophysics Data System (ADS)

Preissler, Natalie; Bierwagen, Oliver; Ramu, Ashok T.; Speck, James S.

2013-08-01

A comprehensive study of the room-temperature electrical and electrothermal transport of single-crystalline indium oxide (In2O3) and indium tin oxide (ITO) films over a wide range of electron concentrations is reported. We measured the room-temperature Hall mobility μH and Seebeck coefficient S of unintentionally doped and Sn-doped high-quality, plasma-assisted molecular-beam-epitaxy-grown In2O3 for volume Hall electron concentrations nH from 7×1016 cm-3 (unintentionally doped) to 1×1021 cm-3 (highly Sn-doped, ITO). The resulting empirical S(nH) relation can be directly used in other In2O3 samples to estimate the volume electron concentration from simple Seebeck coefficient measurements. The mobility and Seebeck coefficient were modeled by a numerical solution of the Boltzmann transport equation. Ionized impurity scattering and polar optical phonon scattering were found to be the dominant scattering mechanisms. Acoustic phonon scattering was found to be negligible. Fitting the temperature-dependent mobility above room temperature of an In2O3 film with high mobility allowed us to find the effective Debye temperature (ΘD=700 K) and number of phonon modes (NOPML=1.33) that best describe the polar optical phonon scattering. The modeling also yielded the Hall scattering factor rH as a function of electron concentration, which is not negligible (rH≈1.4) at nondegenerate electron concentrations. Fitting the Hall-scattering-factor corrected concentration-dependent Seebeck coefficient S(n) for nondegenerate samples to the numerical solution of the Boltzmann transport equation and to widely used, simplified equations allowed us to extract an effective electron mass of m*=(0.30±0.03)me (with free electron mass me). The modeled mobility and Seebeck coefficient based on polar optical phonon and ionized impurity scattering describes the experimental results very accurately up to electron concentrations of 1019 cm-3, and qualitatively explains a mobility plateau or local maximum around 1020 cm-3. Ionized impurity scattering with doubly charged donors best describes the mobility in our unintentionally doped films, consistent with oxygen vacancies as unintentional shallow donors, whereas singly charged donors best describe our Sn-doped films. Our modeling yields a (phonon-limited) maximum theoretical drift mobility and Hall mobility of μ=190 cm2/Vs and μH=270 cm2/Vs, respectively. Simplified equations for the Seebeck coefficient describe the measured values in the nondegenerate regime using a Seebeck scattering parameter of r=-0.55 (which is consistent with the determined Debye temperature), and provide an estimate of the Seebeck coefficient to lower electron concentrations. The simplified equations fail to describe the Seebeck coefficient around the Mott transition (nMott=5.5×1018 cm-3) from nondegenerate to degenerate electron concentrations, whereas the numerical modeling accurately describes this region.

Solution-Processed Donor-Acceptor Polymer Nanowire Network Semiconductors For High-Performance Field-Effect Transistors

PubMed Central

Lei, Yanlian; Deng, Ping; Li, Jun; Lin, Ming; Zhu, Furong; Ng, Tsz-Wai; Lee, Chun-Sing; Ong, Beng S.

2016-01-01

Organic field-effect transistors (OFETs) represent a low-cost transistor technology for creating next-generation large-area, flexible and ultra-low-cost electronics. Conjugated electron donor-acceptor (D-A) polymers have surfaced as ideal channel semiconductor candidates for OFETs. However, high-molecular weight (MW) D-A polymer semiconductors, which offer high field-effect mobility, generally suffer from processing complications due to limited solubility. Conversely, the readily soluble, low-MW D-A polymers give low mobility. We report herein a facile solution process which transformed a lower-MW, low-mobility diketopyrrolopyrrole-dithienylthieno[3,2-b]thiophene (I) into a high crystalline order and high-mobility semiconductor for OFETs applications. The process involved solution fabrication of a channel semiconductor film from a lower-MW (I) and polystyrene blends. With the help of cooperative shifting motion of polystyrene chain segments, (I) readily self-assembled and crystallized out in the polystyrene matrix as an interpenetrating, nanowire semiconductor network, providing significantly enhanced mobility (over 8 cm2V−1s−1), on/off ratio (107), and other desirable field-effect properties that meet impactful OFET application requirements. PMID:27091315

Theoretical study of anisotropic mobility in ladder-type molecule organic semiconductors

NASA Astrophysics Data System (ADS)

Wei, Hui-Ling; Liu, Yu-Fang

2014-09-01

The properties of two ladder-type semiconductors {M1: 2,2'-(2,7-dihexy1-4,9-dihydro- s-indaceno[1,2- b:5,6- b']dithiophene-4,9-diylidene) dimalononitrile and M2: 2,7-dihexy1-4,9-dihydro- s-indaceno[1,2- b:5,6- b']dithiophene-4,9-dione} as the n-type and ambipolar organic materials are systematically investigated using the first-principle density functional theory combined with the Marcus-Hush electron transfer theory. It is found that the substitution of M1 induces large changes in its electron-transfer mobility of 1.370 cm2 V-1 s-1. M2 has both large electron- and hole-transfer mobility of 0.420 and 0.288 cm2 V-1 s-1, respectively, which indicates that M2 is potentially a high efficient ambipolar organic semiconducting material. Both the M1 and M2 crystals show remarkable anisotropic behavior. A proper design of the n-type and ambipolar organic electronic materials, which may have high mobility performance, is suggested based on the investigated two molecules.

Induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures.

PubMed

Wan, Zhong; Kazakov, Aleksandr; Manfra, Michael J; Pfeiffer, Loren N; West, Ken W; Rokhinson, Leonid P

2015-06-11

Search for Majorana fermions renewed interest in semiconductor-superconductor interfaces, while a quest for higher-order non-Abelian excitations demands formation of superconducting contacts to materials with fractionalized excitations, such as a two-dimensional electron gas in a fractional quantum Hall regime. Here we report induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures and development of highly transparent semiconductor-superconductor ohmic contacts. Supercurrent with characteristic temperature dependence of a ballistic junction has been observed across 0.6 μm, a regime previously achieved only in point contacts but essential to the formation of well separated non-Abelian states. High critical fields (>16 T) in NbN contacts enables investigation of an interplay between superconductivity and strongly correlated states in a two-dimensional electron gas at high magnetic fields.

Induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures

PubMed Central

Wan, Zhong; Kazakov, Aleksandr; Manfra, Michael J.; Pfeiffer, Loren N.; West, Ken W.; Rokhinson, Leonid P.

2015-01-01

Search for Majorana fermions renewed interest in semiconductor–superconductor interfaces, while a quest for higher-order non-Abelian excitations demands formation of superconducting contacts to materials with fractionalized excitations, such as a two-dimensional electron gas in a fractional quantum Hall regime. Here we report induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures and development of highly transparent semiconductor–superconductor ohmic contacts. Supercurrent with characteristic temperature dependence of a ballistic junction has been observed across 0.6 μm, a regime previously achieved only in point contacts but essential to the formation of well separated non-Abelian states. High critical fields (>16 T) in NbN contacts enables investigation of an interplay between superconductivity and strongly correlated states in a two-dimensional electron gas at high magnetic fields. PMID:26067452

Investigation of AlGaN/GaN high electron mobility transistor structures on 200-mm silicon (111) substrates employing different buffer layer configurations.

PubMed

Lee, H-P; Perozek, J; Rosario, L D; Bayram, C

2016-11-21

AlGaN/GaN high electron mobility transistor (HEMT) structures are grown on 200-mm diameter Si(111) substrates by using three different buffer layer configurations: (a) Thick-GaN/3 × {Al x Ga 1-x N}/AlN, (b) Thin-GaN/3 × {Al x Ga 1-x N}/AlN, and (c) Thin-GaN/AlN, so as to have crack-free and low-bow (<50 μm) wafer. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, high resolution-cross section transmission electron microscopy, optical microscopy, atomic-force microscopy, cathodoluminescence, Raman spectroscopy, X-ray diffraction (ω/2θ scan and symmetric/asymmetric ω scan (rocking curve scan), reciprocal space mapping) and Hall effect measurements are employed to study the structural, optical, and electrical properties of these AlGaN/GaN HEMT structures. The effects of buffer layer stacks (i.e. thickness and content) on defectivity, stress, and two-dimensional electron gas (2DEG) mobility and 2DEG concentration are reported. It is shown that 2DEG characteristics are heavily affected by the employed buffer layers between AlGaN/GaN HEMT structures and Si(111) substrates. Particularly, we report that in-plane stress in the GaN layer affects the 2DEG mobility and 2DEG carrier concentration significantly. Buffer layer engineering is shown to be essential for achieving high 2DEG mobility (>1800 cm 2 /V∙s) and 2DEG carrier concentration (>1.0 × 10 13  cm -2 ) on Si(111) substrates.

Investigation of AlGaN/GaN high electron mobility transistor structures on 200-mm silicon (111) substrates employing different buffer layer configurations

PubMed Central

Lee, H.-P.; Perozek, J.; Rosario, L. D.; Bayram, C.

2016-01-01

AlGaN/GaN high electron mobility transistor (HEMT) structures are grown on 200-mm diameter Si(111) substrates by using three different buffer layer configurations: (a) Thick-GaN/3 × {AlxGa1−xN}/AlN, (b) Thin-GaN/3 × {AlxGa1−xN}/AlN, and (c) Thin-GaN/AlN, so as to have crack-free and low-bow (<50 μm) wafer. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, high resolution-cross section transmission electron microscopy, optical microscopy, atomic-force microscopy, cathodoluminescence, Raman spectroscopy, X-ray diffraction (ω/2θ scan and symmetric/asymmetric ω scan (rocking curve scan), reciprocal space mapping) and Hall effect measurements are employed to study the structural, optical, and electrical properties of these AlGaN/GaN HEMT structures. The effects of buffer layer stacks (i.e. thickness and content) on defectivity, stress, and two-dimensional electron gas (2DEG) mobility and 2DEG concentration are reported. It is shown that 2DEG characteristics are heavily affected by the employed buffer layers between AlGaN/GaN HEMT structures and Si(111) substrates. Particularly, we report that in-plane stress in the GaN layer affects the 2DEG mobility and 2DEG carrier concentration significantly. Buffer layer engineering is shown to be essential for achieving high 2DEG mobility (>1800 cm2/V∙s) and 2DEG carrier concentration (>1.0 × 1013 cm−2) on Si(111) substrates. PMID:27869222

Proton Irradiation-Induced Metal Voids in Gallium Nitride High Electron Mobility Transistors

DTIC Science & Technology

2015-09-01

13. ABSTRACT (maximum 200 words) Gallium nitride/aluminum gallium nitride high electron mobility transistors with nickel/ gold (Ni/Au) and...platinum/ gold (Pt/Au) gating are irradiated with 2 MeV protons. Destructive physical analysis revealed material voids underneath the gate finger of the...nickel/ gold (Ni/Au) and platinum/ gold (Pt/Au) gating are irradiated with 2 MeV protons. Destructive physical analysis revealed material voids underneath

DC and small-signal physical models for the AlGaAs/GaAs high electron mobility transistor

NASA Technical Reports Server (NTRS)

Sarker, J. C.; Purviance, J. E.

1991-01-01

Analytical and numerical models are developed for the microwave small-signal performance, such as transconductance, gate-to-source capacitance, current gain cut-off frequency and the optimum cut-off frequency of the AlGaAs/GaAs High Electron Mobility Transistor (HEMT), in both normal and compressed transconductance regions. The validated I-V characteristics and the small-signal performances of four HeMT's are presented.

All-printed diode operating at 1.6 GHz

PubMed Central

Sani, Negar; Robertsson, Mats; Cooper, Philip; Wang, Xin; Svensson, Magnus; Andersson Ersman, Peter; Norberg, Petronella; Nilsson, Marie; Nilsson, David; Liu, Xianjie; Hesselbom, Hjalmar; Akesso, Laurent; Fahlman, Mats; Crispin, Xavier; Engquist, Isak; Berggren, Magnus; Gustafsson, Göran

2014-01-01

Printed electronics are considered for wireless electronic tags and sensors within the future Internet-of-things (IoT) concept. As a consequence of the low charge carrier mobility of present printable organic and inorganic semiconductors, the operational frequency of printed rectifiers is not high enough to enable direct communication and powering between mobile phones and printed e-tags. Here, we report an all-printed diode operating up to 1.6 GHz. The device, based on two stacked layers of Si and NbSi2 particles, is manufactured on a flexible substrate at low temperature and in ambient atmosphere. The high charge carrier mobility of the Si microparticles allows device operation to occur in the charge injection-limited regime. The asymmetry of the oxide layers in the resulting device stack leads to rectification of tunneling current. Printed diodes were combined with antennas and electrochromic displays to form an all-printed e-tag. The harvested signal from a Global System for Mobile Communications mobile phone was used to update the display. Our findings demonstrate a new communication pathway for printed electronics within IoT applications. PMID:25002504

Extreme mobility enhancement of two-dimensional electron gases at oxide interfaces by charge-transfer-induced modulation doping

NASA Astrophysics Data System (ADS)

Chen, Y. Z.; Trier, F.; Wijnands, T.; Green, R. J.; Gauquelin, N.; Egoavil, R.; Christensen, D. V.; Koster, G.; Huijben, M.; Bovet, N.; Macke, S.; He, F.; Sutarto, R.; Andersen, N. H.; Sulpizio, J. A.; Honig, M.; Prawiroatmodjo, G. E. D. K.; Jespersen, T. S.; Linderoth, S.; Ilani, S.; Verbeeck, J.; van Tendeloo, G.; Rijnders, G.; Sawatzky, G. A.; Pryds, N.

2015-08-01

Two-dimensional electron gases (2DEGs) formed at the interface of insulating complex oxides promise the development of all-oxide electronic devices. These 2DEGs involve many-body interactions that give rise to a variety of physical phenomena such as superconductivity, magnetism, tunable metal-insulator transitions and phase separation. Increasing the mobility of the 2DEG, however, remains a major challenge. Here, we show that the electron mobility is enhanced by more than two orders of magnitude by inserting a single-unit-cell insulating layer of polar La1-xSrxMnO3 (x = 0, 1/8, and 1/3) at the interface between disordered LaAlO3 and crystalline SrTiO3 produced at room temperature. Resonant X-ray spectroscopy and transmission electron microscopy show that the manganite layer undergoes unambiguous electronic reconstruction, leading to modulation doping of such atomically engineered complex oxide heterointerfaces. At low temperatures, the modulation-doped 2DEG exhibits Shubnikov-de Haas oscillations and fingerprints of the quantum Hall effect, demonstrating unprecedented high mobility and low electron density.

High mobility La-doped BaSnO3 on non-perovskite MgO substrate

NASA Astrophysics Data System (ADS)

Kim, Youjung; Shin, Juyeon; Kim, Young Mo; Char, Kookrin

(Ba,La)SnO3 is a transparent perovskite oxide with high electron mobility and excellent oxygen stability. Field effect device with (Ba,La)SnO3 channel was reported to show good output characteristics on STO substrate. Here, we fabricated (Ba,La)SnO3\\ films and field effect devices with (Ba,La)SnO3 channel on non-perovskite MgO substrates, which are available in large size wafers. X-ray diffraction and transmission electron microscope (TEM) images of (Ba,La)SnO3\\ films on MgO substrates show that the films are epitaxial with many threading dislocations. (Ba,La)SnO3 exhibits the high mobility with 97.2 cm2/Vs at 2 % La doping on top of 150 nm thick BaSnO3 buffer layer. Excellent carrier modulation was observed in field effect devices. FET performances on MgO substrates are slightly better than those on SrTiO3 substrates in spite of the higher dislocation density on MgO than on SrTiO3 substrates. These high mobility BaSnO3 thin films and transistors on MgO substrates will accelerate development for applications in high temperature and high power electronics. Samsung Science and Technology Foundation.

Proton irradiation effects on gallium nitride-based devices

NASA Astrophysics Data System (ADS)

Karmarkar, Aditya P.

Proton radiation effects on state-of-the-art gallium nitride-based devices were studied using Schottky diodes and high electron-mobility transistors. The device degradation was studied over a wide range of proton fluences. This study allowed for a correlation between proton irradiation effects between different types of devices and enhanced the understanding of the mechanisms responsible for radiation damage in GaN-based devices. Proton irradiation causes reduced carrier concentration and increased series resistance and ideality factor in Schottky diodes. 1.0-MeV protons cause greater degradation than 1.8-MeV protons because of their higher non-ionizing energy loss. The displacement damage in Schottky diodes recovers during annealing. High electron-mobility transistors exhibit extremely high radiation tolerance, continuing to perform up to a fluence of ˜1014 cm-2 of 1.8-MeV protons. Proton irradiation creates defect complexes in the thin-film structure. Decreased sheet carrier mobility due to increased carrier scattering and decreased sheet carrier density due to carrier removal by the defect centers are the primary damage mechanisms. Interface disorder at either the Schottky or the Ohmic contact plays a relatively unimportant part in overall device degradation in both Schottky diodes and high electron-mobility transistors.

Response of a 2DEG to Microwave Irradiation

NASA Astrophysics Data System (ADS)

Moreau, S.; Fedorych, O. M.; Sadowski, M. L.; Potemski, M.; Studenikin, S.; Austing, G.; Sachrajda, A. S.; Saku, T.; Hirayama, Y.

In this paper, we study the behavior of a high mobility two dimensional electron gas under microwave irradiation by means of magneto-photoluminescence (PL) and absorption measurements. The high mobility sample investigated is a 15nm wide GaAs/AlGaAs quantum well with an electron concentration between 1-2×1011cm-2, tunable by visible-light illumination. Structures in the microwave absorption at 40-60GHz are identified as geometrically confined magneto-plasmons.

Kinase detection with gallium nitride based high electron mobility transistors

PubMed Central

Makowski, Matthew S.; Bryan, Isaac; Sitar, Zlatko; Arellano, Consuelo; Xie, Jinqiao; Collazo, Ramon; Ivanisevic, Albena

2013-01-01

A label-free kinase detection system was fabricated by the adsorption of gold nanoparticles functionalized with kinase inhibitor onto AlGaN/GaN high electron mobility transistors (HEMTs). The HEMTs were operated near threshold voltage due to the greatest sensitivity in this operational region. The Au NP/HEMT biosensor system electrically detected 1 pM SRC kinase in ionic solutions. These results are pertinent to drug development applications associated with kinase sensing. PMID:23918992

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.

Mobile health platform for pressure ulcer monitoring with electronic health record integration.

PubMed

Rodrigues, Joel J P C; Pedro, Luís M C C; Vardasca, Tomé; de la Torre-Díez, Isabel; Martins, Henrique M G

2013-12-01

Pressure ulcers frequently occur in patients with limited mobility, for example, people with advanced age and patients wearing casts or prostheses. Mobile information communication technologies can help implement ulcer care protocols and the monitoring of patients with high risk, thus preventing or improving these conditions. This article presents a mobile pressure ulcer monitoring platform (mULCER), which helps control a patient's ulcer status during all stages of treatment. Beside its stand-alone version, it can be integrated with electronic health record systems as mULCER synchronizes ulcer data with any electronic health record system using HL7 standards. It serves as a tool to integrate nursing care among hospital departments and institutions. mULCER was experimented with in different mobile devices such as LG Optimus One P500, Samsung Galaxy Tab, HTC Magic, Samsung Galaxy S, and Samsung Galaxy i5700, taking into account the user's experience of different screen sizes and processing characteristics.

Ambipolar nature of dimethyl benzo difuran (DMBDF) molecule: A charge transport study

NASA Astrophysics Data System (ADS)

Sahoo, Smruti Ranjan; Sahu, Sridhar

2017-05-01

We describe a theoretical study of the charge transport properties of the organic dimethyl benzo difuran (DMBDF) molecule based on density functional theory (DFT). Reorganization energy, ionization potential (IP), electron affinity (EA), energy gaps, transfer integral (t) and charge mobility (μ) has been studied to depict the transport properties in the conjugated organic molecules. We computed, large homo transfer integral and IP value leading to high hole mobility (4.46 cm2/V sec). However, the electron reorganization energy (0.34 eV) and the electron mobility of 1.62 cm2/V sec, infers that the DMBDF organic molecule bears an ambipolar character.

Solution-Processed Transistors Using Colloidal Nanocrystals with Composition-Matched Molecular "Solders": Approaching Single Crystal Mobility.

PubMed

Jang, Jaeyoung; Dolzhnikov, Dmitriy S; Liu, Wenyong; Nam, Sooji; Shim, Moonsub; Talapin, Dmitri V

2015-10-14

Crystalline silicon-based complementary metal-oxide-semiconductor transistors have become a dominant platform for today's electronics. For such devices, expensive and complicated vacuum processes are used in the preparation of active layers. This increases cost and restricts the scope of applications. Here, we demonstrate high-performance solution-processed CdSe nanocrystal (NC) field-effect transistors (FETs) that exhibit very high carrier mobilities (over 400 cm(2)/(V s)). This is comparable to the carrier mobilities of crystalline silicon-based transistors. Furthermore, our NC FETs exhibit high operational stability and MHz switching speeds. These NC FETs are prepared by spin coating colloidal solutions of CdSe NCs capped with molecular solders [Cd2Se3](2-) onto various oxide gate dielectrics followed by thermal annealing. We show that the nature of gate dielectrics plays an important role in soldered CdSe NC FETs. The capacitance of dielectrics and the NC electronic structure near gate dielectric affect the distribution of localized traps and trap filling, determining carrier mobility and operational stability of the NC FETs. We expand the application of the NC soldering process to core-shell NCs consisting of a III-V InAs core and a CdSe shell with composition-matched [Cd2Se3](2-) molecular solders. Soldering CdSe shells forms nanoheterostructured material that combines high electron mobility and near-IR photoresponse.

Improved performance of InSe field-effect transistors by channel encapsulation

NASA Astrophysics Data System (ADS)

Liang, Guangda; Wang, Yiming; Han, Lin; Yang, Zai-Xing; Xin, Qian; Kudrynskyi, Zakhar R.; Kovalyuk, Zakhar D.; Patanè, Amalia; Song, Aimin

2018-06-01

Due to the high electron mobility and photo-responsivity, InSe is considered as an excellent candidate for next generation electronics and optoelectronics. In particular, in contrast to many high-mobility two-dimensional (2D) materials, such as phosphorene, InSe is more resilient to oxidation in air. Nevertheless, its implementation in future applications requires encapsulation techniques to prevent the adsorption of gas molecules on its surface. In this work, we use a common lithography resist, poly(methyl methacrylate) (PMMA) to encapsulate InSe-based field-effect transistors (FETs). The encapsulation of InSe by PMMA improves the electrical stability of the FETs under a gate bias stress, and increases both the drain current and electron mobility. These findings indicate the effectiveness of the PMMA encapsulation method, which could be applied to other 2D materials.

P-doping-free III-nitride high electron mobility light-emitting diodes and transistors

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

Li, Baikui; Tang, Xi; Chen, Kevin J., E-mail: eekjchen@ust.hk

2014-07-21

We report that a simple metal-AlGaN/GaN Schottky diode is capable of producing GaN band-edge ultraviolet emission at 3.4 eV at a small forward bias larger than ∼2 V at room temperature. Based on the surface states distribution of AlGaN, a mature impact-ionization-induced Fermi-level de-pinning model is proposed to explain the underlying mechanism of the electroluminescence (EL) process. By experimenting with different Schottky metals, Ni/Au and Pt/Au, we demonstrated that this EL phenomenon is a “universal” property of metal-AlGaN/GaN Schottky diodes. Since this light-emitting Schottky diode shares the same active structure and fabrication processes as the AlGaN/GaN high electron mobility transistors, straight-forward andmore » seamless integration of photonic and electronic functional devices has been demonstrated on doping-free III-nitride heterostructures. Using a semitransparent Schottky drain electrode, an AlGaN/GaN high electron mobility light-emitting transistor is demonstrated.« less

Electroluminescence of hot electrons in AlGaN/GaN high-electron-mobility transistors under radio frequency operation

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

Brazzini, Tommaso, E-mail: tommaso.brazzini@bristol.ac.uk; Sun, Huarui; Uren, Michael J.

2015-05-25

Hot electrons in AlGaN/GaN high electron mobility transistors are studied during radio frequency (RF) and DC operation by means of electroluminescence (EL) microscopy and spectroscopy. The measured EL intensity is decreased under RF operation compared to DC at the same average current, indicating a lower hot electron density. This is explained by averaging the DC EL intensity over the measured load line used in RF measurements, giving reasonable agreement. In addition, the hot electron temperature is lower by up to 15% under RF compared to DC, again at least partially explainable by the weighted averaging along the specific load line.more » However, peak electron temperature under RF occurs at high V{sub DS} and low I{sub DS} where EL is insignificant suggesting that any wear-out differences between RF and DC stress of the devices will depend on the balance between hot-carrier and field driven degradation mechanisms.« less

Electron heating due to microwave photoexcitation in the high mobility GaAs/AlGaAs two dimensional electron system

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

Ramanayaka, A. N.; Mani, R. G.; Wegscheider, W.

2013-12-04

We extract the electron temperature in the microwave photo-excited high mobility GaAs/AlGaAs two dimensional electron system (2DES) by studying the influence of microwave radiation on the amplitude of Shubnikov-de Haas oscillations (SdHOs) in a regime where the cyclotron frequency, ω{sub c}, and the microwave angular frequency, ω, satisfy 2ω ≤ ω{sub c} ≤ 3.5ω The results indicate that increasing the incident microwave power has a weak effect on the amplitude of the SdHOs and therefore the electron temperature, in comparison to the influence of modest temperature changes on the dark-specimen SdH effect. The results indicate negligible electron heating under modestmore » microwave photo-excitation, in good agreement with theoretical predictions.« less

The Current Collapse in AlGaN/GaN High-Electron Mobility Transistors Can Originate from the Energy Relaxation of Channel Electrons?

PubMed Central

Mao, Ling-Feng; Ning, Huan-Sheng; Wang, Jin-Yan

2015-01-01

Influence of the energy relaxation of the channel electrons on the performance of AlGaN/GaN high-electron mobility transistors (HEMTs) has been investigated using self-consistent solution to the coupled Schrödinger equation and Poisson equation. The first quantized energy level in the inversion layer rises and the average channel electron density decreases when the channel electric field increases from 20 kV/cm to 120 kV/cm. This research also demonstrates that the energy relaxation of the channel electrons can lead to current collapse and suggests that the energy relaxation should be considered in modeling the performance of AlGaN/GaN HEMTs such as, the gate leakage current, threshold voltage, source-drain current, capacitance-voltage curve, etc. PMID:26039589

The Current Collapse in AlGaN/GaN High-Electron Mobility Transistors Can Originate from the Energy Relaxation of Channel Electrons?

PubMed

Mao, Ling-Feng; Ning, Huan-Sheng; Wang, Jin-Yan

2015-01-01

Influence of the energy relaxation of the channel electrons on the performance of AlGaN/GaN high-electron mobility transistors (HEMTs) has been investigated using self-consistent solution to the coupled Schrödinger equation and Poisson equation. The first quantized energy level in the inversion layer rises and the average channel electron density decreases when the channel electric field increases from 20 kV/cm to 120 kV/cm. This research also demonstrates that the energy relaxation of the channel electrons can lead to current collapse and suggests that the energy relaxation should be considered in modeling the performance of AlGaN/GaN HEMTs such as, the gate leakage current, threshold voltage, source-drain current, capacitance-voltage curve, etc.

Charge-transfer mobility and electrical conductivity of PANI as conjugated organic semiconductors

NASA Astrophysics Data System (ADS)

Zhang, Yahong; Duan, Yuping; Song, Lulu; Zheng, Daoyuan; Zhang, Mingxing; Zhao, Guangjiu

2017-09-01

The intramolecular charge transfer properties of a phenyl-end-capped aniline tetramer (ANIH) and a chloro-substituted derivative (ANICl) as organic semiconductors were theoretically studied through the first-principles calculation based on the Marcus-Hush theory. The reorganization energies, intermolecular electronic couplings, angular resolution anisotropic mobilities, and density of states of the two crystals were evaluated. The calculated results demonstrate that both ANIH and ANICl crystals show the higher electron transfer mobilities than the hole-transfer mobilities, which means that the two crystals should prefer to function as n-type organic semiconductors. Furthermore, the angle dependence mobilities of the two crystals show remarkable anisotropic character. The maximum mobility μmax of ANIH and ANICl crystals is 1.3893 and 0.0272 cm2 V-1 s-1, which appear at the orientation angles near 176°/356° and 119°/299° of a conducting channel on the a-b reference plane. It is synthetically evaluated that the ANIH crystal possesses relatively lower reorganization energy, higher electronic coupling, and electron transfer mobility, which means that the ANIH crystal may be the more ideal candidate as a high performance n-type organic semiconductor material. The systematic theoretical studies on organic crystals should be conducive to evaluating the charge-transport properties and designing higher performance organic semiconductor materials.

Charge-transfer mobility and electrical conductivity of PANI as conjugated organic semiconductors.

PubMed

Zhang, Yahong; Duan, Yuping; Song, Lulu; Zheng, Daoyuan; Zhang, Mingxing; Zhao, Guangjiu

2017-09-21

The intramolecular charge transfer properties of a phenyl-end-capped aniline tetramer (ANIH) and a chloro-substituted derivative (ANICl) as organic semiconductors were theoretically studied through the first-principles calculation based on the Marcus-Hush theory. The reorganization energies, intermolecular electronic couplings, angular resolution anisotropic mobilities, and density of states of the two crystals were evaluated. The calculated results demonstrate that both ANIH and ANICl crystals show the higher electron transfer mobilities than the hole-transfer mobilities, which means that the two crystals should prefer to function as n-type organic semiconductors. Furthermore, the angle dependence mobilities of the two crystals show remarkable anisotropic character. The maximum mobility μ max of ANIH and ANICl crystals is 1.3893 and 0.0272 cm 2 V -1 s -1 , which appear at the orientation angles near 176°/356° and 119°/299° of a conducting channel on the a-b reference plane. It is synthetically evaluated that the ANIH crystal possesses relatively lower reorganization energy, higher electronic coupling, and electron transfer mobility, which means that the ANIH crystal may be the more ideal candidate as a high performance n-type organic semiconductor material. The systematic theoretical studies on organic crystals should be conducive to evaluating the charge-transport properties and designing higher performance organic semiconductor materials.

Low-resistance gateless high electron mobility transistors using three-dimensional inverted pyramidal AlGaN/GaN surfaces

NASA Astrophysics Data System (ADS)

So, Hongyun; Senesky, Debbie G.

2016-01-01

In this letter, three-dimensional gateless AlGaN/GaN high electron mobility transistors (HEMTs) were demonstrated with 54% reduction in electrical resistance and 73% increase in surface area compared with conventional gateless HEMTs on planar substrates. Inverted pyramidal AlGaN/GaN surfaces were microfabricated using potassium hydroxide etched silicon with exposed (111) surfaces and metal-organic chemical vapor deposition of coherent AlGaN/GaN thin films. In addition, electrical characterization of the devices showed that a combination of series and parallel connections of the highly conductive two-dimensional electron gas along the pyramidal geometry resulted in a significant reduction in electrical resistance at both room and high temperatures (up to 300 °C). This three-dimensional HEMT architecture can be leveraged to realize low-power and reliable power electronics, as well as harsh environment sensors with increased surface area.

Electron mobility enhancement in ZnO thin films via surface modification by carboxylic acids

NASA Astrophysics Data System (ADS)

Spalenka, Josef W.; Gopalan, Padma; Katz, Howard E.; Evans, Paul G.

2013-01-01

Modifying the surface of polycrystalline ZnO films using a monolayer of organic molecules with carboxylic acid attachment groups increases the field-effect electron mobility and zero-bias conductivity, resulting in improved transistors and transparent conductors. The improvement is consistent with the passivation of defects via covalent bonding of the carboxylic acid and is reversible by exposure to a UV-ozone lamp. The properties of the solvent used for the attachment are crucial because solvents with high acid dissociation constants (Ka) for carboxylic acids lead to high proton activities and etching of the nanometers-thick ZnO films, masking the electronic effect.

Botulinum toxin detection using AlGaN /GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Wang, Yu-Lin; Chu, B. H.; Chen, K. H.; Chang, C. Y.; Lele, T. P.; Tseng, Y.; Pearton, S. J.; Ramage, J.; Hooten, D.; Dabiran, A.; Chow, P. P.; Ren, F.

2008-12-01

Antibody-functionalized, Au-gated AlGaN /GaN high electron mobility transistors (HEMTs) were used to detect botulinum toxin. The antibody was anchored to the gate area through immobilized thioglycolic acid. The AlGaN /GaN HEMT drain-source current showed a rapid response of less than 5s when the target toxin in a buffer was added to the antibody-immobilized surface. We could detect a range of concentrations from 1to10ng/ml. These results clearly demonstrate the promise of field-deployable electronic biological sensors based on AlGaN /GaN HEMTs for botulinum toxin detection.

Center for High-Frequency Microelectronics

DTIC Science & Technology

1992-08-31

34 IEEE Transactions on Electron Devices, 38, No. 6, pp. 1324-1333, June 1991. 185. C. C. Chen, R. K. Mains and G. I. Haddad, " High - Power Generation in...Weiss, J. Hu and W.-P. Hong, "Electronic 0 Properties of Power High Electron Mobility Transistors," Conference on Ballistic Electrons for Transistors...method at higher frequencies than previously believed. - Calculations of high - power generation modes in Si IMPATT devices in the 100-200 GHz range have

ANYmal - A Highly Mobile and Dynamic Quadrupedal Robot

DTIC Science & Technology

2016-10-09

ANYmal - A Highly Mobile and Dynamic Quadrupedal Robot * Marco Hutter1, Christian Gehring2, Dominic Jud1, Andreas Lauber1, C. Dario Bellicoso1...Abstract— This paper introduces ANYmal, a quadrupedal robot that features outstanding mobility and dynamic motion capability. Thanks to novel...compliant joint modules with integrated electronics, the 30 kg, 0.5 m tall robotic dog is torque controllable and very robust against impulsive loads during

AlGaN/GaN HEMTs regrown by MBE on epi-ready semi-insulating GaN-on-sapphire with inhibited interface contamination

NASA Astrophysics Data System (ADS)

Cordier, Y.; Azize, M.; Baron, N.; Chenot, S.; Tottereau, O.; Massies, J.

2007-11-01

In this work, we show that, by carefully designing the subsurface Fe doping profile in SI-GaN templates grown by MOVPE and by optimizing the MBE regrowth conditions, a highly resistive GaN buffer can be achieved on these epi-ready GaN-on-sapphire templates without any addition of acceptors during the regrowth. As a result, high-quality high electron mobility transistors can be fabricated. Furthermore, we report on the excellent properties of two-dimensional electron gas and device performances with electron mobility greater than 2000 cm 2/V s at room temperature and off-state buffer leakage currents as low as 5 μA/mm at 100 V.

Emission and detection of surface acoustic waves by AlGaN/GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Shao, Lei; Zhang, Meng; Banerjee, Animesh; Bhattacharya, Pallab; Pipe, Kevin P.

2011-12-01

Using integrated interdigital transducers (IDTs), we demonstrate the emission of surface acoustic waves (SAWs) by AlGaN/GaN high electron mobility transistors (HEMTs) under certain bias conditions through dynamic screening of the HEMTs vertical field by modulation of its two-dimensional electron gas. We show that a strong SAW signal can be detected if the IDT geometry replicates the HEMT electrode geometry at which RF bias is applied. In addition to characterizing SAW emission during both gate-source and drain-source modulation, we demonstrate SAW detection by HEMTs. Integrated HEMT-IDT structures could enable real-time evaluation of epitaxial degradation as well as high-speed, amplified detection of SAWs.

Wide bandgap BaSnO3 films with room temperature conductivity exceeding 104 S cm−1

PubMed Central

Prakash, Abhinav; Xu, Peng; Faghaninia, Alireza; Shukla, Sudhanshu; Ager, Joel W.; Lo, Cynthia S.; Jalan, Bharat

2017-01-01

Wide bandgap perovskite oxides with high room temperature conductivities and structural compatibility with a diverse family of organic/inorganic perovskite materials are of significant interest as transparent conductors and as active components in power electronics. Such materials must also possess high room temperature mobility to minimize power consumption and to enable high-frequency applications. Here, we report n-type BaSnO3 films grown using hybrid molecular beam epitaxy with room temperature conductivity exceeding 104 S cm−1. Significantly, these films show room temperature mobilities up to 120 cm2 V−1 s−1 even at carrier concentrations above 3 × 1020 cm−3 together with a wide bandgap (3 eV). We examine the mobility-limiting scattering mechanisms by calculating temperature-dependent mobility, and Seebeck coefficient using the Boltzmann transport framework and ab-initio calculations. These results place perovskite oxide semiconductors for the first time on par with the highly successful III–N system, thereby bringing all-transparent, high-power oxide electronics operating at room temperature a step closer to reality. PMID:28474675

Wide bandgap BaSnO 3 films with room temperature conductivity exceeding 10 4 S cm -1

DOE PAGES

Prakash, Abhinav; Xu, Peng; Faghaninia, Alireza; ...

2017-05-05

Wide bandgap perovskite oxides with high room temperature conductivities and structural compatibility with a diverse family of organic/inorganic perovskite materials are of sign ificant interest as transparent conductors and as active components in power electronics. Such materials must also possess high room temperature mobility to minimize power consumption and to enable high-frequency applications. Here, we report n-type BaSnO 3 films grown using hybrid molecular beam epitaxy with room temperature conductivity exceeding 10 4 S cm -1 . Significantly, these films show room temperature mobilities up to 120 cm 2 V -1 s -1 even at carrier concentrations abovemore » 3 × 10 20 cm -3 together with a wide bandgap (3 eV). We examine the mobility-limiting scattering mechanisms by calculating temperature-dependent mobility, and Seebeck coefficient using the Boltzmann transport framework and ab-initio calculations. These results place perovskite oxide semiconductors for the first time on par with the highly successful III-N system, thereby bringing all-transparent, high-power oxide electronics operating at room temperature a step closer to reality.« less

Carrier mobility degradation due to high dose implantation in ultrathin unstrained and strained silicon-on-insulator films

NASA Astrophysics Data System (ADS)

Dupré, C.; Ernst, T.; Hartmann, J.-M.; Andrieu, F.; Barnes, J.-P.; Rivallin, P.; Faynot, O.; Deleonibus, S.; Fazzini, P. F.; Claverie, A.; Cristoloveanu, S.; Ghibaudo, G.; Cristiano, F.

2007-11-01

Based on electrical measurements and transmission electron microscopy (TEM) imaging, we propose an explanation for the electron and hole mobility degradation with gate length reduction in metal-oxide-semiconductor field effect transistors (MOSFETs). We demonstrate that ion implantation, normally used for source/drain doping, is responsible for transport degradation for short-channel devices. Implantation impact on electrons and holes mobility was investigated both on silicon-on-insulator (SOI) and tensile strained silicon-on-insulator (sSOI) substrates. Wafers with ultrathin Si films (from 8 to 35 nm) were Ge implanted at 3 keV and various concentrations (from 5×1014 to 2×1015 atoms cm-2), then annealed at 600 °C for 1 h. Secondary ion mass spectrometry enabled us to quantify the Ge-implanted atoms concentrations. The end-of-range defects impact on mobility was investigated with the pseudo-MOSFET technique. Measurements showed a mobility decrease as the implantation dose increased. We demonstrated that sSOI mobility is more sensitive to implantation than SOI mobility, without any implantation-induced strain relaxation in sSOI (checked using the ultraviolet Raman technique). A 36% (25%) holes (electrons) mobility degradation was measured for sSOI, while SOI presented a 21% mobility degradation for holes and 5% for electrons. Finally, the electrical results were compared with morphological studies. Plan-view TEM showed the presence of interstitial defects formed during ion implantation and annealing. The defect density was estimated to be two times higher in sSOI than in SOI, which is in full agreement with electrical results mentioned before. The results are relevant for the optimization of the source and drain regions of advanced nanoscale SOI and sSOI transistors.

Electron-acoustic phonon coupling in single crystal CH3NH3PbI3 perovskites revealed by coherent acoustic phonons

NASA Astrophysics Data System (ADS)

Mante, Pierre-Adrien; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.; Yartsev, Arkady

2017-02-01

Despite the great amount of attention CH3NH3PbI3 has received for its solar cell application, intrinsic properties of this material are still largely unknown. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. We apply this method to characterize a CH3NH3PbI3 single crystal. We measure the acoustic phonon properties and characterize electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. Our results reveal high electron and hole mobilities of 2,800 and 9,400 cm2 V-1 s-1, respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH3NH3PbI3.

Balance the Carrier Mobility To Achieve High Performance Exciplex OLED Using a Triazine-Based Acceptor.

PubMed

Hung, Wen-Yi; Chiang, Pin-Yi; Lin, Shih-Wei; Tang, Wei-Chieh; Chen, Yi-Ting; Liu, Shih-Hung; Chou, Pi-Tai; Hung, Yi-Tzu; Wong, Ken-Tsung

2016-02-01

A star-shaped 1,3,5-triazine/cyano hybrid molecule CN-T2T was designed and synthesized as a new electron acceptor for efficient exciplex-based OLED emitter by mixing with a suitable electron donor (Tris-PCz). The CN-T2T/Tris-PCz exciplex emission shows a high ΦPL of 0.53 and a small ΔET-S = -0.59 kcal/mol, affording intrinsically efficient fluorescence and highly efficient exciton up-conversion. The large energy level offsets between Tris-PCz and CN-T2T and the balanced hole and electron mobility of Tris-PCz and CN-T2T, respectively, ensuring sufficient carrier density accumulated in the interface for efficient generation of exciplex excitons. Employing a facile device structure composed as ITO/4% ReO3:Tris-PCz (60 nm)/Tris-PCz (15 nm)/Tris-PCz:CN-T2T(1:1) (25 nm)/CN-T2T (50 nm)/Liq (0.5 nm)/Al (100 nm), in which the electron-hole capture is efficient without additional carrier injection barrier from donor (or acceptor) molecule and carriers mobilities are balanced in the emitting layer, leads to a highly efficient green exciplex OLED with external quantum efficiency (EQE) of 11.9%. The obtained EQE is 18% higher than that of a comparison device using an exciplex exhibiting a comparable ΦPL (0.50), in which TCTA shows similar energy levels but higher hole mobility as compared with Tris-PCz. Our results clearly indicate the significance of mobility balance in governing the efficiency of exciplex-based OLED. Exploiting the Tris-PCz:CN-T2T exciplex as the host, we further demonstrated highly efficient yellow and red fluorescent OLEDs by doping 1 wt % Rubrene and DCJTB as emitter, achieving high EQE of 6.9 and 9.7%, respectively.

The role of regioregularity, crystallinity, and chain orientation on electron transport in a high-mobility n-type copolymer.

PubMed

Steyrleuthner, Robert; Di Pietro, Riccardo; Collins, Brian A; Polzer, Frank; Himmelberger, Scott; Schubert, Marcel; Chen, Zhihua; Zhang, Shiming; Salleo, Alberto; Ade, Harald; Facchetti, Antonio; Neher, Dieter

2014-03-19

We investigated the correlation between the polymer backbone structural regularity and the charge transport properties of poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenediimide-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} [P(NDI2OD-T2)], a widely studied semiconducting polymer exhibiting high electron mobility and an unconventional micromorphology. To understand the influence of the chemical structure and crystal packing of conventional regioregular P(NDI2OD-T2) [RR-P(NDI2OD-T2)] on the charge transport, the corresponding regioirregular polymer RI-P(NDI2OD-T2) was synthesized. By combining optical, X-ray, and transmission electron microscopy data, we quantitatively characterized the aggregation, crystallization, and backbone orientation of all of the polymer films, which were then correlated to the electron mobilities in electron-only diodes. By carefully selecting the preparation conditions, we were able to obtain RR-P(NDI2OD-T2) films with similar crystalline structure along the three crystallographic axes but with different orientations of the polymer chains with respect to the substrate surface. RI-P(NDI2OD-T2), though exhibiting a rather similar LUMO structure and energy compared with the regioregular counterpart, displayed a very different packing structure characterized by the formation of ordered stacks along the lamellar direction without detectible π-stacking. Vertical electron mobilities were extracted from the space-charge-limited currents in unipolar devices. We demonstrate the anisotropy of the charge transport along the different crystallographic directions and how the mobility depends on π-stacking but is insensitive to the degree or coherence of lamellar stacking. The comparison between the regioregular and regioirregular polymers also shows how the use of large planar functional groups leads to improved charge transport, with mobilities that are less affected by chemical and structural disorder with respect to classic semicrystalline polymers such as poly(3-hexylthiophene).

High-mobility capacitively-induced two-dimensional electrons in a lateral superlattice potential

DOE PAGES

Lu, Tzu -Ming; Laroche, Dominique; Huang, S. -H.; ...

2016-01-01

In the presence of a lateral periodic potential modulation, two-dimensional electrons may exhibit interesting phenomena, such as a graphene-like energy-momentum dispersion, Bloch oscillations, or the Hofstadter butterfly band structure. To create a sufficiently strong potential modulation using conventional semiconductor heterostructures, aggressive device processing is often required, unfortunately resulting in strong disorder that masks the sought-after effects. Here, we report a novel fabrication process flow for imposing a strong lateral potential modulation onto a capacitively induced two-dimensional electron system, while preserving the host material quality. Using this process flow, the electron density in a patterned Si/SiGe heterostructure can be tuned overmore » a wide range, from 4.4 × 10 10 cm –2 to 1.8 × 10 11 cm –2, with a peak mobility of 6.4 × 10 5 cm 2/V·s. The wide density tunability and high electron mobility allow us to observe sequential emergence of commensurability oscillations as the density, the mobility, and in turn the mean free path, increase. Magnetic-field-periodic quantum oscillations associated with various closed orbits also emerge sequentially with increasing density. We show that, from the density dependence of the quantum oscillations, one can directly extract the steepness of the imposed superlattice potential. Lastly, this result is then compared to a conventional lateral superlattice model potential.« less

Annealing shallow Si/SiO2 interface traps in electron-beam irradiated high-mobility metal-oxide-silicon transistors

NASA Astrophysics Data System (ADS)

Kim, J.-S.; Tyryshkin, A. M.; Lyon, S. A.

2017-03-01

Electron-beam (e-beam) lithography is commonly used in fabricating metal-oxide-silicon (MOS) quantum devices but creates defects at the Si/SiO2 interface. Here, we show that a forming gas anneal is effective at removing shallow defects (≤4 meV below the conduction band edge) created by an e-beam exposure by measuring the density of shallow electron traps in two sets of high-mobility MOS field-effect transistors. One set was irradiated with an electron-beam (10 keV, 40 μC/cm2) and was subsequently annealed in forming gas while the other set remained unexposed. Low temperature (335 mK) transport measurements indicate that the forming gas anneal recovers the e-beam exposed sample's peak mobility (14 000 cm2/Vs) to within a factor of two of the unexposed sample's mobility (23 000 cm2/Vs). Using electron spin resonance (ESR) to measure the density of shallow traps, we find that the two sets of devices are nearly identical, indicating the forming gas anneal is sufficient to anneal out shallow defects generated by the e-beam exposure. Fitting the two sets of devices' transport data to a percolation transition model, we extract a T = 0 percolation threshold density in quantitative agreement with our lowest temperature ESR-measured trap densities.

Development and Validation of Mobile Learning Acceptance Measure

ERIC Educational Resources Information Center

Sharma, Sujeet Kumar; Sarrab, Mohamed; Al-Shihi, Hafedh

2017-01-01

The growth of Smartphone usage, increased acceptance of electronic learning (E-learning), the availability of high reliability mobile networks and need for flexibility in learning have resulted in the growth of mobile learning (M-learning). This has led to a tremendous interest in the acceptance behaviors related to M-learning users among the…

Learning and Digital Inclusion: The ELAMP Project

ERIC Educational Resources Information Center

D'Arcy, Kate

2012-01-01

The Electronic Learning and Mobility Project (ELAMP) was a nationally funded project by the Department for Children, Schools and Families, which ran from 2004 to 2010. The main aim of ELAMP was to improve the education of Traveller children, particularly highly mobile learners. ELAMP focussed upon the use of mobile technology and distance learning…

Highly effective field-effect mobility amorphous InGaZnO TFT mediated by directional silver nanowire arrays.

PubMed

Liu, Hung-Chuan; Lai, Yi-Chun; Lai, Chih-Chung; Wu, Bing-Shu; Zan, Hsiao-Wen; Yu, Peichen; Chueh, Yu-Lun; Tsai, Chuang-Chuang

2015-01-14

In this work, we demonstrate sputtered amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs) with a record high effective field-effect mobility of 174 cm(2)/V s by incorporating silver nanowire (AgNW) arrays to channel electron transport. Compared to the reference counterpart without nanowires, the over 5-fold enhancement in the effective field-effect mobility exhibits clear dependence on the orientation as well as the surface coverage ratio of silver nanowires. Detailed material and device analyses reveal that during the room-temperature IGZO sputtering indium and oxygen diffuse into the nanowire matrix while the nanowire morphology and good contact between IGZO and nanowires are maintained. The unchanged morphology and good interfacial contact lead to high mobility and air-ambient-stable characteristics up to 3 months. Neither hysteresis nor degraded bias stress reliability is observed. The proposed AgNW-mediated a-IGZO TFTs are promising for development of large-scale, flexible, transparent electronics.

Optimization of a Differential Ion Mobility Spectrometry-Tandem Mass Spectrometry Method for High-Throughput Analysis of Nicotine and Related Compounds: Application to Electronic Cigarette Refill Liquids.

PubMed

Regueiro, Jorge; Giri, Anupam; Wenzl, Thomas

2016-06-21

Fast market penetration of electronic cigarettes is leading to an exponentially growing number of electronic refill liquids with different nicotine contents and an endless list of flavors. Therefore, rapid and simple methods allowing a fast screening of these products are necessary to detect harmful substances which can negatively impact the health of consumers. In this regard, the present work explores the capabilities of differential ion mobility spectrometry coupled to tandem mass spectrometry for high-throughput analysis of nicotine and 11 related compounds in commercial refill liquids for electronic cigarettes. The influence of main factors affecting the ion mobility separation, such as modifier types and concentration, separation voltage, and temperature, was systematically investigated. Despite small molecular weight differences among the studied compounds, a good separation was achieved in the ion mobility cell under the optimized conditions, which involved the use of ethanol as a polar gas-phase chemical modifier. Indeed, differential ion mobility was able to resolve (resolution >4) nicotine from its structural isomer anabasine without the use of any chromatographic separation. The quantitative performance of the proposed method was then evaluated, showing satisfactory precision (RSD ≤ 16%) and recoveries ranging from 85 to 100% for nicotine, and from 84 to 126% for the rest of the target analytes. Several commercial electronic cigarette refill liquids were analyzed to demonstrate the applicability of the method. In some cases, significant differences were found between labeled and measured levels of nicotine. Anatabine, cotinine, myosmine, and nornicotine were also found in some of the analyzed samples.

High-Performance, Solution-Processed Quantum Dot Light-Emitting Field-Effect Transistors with a Scandium-Incorporated Indium Oxide Semiconductor.

PubMed

He, Penghui; Jiang, Congbiao; Lan, Linfeng; Sun, Sheng; Li, Yizhi; Gao, Peixiong; Zhang, Peng; Dai, Xingqiang; Wang, Jian; Peng, Junbiao; Cao, Yong

2018-05-22

Light-emitting field-effect transistors (LEFETs) have attained great attention due to their special characteristics of both the switching capacity and the electroluminescence capacity. However, high-performance LEFETs with high mobility, high brightness, and high efficiency have not been realized due to the difficulty in developing high electron and hole mobility materials with suitable band structures. In this paper, quantum dot hybrid LEFETs (QD-HLEFETs) combining high-luminous-efficiency quantum dots (QDs) and a solution-processed scandium-incorporated indium oxide (Sc:In 2 O 3 ) semiconductor were demonstrated. The red QD-HLEFET showed high electrical and optical performance with an electron mobility of 0.8 cm 2 V -1 s -1 , a maximum brightness of 13 400 cd/m 2 , and a maximum external quantum efficiency of 8.7%. The high performance of the QD-HLEFET is attributed to the good energy band matching between Sc:In 2 O 3 and QDs and the balanced hole and electron injection (less exciton nonradiative recombination). In addition, incorporation of Sc into In 2 O 3 can suppress the oxygen vacancy and free carrier generation and brings about excellent current and optical modulation (the on/off current ratio is 10 5 and the on/off brightness ratio is 10 6 ).

First-principle simulations of electronic structure in semicrystalline polyethylene

NASA Astrophysics Data System (ADS)

Moyassari, A.; Unge, M.; Hedenqvist, M. S.; Gedde, U. W.; Nilsson, F.

2017-05-01

In order to increase our fundamental knowledge about high-voltage cable insulation materials, realistic polyethylene (PE) structures, generated with a novel molecular modeling strategy, have been analyzed using first principle electronic structure simulations. The PE structures were constructed by first generating atomistic PE configurations with an off-lattice Monte Carlo method and then equilibrating the structures at the desired temperature and pressure using molecular dynamics simulations. Semicrystalline, fully crystalline and fully amorphous PE, in some cases including crosslinks and short-chain branches, were analyzed. The modeled PE had a structure in agreement with established experimental data. Linear-scaling density functional theory (LS-DFT) was used to examine the electronic structure (e.g., spatial distribution of molecular orbitals, bandgaps and mobility edges) on all the materials, whereas conventional DFT was used to validate the LS-DFT results on small systems. When hybrid functionals were used, the simulated bandgaps were close to the experimental values. The localization of valence and conduction band states was demonstrated. The localized states in the conduction band were primarily found in the free volume (result of gauche conformations) present in the amorphous regions. For branched and crosslinked structures, the localized electronic states closest to the valence band edge were positioned at branches and crosslinks, respectively. At 0 K, the activation energy for transport was lower for holes than for electrons. However, at room temperature, the effective activation energy was very low (˜0.1 eV) for both holes and electrons, which indicates that the mobility will be relatively high even below the mobility edges and suggests that charge carriers can be hot carriers above the mobility edges in the presence of a high electrical field.

Molecular beam epitaxial growth of high-quality InSb on InP and GaAs substrates

NASA Technical Reports Server (NTRS)

Oh, J. E.; Bhattacharya, P. K.; Chen, Y. C.; Tsukamoto, S.

1989-01-01

Epitaxial layers of InSb were grown on InP and GaAs substrates by molecular beam epitaxy. The dependence of the epilayer quality on flux ratio, J sub Sb4/J sub In, was studied. Deviation from an optimum value of J sub Sb4/J sub In (approx. 2) during growth led to deterioration in the surface morphology and the electrical and crystalline qualities of the films. Room temperature electron mobilities as high as 70,000 and 53,000 sq cm /V-s were measured in InSb layers grown on InP and GaAs substrates, respectively. Unlike the previous results, the conductivity in these films is n-type even at T = 13 K, and no degradation of the electron mobility due to the high density of dislocations was observed. The measured electron mobilities (and carrier concentrations) at 77 K in InSb layers grown on InP and GaAs substrates are 110,000 sq cm/V-s (3 x 10(15) cm(-3)) and 55,000 sq cm/V-s (4.95 x 10(15) cm(-3)), respectively, suggesting their application to electronic devices at cryogenic temperatures.

Intrinsic mobility limit for anisotropic electron transport in Alq3.

PubMed

Drew, A J; Pratt, F L; Hoppler, J; Schulz, L; Malik-Kumar, V; Morley, N A; Desai, P; Shakya, P; Kreouzis, T; Gillin, W P; Kim, K W; Dubroka, A; Scheuermann, R

2008-03-21

Muon spin relaxation has been used to probe the charge carrier motion in the molecular conductor Alq3 (tris[8-hydroxy-quinoline] aluminum). At 290 K, the magnetic field dependence of the muon spin relaxation corresponds to that expected for highly anisotropic intermolecular electron hopping. Intermolecular mobility in the fast hopping direction has been found to be 0.23+/-0.03 cm2 V-1 s(-1) in the absence of an electric- field gradient, increasing to 0.32+/-0.06 cm2 V-1 s(-1) in an electric field gradient of 1 MV m(-1). These intrinsic mobility values provide an estimate of the upper limit for mobility achievable in bulk material.

Enhancement of hole mobility in InSe monolayer via an InSe and black phosphorus heterostructure.

PubMed

Ding, Yi-Min; Shi, Jun-Jie; Xia, Congxin; Zhang, Min; Du, Juan; Huang, Pu; Wu, Meng; Wang, Hui; Cen, Yu-Lang; Pan, Shu-Hang

2017-10-05

To enhance the low hole mobility (∼40 cm 2 V -1 s -1 ) of InSe monolayer, a novel two-dimensional (2D) van der Waals heterostructure made of InSe and black phosphorus (BP) monolayers with high hole mobility (∼10 3 cm 2 V -1 s -1 ) has been constructed and its structural and electronic properties are investigated using first-principles calculations. We find that the InSe/BP heterostructure exhibits a direct band gap of 1.39 eV and type-II band alignment with electrons (holes) located in the InSe (BP) layer. The band offsets of InSe and BP are 0.78 eV for the conduction band minimum and 0.86 eV for the valence band maximum, respectively. Surprisingly, the hole mobility in the InSe/BP heterostructure exceeds 10 4 cm 2 V -1 s -1 , which is one order of magnitude larger than the hole mobility of BP and three orders larger than that of the InSe monolayer. The electron mobility is also increased to 3 × 10 3 cm 2 V -1 s -1 . The physical reason has been analyzed deeply, and a universal method is proposed to improve the carrier mobility of 2D materials by forming heterostructures with them and other 2D materials with complementary properties. The InSe/BP heterostructure can thus be widely used in nanoscale InSe-based field-effect transistors, photodetectors and photovoltaic devices due to its type-II band alignment and high carrier mobility.

Research the mobile phone operation interfaces for vision-impairment.

PubMed

Yao, Yen-Ting; Leung, Cherng-Yee

2012-01-01

Due to the vision-impaired users commonly having difficulty with mobile-phone function operations and adaption any manufacturer's user interface design, the goals for this research are established for evaluating how to improve for them the function operation convenience and user interfaces of either mobile phones or electronic appliances in the market currently. After applying collecting back 30 effective questionnaires from 30 vision-impairment, the comments have been concluded from this research include: (1) All mobile phone manufactures commonly ignorant of the vision-impairment difficulty with operating mobile phone user interfaces; (2) The vision-impairment preferential with audio alert signals; (3) The vision-impairment incapable of mobile-phone procurement independently unless with assistance from others; (4) Preferential with adding touch-usage interface design by the vision-impairment; in contrast with the least requirement for such functions as braille, enlarging keystroke size and diversifying-function control panel. With exploring the vision-impairment's necessary improvements and obstacles for mobile phone interface operation, this research is established with goals for offering reference possibly applied in electronic appliance design and . Hopefully, the analysis results of this research could be used as data references for designing electronic and high-tech products and promoting more usage convenience for those vision-impaired.

Electron Mobilities and Effective Masses in InGaAs/InAlAs HEMT Structures with High In Content

NASA Astrophysics Data System (ADS)

Yuzeeva, N. A.; Sorokoumova, A. V.; Lunin, R. A.; Oveshnikov, L. N.; Galiev, G. B.; Klimov, E. A.; Lavruchin, D. V.; Kulbachinskii, V. A.

2016-12-01

InxGa_{1-{x}}As/InyAl_{1-{y}}As HEMT structures {δ}-doped by Si were grown by molecular beam epitaxy on InP substrate. We investigated the influence of the In content on the electron mobilities and effective masses in dimensionally quantized subbands. The electron effective masses were determined by the temperature dependence of the amplitude of the Shubnikov-de Haas effect at 1.6 and 4.2 K. We found that the more the In content in quantum well (QW), the less the electron effective masses. The mobilities are higher in HEMT structures with wider and deeper QW. The energy band diagrams were calculated by using Vegard's law for basic parameters. The calculated band diagrams are in a good agreement with the experimental data of photoluminescence spectra.

Gallium Nitride (GaN) High Power Electronics (FY11)

DTIC Science & Technology

2012-01-01

GaN films grown by metal-organic chemical vapor deposition (MOCVD) and ~1010 in films grown by molecular beam epitaxy (MBE) when they are deposited...inductively coupled plasma I-V current-voltage L-HVPE low doped HVPE MBE molecular beam epitaxy MOCVD metal-organic chemical vapor deposition...figure of merit HEMT high electron mobility transistor H-HVPE high doped HVPE HPE high power electronics HVPE hydride vapor phase epitaxy ICP

Tunable electron heating induced giant magnetoresistance in the high mobility GaAs/AlGaAs 2D electron system

DOE PAGES

Wang, Zhuo; Samaraweera, R. L.; Reichl, C.; ...

2016-12-07

Electron-heating induced by a tunable, supplementary dc-current (I dc) helps to vary the observed magnetoresistance in the high mobility GaAs/AlGaAs 2D electron system. The magnetoresistance at B = 0.3 T is shown to progressively change from positive to negative with increasing Idc, yielding negative giant-magnetoresistance at the lowest temperature and highest I dc. A two-term Drude model successfully fits the data at all Idc and T. The results indicate that carrier heating modifies a conductivity correction σ 1, which undergoes sign reversal from positive to negative with increasing I dc, and this is responsible for the observed crossover from positive-more » to negative- magnetoresistance, respectively, at the highest B.« less

Optically detected cyclotron resonance investigations on 4H and 6H SiC: Band-structure and transport properties

NASA Astrophysics Data System (ADS)

Meyer, B. K.; Hofmann, D. M.; Volm, D.; Chen, W. M.; Son, N. T.; Janzén, E.

2000-02-01

We present experimental data on the band-structure and high-mobility transport properties of 6H and 4H-SiC epitaxial films based on optically detected cyclotron resonance investigations. From the orientational dependence of the electron effective mass in 6H-SiC we obtain direct evidence for the camels back nature of the conduction band between the M and L points. The broadening of the resonance signal in 4H-SiC as a function of temperature is used to extract information on electron mobilities and to conclude on the role of the different scattering mechanisms. Under high microwave powers an enhancement of the electron effective mass is found which is explained by a coupling of the electrons with longitudinal optical phonons.

Microsystems, Space Qualified Electronics and Mobile Sensor Platforms for Harsh Environment Applications and Planetary Exploration

NASA Technical Reports Server (NTRS)

Hunter, Gary W.; Okojie, Robert S.; Krasowski, Michael J.; Beheim, Glenn M.; Fralick, Gustave C.; Wrbanek, John D.; Greenberg, Paul S.; Xu, Jennifer

2007-01-01

NASA Glenn Research Center is presently developing and applying a range of sensor and electronic technologies that can enable future planetary missions. These include space qualified instruments and electronics, high temperature sensors for Venus missions, mobile sensor platforms, and Microsystems for detection of a range of chemical species and particulates. A discussion of each technology area and its level of maturity is given. It is concluded that there is a strong need for low power devices which can be mobile and provide substantial characterization of the planetary environment where and when needed. While a given mission will require tailoring of the technology for the application, basic tools which can enable new planetary missions are being developed.

Macroscopic phase separation in high-temperature superconductors

PubMed Central

Wen, Hai-Hu

2000-01-01

High-temperature superconductivity is recovered by introducing extra holes to the Cu-O planes, which initially are insulating with antiferromagnetism. In this paper I present data to show the macroscopic electronic phase separation that is caused by either mobile doping or electronic instability in the overdoped region. My results clearly demonstrate that the electronic inhomogeneity is probably a general feature of high-temperature superconductors. PMID:11027323

High quality and uniformity GaN grown on 150 mm Si substrate using in-situ NH3 pulse flow cleaning process

NASA Astrophysics Data System (ADS)

Ji, Panfeng; Yang, Xuelin; Feng, Yuxia; Cheng, Jianpeng; Zhang, Jie; Hu, Anqi; Song, Chunyan; Wu, Shan; Shen, Jianfei; Tang, Jun; Tao, Chun; Pan, Yaobo; Wang, Xinqiang; Shen, Bo

2017-04-01

By using in-situ NH3 pulse flow cleaning method, we have achieved the repeated growth of high quality and uniformity GaN and AlGaN/GaN high electron mobility transistors (HEMTs) on 150 mm Si substrate. The two dimensional electron gas (2DEG) mobility is 2200 cm2/Vs with an electron density of 7.3 × 1012 cm-2. The sheet resistance is 305 ± 4 Ω/□ with ±1.3% variation. The achievement is attributed to the fact that this method can significantly remove the Al, Ga, etc. metal droplets coating on the post growth flow flange and reactor wall which are difficult to clean by normal bake process under H2 ambient.

Improved linearity in AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors with nonlinear polarization dielectric

NASA Astrophysics Data System (ADS)

Gao, Tao; Xu, Ruimin; Kong, Yuechan; Zhou, Jianjun; Kong, Cen; Dong, Xun; Chen, Tangsheng

2015-06-01

We demonstrate highly improved linearity in a nonlinear ferroelectric of Pb(Zr0.52Ti0.48)-gated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT). Distinct double-hump feature in the transconductance-gate voltage (gm-Vg) curve is observed, yielding remarkable enhancement in gate voltage swing as compared to MIS-HEMT with conventional linear gate dielectric. By incorporating the ferroelectric polarization into a self-consistent calculation, it is disclosed that in addition to the common hump corresponding to the onset of electron accumulation, the second hump at high current level is originated from the nonlinear polar nature of ferroelectric, which enhances the gate capacitance by increasing equivalent dielectric constant nonlinearly. This work paves a way for design of high linearity GaN MIS-HEMT by exploiting the nonlinear properties of dielectric.

Impact of metal gates on remote phonon scattering in titanium nitride/hafnium dioxide n-channel metal-oxide-semiconductor field effect transistors-low temperature electron mobility study

NASA Astrophysics Data System (ADS)

Maitra, Kingsuk; Frank, Martin M.; Narayanan, Vijay; Misra, Veena; Cartier, Eduard A.

2007-12-01

We report low temperature (40-300 K) electron mobility measurements on aggressively scaled [equivalent oxide thickness (EOT)=1 nm] n-channel metal-oxide-semiconductor field effect transistors (nMOSFETs) with HfO2 gate dielectrics and metal gate electrodes (TiN). A comparison is made with conventional nMOSFETs containing HfO2 with polycrystalline Si (poly-Si) gate electrodes. No substantial change in the temperature acceleration factor is observed when poly-Si is replaced with a metal gate, showing that soft optical phonons are not significantly screened by metal gates. A qualitative argument based on an analogy between remote phonon scattering and high-resolution electron energy-loss spectroscopy (HREELS) is provided to explain the underlying physics of the observed phenomenon. It is also shown that soft optical phonon scattering is strongly damped by thin SiO2 interface layers, such that room temperature electron mobility values at EOT=1 nm become competitive with values measured in nMOSFETs with SiON gate dielectrics used in current high performance processors.

Influence of acceptor on charge mobility in stacked π-conjugated polymers

NASA Astrophysics Data System (ADS)

Sun, Shih-Jye; Menšík, Miroslav; Toman, Petr; Gagliardi, Alessio; Král, Karel

2018-02-01

We present a quantum molecular model to calculate mobility of π-stacked P3HT polymer layers with electron acceptor dopants coupled next to side groups in random position with respect to the linear chain. The hole density, the acceptor LUMO energy and the hybridization transfer integral between the acceptor and polymer were found to be very critical factors to the final hole mobility. For a dopant LUMO energy close and high above the top of the polymer valence band we have found a significant mobility increase with the hole concentration and with the dopant LUMO energy approaching the top of the polymer valence band. Higher mobility was achieved for small values of hybridization transfer integral between polymer and the acceptor, corresponding to the case of weakly bound acceptor. Strong couplings between the polymer and the acceptor with Coulomb repulsion interactions induced from the electron localizations was found to suppress the hole mobility.

Mobile Guide System Using Problem-Solving Strategy for Museum Learning: A Sequential Learning Behavioural Pattern Analysis

ERIC Educational Resources Information Center

Sung, Y.-T.; Hou, H.-T.; Liu, C.-K.; Chang, K.-E.

2010-01-01

Mobile devices have been increasingly utilized in informal learning because of their high degree of portability; mobile guide systems (or electronic guidebooks) have also been adopted in museum learning, including those that combine learning strategies and the general audio-visual guide systems. To gain a deeper understanding of the features and…

High mobility In0.75Ga0.25As quantum wells in an InAs phonon lattice

NASA Astrophysics Data System (ADS)

Chen, C.; Holmes, S. N.; Farrer, I.; Beere, H. E.; Ritchie, D. A.

2018-03-01

InGaAs based devices are great complements to silicon for CMOS, as they provide an increased carrier saturation velocity, lower operating voltage and reduced power dissipation (International technology roadmap for semiconductors (www.itrs2.net)). In this work we show that In0.75Ga0.25As quantum wells with a high mobility, 15 000 to 20 000 cm2 V-1 s-1 at ambient temperature, show an InAs-like phonon with an energy of 28.8 meV, frequency of 232 cm-1 that dominates the polar-optical mode scattering from  ˜70 K to 300 K. The measured optical phonon frequency is insensitive to the carrier density modulated with a surface gate or LED illumination. We model the electron scattering mechanisms as a function of temperature and identify mechanisms that limit the electron mobility in In0.75Ga0.25As quantum wells. Background impurity scattering starts to dominate for temperatures  <100 K. In the high mobility In0.75Ga0.25As quantum well, GaAs-like phonons do not couple to the electron gas unlike the case of In0.53Ga0.47As quantum wells.

Single shot spin readout using a cryogenic high-electron-mobility transistor amplifier at sub-Kelvin temperatures

NASA Astrophysics Data System (ADS)

Tracy, L. A.; Luhman, D. R.; Carr, S. M.; Bishop, N. C.; Ten Eyck, G. A.; Pluym, T.; Wendt, J. R.; Lilly, M. P.; Carroll, M. S.

2016-02-01

We use a cryogenic high-electron-mobility transistor circuit to amplify the current from a single electron transistor, allowing for demonstration of single shot readout of an electron spin on a single P donor in Si with 100 kHz bandwidth and a signal to noise ratio of ˜9. In order to reduce the impact of cable capacitance, the amplifier is located adjacent to the Si sample, at the mixing chamber stage of a dilution refrigerator. For a current gain of ˜ 2.7 × 10 3 , the power dissipation of the amplifier is 13 μW, the bandwidth is ˜ 1.3 MHz, and for frequencies above 300 kHz the current noise referred to input is ≤ 70 fA/ √{ Hz } . With this amplification scheme, we are able to observe coherent oscillations of a P donor electron spin in isotopically enriched 28Si with 96% visibility.

Spray-combustion synthesis: Efficient solution route to high-performance oxide transistors

PubMed Central

Yu, Xinge; Smith, Jeremy; Zhou, Nanjia; Zeng, Li; Guo, Peijun; Xia, Yu; Alvarez, Ana; Aghion, Stefano; Lin, Hui; Yu, Junsheng; Chang, Robert P. H.; Bedzyk, Michael J.; Ferragut, Rafael; Marks, Tobin J.; Facchetti, Antonio

2015-01-01

Metal-oxide (MO) semiconductors have emerged as enabling materials for next generation thin-film electronics owing to their high carrier mobilities, even in the amorphous state, large-area uniformity, low cost, and optical transparency, which are applicable to flat-panel displays, flexible circuitry, and photovoltaic cells. Impressive progress in solution-processed MO electronics has been achieved using methodologies such as sol gel, deep-UV irradiation, preformed nanostructures, and combustion synthesis. Nevertheless, because of incomplete lattice condensation and film densification, high-quality solution-processed MO films having technologically relevant thicknesses achievable in a single step have yet to be shown. Here, we report a low-temperature, thickness-controlled coating process to create high-performance, solution-processed MO electronics: spray-combustion synthesis (SCS). We also report for the first time, to our knowledge, indium-gallium-zinc-oxide (IGZO) transistors having densification, nanoporosity, electron mobility, trap densities, bias stability, and film transport approaching those of sputtered films and compatible with conventional fabrication (FAB) operations. PMID:25733848

Spray-combustion synthesis: efficient solution route to high-performance oxide transistors.

PubMed

Yu, Xinge; Smith, Jeremy; Zhou, Nanjia; Zeng, Li; Guo, Peijun; Xia, Yu; Alvarez, Ana; Aghion, Stefano; Lin, Hui; Yu, Junsheng; Chang, Robert P H; Bedzyk, Michael J; Ferragut, Rafael; Marks, Tobin J; Facchetti, Antonio

2015-03-17

Metal-oxide (MO) semiconductors have emerged as enabling materials for next generation thin-film electronics owing to their high carrier mobilities, even in the amorphous state, large-area uniformity, low cost, and optical transparency, which are applicable to flat-panel displays, flexible circuitry, and photovoltaic cells. Impressive progress in solution-processed MO electronics has been achieved using methodologies such as sol gel, deep-UV irradiation, preformed nanostructures, and combustion synthesis. Nevertheless, because of incomplete lattice condensation and film densification, high-quality solution-processed MO films having technologically relevant thicknesses achievable in a single step have yet to be shown. Here, we report a low-temperature, thickness-controlled coating process to create high-performance, solution-processed MO electronics: spray-combustion synthesis (SCS). We also report for the first time, to our knowledge, indium-gallium-zinc-oxide (IGZO) transistors having densification, nanoporosity, electron mobility, trap densities, bias stability, and film transport approaching those of sputtered films and compatible with conventional fabrication (FAB) operations.

High-mobility strained organic semiconductors (Conference Presentation)

NASA Astrophysics Data System (ADS)

Takeya, Jun; Matsui, H.; Kubo, T.; Hausermann, Roger

2016-11-01

Small molecular organic semiconductor crystals form interesting electronic systems of periodically arranged "charge clouds" whose mutual electronic coupling determines whether or not electronic states can be coherent over fluctuating molecules. This presentation focuses on two methods to reduce molecular fluctuation, which strongly restricts mobility of highly mobile charge in single-crystal organic transistors. The first example is to apply external hydrostatic pressure. Using Hall-effect measurement for pentacene FETs, which tells us the extent of the electronic coherence, we found a crossover from hopping-like transport of nearly localized charge to band transport of delocalized charge with full coherence. As the result of temperature dependence measurement, it turned out that reduced molecular fluctuation is mainly responsible for the crossover. The second is to apply uniaxial strain to single-crystal organic FETs. We applied stain by bending thin films of newly synthesized decyldinaphthobenzodithiophene (C10-DNBDT) on plastic substrate so that 3% strain is uniaxially applied. As the result, the room-temperature mobility increased by the factor of 1.7. In-depth analysis using X-ray diffraction (XRD) measurements and density functional theory (DFT) calculations reveal the origin to be the suppression of the thermal fluctuation of the individual molecules, which is confirmed by temperature dependent measurements. Our findings show that compressing the crystal structure directly restricts the vibration of the molecules, thus suppressing dynamic disorder, a unique mechanism in organic semiconductors. Since strain can easily be induced during the fabrication process, these findings can directly be exploited to build high performance organic devices.

Generating free charges by carrier multiplication in quantum dots for highly efficient photovoltaics.

PubMed

Ten Cate, Sybren; Sandeep, C S Suchand; Liu, Yao; Law, Matt; Kinge, Sachin; Houtepen, Arjan J; Schins, Juleon M; Siebbeles, Laurens D A

2015-02-17

CONSPECTUS: In a conventional photovoltaic device (solar cell or photodiode) photons are absorbed in a bulk semiconductor layer, leading to excitation of an electron from a valence band to a conduction band. Directly after photoexcitation, the hole in the valence band and the electron in the conduction band have excess energy given by the difference between the photon energy and the semiconductor band gap. In a bulk semiconductor, the initially hot charges rapidly lose their excess energy as heat. This heat loss is the main reason that the theoretical efficiency of a conventional solar cell is limited to the Shockley-Queisser limit of ∼33%. The efficiency of a photovoltaic device can be increased if the excess energy is utilized to excite additional electrons across the band gap. A sufficiently hot charge can produce an electron-hole pair by Coulomb scattering on a valence electron. This process of carrier multiplication (CM) leads to formation of two or more electron-hole pairs for the absorption of one photon. In bulk semiconductors such as silicon, the energetic threshold for CM is too high to be of practical use. However, CM in nanometer sized semiconductor quantum dots (QDs) offers prospects for exploitation in photovoltaics. CM leads to formation of two or more electron-hole pairs that are initially in close proximity. For photovoltaic applications, these charges must escape from recombination. This Account outlines our recent progress in the generation of free mobile charges that result from CM in QDs. Studies of charge carrier photogeneration and mobility were carried out using (ultrafast) time-resolved laser techniques with optical or ac conductivity detection. We found that charges can be extracted from photoexcited PbS QDs by bringing them into contact with organic electron and hole accepting materials. However, charge localization on the QD produces a strong Coulomb attraction to its counter charge in the organic material. This limits the production of free charges that can contribute to the photocurrent in a device. We show that free mobile charges can be efficiently produced via CM in solids of strongly coupled PbSe QDs. Strong electronic coupling between the QDs resulted in a charge carrier mobility of the order of 1 cm(2) V(-1) s(-1). This mobility is sufficiently high so that virtually all electron-hole pairs escape from recombination. The impact of temperature on the CM efficiency in PbSe QD solids was also studied. We inferred that temperature has no observable effect on the rate of cooling of hot charges nor on the CM rate. We conclude that exploitation of CM requires that charges have sufficiently high mobility to escape from recombination. The contribution of CM to the efficiency of photovoltaic devices can be further enhanced by an increase of the CM efficiency above the energetic threshold of twice the band gap. For large-scale applications in photovoltaic devices, it is important to develop abundant and nontoxic materials that exhibit efficient CM.

Zigzag-Elongated Fused π-Electronic Core: A Molecular Design Strategy to Maximize Charge-Carrier Mobility.

PubMed

Yamamoto, Akito; Murata, Yoshinori; Mitsui, Chikahiko; Ishii, Hiroyuki; Yamagishi, Masakazu; Yano, Masafumi; Sato, Hiroyasu; Yamano, Akihito; Takeya, Jun; Okamoto, Toshihiro

2018-01-01

Printed and flexible electronics requires solution-processable organic semiconductors with a carrier mobility (μ) of ≈10 cm 2 V -1 s -1 as well as high chemical and thermal durability. In this study, chryseno[2,1- b :8,7- b ']dithiophene (ChDT) and its derivatives, which have a zigzag-elongated fused π-electronic core (π-core) and a peculiar highest occupied molecular orbital (HOMO) configuration, are reported as materials with conceptually new semiconducting π-cores. ChDT and its derivatives are prepared by a versatile synthetic procedure. A comprehensive investigation reveals that the ChDT π-core exhibits increasing structural stability in the bulk crystal phase, and that it is unaffected by a variation of the transfer integral, induced by the perpetual molecular motion of organic materials owing to the combination of its molecular shape and its particular HOMO configuration. Notably, ChDT derivatives exhibit excellent chemical and thermal stability, high charge-carrier mobility under ambient conditions (μ ≤ 10 cm 2 V -1 s -1 ), and a crystal phase that is highly stable, even at temperatures above 250 °C.

AlGaAs/InGaAs/AlGaAs double pulse doped pseudomorphic high electron mobility transistor structures on InGaAs substrates

NASA Astrophysics Data System (ADS)

Hoke, W. E.; Lyman, P. S.; Mosca, J. J.; McTaggart, R. A.; Lemonias, P. J.; Beaudoin, R. M.; Torabi, A.; Bonner, W. A.; Lent, B.; Chou, L.-J.; Hsieh, K. C.

1997-10-01

Double pulse doped AlGaAs/InGaAs/AlGaAs pseudomorphic high electron mobility transistor (PHEMT) structures have been grown on InxGa1-xAs (x=0.025-0.07) substrates using molecular beam epitaxy. A strain compensated, AlGaInAs/GaAs superlattice was used for improved resistivity and breakdown. Excellent electrical and optical properties were obtained for 110-Å-thick InGaAs channel layers with indium concentrations up to 31%. A room temperature mobility of 6860 cm2/V s with 77 K sheet density of 4.0×1012cm-2 was achieved. The InGaAs channel photoluminescence intensity was equivalent to an analogous structure on a GaAs substrate. To reduce strain PHEMT structures with a composite InGaP/AlGaAs Schottky layer were also grown. The structures also exhibited excellent electrical and optical properties. Transmission electron micrographs showed planar channel interfaces for highly strained In0.30Ga0.70As channel layers.

1.5-V-threshold-voltage Schottky barrier normally-off AlGaN/GaN high-electron-mobility transistors with f T/f max of 41/125 GHz

NASA Astrophysics Data System (ADS)

Hou, Bin; Ma, Xiaohua; Yang, Ling; Zhu, Jiejie; Zhu, Qing; Chen, Lixiang; Mi, Minhan; Zhang, Hengshuang; Zhang, Meng; Zhang, Peng; Zhou, Xiaowei; Hao, Yue

2017-07-01

In this paper, a normally-off AlGaN/GaN high-electron-mobility transistors (HEMT) fabricated using inductively coupled plasma (ICP) CF4 plasma recessing and an implantation technique is reported. A gate-to-channel distance of ˜10 nm and an equivalent negative fluorine sheet charge density of -1.21 × 1013 cm-2 extracted using a simple threshold voltage (V th) analytical model result in a high V th of 1.5 V, a peak transconductance of 356 mS/mm, and a subthreshold slope of 133 mV/decade. A small degradation of channel mobility leads to a high RF performance with f T/f max of 41/125 GHz, resulting in a record high f T × L g product of 10.66 GHz·µm among Schottky barrier AlGaN/GaN normally-off HEMTs with V th exceeding 1 V, to the best of our knowledge.

Development of an electronic medical report delivery system to 3G GSM mobile (cellular) phones for a medical imaging department.

PubMed

Lim, Eugene Y; Lee, Chiang; Cai, Weidong; Feng, Dagan; Fulham, Michael

2007-01-01

Medical practice is characterized by a high degree of heterogeneity in collaborative and cooperative patient care. Fast and effective communication between medical practitioners can improve patient care. In medical imaging, the fast delivery of medical reports to referring medical practitioners is a major component of cooperative patient care. Recently, mobile phones have been actively deployed in telemedicine applications. The mobile phone is an ideal medium to achieve faster delivery of reports to the referring medical practitioners. In this study, we developed an electronic medical report delivery system from a medical imaging department to the mobile phones of the referring doctors. The system extracts a text summary of medical report and a screen capture of diagnostic medical image in JPEG format, which are transmitted to 3G GSM mobile phones.

Structure and transport in high pressure oxygen sputter-deposited BaSnO{sub 3−δ}

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

Ganguly, Koustav; Ambwani, Palak; Xu, Peng

BaSnO{sub 3} has recently been identified as a high mobility wide gap semiconductor with significant potential for room temperature oxide electronics. Here, a detailed study of the high pressure oxygen sputter-deposition, microstructure, morphology, and stoichiometry of epitaxial BaSnO{sub 3} on SrTiO{sub 3}(001) and MgO(001) is reported, optimized conditions resulting in single-phase, relaxed, close to stoichiometric films. Most significantly, vacuum annealing is established as a facile route to n-doped BaSnO{sub 3−δ}, leading to electron densities above 10{sup 19} cm{sup −3}, 5 mΩ cm resistivities, and room temperature mobility of 20 cm{sup 2} V{sup −1} s{sup −1} in 300-Å-thick films on MgO(001).more » Mobility limiting factors, and the substantial scope for their improvement, are discussed.« less

Enhanced performance of the Westinghouse Series 1000 Mobile Satellite Telephone System

NASA Technical Reports Server (NTRS)

Martinson, Richard E.

1995-01-01

The Westinghouse Series 1000 Mobile Satellite Telephone System is designed for land mobile, maritime, and fixed site land applications. The product currently operates on the Optus Mobilesat system in Australia and will operate on American Mobile Satellite Corporation's (AMSC) Skycell service in the U.S. and TMI Communications' (TMIC) MSAT service in Canada. The architecture allows the same transceiver electronics to be used for diverse mobile applications. Advanced antenna designs have made land mobile satellite communications a reality. This paper details the unique high performance product and its configuration for the vehicle mounted land mobile application.

Solution-processable ambipolar diketopyrrolopyrrole-selenophene polymer with unprecedentedly high hole and electron mobilities.

PubMed

Lee, Junghoon; Han, A-Reum; Kim, Jonggi; Kim, Yiho; Oh, Joon Hak; Yang, Changduk

2012-12-26

There is a fast-growing demand for polymer-based ambipolar thin-film transistors (TFTs), in which both n-type and p-type transistor operations are realized in a single layer, while maintaining simplicity in processing. Research progress toward this end is essentially fueled by molecular engineering of the conjugated backbones of the polymers and the development of process architectures for device fabrication, which has recently led to hole and electron mobilities of more than 1.0 cm(2) V(-1) s(-1). However, ambipolar polymers with even higher performance are still required. By taking into account both the conjugated backbone and side chains of the polymer component, we have developed a dithienyl-diketopyrrolopyrrole (TDPP) and selenophene containing polymer with hybrid siloxane-solubilizing groups (PTDPPSe-Si). A synergistic combination of rational polymer backbone design, side-chain dynamics, and solution processing affords an enormous boost in ambipolar TFT performance, resulting in unprecedentedly high hole and electron mobilities of 3.97 and 2.20 cm(2) V(-1) s(-1), respectively.

Wedge-Shaped GaN Nanowalls: A Potential Candidate for Two-Dimensional Electronics and Spintronics

NASA Astrophysics Data System (ADS)

Deb, Swarup; Dhar, Subhabrata

Schrödingerand Poisson equations are solved self-consistently in order to obtain the potential and charge density distribution in n-type GaN nanowalls tapered along c-axis by different angles. The study shows two-dimensional (2D) quantum confinement of electrons in the central vertical plane of the wall for the entire range of tapering. Calculation of room temperature electron mobility in the 2D channel shows a steady decrease with the increase of the inclination angle of the side facets with respect to the base. However, it is interesting to note that the mobility remains to be much larger than that of bulk GaN even for the inclination angle of 65∘. The properties of high mobility and the vertical orientation of the 2DEG plane in this system can be exploited in fabricating highly conducting transparent interconnects and field effect transistors, which can lead to large scale integration of 2D devices in future.

Wavefunction Properties and Electronic Band Structures of High-Mobility Semiconductor Nanosheet MoS2

NASA Astrophysics Data System (ADS)

Baik, Seung Su; Lee, Hee Sung; Im, Seongil; Choi, Hyoung Joon; Ccsaemp Team; Edl Team

2014-03-01

Molybdenum disulfide (MoS2) nanosheet is regarded as one of the most promising alternatives to the current semiconductors due to its significant band-gap and electron-mobility enhancement upon exfoliating. To elucidate such thickness-dependent properties, we have studied the electronic band structures of bulk and monolayer MoS2 by using the first-principles density-functional method as implemented in the SIESTA code. Based on the wavefunction analyses at the conduction band minimum (CBM) points, we have investigated possible origins of mobility difference between bulk and monolayer MoS2. We provide formation energies of substitutional impurities at the Mo and S sites, and discuss feasible electron sources which may induce a significant difference in the carrier lifetime. This work was supported by NRF of Korea (Grant Nos. 2009-0079462 and 2011-0018306), Nano-Material Technology Development Program (2012M3a7B4034985), and KISTI supercomputing center (Project No. KSC-2013-C3-008). Center for Computational Studies of Advanced Electronic Material Properties.

A novel analytical model for scattering limited electron transport in nano-dimensional InAlAs/InGaAs heterostructure for cryogenic applications

NASA Astrophysics Data System (ADS)

Sharma, Neetika; Verma, Neha; Jogi, Jyotika

2017-11-01

This paper models the scattering limited electron transport in a nano-dimensional In0.52Al0.48As/In0.53Ga0.47As/InP heterostructure. An analytical model for temperature dependent sheet carrier concentration and carrier mobility in a two dimensional electron gas, confined in a triangular potential well has been developed. The model accounts for all the major scattering process including ionized impurity scattering and lattice scattering. Quantum mechanical variational technique is employed for studying the intrasubband scattering mechanism in the two dimensional electron gas. Results of various scattering limited structural parameters such as energy band-gap and functional parameters such as sheet carrier concentration, scattering rate and mobility are presented. The model corroborates the dominance of ionized impurity scattering mechanism at low temperatures and that of lattice scattering at high temperatures, both in turn limiting the carrier mobility. Net mobility obtained taking various scattering mechanisms into account has been found in agreement with earlier reported results, thus validating the model.

Monolithic barrier-all-around high electron mobility transistor with planar GaAs nanowire channel.

PubMed

Miao, Xin; Zhang, Chen; Li, Xiuling

2013-06-12

High-quality growth of planar GaAs nanowires (NWs) with widths as small as 35 nm is realized by comprehensively mapping the parameter space of group III flow, V/III ratio, and temperature as the size of the NWs scales down. Using a growth mode modulation scheme for the NW and thin film barrier layers, monolithically integrated AlGaAs barrier-all-around planar GaAs NW high electron mobility transistors (NW-HEMTs) are achieved. The peak extrinsic transconductance, drive current, and effective electron velocity are 550 μS/μm, 435 μA/μm, and ~2.9 × 10(7) cm/s, respectively, at 2 V supply voltage with a gate length of 120 nm. The excellent DC performance demonstrated here shows the potential of this bottom-up planar NW technology for low-power high-speed very-large-scale-integration (VLSI) circuits.

Graphene/Pentacene Barristor with Ion-Gel Gate Dielectric: Flexible Ambipolar Transistor with High Mobility and On/Off Ratio.

PubMed

Oh, Gwangtaek; Kim, Jin-Soo; Jeon, Ji Hoon; Won, EunA; Son, Jong Wan; Lee, Duk Hyun; Kim, Cheol Kyeom; Jang, Jingon; Lee, Takhee; Park, Bae Ho

2015-07-28

High-quality channel layer is required for next-generation flexible electronic devices. Graphene is a good candidate due to its high carrier mobility and unique ambipolar transport characteristics but typically shows a low on/off ratio caused by gapless band structure. Popularly investigated organic semiconductors, such as pentacene, suffer from poor carrier mobility. Here, we propose a graphene/pentacene channel layer with high-k ion-gel gate dielectric. The graphene/pentacene device shows both high on/off ratio and carrier mobility as well as excellent mechanical flexibility. Most importantly, it reveals ambipolar behaviors and related negative differential resistance, which are controlled by external bias. Therefore, our graphene/pentacene barristor with ion-gel gate dielectric can offer various flexible device applications with high performances.

Cyclotron resonance spectroscopy in a high mobility two dimensional electron gas using characteristic matrix methods.

PubMed

Hilton, David J

2012-12-31

We develop a new characteristic matrix-based method to analyze cyclotron resonance experiments in high mobility two-dimensional electron gas samples where direct interference between primary and satellite reflections has previously limited the frequency resolution. This model is used to simulate experimental data taken using terahertz time-domain spectroscopy that show multiple pulses from the substrate with a separation of 15 ps that directly interfere in the time-domain. We determine a cyclotron dephasing lifetime of 15.1 ± 0.5 ps at 1.5 K and 5.0 ± 0.5 ps at 75 K.

Influence of polymer dielectrics on C60-based field-effect transistors

NASA Astrophysics Data System (ADS)

Zhou, Jianlin; Zhang, Fujia; Lan, Lifeng; Wen, Shangsheng; Peng, Junbiao

2007-12-01

Fullerene C60 organic field-effect transistors (OFETs) have been fabricated based on two different polymer dielectric materials, poly(methylmethacrylate) (PMMA) and cross-linkable poly(4-vinylphenol). The large grain size of C60 film and small number of traps at the interface of PMMA /C60 were obtained with high electron mobility of 0.66cm2/Vs in the PMMA transistor. The result suggests that the C60 semiconductor cooperating with polymer dielectric is a promising application in the fabrication of n-type organic transistors because of low threshold voltage and high electron mobility.

Two-dimensional numerical model for the high electron mobility transistor

NASA Astrophysics Data System (ADS)

Loret, Dany

1987-11-01

A two-dimensional numerical drift-diffusion model for the High Electron Mobility Transistor (HEMT) is presented. Special attention is paid to the modeling of the current flow over the heterojunction. A finite difference scheme is used to solve the equations, and a variable mesh spacing was implemented to cope with the strong variations of functions near the heterojunction. Simulation results are compared to experimental data for a 0.7 μm gate length device. Small-signal transconductances and cut-off frequency obtained from the 2-D model agree well with the experimental values from S-parameter measurements. It is shown that the numerical models give good insight into device behaviour, including important parasitic effects such as electron injection into the bulk GaAs.

Enhancing Hole Mobility in III-V Semiconductors

DTIC Science & Technology

2012-05-21

acteristics of the digital superlattice (n¼1,0, andþ 1) that was used in the metamorphic buffer. The GaSb channel peak gets buried in the n¼ 0...materials have been used for a variety of analog and high frequency applications driven by the high electron mobilities in III-V materials. On the other...hand, the hole mobility in III-V materials has always lagged compared to group-IV semiconductors such as germanium. In this paper, we explore the use

77 FR 18860 - Certain Consumer Electronics, Including Mobile Phones and Tablets; Notice of Receipt of Complaint...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-28

... INTERNATIONAL TRADE COMMISSION [DN 2885] Certain Consumer Electronics, Including Mobile Phones and.... International Trade Commission has received a complaint entitled Certain Consumer Electronics, Including Mobile... electronics, including mobile phones and tablets. The complaint names as respondents ASUSTeK Computer, Inc. of...

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.

Characterization of N-polar AlN in GaN/AlN/(Al,Ga)N heterostructures grown by metal-organic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Li, Haoran; Mazumder, Baishakhi; Bonef, Bastien; Keller, Stacia; Wienecke, Steven; Speck, James S.; Denbaars, Steven P.; Mishra, Umesh K.

2017-11-01

In GaN/(Al,Ga)N high-electron-mobility transistors (HEMT), AlN interlayer between GaN channel and AlGaN barrier suppresses alloy scattering and significantly improves the electron mobility of the two-dimensional electron gas. While high concentrations of gallium were previously observed in Al-polar AlN interlayers grown by metal-organic chemical vapor deposition, the N-polar AlN (Al x Ga1-x N) films examined by atom probe tomography in this study exhibited aluminum compositions (x) equal to or higher than 95% over a wide range of growth conditions. The also investigated AlN interlayer in a N-polar GaN/AlN/AlGaN/ S.I. GaN HEMT structure possessed a similarly high x content.

Charge transport in organic molecular semiconductors from first principles: The bandlike hole mobility in a naphthalene crystal

NASA Astrophysics Data System (ADS)

Lee, Nien-En; Zhou, Jin-Jian; Agapito, Luis A.; Bernardi, Marco

2018-03-01

Predicting charge transport in organic molecular crystals is notoriously challenging. Carrier mobility calculations in organic semiconductors are dominated by quantum chemistry methods based on charge hopping, which are laborious and only moderately accurate. We compute from first principles the electron-phonon scattering and the phonon-limited hole mobility of naphthalene crystal in the framework of ab initio band theory. Our calculations combine GW electronic bandstructures, ab initio electron-phonon scattering, and the Boltzmann transport equation. The calculated hole mobility is in very good agreement with experiment between 100 -300 K , and we can predict its temperature dependence with high accuracy. We show that scattering between intermolecular phonons and holes regulates the mobility, though intramolecular phonons possess the strongest coupling with holes. We revisit the common belief that only rigid molecular motions affect carrier dynamics in organic molecular crystals. Our paper provides a quantitative and rigorous framework to compute charge transport in organic crystals and is a first step toward reconciling band theory and carrier hopping computational methods.

Intrinsic Electron Mobility Exceeding 10³ cm²/(V s) in Multilayer InSe FETs.

PubMed

Sucharitakul, Sukrit; Goble, Nicholas J; Kumar, U Rajesh; Sankar, Raman; Bogorad, Zachary A; Chou, Fang-Cheng; Chen, Yit-Tsong; Gao, Xuan P A

2015-06-10

Graphene-like two-dimensional (2D) materials not only are interesting for their exotic electronic structure and fundamental electronic transport or optical properties but also hold promises for device miniaturization down to atomic thickness. As one material belonging to this category, InSe, a III-VI semiconductor, not only is a promising candidate for optoelectronic devices but also has potential for ultrathin field effect transistor (FET) with high mobility transport. In this work, various substrates such as PMMA, bare silicon oxide, passivated silicon oxide, and silicon nitride were used to fabricate multilayer InSe FET devices. Through back gating and Hall measurement in four-probe configuration, the device's field effect mobility and intrinsic Hall mobility were extracted at various temperatures to study the material's intrinsic transport behavior and the effect of dielectric substrate. The sample's field effect and Hall mobilities over the range of 20-300 K fall in the range of 0.1-2.0 × 10(3) cm(2)/(V s), which are comparable or better than the state of the art FETs made of widely studied 2D transition metal dichalcogenides.

High-Performance Fluorescent Organic Light-Emitting Diodes Utilizing an Asymmetric Anthracene Derivative as an Electron-Transporting Material.

PubMed

Zhang, Dongdong; Song, Xiaozeng; Li, Haoyuan; Cai, Minghan; Bin, Zhengyang; Huang, Tianyu; Duan, Lian

2018-05-17

Fluorescent organic light-emitting diodes with thermally activated delayed fluorescent sensitizers (TSF-OLEDs) have aroused wide attention, the power efficiencies of which, however, are limited by the mutual exclusion of high electron-transport mobility and large triplet energy of electron-transporting materials (ETMs). Here, an asymmetric anthracene derivative with electronic properties manipulated by different side groups is developed as an ETM to promote TSF-OLED performances. Multiple intermolecular interactions are observed, leading to a kind of "cable-like packing" in the crystal and favoring the simultaneous realization of high electron-transporting mobility and good exciton-confinement ability, albeit the low triplet energy of the ETM. The optimized TSF-OLEDs exhibit a record-high maximum external quantum efficiency/power efficiency of 24.6%/76.0 lm W -1 , which remain 23.8%/69.0 lm W -1 at a high luminance of even 5000 cd m -2 with an extremely low operation voltage of 3.14 V. This work opens a new paradigm for designing ETMs and also paves the way toward practical application of TSF-OLEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Scatterings and Quantum Effects in (Al ,In )N /GaN Heterostructures for High-Power and High-Frequency Electronics

NASA Astrophysics Data System (ADS)

Wang, Leizhi; Yin, Ming; Khan, Asif; Muhtadi, Sakib; Asif, Fatima; Choi, Eun Sang; Datta, Timir

2018-02-01

Charge transport in the wide-band-gap (Al ,In )N /GaN heterostructures with high carrier density approximately 2 ×1013 cm-2 is investigated over a large range of temperature (270 mK ≤T ≤280 K ) and magnetic field (0 ≤B ≤18 T ). We observe the first evidence of weak localization in the two-dimensional electron gas in this system. From the Shubnikov-de Haas (SdH) oscillations a relatively light effective mass of 0.23 me is determined. Furthermore, the linear dependence with temperature (T <20 K ) of the inelastic scattering rate (τi-1∝T ) is attributed to the phase breaking by electron-electron scattering. Also in the same temperature range the less-than unit ratio of quantum lifetime to Hall transport time (τq/τt<1 ) is taken to signify the dominance of small-angle scattering. Above 20 K, with increasing temperature scattering changes from acoustic phonon to optical phonon scattering, resulting in a rapid decrease in carrier mobility and increase in sheet resistance. Suppression of such scatterings will lead to higher mobility and a way forward to high-power and high-frequency electronics.

n-Channel semiconductor materials design for organic complementary circuits.

PubMed

Usta, Hakan; Facchetti, Antonio; Marks, Tobin J

2011-07-19

Organic semiconductors have unique properties compared to traditional inorganic materials such as amorphous or crystalline silicon. Some important advantages include their adaptability to low-temperature processing on flexible substrates, low cost, amenability to high-speed fabrication, and tunable electronic properties. These features are essential for a variety of next-generation electronic products, including low-power flexible displays, inexpensive radio frequency identification (RFID) tags, and printable sensors, among many other applications. Accordingly, the preparation of new materials based on π-conjugated organic molecules or polymers has been a central scientific and technological research focus over the past decade. Currently, p-channel (hole-transporting) materials are the leading class of organic semiconductors. In contrast, high-performance n-channel (electron-transporting) semiconductors are relatively rare, but they are of great significance for the development of plastic electronic devices such as organic field-effect transistors (OFETs). In this Account, we highlight the advances our team has made toward realizing moderately and highly electron-deficient n-channel oligomers and polymers based on oligothiophene, arylenediimide, and (bis)indenofluorene skeletons. We have synthesized and characterized a "library" of structurally related semiconductors, and we have investigated detailed structure-property relationships through optical, electrochemical, thermal, microstructural (both single-crystal and thin-film), and electrical measurements. Our results reveal highly informative correlations between structural parameters at various length scales and charge transport properties. We first discuss oligothiophenes functionalized with perfluoroalkyl and perfluoroarene substituents, which represent the initial examples of high-performance n-channel semiconductors developed in this project. The OFET characteristics of these compounds are presented with an emphasis on structure-property relationships. We then examine the synthesis and properties of carbonyl-functionalized oligomers, which constitute second-generation n-channel oligothiophenes, in both vacuum- and solution-processed FETs. These materials have high carrier mobilities and good air stability. In parallel, exceptionally electron-deficient cyano-functionalized arylenediimide derivatives are discussed as early examples of thermodynamically air-stable, high-performance n-channel semiconductors; they exhibit record electron mobilities of up to 0.64 cm(2)/V·s. Furthermore, we provide an overview of highly soluble ladder-type macromolecular semiconductors as OFET components, which combine ambient stability with solution processibility. A high electron mobility of 0.16 cm(2)/V·s is obtained under ambient conditions for solution-processed films. Finally, examples of polymeric n-channel semiconductors with electron mobilities as high as 0.85 cm(2)/V·s are discussed; these constitute an important advance toward fully printed polymeric electronic circuitry. Density functional theory (DFT) computations reveal important trends in molecular physicochemical and semiconducting properties, which, when combined with experimental data, shed new light on molecular charge transport characteristics. Our data provide the basis for a fundamental understanding of charge transport in high-performance n-channel organic semiconductors. Moreover, our results provide a road map for developing functional, complementary organic circuitry, which requires combining p- and n-channel transistors.

Flexible black phosphorus ambipolar transistors, circuits and AM demodulator.

PubMed

Zhu, Weinan; Yogeesh, Maruthi N; Yang, Shixuan; Aldave, Sandra H; Kim, Joon-Seok; Sonde, Sushant; Tao, Li; Lu, Nanshu; Akinwande, Deji

2015-03-11

High-mobility two-dimensional (2D) semiconductors are desirable for high-performance mechanically flexible nanoelectronics. In this work, we report the first flexible black phosphorus (BP) field-effect transistors (FETs) with electron and hole mobilities superior to what has been previously achieved with other more studied flexible layered semiconducting transistors such as MoS2 and WSe2. Encapsulated bottom-gated BP ambipolar FETs on flexible polyimide afforded maximum carrier mobility of about 310 cm(2)/V·s with field-effect current modulation exceeding 3 orders of magnitude. The device ambipolar functionality and high-mobility were employed to realize essential circuits of electronic systems for flexible technology including ambipolar digital inverter, frequency doubler, and analog amplifiers featuring voltage gain higher than other reported layered semiconductor flexible amplifiers. In addition, we demonstrate the first flexible BP amplitude-modulated (AM) demodulator, an active stage useful for radio receivers, based on a single ambipolar BP transistor, which results in audible signals when connected to a loudspeaker or earphone. Moreover, the BP transistors feature mechanical robustness up to 2% uniaxial tensile strain and up to 5000 bending cycles.

TFB:TPDSi2 interfacial layer usable in organic photovoltaic cells

DOEpatents

Marks, Iobin J [Evanston, IL; Hains, Alexander W [Evanston, IL

2011-02-15

The present invention, in one aspect, relates to a solar cell. In one embodiment, the solar cell includes an anode; an active organic layer comprising an electron-donating organic material and an electron-accepting organic material; and an interfacial layer formed between the anode and active organic layer, where the interfacial layer comprises a hole-transporting polymer characterized with a hole-mobility higher than that of the electron-donating organic material in the active organic layer, and a small molecule that has a high hole-mobility and is capable of crosslinking on contact with air.

Integrating AlGaN/GaN high electron mobility transistor with Si: A comparative study of integration schemes

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

Mohan, Nagaboopathy; Raghavan, Srinivasan; Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore 560012

2015-10-07

AlGaN/GaN high electron mobility transistor stacks deposited on a single growth platform are used to compare the most common transition, AlN to GaN, schemes used for integrating GaN with Si. The efficiency of these transitions based on linearly graded, step graded, interlayer, and superlattice schemes on dislocation density reduction, stress management, surface roughness, and eventually mobility of the 2D-gas are evaluated. In a 500 nm GaN probe layer deposited, all of these transitions result in total transmission electron microscopy measured dislocations densities of 1 to 3 × 10{sup 9}/cm{sup 2} and <1 nm surface roughness. The 2-D electron gas channels formed atmore » an AlGaN-1 nm AlN/GaN interface deposited on this GaN probe layer all have mobilities of 1600–1900 cm{sup 2}/V s at a carrier concentration of 0.7–0.9 × 10{sup 13}/cm{sup 2}. Compressive stress and changes in composition in GaN rich regions of the AlN-GaN transition are the most effective at reducing dislocation density. Amongst all the transitions studied the step graded transition is the one that helps to implement this feature of GaN integration in the simplest and most consistent manner.« less

A mobile robot system for ground servicing operations on the space shuttle

NASA Astrophysics Data System (ADS)

Dowling, K.; Bennett, R.; Blackwell, M.; Graham, T.; Gatrall, S.; O'Toole, R.; Schempf, H.

1992-11-01

A mobile system for space shuttle servicing, the Tessellator, has been configured, designed and is currently being built and integrated. Robot tasks include chemical injection and inspection of the shuttle's thermal protection system. This paper outlines tasks, rationale, and facility requirements for the development of this system. A detailed look at the mobile system and manipulator follow with a look at mechanics, electronics, and software. Salient features of the mobile robot include omnidirectionality, high reach, high stiffness and accuracy with safety and self-reliance integral to all aspects of the design. The robot system is shown to meet task, facility, and NASA requirements in its design resulting in unprecedented specifications for a mobile-manipulation system.

A mobile robot system for ground servicing operations on the space shuttle

NASA Technical Reports Server (NTRS)

Dowling, K.; Bennett, R.; Blackwell, M.; Graham, T.; Gatrall, S.; O'Toole, R.; Schempf, H.

1992-01-01

A mobile system for space shuttle servicing, the Tessellator, has been configured, designed and is currently being built and integrated. Robot tasks include chemical injection and inspection of the shuttle's thermal protection system. This paper outlines tasks, rationale, and facility requirements for the development of this system. A detailed look at the mobile system and manipulator follow with a look at mechanics, electronics, and software. Salient features of the mobile robot include omnidirectionality, high reach, high stiffness and accuracy with safety and self-reliance integral to all aspects of the design. The robot system is shown to meet task, facility, and NASA requirements in its design resulting in unprecedented specifications for a mobile-manipulation system.

The role of polarization coulomb field scattering in the electron mobility of AlGaN/AlN/GaN heterostructure field-effect transistors

NASA Astrophysics Data System (ADS)

Liu, Yan; Lin, Zhaojun; Zhao, Jingtao; Yang, Ming; Shi, Wenjing; Lv, Yuanjie; Feng, Zhihong

2016-04-01

The electron mobility for the prepared AlGaN/AlN/GaN heterostructure field-effect transistor (HFET) with the ratio of the gate length to the drain-to-source distance being less than 1/2 has been studied by comparing the measured electron mobility with the theoretical value. The measured electron mobility is derived from the measured capacitance-voltage (C-V) and current-voltage (I-V) characteristics, and the theoretical mobility is determined by using Matthiessen's law, involving six kinds of important scattering mechanisms. For the prepared device at room temperature, longitudinal optical phonon scattering (LO scattering) was found to have a remarkable effect on the value of the electron mobility, and polarization Coulomb field scattering (PCF scattering ) was found to be important to the changing trend of the electron mobility versus the two-dimensional electron gas (2DEG) density.

The use of mobile learning application to the fundament of digital electronics course

NASA Astrophysics Data System (ADS)

Rakhmawati, L.; Firdha, A.

2018-01-01

A new trend in e-learning is known as Mobile Learning. Learning through mobile phones have become part of the educative process. Thus, the purposes of this study are to develop a mobile application for the Fundament of Digital Electronics course that consists of number systems operation, logic gates, and Boolean Algebra, and to assess the readiness, perceptions, and effectiveness of students in the use of mobile devices for learning in the classroom. This research uses Research and Development (R&D) method. The design used in this research, by doing treatment in one class and observing by using Android-based mobile application instructional media. The result obtained from this research shows that the test has 80 % validity aspect, 82 % of the user from senior high school students gives a positive response in using the application of mobile learning, and based on the result of post-test, 90, 90% students passed the exam. At last, it can be concluded that the use of the mobile learning application makes the learning process more effective when it is used in the teaching-learning process.

Flexible polymer transistors with high pressure sensitivity for application in electronic skin and health monitoring

NASA Astrophysics Data System (ADS)

Schwartz, Gregor; Tee, Benjamin C.-K.; Mei, Jianguo; Appleton, Anthony L.; Kim, Do Hwan; Wang, Huiliang; Bao, Zhenan

2013-05-01

Flexible pressure sensors are essential parts of an electronic skin to allow future biomedical prostheses and robots to naturally interact with humans and the environment. Mobile biomonitoring in long-term medical diagnostics is another attractive application for these sensors. Here we report the fabrication of flexible pressure-sensitive organic thin film transistors with a maximum sensitivity of 8.4 kPa-1, a fast response time of <10 ms, high stability over >15,000 cycles and a low power consumption of <1 mW. The combination of a microstructured polydimethylsiloxane dielectric and the high-mobility semiconducting polyisoindigobithiophene-siloxane in a monolithic transistor design enabled us to operate the devices in the subthreshold regime, where the capacitance change upon compression of the dielectric is strongly amplified. We demonstrate that our sensors can be used for non-invasive, high fidelity, continuous radial artery pulse wave monitoring, which may lead to the use of flexible pressure sensors in mobile health monitoring and remote diagnostics in cardiovascular medicine.

Enhanced and continuous electrostatic carrier doping on the SrTiO3 surface

PubMed Central

Eyvazov, A. B.; Inoue, I. H.; Stoliar, P.; Rozenberg, M. J.; Panagopoulos, C.

2013-01-01

Paraelectrical tuning of a charge carrier density as high as 1013 cm−2 in the presence of a high electronic carrier mobility on the delicate surfaces of correlated oxides, is a key to the technological breakthrough of a field effect transistor (FET) utilising the metal-nonmetal transition. Here we introduce the Parylene-C/Ta2O5 hybrid gate insulator and fabricate FET devices on single-crystalline SrTiO3, which has been regarded as a bedrock material for oxide electronics. The gate insulator accumulates up to ~1013cm−2 carriers, while the field-effect mobility is kept at 10 cm2/Vs even at room temperature. Further to the exceptional performance of our devices, the enhanced compatibility of high carrier density and high mobility revealed the mechanism for the long standing puzzle of the distribution of electrostatically doped carriers on the surface of SrTiO3. Namely, the formation and continuous evolution of field domains and current filaments.

Flexible polymer transistors with high pressure sensitivity for application in electronic skin and health monitoring.

PubMed

Schwartz, Gregor; Tee, Benjamin C-K; Mei, Jianguo; Appleton, Anthony L; Kim, Do Hwan; Wang, Huiliang; Bao, Zhenan

2013-01-01

Flexible pressure sensors are essential parts of an electronic skin to allow future biomedical prostheses and robots to naturally interact with humans and the environment. Mobile biomonitoring in long-term medical diagnostics is another attractive application for these sensors. Here we report the fabrication of flexible pressure-sensitive organic thin film transistors with a maximum sensitivity of 8.4 kPa(-1), a fast response time of <10 ms, high stability over >15,000 cycles and a low power consumption of <1 mW. The combination of a microstructured polydimethylsiloxane dielectric and the high-mobility semiconducting polyisoindigobithiophene-siloxane in a monolithic transistor design enabled us to operate the devices in the subthreshold regime, where the capacitance change upon compression of the dielectric is strongly amplified. We demonstrate that our sensors can be used for non-invasive, high fidelity, continuous radial artery pulse wave monitoring, which may lead to the use of flexible pressure sensors in mobile health monitoring and remote diagnostics in cardiovascular medicine.

High Stability Performance of Quinary Indium Gallium Zinc Aluminum Oxide Films and Thin-Film Transistors Deposited Using Vapor Cooling Condensation Method

NASA Astrophysics Data System (ADS)

Lin, Yung-Hao; Lee, Ching-Ting

2017-08-01

High-quality indium gallium zinc aluminum oxide (IGZAO) thin films with various Al contents have been deposited using the vapor cooling condensation method. The electron mobility of the IGZAO films was improved by 89.4% on adding Al cation to IGZO film. The change in the electron concentration and mobility of the IGZAO films was 7.3% and 7.0%, respectively, when the temperature was changed from 300 K to 225 K. These experimental results confirm the high performance and stability of the IGZAO films. The performance stability mechanisms of IGZAO thin-film transistors (TFTs) were investigated in comparison with IGZO TFTs.

Investigation of trap states in Al2O3 InAlN/GaN metal-oxide-semiconductor high-electron-mobility transistors

NASA Astrophysics Data System (ADS)

Zhang, Peng; Zhao, Sheng-Lei; Xue, Jun-Shuai; Zhu, Jie-Jie; Ma, Xiao-Hua; Zhang, Jin-Cheng; Hao, Yue

2015-12-01

In this paper the trapping effects in Al2O3/In0.17Al0.83N/GaN MOS-HEMT (here, HEMT stands for high electron mobility transistor) are investigated by frequency-dependent capacitance and conductance analysis. The trap states are found at both the Al2O3/InAlN and InAlN/GaN interface. Trap states in InAlN/GaN heterostructure are determined to have mixed de-trapping mechanisms, emission, and tunneling. Part of the electrons captured in the trap states are likely to tunnel into the two-dimensional electron gas (2DEG) channel under serious band bending and stronger electric field peak caused by high Al content in the InAlN barrier, which explains the opposite voltage dependence of time constant and relation between the time constant and energy of the trap states. Project supported by the Program for National Natural Science Foundation of China (Grant Nos. 61404100 and 61306017).

76 FR 24051 - In the Matter of Certain Electronic Devices, Including Mobile Phones, Mobile Tablets, Portable...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-29

..., Including Mobile Phones, Mobile Tablets, Portable Music Players, and Computers, and Components Thereof... certain electronic devices, including mobile phones, mobile tablets, portable music players, and computers... mobile phones, mobile tablets, portable music players, and computers, and components thereof that...

Improving crystallization and electron mobility of indium tin oxide by carbon dioxide and hydrogen dual-step plasma treatment

NASA Astrophysics Data System (ADS)

Wang, Fengyou; Du, Rongchi; Ren, Qianshang; Wei, Changchun; Zhao, Ying; Zhang, Xiaodan

2017-12-01

Obtaining high conductivity indium tin oxide (ITO) films simultaneously with a "soft-deposited" (low temperature, low ions bombardment) and cost-efficient deposition process are critical aspect for versatile photo-electronic devices application. Usually, the low-cost "soft-deposited" process could be achieved via evaporation technique, but with scarifying the conductivity of the films. Here, we show a CO2 and H2 two-step plasma (TSP) post-treatment applied to ITO films prepared by reactive thermal evaporation (RTE), allows to meet the special trade-off between the deposition techniques and the electrical properties. Upon treatment, an increase in electron concentration and electron mobility is observed, which subsequently resulting a low sheet resistivity. The mobility reaches high values of 80.9 cm2/Vs for the TSP treated ∼100 nm thickness samples. From a combination of X-ray photoelectron spectroscopy and opto-electronic measurements, it demonstrated that: during the TSP process, the first-step CO2 plasma treatment could promote the crystallinity of the RTE ITO films. While the electron traps density at grain boundaries of polycrystalline RTE ITO films could be passivated by hydrogen atom during the second-step H2 plasma treatment. These results inspired that the TSP treatment process has significant application prospects owing to the outstanding electrical properties enhancement for "soft-deposited" RTE ITO films.

High-mobility low-temperature ZnO transistors with low-voltage operation

NASA Astrophysics Data System (ADS)

Bong, Hyojin; Lee, Wi Hyoung; Lee, Dong Yun; Kim, Beom Joon; Cho, Jeong Ho; Cho, Kilwon

2010-05-01

Low voltage high mobility n-type thin film transistors (TFTs) based on sol-gel processed zinc oxide (ZnO) were fabricated using a high capacitance ion gel gate dielectric. The ion gel gated solution-processed ZnO TFTs were found to exhibit excellent electrical properties. TFT carrier mobilities were 13 cm2/V s, ON/OFF current ratios were 105, regardless of the sintering temperature used for the preparation of the ZnO thin films. Ion gel gated ZnO TFTs are successfully demonstrated on plastic substrates for the large area flexible electronics.

Structured back gates for high-mobility two-dimensional electron systems using oxygen ion implantation

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

Berl, M., E-mail: mberl@phys.ethz.ch; Tiemann, L.; Dietsche, W.

2016-03-28

We present a reliable method to obtain patterned back gates compatible with high mobility molecular beam epitaxy via local oxygen ion implantation that suppresses the conductivity of an 80 nm thick silicon doped GaAs epilayer. Our technique was optimized to circumvent several constraints of other gating and implantation methods. The ion-implanted surface remains atomically flat which allows unperturbed epitaxial overgrowth. We demonstrate the practical application of this gating technique by using magneto-transport spectroscopy on a two-dimensional electron system (2DES) with a mobility exceeding 20 × 10{sup 6} cm{sup 2}/V s. The back gate was spatially separated from the Ohmic contacts of the 2DES,more » thus minimizing the probability for electrical shorts or leakage and permitting simple contacting schemes.« less

Mobility spectrum analytical approach for intrinsic band picture of Ba(FeAs)2

NASA Astrophysics Data System (ADS)

Huynh, K. K.; Tanabe, Y.; Urata, T.; Heguri, S.; Tanigaki, K.; Kida, T.; Hagiwara, M.

2014-09-01

Unconventional high temperature superconductivity as well as three-dimensional bulk Dirac cone quantum states arising from the unique d-orbital topology have comprised an intriguing research area in physics. Here we apply a special analytical approach using a mobility spectrum, in which the carrier number is conveniently described as a function of mobility without any hypothesis, both on the types and the numbers of carriers, for the interpretations of longitudinal and transverse electric transport of high quality single crystal Ba(FeAs)2 in a wide range of magnetic fields. We show that the majority carriers are accommodated in large parabolic hole and electron pockets with very different topology as well as remarkably different mobility spectra, whereas the minority carriers reside in Dirac quantum states with the largest mobility as high as 70,000 cm2(Vs)-1. The deduced mobility spectra are discussed and compared to the reported sophisticated first principle band calculations.

Remarkably High Mobility Thin-Film Transistor on Flexible Substrate by Novel Passivation Material.

PubMed

Shih, Cheng Wei; Chin, Albert

2017-04-25

High mobility thin-film transistor (TFT) is crucial for future high resolution and fast response flexible display. Remarkably high performance TFT, made at room temperature on flexible substrate, is achieved with record high field-effect mobility (μ FE ) of 345 cm 2 /Vs, small sub-threshold slope (SS) of 103 mV/dec, high on-current/off-current (I ON /I OFF ) of 7 × 10 6 , and a low drain-voltage (V D ) of 2 V for low power operation. The achieved mobility is the best reported data among flexible electronic devices, which is reached by novel HfLaO passivation material on nano-crystalline zinc-oxide (ZnO) TFT to improve both I ON and I OFF . From X-ray photoelectron spectroscopy (XPS) analysis, the non-passivated device has high OH-bonding intensity in nano-crystalline ZnO, which damage the crystallinity, create charged scattering centers, and form potential barriers to degrade mobility.

An enzymatic biosensor based on three-dimensional ZnO nanotetrapods spatial net modified AlGaAs/GaAs high electron mobility transistors

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

Song, Yu; Bioengineering Program, Lehigh University, Bethlehem, Pennsylvania 18015; Zhang, Xiaohui

2014-11-24

We designed and constructed three dimensional (3D) zinc oxide Nanotetrapods (T-ZnOs) modified AlGaAs/GaAs high electron mobility transistors (HEMTs) for enzymatic uric acid (UA) detection. The chemical vapor deposition synthesized T-ZnOs was distributed on the gate areas of HEMTs in order to immobilize uricase and improve the sensitivity of the HEMTs. Combining with the high efficiency of enzyme immobilization by T-ZnOs and high sensitivity from HEMT, the as-constructed uricase/T-ZnOs/HEMTs biosensor showed fast response towards UA at ∼1 s, wide linear range from 0.2 nM to 0.2 mM and the low detect limit at 0.2 nM. The results point out an avenue to design electronic devicemore » as miniaturized lab-on-chip device for high sensitive and specific in biomedical and clinical diagnosis applications.« less

Improved linearity in AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors with nonlinear polarization dielectric

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

Gao, Tao; Science and Technology on Monolithic Integrated Circuits and Modules Laboratory, Nanjing Electronic Devices Institute, Nanjing 210016; Xu, Ruimin

2015-06-15

We demonstrate highly improved linearity in a nonlinear ferroelectric of Pb(Zr{sub 0.52}Ti{sub 0.48})-gated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT). Distinct double-hump feature in the transconductance-gate voltage (g{sub m}-V{sub g}) curve is observed, yielding remarkable enhancement in gate voltage swing as compared to MIS-HEMT with conventional linear gate dielectric. By incorporating the ferroelectric polarization into a self-consistent calculation, it is disclosed that in addition to the common hump corresponding to the onset of electron accumulation, the second hump at high current level is originated from the nonlinear polar nature of ferroelectric, which enhances the gate capacitance by increasing equivalent dielectricmore » constant nonlinearly. This work paves a way for design of high linearity GaN MIS-HEMT by exploiting the nonlinear properties of dielectric.« less

Description of a Mobile-based Electronic Informed Consent System Development.

PubMed

Hwang, Min-A; Kwak, In Ja

2015-01-01

Seoul National University Hospital constructed and implemented a computer-based informed consent system in December 2011. As of 2013, 30% of the informed consents were still filled out manually on paper. Patients and medical staff continuously suggested the implementation of a system for electronic informed consent using portable devices. Therefore, a mobile-based system for electronic informed consent was developed in 2013 to prevent the issues that arise with computer-based systems and paper informed consent. The rate of filling out electronic informed consent increased from 69% to 95% following the implementation of the mobile-based electronic informed consent. This construction of a mobile-based electronic informed consent system would be a good reference point for the development of a mobile-based Electronic Medical Record and for various mobile system environments in medical institutions.

Direct Growth of High Mobility and Low-Noise Lateral MoS2 -Graphene Heterostructure Electronics.

PubMed

Behranginia, Amirhossein; Yasaei, Poya; Majee, Arnab K; Sangwan, Vinod K; Long, Fei; Foss, Cameron J; Foroozan, Tara; Fuladi, Shadi; Hantehzadeh, Mohammad Reza; Shahbazian-Yassar, Reza; Hersam, Mark C; Aksamija, Zlatan; Salehi-Khojin, Amin

2017-08-01

Reliable fabrication of lateral interfaces between conducting and semiconducting 2D materials is considered a major technological advancement for the next generation of highly packed all-2D electronic circuitry. This study employs seed-free consecutive chemical vapor deposition processes to synthesize high-quality lateral MoS 2 -graphene heterostructures and comprehensively investigated their electronic properties through a combination of various experimental techniques and theoretical modeling. These results show that the MoS 2 -graphene devices exhibit an order of magnitude higher mobility and lower noise metrics compared to conventional MoS 2 -metal devices as a result of energy band rearrangement and smaller Schottky barrier height at the contacts. These findings suggest that MoS 2 -graphene in-plane heterostructures are promising materials for the scale-up of all-2D circuitry with superlative electrical performance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Single shot spin readout with a cryogenic high-electron-mobility transistor amplifier at sub-Kelvin temperatures

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

Tracy, Lisa A.; Luhman, Dwight R.; Carr, Stephen M.

We use a cryogenic high-electron-mobility transistor circuit to amplify the current from a single electron transistor, allowing for demonstration of single shot readout of an electron spin on a single P donor in Si with 100 kHz bandwidth and a signal to noise ratio of ~9. In order to reduce the impact of cable capacitance, the amplifier is located adjacent to the Si sample, at the mixing chamber stage of a dilution refrigerator. For a current gain of ~2.7 x 10 3 the power dissipation of the amplifier is 13 μW, the bandwidth is ~1.3 MHz, and for frequencies abovemore » 300 kHz the current noise referred to input is ≤ 70 fA/√Hz. Furthermore, with this amplification scheme, we are able to observe coherent oscillations of a P donor electron spin in isotopically enriched 28Si with 96% visibility.« less

Single shot spin readout with a cryogenic high-electron-mobility transistor amplifier at sub-Kelvin temperatures

DOE PAGES

Tracy, Lisa A.; Luhman, Dwight R.; Carr, Stephen M.; ...

2016-02-08

We use a cryogenic high-electron-mobility transistor circuit to amplify the current from a single electron transistor, allowing for demonstration of single shot readout of an electron spin on a single P donor in Si with 100 kHz bandwidth and a signal to noise ratio of ~9. In order to reduce the impact of cable capacitance, the amplifier is located adjacent to the Si sample, at the mixing chamber stage of a dilution refrigerator. For a current gain of ~2.7 x 10 3 the power dissipation of the amplifier is 13 μW, the bandwidth is ~1.3 MHz, and for frequencies abovemore » 300 kHz the current noise referred to input is ≤ 70 fA/√Hz. Furthermore, with this amplification scheme, we are able to observe coherent oscillations of a P donor electron spin in isotopically enriched 28Si with 96% visibility.« less

Extraction of carrier mobility and interface trap density in InGaAs metal oxide semiconductor structures using gated Hall method

NASA Astrophysics Data System (ADS)

Chidambaram, Thenappan

III-V semiconductors are potential candidates to replace Si as a channel material in next generation CMOS integrated circuits owing to their superior carrier mobilities. Low density of states (DOS) and typically high interface and border trap densities (Dit) in high mobility group III-V semiconductors provide difficulties in quantification of Dit near the conduction band edge. The trap response above the threshold voltage of a MOSFET can be very fast, and conventional Dit extraction methods, based on capacitance/conductance response (CV methods) of MOS capacitors at frequencies <1MHz, cannot distinguish conducting and trapped carriers. In addition, the CV methods have to deal with high dispersion in the accumulation region that makes it a difficult task to measure the true oxide capacitance, Cox value. Another implication of these properties of III-V interfaces is an ambiguity of determination of electron density in the MOSFET channel. Traditional evaluation of carrier density by integration of the C-V curve, gives incorrect values for D it and mobility. Here we employ gated Hall method to quantify the D it spectrum at the high-K oxide/III-V semiconductor interface for buried and surface channel devices using Hall measurement and capacitance-voltage data. Determination of electron density directly from Hall measurements allows for obtaining true mobility values.

Cryogenic, low-noise high electron mobility transistor amplifiers for the Deep Space Network

NASA Technical Reports Server (NTRS)

Bautista, J. J.

1993-01-01

The rapid advances recently achieved by cryogenically cooled high electron mobility transistor (HEMT) low-noise amplifiers (LNA's) in the 1- to 10-GHz range are making them extremely competitive with maser amplifiers. In order to address future spacecraft navigation, telemetry, radar, and radio science needs, the Deep Space Network is investing both maser and HEMT amplifiers for its Ka-band (32-GHz) downlink capability. This article describes the current state cryogenic HEMT LNA development at Ka-band for the DSN. Noise performance results at S-band (2.3 GHz) and X-band (8.5 GHz) for HEMT's and masers are included for completeness.

Degradation and annealing effects caused by oxygen in AlGaN/GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Jiang, R.; Shen, X.; Chen, J.; Duan, G. X.; Zhang, E. X.; Fleetwood, D. M.; Schrimpf, R. D.; Kaun, S. W.; Kyle, E. C. H.; Speck, J. S.; Pantelides, S. T.

2016-07-01

Hot-carrier degradation and room-temperature annealing effects are investigated in unpassivated ammonia-rich AlGaN/GaN high electron mobility transistors. Devices exhibit a fast recovery when annealed after hot carrier stress with all pins grounded. The recovered peak transconductance can exceed the original value, an effect that is not observed in control passivated samples. Density functional theory calculations suggest that dehydrogenation of pre-existing ON-H defects in AlGaN plays a significant role in the observed hot carrier degradation, and the resulting bare ON can naturally account for the "super-recovery" in the peak transconductance.

Zigzag‐Elongated Fused π‐Electronic Core: A Molecular Design Strategy to Maximize Charge‐Carrier Mobility

PubMed Central

Yamamoto, Akito; Murata, Yoshinori; Mitsui, Chikahiko; Yamagishi, Masakazu; Yano, Masafumi; Sato, Hiroyasu; Yamano, Akihito; Takeya, Jun

2017-01-01

Abstract Printed and flexible electronics requires solution‐processable organic semiconductors with a carrier mobility (μ) of ≈10 cm2 V−1 s−1 as well as high chemical and thermal durability. In this study, chryseno[2,1‐b:8,7‐b′]dithiophene (ChDT) and its derivatives, which have a zigzag‐elongated fused π‐electronic core (π‐core) and a peculiar highest occupied molecular orbital (HOMO) configuration, are reported as materials with conceptually new semiconducting π‐cores. ChDT and its derivatives are prepared by a versatile synthetic procedure. A comprehensive investigation reveals that the ChDT π‐core exhibits increasing structural stability in the bulk crystal phase, and that it is unaffected by a variation of the transfer integral, induced by the perpetual molecular motion of organic materials owing to the combination of its molecular shape and its particular HOMO configuration. Notably, ChDT derivatives exhibit excellent chemical and thermal stability, high charge‐carrier mobility under ambient conditions (μ ≤ 10 cm2 V−1 s−1), and a crystal phase that is highly stable, even at temperatures above 250 °C. PMID:29375963

High Electron Mobility Thin‐Film Transistors Based on Solution‐Processed Semiconducting Metal Oxide Heterojunctions and Quasi‐Superlattices

PubMed Central

Lin, Yen‐Hung; Faber, Hendrik; Labram, John G.; Stratakis, Emmanuel; Sygellou, Labrini; Kymakis, Emmanuel; Hastas, Nikolaos A.; Li, Ruipeng; Zhao, Kui; Amassian, Aram; Treat, Neil D.; McLachlan, Martyn

2015-01-01

High mobility thin‐film transistor technologies that can be implemented using simple and inexpensive fabrication methods are in great demand because of their applicability in a wide range of emerging optoelectronics. Here, a novel concept of thin‐film transistors is reported that exploits the enhanced electron transport properties of low‐dimensional polycrystalline heterojunctions and quasi‐superlattices (QSLs) consisting of alternating layers of In2O3, Ga2O3, and ZnO grown by sequential spin casting of different precursors in air at low temperatures (180–200 °C). Optimized prototype QSL transistors exhibit band‐like transport with electron mobilities approximately a tenfold greater (25–45 cm2 V−1 s−1) than single oxide devices (typically 2–5 cm2 V−1 s−1). Based on temperature‐dependent electron transport and capacitance‐voltage measurements, it is argued that the enhanced performance arises from the presence of quasi 2D electron gas‐like systems formed at the carefully engineered oxide heterointerfaces. The QSL transistor concept proposed here can in principle extend to a range of other oxide material systems and deposition methods (sputtering, atomic layer deposition, spray pyrolysis, roll‐to‐roll, etc.) and can be seen as an extremely promising technology for application in next‐generation large area optoelectronics such as ultrahigh definition optical displays and large‐area microelectronics where high performance is a key requirement. PMID:27660741

Two-dimensional electron gas characteristics of InP-based high electron mobility transistor terahertz detector

NASA Astrophysics Data System (ADS)

Li, Jin-Lun; Cui, Shao-Hui; Xu, Jian-Xing; Cui, Xiao-Ran; Guo, Chun-Yan; Ma, Ben; Ni, Hai-Qiao; Niu, Zhi-Chuan

2018-04-01

Not Available Project supported by the Foundation for Scientific Instrument and Equipment Development, Chinese Academy of Sciences (Grant No. YJKYYQ20170032) and the National Natural Science Foundation of China (Grant No. 61435012).

Effect of strain on the electron effective mobility in biaxially strained silicon inversion layers: An experimental and theoretical analysis via atomic force microscopy measurements and Kubo-Greenwood mobility calculations

NASA Astrophysics Data System (ADS)

Bonno, Olivier; Barraud, Sylvain; Mariolle, Denis; Andrieu, François

2008-03-01

Recently, in order to explain the long-channel electron effective mobility at a high sheet carrier density in strained silicon channel transistors, it has been suggested by [M. V. Fischetti, F. Gamiz, and W. Hansch, J. Appl. Phys. 92, 7230 (2002)] that biaxial tensile strain should smooth the Si/SiO2 interface. To address this topic, the roughness properties of biaxial strained silicon-on-insulator (s-SOI) films are investigated by means of atomic force microscopy. Through in-depth statistical analysis of the digitalized surface profiles, the roughness parameters are extracted for unstrained and strained SOI films, with 0.8% biaxial tensile strain. Especially, it is found that strain significantly reduces the roughness amplitude. Then, mobility calculations in SOI and s-SOI inversion layers are performed in the framework of the Kubo-Greenwood formalism. The model accounts for the main scattering mechanisms that are dominant in the high electron density range, namely phonon and surface roughness. Special attention has been paid to the modeling of the latter by accounting for all the contributions of the potential which arise from the deformed rough interface, and by using a multisubband wavelength-dependent screening model. This model is then applied to study the influence of the surface morphology on the mobility in s-SOI inversion layers. In this context, the mobility gain between s-SOI and unstrained SOI layers is found to agree significantly better with experimental data if the strain-induced decrease of the roughness amplitude is taken into account.

Application of nonlocal plasma technology for controlling plasma conductivity

NASA Astrophysics Data System (ADS)

Yuan, Chengxun; Demidov, V. I.; Kudryavtsev, A. A.; Kurlyandskaya, I. P.; Rudakova, T. V.; Zhou, Z. X.

2017-10-01

A promising approach for better control of the plasma parameters involves the exploitation of peculiarities of plasmas with a nonlocal electron energy distribution. Nonlocal plasma technology (NLP-technology) is based on the effect of energetic electrons in the plasma volume. In this work, an experimental study of influence of the chemo-ionization processes on non-stationary plasma conductivity has been conducted. Due to energetic, supra-thermal electrons, which appear in the chemo-ionization reactions, the highly non-equilibrium and time dependent nonlocal electron energy distribution function is formed. In such a plasma thermal electrons always have positive conductivity (mobility), while supra-thermal, energetic electrons may have negative conductivity in heavy (argon, krypton and xenon) noble gases dependently on conditions. Experiments demonstrate that this effect may lead to the non-monotonic temporal behavior of plasma conductivity and may potentially create the negative electron mobility.

Artificial semiconductor/insulator superlattice channel structure for high-performance oxide thin-film transistors

PubMed Central

Ahn, Cheol Hyoun; Senthil, Karuppanan; Cho, Hyung Koun; Lee, Sang Yeol

2013-01-01

High-performance thin-film transistors (TFTs) are the fundamental building blocks in realizing the potential applications of the next-generation displays. Atomically controlled superlattice structures are expected to induce advanced electric and optical performance due to two-dimensional electron gas system, resulting in high-electron mobility transistors. Here, we have utilized a semiconductor/insulator superlattice channel structure comprising of ZnO/Al2O3 layers to realize high-performance TFTs. The TFT with ZnO (5 nm)/Al2O3 (3.6 nm) superlattice channel structure exhibited high field effect mobility of 27.8 cm2/Vs, and threshold voltage shift of only < 0.5 V under positive/negative gate bias stress test during 2 hours. These properties showed extremely improved TFT performance, compared to ZnO TFTs. The enhanced field effect mobility and stability obtained for the superlattice TFT devices were explained on the basis of layer-by-layer growth mode, improved crystalline nature of the channel layers, and passivation effect of Al2O3 layers. PMID:24061388

Correlation between active layer thickness and ambient gas stability in IGZO thin-film transistors

NASA Astrophysics Data System (ADS)

Gao, Xu; Lin, Meng-Fang; Mao, Bao-Hua; Shimizu, Maki; Mitoma, Nobuhiko; Kizu, Takio; Ou-Yang, Wei; Nabatame, Toshihide; Liu, Zhi; Tsukagoshi, Kazuhito; Wang, Sui-Dong

2017-01-01

Decreasing the active layer thickness has been recently reported as an alternative way to achieve fully depleted oxide thin-film transistors for the realization of low-voltage operations. However, the correlation between the active layer thickness and device resistivity to environmental changes is still unclear, which is important for the optimized design of oxide thin-film transistors. In this work, the ambient gas stability of IGZO thin-film transistors is found to be strongly correlated to the IGZO thickness. The TFT with the thinnest IGZO layer shows the highest intrinsic electron mobility in a vacuum, which is greatly reduced after exposure to O2/air. The device with a thick IGZO layer shows similar electron mobility in O2/air, whereas the mobility variation measured in the vacuum is absent. The thickness dependent ambient gas stability is attributed to a high-mobility region in the IGZO surface vicinity with less sputtering-induced damage, which will become electron depleted in O2/air due to the electron transfer to adsorbed gas molecules. The O2 adsorption and deduced IGZO surface band bending is demonstrated by the ambient-pressure x-ray photoemission spectroscopy results.

High-electron-mobility GaN grown on free-standing GaN templates by ammonia-based molecular beam epitaxy

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

Kyle, Erin C. H., E-mail: erinkyle@umail.ucsb.edu; Kaun, Stephen W.; Burke, Peter G.

2014-05-21

The dependence of electron mobility on growth conditions and threading dislocation density (TDD) was studied for n{sup −}-GaN layers grown by ammonia-based molecular beam epitaxy. Electron mobility was found to strongly depend on TDD, growth temperature, and Si-doping concentration. Temperature-dependent Hall data were fit to established transport and charge-balance equations. Dislocation scattering was analyzed over a wide range of TDDs (∼2 × 10{sup 6} cm{sup −2} to ∼2 × 10{sup 10} cm{sup −2}) on GaN films grown under similar conditions. A correlation between TDD and fitted acceptor states was observed, corresponding to an acceptor state for almost every c lattice translation along each threading dislocation. Optimizedmore » GaN growth on free-standing GaN templates with a low TDD (∼2 × 10{sup 6} cm{sup −2}) resulted in electron mobilities of 1265 cm{sup 2}/Vs at 296 K and 3327 cm{sup 2}/Vs at 113 K.« less

Electron–acoustic phonon coupling in single crystal CH 3NH 3PbI 3 perovskites revealed by coherent acoustic phonons

DOE PAGES

Mante, Pierre-Adrien; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.; ...

2017-02-08

The intrinsic properties of CH 3NH 3PbI 3 are still largely unknown in spite of the great amount of attention it has received for its solar cell application. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. Furthermore, we apply this method to characterize a CH 3NH 3PbI 3 single crystal.We measure the acoustic phonon properties and characterizemore » electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. These results reveal high electron and hole mobilities of 2,800 and 9,400 cm 2V -1 s -1 , respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH 3NH 3PbI 3.« less

Electron–acoustic phonon coupling in single crystal CH 3NH 3PbI 3 perovskites revealed by coherent acoustic phonons

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

Mante, Pierre-Adrien; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.

The intrinsic properties of CH 3NH 3PbI 3 are still largely unknown in spite of the great amount of attention it has received for its solar cell application. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. Furthermore, we apply this method to characterize a CH 3NH 3PbI 3 single crystal.We measure the acoustic phonon properties and characterizemore » electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. These results reveal high electron and hole mobilities of 2,800 and 9,400 cm 2V -1 s -1 , respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH 3NH 3PbI 3.« less

Role of electron-phonon coupling and thermal expansion on band gaps, carrier mobility, and interfacial offsets in kesterite thin-film solar cells

NASA Astrophysics Data System (ADS)

Monserrat, Bartomeu; Park, Ji-Sang; Kim, Sunghyun; Walsh, Aron

2018-05-01

The efficiencies of solar cells based on kesterite Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) are limited by a low open-circuit voltage due to high rates of non-radiative electron-hole recombination. To probe the origin of this bottleneck, we calculate the band offset of CZTS(Se) with CdS, confirming a weak spike of 0.1 eV for CZTS/wurtzite-CdS and a strong spike of 0.4 eV for CZTSe/wurtzite-CdS. We also consider the effects of temperature on the band alignment, finding that increasing temperature significantly enhances the spike-type offset. We further resolve an outstanding discrepancy between the measured and calculated phonon frequencies for the kesterites, and use these to estimate the upper limit of electron and hole mobilities based on optic phonon Fröhlich scattering, which uncovers an intrinsic asymmetry with faster (minority carrier) electron mobility.

LaTiO3/KTaO3 interfaces: A new two-dimensional electron gas system

NASA Astrophysics Data System (ADS)

Zou, K.; Ismail-Beigi, Sohrab; Kisslinger, Kim; Shen, Xuan; Su, Dong; Walker, F. J.; Ahn, C. H.

2015-03-01

We report a new 2D electron gas (2DEG) system at the interface between a Mott insulator, LaTiO3, and a band insulator, KTaO3. For LaTiO3/KTaO3 interfaces, we observe metallic conduction from 2 K to 300 K. One serious technological limitation of SrTiO3-based conducting oxide interfaces for electronics applications is the relatively low carrier mobility (0.5-10 cm2/V s) of SrTiO3 at room temperature. By using KTaO3, we achieve mobilities in LaTiO3/KTaO3 interfaces as high as 21 cm2/V s at room temperature, over a factor of 3 higher than observed in doped bulk SrTiO3. By density functional theory, we attribute the higher mobility in KTaO3 2DEGs to the smaller effective mass for electrons in KTaO3.

Different electronic and charge-transport properties of four organic semiconductors Tetraazaperopyrenes derivatives

NASA Astrophysics Data System (ADS)

Shi, Yarui; Wei, Huiling; Liu, Yufang

2015-03-01

Tetraazaperopyrenes (TAPPs) derivatives are high-performance n-type organic semiconductor material families with the remarkable long-term stabilities. The charge carrier mobilities in TAPPs derivatives crystals were calculated by the density functional theory (DFT) method combined with the Marcus-Hush electron-transfer theory. The existence of considerable C-H…F-C bonding defines the conformation of the molecular structure and contributes to its stability. We illustrated how it is possible to control the electronic and charge-transport parameters of TAPPs derivatives as a function of the positions, a type of the substituents. It is found that the core substitution of TAPPs has a drastic influence on the charge-transport mobilities. The maximum electron mobility value of the core-brominated 2,9-bis (perfluoroalkyl)-substituted TAPPs is 0.521 cm2 V-1 s-1, which appear in the orientation angle 95° and 275°. The results demonstrate that the TAPPs with bromine substituents in ortho positions exhibit the best charge-transfer efficiency among the four different TAPP derivatives.

Bulk contribution to magnetotransport properties of low-defect-density Bi2Te3 topological insulator thin films

NASA Astrophysics Data System (ADS)

Ngabonziza, P.; Wang, Y.; Brinkman, A.

2018-04-01

An important challenge in the field of topological materials is to carefully disentangle the electronic transport contribution of the topological surface states from that of the bulk. For Bi2Te3 topological insulator samples, bulk single crystals and thin films exposed to air during fabrication processes are known to be bulk conducting, with the chemical potential in the bulk conduction band. For Bi2Te3 thin films grown by molecular beam epitaxy, we combine structural characterization (transmission electron microscopy), chemical surface analysis as function of time (x-ray photoelectron spectroscopy) and magnetotransport analysis to understand the low defect density and record high bulk electron mobility once charge is doped into the bulk by surface degradation. Carrier densities and electronic mobilities extracted from the Hall effect and the quantum oscillations are consistent and reveal a large bulk carrier mobility. Because of the cylindrical shape of the bulk Fermi surface, the angle dependence of the bulk magnetoresistance oscillations is two dimensional in nature.

Unraveling Unprecedented Charge Carrier Mobility through Structure Property Relationship of Four Isomers of Didodecyl[1]benzothieno[3,2-b][1]benzothiophene.

PubMed

Tsutsui, Yusuke; Schweicher, Guillaume; Chattopadhyay, Basab; Sakurai, Tsuneaki; Arlin, Jean-Baptiste; Ruzié, Christian; Aliev, Almaz; Ciesielski, Artur; Colella, Silvia; Kennedy, Alan R; Lemaur, Vincent; Olivier, Yoann; Hadji, Rachid; Sanguinet, Lionel; Castet, Frédéric; Osella, Silvio; Dudenko, Dmytro; Beljonne, David; Cornil, Jérôme; Samorì, Paolo; Seki, Shu; Geerts, Yves H

2016-09-01

The structural and electronic properties of four isomers of didodecyl[1]-benzothieno[3,2-b][1]benzothiophene (C12-BTBT) have been investigated. Results show the strong impact of the molecular packing on charge carrier transport and electronic polarization properties. Field-induced time-resolved microwave conductivity measurements unravel an unprecedented high average interfacial mobility of 170 cm(2) V(-1) s(-1) for the 2,7-isomer, holding great promise for the field of organic electronics. © 2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The mobility and diffusion of ions in gases

NASA Technical Reports Server (NTRS)

Mcdaniel, E. W.; Mason, E. A.

1973-01-01

Experimental and theoretical aspects of the mobility and diffusion of ions in gases are studied in detail. Some of the subjects discussed include ion-ion interaction, boundary condition and ion and electron behavior. Also discussed in separate chapters are the problems of the diffusion coefficients and the afterglow techniques. Finally, a special chapter studies the kinetic theory of diffusion and mobility, stressing the low-, medium- and high-field theory.

AlGaN/GaN heterostructures with an AlGaN layer grown directly on reactive-ion-etched GaN showing a high electron mobility (>1300 cm2 V-1 s-1)

NASA Astrophysics Data System (ADS)

Yamamoto, Akio; Makino, Shinya; Kanatani, Keito; Kuzuhara, Masaaki

2018-04-01

In this study, the metal-organic-vapor-phase-epitaxial growth behavior and electrical properties of AlGaN/GaN structures prepared by the growth of an AlGaN layer on a reactive-ion-etched (RIE) GaN surface without regrown GaN layers were investigated. The annealing of RIE-GaN surfaces in NH3 + H2 atmosphere, employed immediately before AlGaN growth, was a key process in obtaining a clean GaN surface for AlGaN growth, that is, in obtaining an electron mobility as high as 1350 cm2 V-1 s-1 in a fabricated AlGaN/RIE-GaN structure. High-electron-mobility transistors (HEMTs) were successfully fabricated with AlGaN/RIE-GaN wafers. With decreasing density of dotlike defects observed on the surfaces of AlGaN/RIE-GaN wafers, both two-dimensional electron gas properties of AlGaN/RIE-GaN structures and DC characteristics of HEMTs were markedly improved. Since dotlike defect density was markedly dependent on RIE lot, rather than on growth lot, surface contaminations of GaN during RIE were believed to be responsible for the formation of dotlike defects and, therefore, for the inferior electrical properties.

Electronics Devices and Materials

DTIC Science & Technology

2008-03-17

Molecular -bea epitaxy MCNPX ............... Software code Misse6 ................. Satellite expected to carry ORMatE-I Misse7...patterning using electron beam lithography), spaces (class 1000 clean benches), and skills (appropriate mix of skilled technicians and professionals...34 Process samples for various projects such as Antimode Base High Electron Mobility Transistors ( HEMT ) and Double Heterojuction Bipolar Transistors

Analysis of energy states where electrons and holes coexist in pseudomorphically strained InAs high-electron-mobility transistors

NASA Astrophysics Data System (ADS)

Nishio, Yui; Sato, Takato; Hirayama, Naomi; Iida, Tsutomu; Takanashi, Yoshifumi

2016-04-01

In strained high-electron-mobility transistors (HEMTs) with InAs as the channel, excess electrons and holes are generated in the drain region by impact ionization. In the source region, electrons are injected to recombine with accumulated holes by the Auger process. This causes the shift of the gate potential, V GS,shift, for HEMTs. For a system where electrons and holes coexist, we established a theory taking into account the nonparabolicity of the conduction band in the InAs channel. This theory enables us to rigorously determine not only the energy states and the concentration profiles for both carriers but also the V GS,shift due to an accumulation of holes. We have derived the Auger recombination theory which takes into account the Fermi-Dirac statistics and is applicable to an arbitrary shape of potential energy. The Auger recombination lifetime τA for InAs-PHEMTs was estimated as a function of the sheet hole concentration, p s, and τA was on the order of psec for p s exceeding 1012 cm-2.

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

Stolterfoht, Martin; Armin, Ardalan; Pandey, Ajay K.

Photovoltaic performance in relation to charge transport is studied in efficient (7.6%) organic solar cells (PTB7:PC{sub 71}BM). Both electron and hole mobilities are experimentally measured in efficient solar cells using the resistance dependent photovoltage technique, while the inapplicability of classical techniques, such as space charge limited current and photogenerated charge extraction by linearly increasing voltage is discussed. Limits in the short-circuit current originate from optical losses, while charge transport is shown not to be a limiting process. Efficient charge extraction without recombination can be achieved with a mobility of charge carriers much lower than previously expected. The presence of dispersivemore » transport with strongly distributed mobilities in high efficiency solar cells is demonstrated. Reduced non-Langevin recombination is shown to be beneficial for solar cells with imbalanced, low, and dispersive electron and hole mobilities.« less

Electron Scattering and Doping Mechanisms in Solid-Phase-Crystallized In2O3:H Prepared by Atomic Layer Deposition.

PubMed

Macco, Bart; Knoops, Harm C M; Kessels, Wilhelmus M M

2015-08-05

Hydrogen-doped indium oxide (In2O3:H) has recently emerged as an enabling transparent conductive oxide for solar cells, in particular for silicon heterojunction solar cells because its high electron mobility (>100 cm(2)/(V s)) allows for a simultaneously high electrical conductivity and optical transparency. Here, we report on high-quality In2O3:H prepared by a low-temperature atomic layer deposition (ALD) process and present insights into the doping mechanism and the electron scattering processes that limit the carrier mobility in such films. The process consists of ALD of amorphous In2O3:H at 100 °C and subsequent solid-phase crystallization at 150-200 °C to obtain large-grained polycrystalline In2O3:H films. The changes in optoelectronic properties upon crystallization have been monitored both electrically by Hall measurements and optically by analysis of the Drude response. After crystallization, an excellent carrier mobility of 128 ± 4 cm(2)/(V s) can be obtained at a carrier density of 1.8 × 10(20) cm(-3), irrespective of the annealing temperature. Temperature-dependent Hall measurements have revealed that electron scattering is dominated by unavoidable phonon and ionized impurity scattering from singly charged H-donors. Extrinsic defect scattering related to material quality such as grain boundary and neutral impurity scattering was found to be negligible in crystallized films indicating that the carrier mobility is maximized. Furthermore, by comparison of the absolute H-concentration and the carrier density in crystallized films, it is deduced that <4% of the incorporated H is an active dopant in crystallized films. Therefore, it can be concluded that inactive H atoms do not (significantly) contribute to defect scattering, which potentially explains why In2O3:H films are capable of achieving a much higher carrier mobility than conventional In2O3:Sn (ITO).

Photovoltaic Bias Generator

DTIC Science & Technology

2018-02-01

Research Laboratory Sensors and Electron Devices Directorate (ATTN: RDRL-SER-M) 2800 Powder Mill Rd Adelphi, MD 20783-1138 8. PERFORMING...that may be set between 200 mV and 400 mV, developed for an application using gallium arsenide pseudomorphic high electron mobility transistor

Investigation of gate-diode degradation in normally-off p-GaN/AlGaN/GaN high-electron-mobility transistors

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

Ťapajna, M., E-mail: milan.tapajna@savba.sk; Kuzmík, J.; Hilt, O.

2015-11-09

Gate diode conduction mechanisms were analyzed in normally-off p-GaN/AlGaN/GaN high-electron mobility transistors grown on Si wafers before and after forward bias stresses. Electrical characterization of the gate diodes indicates forward current to be limited by channel electrons injected through the AlGaN/p-GaN triangular barrier promoted by traps. On the other hand, reverse current was found to be consistent with carrier generation-recombination processes in the AlGaN layer. Soft breakdown observed after ∼10{sup 5 }s during forward bias stress at gate voltage of 7 V was attributed to formation of conductive channel in p-GaN/AlGaN gate stack via trap generation and percolation mechanism, likely due tomore » coexistence of high electric field and high forward current density. Possible enhancement of localized conductive channels originating from spatial inhomogeneities is proposed to be responsible for the degradation.« less

Bay-annulated indigo (BAI) as an excellent electron accepting building block for high performance organic semiconductors

DOEpatents

Liu, Yi; He, Bo; Pun, Andrew

2015-11-24

A novel electron acceptor based on bay-annulated indigo (BAI) was synthesized and used for the preparation of a series of high performance donor-acceptor small molecules and polymers. The resulting materials possess low-lying LUMO energy level and small HOMO-LUMO gaps, while their films exhibited high crystallinity upon thermal treatment, commensurate with high field effect mobilities and ambipolar transfer characteristics.

Bay-annulated indigo (BAI) as an excellent electron accepting building block for high performance organic semiconductors

DOEpatents

Liu, Yi; He, Bo; Pun, Andrew

2016-04-19

A novel electron acceptor based on bay-annulated indigo (BAI) was synthesized and used for the preparation of a series of high performance donor-acceptor small molecules and polymers. The resulting materials possess low-lying LUMO energy level and small HOMO-LUMO gaps, while their films exhibited high crystallinity upon thermal treatment, commensurate with high field effect mobilities and ambipolar transfer characteristics.

Fully Solution-Processed Flexible Organic Thin Film Transistor Arrays with High Mobility and Exceptional Uniformity

PubMed Central

Fukuda, Kenjiro; Takeda, Yasunori; Mizukami, Makoto; Kumaki, Daisuke; Tokito, Shizuo

2014-01-01

Printing fully solution-processed organic electronic devices may potentially revolutionize production of flexible electronics for various applications. However, difficulties in forming thin, flat, uniform films through printing techniques have been responsible for poor device performance and low yields. Here, we report on fully solution-processed organic thin-film transistor (TFT) arrays with greatly improved performance and yields, achieved by layering solution-processable materials such as silver nanoparticle inks, organic semiconductors, and insulating polymers on thin plastic films. A treatment layer improves carrier injection between the source/drain electrodes and the semiconducting layer and dramatically reduces contact resistance. Furthermore, an organic semiconductor with large-crystal grains results in TFT devices with shorter channel lengths and higher field-effect mobilities. We obtained mobilities of over 1.2 cm2 V−1 s−1 in TFT devices with channel lengths shorter than 20 μm. By combining these fabrication techniques, we built highly uniform organic TFT arrays with average mobility levels as high as 0.80 cm2 V−1 s−1 and ideal threshold voltages of 0 V. These results represent major progress in the fabrication of fully solution-processed organic TFT device arrays. PMID:24492785

Demonstration of Confined Electron Gas and Steep-Slope Behavior in Delta-Doped GaAs-AlGaAs Core-Shell Nanowire Transistors.

PubMed

Morkötter, S; Jeon, N; Rudolph, D; Loitsch, B; Spirkoska, D; Hoffmann, E; Döblinger, M; Matich, S; Finley, J J; Lauhon, L J; Abstreiter, G; Koblmüller, G

2015-05-13

Strong surface and impurity scattering in III-V semiconductor-based nanowires (NW) degrade the performance of electronic devices, requiring refined concepts for controlling charge carrier conductivity. Here, we demonstrate remote Si delta (δ)-doping of radial GaAs-AlGaAs core-shell NWs that unambiguously exhibit a strongly confined electron gas with enhanced low-temperature field-effect mobilities up to 5 × 10(3) cm(2) V(-1) s(-1). The spatial separation between the high-mobility free electron gas at the NW core-shell interface and the Si dopants in the shell is directly verified by atom probe tomographic (APT) analysis, band-profile calculations, and transport characterization in advanced field-effect transistor (FET) geometries, demonstrating powerful control over the free electron gas density and conductivity. Multigated NW-FETs allow us to spatially resolve channel width- and crystal phase-dependent variations in electron gas density and mobility along single NW-FETs. Notably, dc output and transfer characteristics of these n-type depletion mode NW-FETs reveal excellent drain current saturation and record low subthreshold slopes of 70 mV/dec at on/off ratios >10(4)-10(5) at room temperature.

78 FR 23593 - Certain Mobile Electronic Devices Incorporating Haptics; Termination of Investigation

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-19

... INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-834] Certain Mobile Electronic Devices... this investigation may be viewed on the Commission's electronic docket (EDIS) at http://edis.usitc.gov... mobile electronic devices incorporating haptics that infringe certain claims of six Immersion patents. 77...

Numerical simulation of offset-drain amorphous oxide-based thin-film transistors

NASA Astrophysics Data System (ADS)

Jeong, Jaewook

2016-11-01

In this study, we analyzed the electrical characteristics of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with an offset-drain structure by technology computer aided design (TCAD) simulation. When operating in a linear region, an enhancement-type TFT shows poor field-effect mobility because most conduction electrons are trapped in acceptor-like defects in an offset region when the offset length (L off) exceeds 0.5 µm, whereas a depletion-type TFT shows superior field-effect mobility owing to the high free electron density in the offset region compared with the trapped electron density. When operating in the saturation region, both types of TFTs show good field-effect mobility comparable to that of a reference TFT with a large gate overlap. The underlying physics of the depletion and enhancement types of offset-drain TFTs are systematically analyzed.

A novel plasmonic interferometry and the potential applications

NASA Astrophysics Data System (ADS)

Ali, J.; Pornsuwancharoen, N.; Youplao, P.; Aziz, M. S.; Chiangga, S.; Jaglan, J.; Amiri, I. S.; Yupapin, P.

2018-03-01

In this article, we have proposed the plasmonic interferometry concept and analytical details given. By using the conventional optical interferometry, which can be simply calculated by using the relationship between the electric field and electron mobility, the interference mobility visibility (fringe visibility) can be observed. The surface plasmons in the sensing arm of the Michelson interferometer is constructed by the stacked layers of the silicon-graphene-gold, allows to characterize the spatial resolution of light beams in terms of the electron mobility down to 100-nm scales, with measured coherence lengths as low as ∼100 nm for an incident wavelength of 1550 nm. We have demonstrated a compact plasmonic interferometer that can apply to the electron mean free paths measurement, from which the precise determination can be used for the high-resolution mean free path measurement and sensing applications. This system provides the practical simulation device parameters that can be fabricated and tested by the experimental platform.

Electro-Thermo-Mechanical Transient Modeling of Stress Development in AlGaN/GaN High Electron Mobility Transistors (HEMTs) (Postprint)

DTIC Science & Technology

2014-02-01

Applied Drain Voltage Ids Drain-to-Source current MPa Megapascals σxx x-Component of Stress INTRODUCTION Gallium nitride (GaN) based high electron...the thermodynamic model to obtain the current densities within a semiconductor device. In doing so, it is possible to determine the electric

Exploring the Use of Electronic Mobile Technologies among Distance Learners in Rural Communities for Safe and Disruptive Learning

ERIC Educational Resources Information Center

Ntloedibe-Kuswani, Gomang Seratwa

2013-01-01

Several studies indicated the potential of electronic mobile technologies in reaching (safe learning) under-served communities and engaging (disruptive learning) disadvantaged peoples affording them learning experiences. However, the potential benefits of (electronic mobile learning) e-mobile learning have not been well understood from the…

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

Yu, Sangbae; Yoon, Daseob; Son, Junwoo, E-mail: jwson@postech.ac.kr

We report the enhancement of room-temperature electron mobility in La-doped BaSnO{sub 3} (LBSO) thin films with thermal strain induced by high temperature nitrogen (N{sub 2}) annealing. Simple annealing under an N{sub 2} environment consistently doubled the electron mobility of the LBSO films on the SrTiO{sub 3} (STO) substrates to as high as 78 cm{sup 2} V{sup −1} s{sup −1} at a carrier concentration of 4.0 × 10{sup 20 }cm{sup −3}. This enhancement is mainly attributed to annihilation of extended defects as a consequence of compressive strain induced by the difference in the thermal expansion coefficients of LBSO and STO. Our study suggests that thermalmore » strain can be exploited to reduce extended defects and to facilitate electron transport in transparent oxide semiconductors.« less

Unfolding the band structure of disordered solids: From bound states to high-mobility Kane fermions

NASA Astrophysics Data System (ADS)

Rubel, O.; Bokhanchuk, A.; Ahmed, S. J.; Assmann, E.

2014-09-01

Supercells are often used in ab initio calculations to model compound alloys, surfaces, and defects. One of the main challenges of supercell electronic structure calculations is to recover the Bloch character of electronic eigenstates perturbed by disorder. Here we apply the spectral weight approach to unfolding the electronic structure of group III-V and II-VI semiconductor solid solutions. The illustrative examples include formation of donorlike states in dilute Ga(PN) and associated enhancement of its optical activity, direct observation of the valence band anticrossing in dilute GaAs:Bi, and a topological band crossover in ternary (HgCd)Te alloy accompanied by emergence of high-mobility Kane fermions. The analysis facilitates interpretation of optical and transport characteristics of alloys that are otherwise ambiguous in traditional first-principles supercell calculations.

76 FR 41522 - In the Matter of Certain Electronic Devices, Including Mobile Phones, Mobile Tablets, Portable...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-14

... INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-771] In the Matter of Certain Electronic Devices, Including Mobile Phones, Mobile Tablets, Portable Music Players, and Computers, and Components... certain mobile phones, mobile tablets, portable music players, and computers. 76 FR 24051 (Apr. 29, 2011...

Modeling and Design of GaN High Electron Mobility Transistors and Hot Electron Transistors through Monte Carlo Particle-based Device Simulations

NASA Astrophysics Data System (ADS)

Soligo, Riccardo

In this work, the insight provided by our sophisticated Full Band Monte Carlo simulator is used to analyze the behavior of state-of-art devices like GaN High Electron Mobility Transistors and Hot Electron Transistors. Chapter 1 is dedicated to the description of the simulation tool used to obtain the results shown in this work. Moreover, a separate section is dedicated the set up of a procedure to validate to the tunneling algorithm recently implemented in the simulator. Chapter 2 introduces High Electron Mobility Transistors (HEMTs), state-of-art devices characterized by highly non linear transport phenomena that require the use of advanced simulation methods. The techniques for device modeling are described applied to a recent GaN-HEMT, and they are validated with experimental measurements. The main techniques characterization techniques are also described, including the original contribution provided by this work. Chapter 3 focuses on a popular technique to enhance HEMTs performance: the down-scaling of the device dimensions. In particular, this chapter is dedicated to lateral scaling and the calculation of a limiting cutoff frequency for a device of vanishing length. Finally, Chapter 4 and Chapter 5 describe the modeling of Hot Electron Transistors (HETs). The simulation approach is validated by matching the current characteristics with the experimental one before variations of the layouts are proposed to increase the current gain to values suitable for amplification. The frequency response of these layouts is calculated, and modeled by a small signal circuit. For this purpose, a method to directly calculate the capacitance is developed which provides a graphical picture of the capacitative phenomena that limit the frequency response in devices. In Chapter 5 the properties of the hot electrons are investigated for different injection energies, which are obtained by changing the layout of the emitter barrier. Moreover, the large signal characterization of the HET is shown for different layouts, where the collector barrier was scaled.

Quantifying electronic band interactions in van der Waals materials using angle-resolved reflected-electron spectroscopy.

PubMed

Jobst, Johannes; van der Torren, Alexander J H; Krasovskii, Eugene E; Balgley, Jesse; Dean, Cory R; Tromp, Rudolf M; van der Molen, Sense Jan

2016-11-29

High electron mobility is one of graphene's key properties, exploited for applications and fundamental research alike. Highest mobility values are found in heterostructures of graphene and hexagonal boron nitride, which consequently are widely used. However, surprisingly little is known about the interaction between the electronic states of these layered systems. Rather pragmatically, it is assumed that these do not couple significantly. Here we study the unoccupied band structure of graphite, boron nitride and their heterostructures using angle-resolved reflected-electron spectroscopy. We demonstrate that graphene and boron nitride bands do not interact over a wide energy range, despite their very similar dispersions. The method we use can be generally applied to study interactions in van der Waals systems, that is, artificial stacks of layered materials. With this we can quantitatively understand the 'chemistry of layers' by which novel materials are created via electronic coupling between the layers they are composed of.

Reduced mobility and PPC in In(.20)Ga(.80)As / Al(.23)Ga(.77)As HEMT structure

NASA Technical Reports Server (NTRS)

Schacham, S. E.; Mena, Rafael A.; Haugland, Edward J.; Alterovitz, Samuel A.

1992-01-01

Transport properties of a pseudomorphic In(.20)Ga(.80)As/Al(.23)Ga(.77)As High Electron Mobility Transistor (HEMT) structure were measured by Hall and SdH techniques. Two samples of identical structures but with different doping levels were compared. Low temperature mobility measurements as a function of concentration coincides with the onset of second subband occupancy, indicating that the decrease in mobility is due to intersubband scattering. In spite of the low Al content (23 percent), large persistent photoconductivity (PPC) was observed in the highly doped sample only, showing a direct correlation between the PPC and doping concentration of the barrier layer.

Plasma-assisted Molecular Beam Epitaxy of N-polar InAlN-barrier High-electron-mobility Transistors.

PubMed

Hardy, Matthew T; Storm, David F; Katzer, D Scott; Downey, Brian P; Nepal, Neeraj; Meyer, David J

2016-11-24

Plasma-assisted molecular beam epitaxy is well suited for the epitaxial growth of III-nitride thin films and heterostructures with smooth, abrupt interfaces required for high-quality high-electron-mobility transistors (HEMTs). A procedure is presented for the growth of N-polar InAlN HEMTs, including wafer preparation and growth of buffer layers, the InAlN barrier layer, AlN and GaN interlayers and the GaN channel. Critical issues at each step of the process are identified, such as avoiding Ga accumulation in the GaN buffer, the role of temperature on InAlN compositional homogeneity, and the use of Ga flux during the AlN interlayer and the interrupt prior to GaN channel growth. Compositionally homogeneous N-polar InAlN thin films are demonstrated with surface root-mean-squared roughness as low as 0.19 nm and InAlN-based HEMT structures are reported having mobility as high as 1,750 cm 2 /V∙sec for devices with a sheet charge density of 1.7 x 10 13 cm -2 .

Using Mobile Phones in Support of Student Learning in Secondary Science Inquiry Classrooms

ERIC Educational Resources Information Center

Khoo, Elaine; Otrel-Cass, Kathrin

2017-01-01

This paper reports on findings from a research project concerned with how electronic networking tools (e-networked tools), such as the Internet, online forums, and mobile technologies, can support authentic science inquiry in junior secondary classrooms. It focuses on three qualitative case studies involving science teachers from two high schools…

Performance Analysis of GaN Capping Layer Thickness on GaN/AlGaN/GaN High Electron Mobility Transistors.

PubMed

Sharma, N; Periasamy, C; Chaturvedi, N

2018-07-01

In this paper, we present an investigation of the impact of GaN capping layer and AlGaN layer thickness on the two-dimensional (2D)-electron mobility and the carrier concentration which was formed close to the AlGaN/GaN buffer layer for Al0.25Ga0.75N/GaN and GaN/Al0.25Ga0.75N/GaN heterostructures deposited on sapphire substrates. The results of our analysis clearly indicate that expanding the GaN capping layer thickness from 1 nm to 100 nm prompts an increment in the electron concentration at hetero interface. As consequence of which drain current was additionally increments with GaN cap layer thicknesses, and eventually saturates at approximately 1.85 A/mm for capping layer thickness greater than 40 nm. Interestingly, for the same structure, the 2D-electron mobility, decrease monotonically with GaN capping layer thickness, and saturate at approximately 830 cm2/Vs for capping layer thickness greater than 50 nm. A device with a GaN cap layer didn't exhibit gate leakage current. Furthermore, it was observed that the carrier concentration was first decrease 1.03 × 1019/cm3 to 6.65 × 1018/cm3 with AlGaN Layer thickness from 5 to 10 nm and after that it increases with the AlGaN layer thickness from 10 to 30 nm. The same trend was followed for electric field distributions. Electron mobility decreases monotonically with AlGaN layer thickness. Highest electron mobility 1354 cm2/Vs were recorded for the AlGaN layer thickness of 5 nm. Results obtained are in good agreement with published experimental data.

Understanding Local and Macroscopic Electron Mobilities in the Fullerene Network of Conjugated Polymer-based Solar Cells. Time-Resolved Microwave Conductivity and Theory

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

Aguirre, Jordan C.; Arntsen, Christopher D.; Hernandez, Samuel

2013-09-23

The efficiency of bulk heterojunction (BHJ) organic photovoltaics is sensitive to the morphology of the fullerene network that transports electrons through the device. This sensitivity makes it difficult to distinguish the contrasting roles of local electron mobility (how easily electrons can transfer between neighboring fullerene molecules) and macroscopic electron mobility (how well-connected is the fullerene network on device length scales) in solar cell performance. In this work, a combination of density functional theory (DFT) calculations, flash-photolysis time-resolved microwave conductivity (TRMC) experiments, and space-charge-limit current (SCLC) mobility estimates are used to examine the roles of local and macroscopic electron mobility inmore » conjugated polymer/fullerene BHJ photovoltaics. The local mobility of different pentaaryl fullerene derivatives (so-called ‘shuttlecock’ molecules) is similar, so that differences in solar cell efficiency and SCLC mobilities result directly from the different propensities of these molecules to self-assemble on macroscopic length scales. These experiments and calculations also demonstrate that the local mobility of phenyl-C60 butyl methyl ester (PCBM) is an order of magnitude higher than that of other fullerene derivatives, explaining why PCBM has been the acceptor of choice for conjugated polymer BHJ devices even though it does not form an optimal macroscopic network. The DFT calculations indicate that PCBM's superior local mobility comes from the near-spherical nature of its molecular orbitals, which allow strong electronic coupling between adjacent molecules. In combination, DFT and TRMC techniques provide a tool for screening new fullerene derivatives for good local mobility when designing new molecules that can improve on the macroscopic electron mobility offered by PCBM.« less

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

Portable data collection terminal in the automated power consumption measurement system

NASA Astrophysics Data System (ADS)

Vologdin, S. V.; Shushkov, I. D.; Bysygin, E. K.

2018-01-01

Aim of efficiency increasing, automation process of electric energy data collection and processing is very important at present time. High cost of classic electric energy billing systems prevent from its mass application. Udmurtenergo Branch of IDGC of Center and Volga Region developed electronic automated system called “Mobile Energy Billing” based on data collection terminals. System joins electronic components based on service-oriented architecture, WCF services. At present time all parts of Udmurtenergo Branch electric network are connected to “Mobile Energy Billing” project. System capabilities are expanded due to flexible architecture.

Synthesis, structural characterization and mobility measurement of electron accepting pyrazine derivatives

NASA Astrophysics Data System (ADS)

Lai, William W.

Several pyrazine based cyano aza derivatives have been synthesized and electronic devices made from them. Hole and electron mobilities were measured using a time of flight (TOF) method with silicon wafers as both the substrate and charge carrier generation layer. The high density of charge carriers generated from silicon allowed for film layers as thin as 100nm and up to 250nm. Two compounds, 2,3,6,7-tetracyano-1,4,5,8-tetraazanapthalene (TCNN) and 2,3,6,7-tetracyano-9,10-dioctyl-1,4,5,6,9,10-hexaazaanthracene (DOA) were shown to be good electron acceptors. The potentials at which TCNN and DOA are reduced was -0.03 and -1.5 volts respectively. Electron mobilities of both compounds were found to be 2x10-5 cm2V˙s . The previously unreported oxidation potential of 2,3,6,7-tetracyano-9,10-dioctyl 1,4,5,6,9,10-hexaazaanthracene was measured and the hole mobility was determined to be 2x10-5 cm2V˙s . In the case of DOA, the charge carrier density of the electron carriers was comparable to that of the charge carrier density of the hole carriers. In contrast, the electron TOF signal of TCNN, which does not exhibit an oxidation, is greater than the hole TOF signal by roughly 200 fold. The inability for TCNN to act as a hole carrier was remedied by combining it with tetrathiafulvalene (TTF) as an electron donor. Crystals of the 1:1 complex were grown and the solved structure revealed segregated stacking. Conductivity measurements, by both two and four point methods determined the range of conductivity ranging from 10-5 to 10-6 Scm . The electron and hole mobility of the material was determined to be 2x10-5 and 2x10-6 cm2V˙s respectively. With the complementary TTF:TCNN system, the electron V-s and hole TOF signals were comparable, indicating a material that can equally conduct electrons or holes.

Influence of a parallel magnetic field on the microwave photoconductivity in a high-mobility two-dimensional electron system

NASA Astrophysics Data System (ADS)

Yang, C. L.; Du, R. R.; Pfeiffer, L. N.; West, K. W.

2006-07-01

Using a two-axis magnet, we have studied experimentally the influence of a parallel magnetic field (B//) on microwave-induced resistance oscillations (MIROs) and zero-resistance states (ZRS) previously discovered in a high-mobility two-dimensional electron system. We have observed a strong suppression of MIRO/ZRS by a modest B//˜1T . In Hall bar samples, magnetoplasmon resonance (MPR) has also been observed concurrently with the MIRO/ZRS. In contrast to the suppression of MIRO/ZRS, the MPR peak is apparently enhanced by B// . These findings cannot be explained by a simple modification of single-particle energy spectrum and/or scattering parameters by B// .

SnO2-gated AlGaN/GaN high electron mobility transistors based oxygen sensors

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

Hung, S.T.; Chung, Chi-Jung; Chen, Chin Ching

2012-01-01

Hydrothermally grown SnO2 was integrated with AlGaN/GaN high electron mobility transistor (HEMT) sensor as the gate electrode for oxygen detection. The crystalline of the SnO2 was improved after annealing at 400 C. The grain growth kinetics of the SnO2 nanomaterials, together with the O2 gas sensing properties and sensing mechanism of the SnO2 gated HEMT sensors were investigated. Detection of 1% oxygen in nitrogen at 100 C was possible. A low operation temperature and low power consumption oxygen sensor can be achieved by combining the SnO2 films with the AlGaN/GaN HEMT structure

Degradation and annealing effects caused by oxygen in AlGaN/GaN high electron mobility transistors

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

Jiang, R., E-mail: rong.jiang@vanderbilt.edu; Chen, J.; Duan, G. X.

Hot-carrier degradation and room-temperature annealing effects are investigated in unpassivated ammonia-rich AlGaN/GaN high electron mobility transistors. Devices exhibit a fast recovery when annealed after hot carrier stress with all pins grounded. The recovered peak transconductance can exceed the original value, an effect that is not observed in control passivated samples. Density functional theory calculations suggest that dehydrogenation of pre-existing O{sub N}-H defects in AlGaN plays a significant role in the observed hot carrier degradation, and the resulting bare O{sub N} can naturally account for the “super-recovery” in the peak transconductance.

Synthesis of poly(benzothiadiazole-co-dithienobenzodithiophenes) and effect of thiophene insertion for high-performance polymer solar cells.

PubMed

Yun, Hui-Jun; Lee, Yun-Ji; Yoo, Seung-Jin; Chung, Dae Sung; Kim, Yun-Hi; Kwon, Soon-Ki

2013-09-23

We describe herein the synthesis of novel donor-acceptor conjugated polymers with dithienobenzodithiophenes (DTBDT) as the electron donor and 2,1,3-benzothiadiazole as the electron acceptor for high-performance organic photovoltaics (OPVs). We studied the effects of strategically inserting thiophene into the DTBDT as a substituent on the skeletal structure on the opto-electronic performances of fabricated devices. From UV/Vis absorption, electrochemical, and field-effect transistor analyses, we found that the thiophene-containing DTBDT derivative can substantially increase the orbital overlap area between adjacent conjugated chains and thus dramatically enhance charge-carrier mobility up to 0.55 cm(2)  V(-1)  s(-1). The outstanding charge-transport characteristics of this polymer allowed the realization of high-performance organic solar cells with a power conversion efficiency (PCE) of 5.1 %. Detailed studies on the morphological factors that enable the maximum PCE of the polymer solar cells are discussed along with a hole/electron mobility analysis based on the space-charge-limited current model. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Role of intermolecular charge delocalization and its dimensionality in efficient band-like electron transport in crystalline 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane (F2-TCNQ).

PubMed

Sosorev, Andrey Yu

2017-09-27

Theoretical understanding of charge transport in organic semiconductors is exclusively important for organic electronics, but still remains a subject of debate. The recently discovered record-high band-like electron mobility in single crystals of 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane (F 2 -TCNQ) is challenging from the theoretical viewpoint. First, the very small size of the F 2 -TCNQ molecule implies high reorganization energy that seems incompatible with efficient charge transport. Second, it is not clear why the crystals of a similar compound, 7,7,8,8-tetracyanoquinodimethane (TCNQ), show an inefficient hopping electron transport mechanism. To address these issues, we apply DFT and QM/MM calculations to the F n -TCNQ (n = 0,2,4) crystal series. We show that multidimensional intermolecular charge delocalization is of key importance for efficient charge transport in materials consisting of small-sized molecules, and commonly used guidelines for the search for high-mobility organic semiconductors are to be corrected.

TEM-EELS Investigation of Boron and Phosphorus Passivated 4H-SiC/SiO2 Interface Structures

NASA Astrophysics Data System (ADS)

Klingshirn, Christopher; Taillon, Joshua; Liu, Gang; Dhar, Sarit; Feldman, Leonard; Zheleva, Tsvetanka; Lelis, Aivars; Salamanca-Riba, Lourdes

A high density of electronic defects at the SiC/SiO2 interface adversely affects SiC-based metal oxide semiconductor devices. Various treatments are known to improve device performance. Annealing in a nitric oxide (NO) environment, for example, passivates electronic defects at the interface and raises the carrier mobility in the active region to 35-40 cm2/Vs, but the effect saturates after about 60 minutes of annealing. Passivation with phosphorus or boron improves upon NO by a factor of 2, increasing the mobility to over 90 cm2/Vs.2 We investigate the chemical and structural effects of these treatments on the SiC/SiO2 transition layer using high-resolution transmission electron microscopy (HRTEM) and high angle annular dark field (HAADF). Electron energy loss spectroscopy Spectrum Imaging (EELS SI) collected across the transition region allow identification of the width, composition and types of bonding at the transition layer. Advanced machine learning techniques applied to the EELS data reveal intermediate bonding states within this region. Supported by ARL under Grant No. W911NF1420110.

Recent Progress of Self-Powered Sensing Systems for Wearable Electronics.

PubMed

Lou, Zheng; Li, La; Wang, Lili; Shen, Guozhen

2017-12-01

Wearable/flexible electronic sensing systems are considered to be one of the key technologies in the next generation of smart personal electronics. To realize personal portable devices with mobile electronics application, i.e., wearable electronic sensors that can work sustainably and continuously without an external power supply are highly desired. The recent progress and advantages of wearable self-powered electronic sensing systems for mobile or personal attachable health monitoring applications are presented. An overview of various types of wearable electronic sensors, including flexible tactile sensors, wearable image sensor array, biological and chemical sensor, temperature sensors, and multifunctional integrated sensing systems is provided. Self-powered sensing systems with integrated energy units are then discussed, separated as energy harvesting self-powered sensing systems, energy storage integrated sensing systems, and all-in-on integrated sensing systems. Finally, the future perspectives of self-powered sensing systems for wearable electronics are discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon phosphide monolayers with superior carrier mobility

NASA Astrophysics Data System (ADS)

Wang, Gaoxue; Pandey, Ravindra; Karna, Shashi P.

2016-04-01

Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great promise for applications in high-performance electronics and optoelectronics.Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great promise for applications in high-performance electronics and optoelectronics. Electronic supplementary information (ESI) available: Fig. S1 cohesive energy and structure of the CP monolayer with various stoichiometric compositions obtained using CALYPSO, Fig. S2 history of CALYPSO steps and structure of the CP monolayer, Fig. S3 phonon dispersion with DFT-D2 functional, Fig. S4 band structure for β-CP using the DFT-PBE and DFT-D2 functional forms, Fig. S5 strain energy curves, Fig. S6 projected band structure for α-CP, Fig. S7 projected band structure for β-CP, Fig. S8 projected band structure for γ-CP, Fig. S9 band structures obtained with the GGA-PBE and HSE06 functional; Table S1 lattice parameters with the DFT-D2 functional form; Video S1 AIMD simulation of α-CP at 300 K, Video S2 AIMD simulation of β-CP at 300 K, Video S3 AIMD simulation of γ-CP at 300 K. See DOI: 10.1039/c6nr00498a

Chain conformations dictate multiscale charge transport phenomena in disordered semiconducting polymers

PubMed Central

Noriega, Rodrigo; Salleo, Alberto; Spakowitz, Andrew J.

2013-01-01

Existing models for the electronic properties of conjugated polymers do not capture the spatial arrangement of the disordered macromolecular chains over which charge transport occurs. Here, we present an analytical and computational description in which the morphology of individual polymer chains is dictated by well-known statistical models and the electronic coupling between units is determined using Marcus theory. The multiscale transport of charges in these materials (high mobility at short length scales, low mobility at long length scales) is naturally described with our framework. Additionally, the dependence of mobility with electric field and temperature is explained in terms of conformational variability and spatial correlation. Our model offers a predictive approach to connecting processing conditions with transport behavior. PMID:24062459

Chain conformations dictate multiscale charge transport phenomena in disordered semiconducting polymers.

PubMed

Noriega, Rodrigo; Salleo, Alberto; Spakowitz, Andrew J

2013-10-08

Existing models for the electronic properties of conjugated polymers do not capture the spatial arrangement of the disordered macromolecular chains over which charge transport occurs. Here, we present an analytical and computational description in which the morphology of individual polymer chains is dictated by well-known statistical models and the electronic coupling between units is determined using Marcus theory. The multiscale transport of charges in these materials (high mobility at short length scales, low mobility at long length scales) is naturally described with our framework. Additionally, the dependence of mobility with electric field and temperature is explained in terms of conformational variability and spatial correlation. Our model offers a predictive approach to connecting processing conditions with transport behavior.

High Performance 50 nm InAlAs/In0.75GaAs Metamorphic High Electron Mobility Transistors with Si3N4 Passivation on Thin InGaAs Layer

NASA Astrophysics Data System (ADS)

Yeon, Seongjin; Seo, Kwangseok

2008-04-01

We fabricated 50 nm InAlAs/InGaAs metamorphic high electron mobility transistors (HEMTs) with a very thin barrier. Through the reduction of the gate-channel distance (dGC) in the epitaxial structure, a channel aspect ratio (ARC) of over three was achieved when Lg was 50 nm. We inserted a thin InGaAs layer as a protective layer, and tested various gate structures to reduce surface problems induced by barrier shrinkage and to optimize the device characteristics. Through the optimization of the gate structure with the thin InGaAs layer, the fabricated 50 nm metamorphic HEMT exhibited high DC and RF characteristics, Gm of 1.5 S/mm, and fT of 490 GHz.

76 FR 18247 - Notice of Receipt of Complaint; Solicitation of Comments Relating to the Public Interest

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-01

... Certain Electronic Devices, Including Mobile Phones, Mobile Tablets, Portable Music Players, and Computers... importation of certain electronic devices, including mobile phones, mobile tablets, portable music players...

Effectiveness of mobile electronic devices in weight loss among overweight and obese populations: a systematic review and meta-analysis.

PubMed

Khokhar, Bushra; Jones, Jessica; Ronksley, Paul E; Armstrong, Marni J; Caird, Jeff; Rabi, Doreen

2014-01-01

Mobile electronic devices, such as mobile phones and PDAs, have emerged as potentially useful tools in the facilitation and maintenance of weight loss. While RCTs have demonstrated a positive impact of mobile interventions, the extent to which mobile electronic devices are more effective than usual care methods is still being debated. Electronic databases were systematically searched for RCTs evaluating the effectiveness of mobile electronic device interventions among overweight and obese adults. Weighted mean difference for change in body weight was the primary outcome. The search strategy yielded 559 citations and of the 108 potentially relevant studies, six met the criteria. A total of 632 participants were included in the six studies reporting a mean change in body weight. Using a random-effects model, the WMD for the effect of using mobile electronic devices on reduction in body weight was -1.09 kg (95% CI -2.12, -0.05). When stratified by the type of mobile electronic device used, it suggests that interventions using mobile phones were effective at achieving weight loss, WMD = -1.78 kg (95% CI -2.92, -0.63). This systematic review and meta-analysis suggests that mobile electronic devices have the potential to facilitate weight loss in overweight and obese populations, but further work is needed to understand if these interventions have sustained benefit and how we can make these mHealth tools most effective on a large scale. As the field of healthcare increasingly utilizes novel mobile technologies, the focus must not be on any one specific device but on the best possible use of these tools to measure and understand behavior. As mobile electronic devices continue to increase in popularity and the associated technology continues to advance, the potential for the use of mobile devices in global healthcare is enormous. More RCTs with larger sample sizes need to be conducted to look at the cost-effectiveness, technical and financial feasibility of adapting such mHealth interventions in a real clinical setting.

Contact Resistance and Channel Conductance of Graphene Field-Effect Transistors under Low-Energy Electron Irradiation

PubMed Central

Giubileo, Filippo; Di Bartolomeo, Antonio; Martucciello, Nadia; Romeo, Francesco; Iemmo, Laura; Romano, Paola; Passacantando, Maurizio

2016-01-01

We studied the effects of low-energy electron beam irradiation up to 10 keV on graphene-based field effect transistors. We fabricated metallic bilayer electrodes to contact mono- and bi-layer graphene flakes on SiO2, obtaining specific contact resistivity ρc≈19 kΩ·µm2 and carrier mobility as high as 4000 cm2·V−1·s−1. By using a highly doped p-Si/SiO2 substrate as the back gate, we analyzed the transport properties of the device and the dependence on the pressure and on the electron bombardment. We demonstrate herein that low energy irradiation is detrimental to the transistor current capability, resulting in an increase in contact resistance and a reduction in carrier mobility, even at electron doses as low as 30 e−/nm2. We also show that irradiated devices recover their pristine state after few repeated electrical measurements. PMID:28335335

Phenomenological view at the two-component physics of cuprates

NASA Astrophysics Data System (ADS)

Teitel'baum, G. B.

2017-08-01

In the search for mechanisms of high- T c superconductivity it is critical to know the electronic spectrum in the pseudogap phase from which superconductivity evolves. The lack of ARPES data for every cuprate family precludes an agreement as to its structure, doping and temperature dependence and the role of charge ordering. No approach has been developed yet to address the issue theoretically, and we limit ourselves by the phenomenological analysis of the experimental data. We argue that, in the Fermi-liquid-like regime ubiquitous in underdoped cuprates, the spectrum consists of holes on the Fermi arcs and an electronic pocket in contrast to the idea of the Fermi surface reconstruction via charge ordering. At high temperatures, the electrons are dragged by holes while at lower temperatures they get decoupled. The longstanding issue of the origin of the negative Hall coefficient in YBCO and Hg1201 at low temperature is resolved: the electronic contribution prevails, as its mobility becomes temperature independent, while the mobility of holes, scattered by the shortwavelength charge density waves, decreases.

Comprehensive approach to intrinsic charge carrier mobility in conjugated organic molecules, macromolecules, and supramolecular architectures.

PubMed

Saeki, Akinori; Koizumi, Yoshiko; Aida, Takuzo; Seki, Shu

2012-08-21

Si-based inorganic electronics have long dominated the semiconductor industry. However, in recent years conjugated polymers have attracted increasing attention because such systems are flexible and offer the potential for low-cost, large-area production via roll-to-roll processing. The state-of-the-art organic conjugated molecular crystals can exhibit charge carrier mobilities (μ) that nearly match or even exceed that of amorphous silicon (1-10 cm(2) V(-1) s(-1)). The mean free path of the charge carriers estimated from these mobilities corresponds to the typical intersite (intermolecular) hopping distances in conjugated organic materials, which strongly suggests that the conduction model for the electronic band structure only applies to μ > 1 cm(2) V(-1) s(-1) for the translational motion of the charge carriers. However, to analyze the transport mechanism in organic electronics, researchers conventionally use a disorder formalism, where μ is usually less than 1 cm(2) V(-1) s(-1) and dominated by impurities, disorders, or defects that disturb the long-range translational motion. In this Account, we discuss the relationship between the alternating-current and direct-current mobilities of charge carriers, using time-resolved microwave conductivity (TRMC) and other techniques including field-effect transistor, time-of-flight, and space-charge limited current. TRMC measures the nanometer-scale mobility of charge carriers under an oscillating microwave electric field with no contact between the semiconductors and the metals. This separation allows us to evaluate the intrinsic charge carrier mobility with minimal trapping effects. We review a wide variety of organic electronics in terms of their charge carrier mobilities, and we describe recent studies of macromolecules, molecular crystals, and supramolecular architecture. For example, a rigid poly(phenylene-co-ethynylene) included in permethylated cyclodextrin shows a high intramolecular hole mobility of 0.5 cm(2) V(-1) s(-1), based on a combination of flash-photolysis TRMC and transient absorption spectroscopy (TAS) measurements. Single-crystal rubrene showed an ambipolarity with anisotropic charge carrier transport along each crystal axis on the nanometer scale. Finally, we describe the charge carrier mobility of a self-assembled nanotube consisting of a large π-plane of hexabenzocoronene (HBC) partially appended with an electron acceptor. The local (intratubular) charge carrier mobility reached 3 cm(2) V(-1) s(-1) for the nanotubes that possessed well-ordered π-stacking, but it dropped to 0.7 cm(2) V(-1) s(-1) in regions that contained greater amounts of the electron acceptor because those molecules reduced the structural integrity of π-stacked HBC arrays. Interestingly, the long-range (intertubular) charge carrier mobility was on the order of 10(-4) cm(2) V(-1) s(-1) and monotonically decreased when the acceptor content was increased. These results suggest the importance of investigating charge carrier mobilities by frequency-dependent charge carrier motion for the development of more efficient organic electronic devices.

CO2 detection using polyethylenimine/starch functionalized AlGaN /GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Chang, C. Y.; Kang, B. S.; Wang, H. T.; Ren, F.; Wang, Y. L.; Pearton, S. J.; Dennis, D. M.; Johnson, J. W.; Rajagopal, P.; Roberts, J. C.; Piner, E. L.; Linthicum, K. J.

2008-06-01

AlGaN /GaN high electron mobility transistors (HEMTs) functionalized with polyethylenimine/starch were used for detecting CO2 with a wide dynamic range of 0.9%-50% balanced with nitrogen at temperatures from 46to220°C. Higher detection sensitivity to CO2 gas was achieved at higher testing temperatures. At a fixed source-drain bias voltage of 0.5V, drain-source current of the functionalized HEMTs showed a sublinear correlation upon exposure to different CO2 concentrations at low temperature. The superlinear relationship was at high temperature. The sensor exhibited a reversible behavior and a repeatable current change of 32 and 47μA with the introduction of 28.57% and 37.5% CO2 at 108°C, respectively.

Demonstration of high mobility and quantum transport in modulation-doped β-(AlxGa1-x)2O3/Ga2O3 heterostructures

NASA Astrophysics Data System (ADS)

Zhang, Yuewei; Neal, Adam; Xia, Zhanbo; Joishi, Chandan; Johnson, Jared M.; Zheng, Yuanhua; Bajaj, Sanyam; Brenner, Mark; Dorsey, Donald; Chabak, Kelson; Jessen, Gregg; Hwang, Jinwoo; Mou, Shin; Heremans, Joseph P.; Rajan, Siddharth

2018-04-01

In this work, we demonstrate a high mobility two-dimensional electron gas (2DEG) formed at the β-(AlxGa1-x)2O3/Ga2O3 interface through modulation doping. Shubnikov-de Haas (SdH) oscillations were observed in the modulation-doped β-(AlxGa1-x)2O3/Ga2O3 structure, indicating a high-quality electron channel formed at the heterojunction interface. The formation of the 2DEG channel was further confirmed by the weak temperature dependence of the carrier density, and the peak low temperature mobility was found to be 2790 cm2/Vs, which is significantly higher than that achieved in bulk-doped Beta-phase Gallium Oxide (β-Ga2O3). The observed SdH oscillations allowed for the extraction of the electron effective mass in the (010) plane to be 0.313 ± 0.015 m0 and the quantum scattering time to be 0.33 ps at 3.5 K. The demonstrated modulation-doped β-(AlxGa1-x)2O3/Ga2O3 structure lays the foundation for future exploration of quantum physical phenomena and semiconductor device technologies based on the β-Ga2O3 material system.

From computational discovery to experimental characterization of a high hole mobility organic crystal

PubMed Central

Sokolov, Anatoliy N.; Atahan-Evrenk, Sule; Mondal, Rajib; Akkerman, Hylke B.; Sánchez-Carrera, Roel S.; Granados-Focil, Sergio; Schrier, Joshua; Mannsfeld, Stefan C.B.; Zoombelt, Arjan P.; Bao, Zhenan; Aspuru-Guzik, Alán

2011-01-01

For organic semiconductors to find ubiquitous electronics applications, the development of new materials with high mobility and air stability is critical. Despite the versatility of carbon, exploratory chemical synthesis in the vast chemical space can be hindered by synthetic and characterization difficulties. Here we show that in silico screening of novel derivatives of the dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene semiconductor with high hole mobility and air stability can lead to the discovery of a new high-performance semiconductor. On the basis of estimates from the Marcus theory of charge transfer rates, we identified a novel compound expected to demonstrate a theoretic twofold improvement in mobility over the parent molecule. Synthetic and electrical characterization of the compound is reported with single-crystal field-effect transistors, showing a remarkable saturation and linear mobility of 12.3 and 16 cm2 V−1 s−1, respectively. This is one of the very few organic semiconductors with mobility greater than 10 cm2 V−1 s−1 reported to date. PMID:21847111

Damping of acoustic flexural phonons in silicene: influence on high-field electronic transport

NASA Astrophysics Data System (ADS)

Rengel, Raúl; Iglesias, José M.; Mokhtar Hamham, El; Martín, María J.

2018-06-01

Silicene is a two-dimensional buckled material with broken horizontal mirror symmetry and Dirac-like dispersion. Under such conditions, flexural acoustic (ZA) phonons play a dominant role. Consequently, it is necessary to consider some suppression mechanism for electron–phonon interactions with long wavelengths in order to reach mobilities useful for electronic applications. In this work, we analyze, by means of an ensemble Monte Carlo simulator, the influence of several possibilities for the description of the effect of ZA phonon damping on electronic transport in silicene. The results show that a hard cutoff situation (total suppression for phonons with a wavelength longer than a critical one), as it has been proposed in the literature, does not yield a realistic picture regarding the electronic distribution function, and it artificially induces a negative differential resistance at moderate and high fields. Sub-parabolic dispersions, on the other hand, may provide a more realistic description in terms of the behavior of the electron distribution in the momentum space, but need extremely short cutoff wavelengths to reach functional mobility and drift velocity values.

Ubiquitous Graphene Electronics on Scotch Tape

PubMed Central

Chung, Yoonyoung; Ho Kim, Hyun; Lee, Sangryun; Lee, Eunho; Won Kim, Seong; Ryu, Seunghwa; Cho, Kilwon

2015-01-01

We report a novel concept of graphene transistors on Scotch tape for use in ubiquitous electronic systems. Unlike common plastic substrates such as polyimide and polyethylene terephthalate, the Scotch tape substrate is easily attached onto various objects such as banknotes, curved surfaces, and human skin, which implies potential applications wherein electronics can be placed in any desired position. Furthermore, the soft Scotch tape serves as an attractive substrate for flexible/foldable electronics that can be significantly bent, or even crumpled. We found that the adhesive layer of the tape with a relatively low shear modulus relaxes the strain when subjected to bending. The capacitance of the gate dielectric made of oxidized aluminum oxide was 1.5 μF cm−2, so that a supply voltage of only 2.5 V was sufficient to operate the devices. As-fabricated graphene transistors on Scotch tape exhibited high electron mobility of 1326 (±155) cm2 V−1 s−1; the transistors still showed high mobility of 1254 (±478) cm2 V−1 s−1 even after they were crumpled. PMID:26220874

High-Performance InGaAs/InP Composite-Channel High Electron Mobility Transistors Grown by Metal-Organic Vapor-Phase Epitaxy

NASA Astrophysics Data System (ADS)

Sugiyama, Hiroki; Kosugi, Toshihiko; Yokoyama, Haruki; Murata, Koichi; Yamane, Yasuro; Tokumitsu, Masami; Enoki, Takatomo

2008-04-01

This paper reports InGaAs/InP composite-channel (CC) high electron mobility transistors (HEMTs) grown by metal-organic vapor-phase epitaxy (MOVPE) with excellent breakdown and high-speed characteristics. Atomic force microscopy (AFM) reveals high-quality heterointerfaces between In(Ga,Al)As and In(Al)P. Fabricated 80-nm-gate CC HEMTs exhibit on- and off-state breakdown (burnout) voltages estimated at higher than 3 and 8 V. An excellent current-gain cutoff frequency ( fT) of 186 GHz is also obtained in the CC HEMTs. The on-wafer uniformity of CC-HEMT characteristics is comparable to those of our mature 100-nm-gate InGaAs single-channel HEMTs. Bias-stress aging tests reveals that the lifetime of CC HEMTs is expected to be comparable to that of our conventional InGaAs single-channel HEMTs.

78 FR 34132 - Certain Portable Electronic Communications Devices, Including Mobile Phones and Components...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-06

... INTERNATIONAL TRADE COMMISSION [Docket No 2958] Certain Portable Electronic Communications Devices, Including Mobile Phones and Components Thereof; Correction to Notice of Receipt of Complaint; Solicitation... of complaint entitled Certain Portable Electronic Communications Devices, Including Mobile Phones and...

77 FR 15390 - Certain Mobile Electronic Devices Incorporating Haptics; Receipt of Amended Complaint...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-15

... INTERNATIONAL TRADE COMMISSION [DN 2875] Certain Mobile Electronic Devices Incorporating Haptics.... International Trade Commission. ACTION: Notice. SUMMARY: Notice is hereby given that the U.S. International Trade Commission has received an amended complaint entitled Certain Mobile Electronic Devices...

Transparent and conductive indium doped cadmium oxide thin films prepared by pulsed filtered cathodic arc deposition

DOE PAGES

Zhu, Yuankun; Mendelsberg, Rueben J.; Zhu, Jiaqi; ...

2012-11-26

Indium doped cadmium oxide (CdO:In) films with different In concentrations were prepared on low-cost glass substrates by pulsed filtered cathodic arc deposition (PFCAD). In this study, it is shown that polycrystalline CdO:In films with smooth surface and dense structure are obtained. In-doping introduces extra electrons leading to remarkable improvements of electron mobility and conductivity, as well as improvement in the optical transmittance due to the Burstein Moss effect. CdO:In films on glass substrates with thickness near 230 nm show low resistivity of 7.23 x 10 -5 Ωcm, high electron mobility of 142 cm 2/Vs, and mean transmittance over 80% frommore » 500-1250 nm (including the glass substrate). These high quality pulsed arc-grown CdO:In films are potentially suitable for high efficiency multi-junction solar cells that harvest a broad range of the solar spectrum.« less

Resonant tunneling assisted propagation and amplification of plasmons in high electron mobility transistors

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

Bhardwaj, Shubhendu; Sensale-Rodriguez, Berardi; Xing, Huili Grace

A rigorous theoretical and computational model is developed for the plasma-wave propagation in high electron mobility transistor structures with electron injection from a resonant tunneling diode at the gate. We discuss the conditions in which low-loss and sustainable plasmon modes can be supported in such structures. The developed analytical model is used to derive the dispersion relation for these plasmon-modes. A non-linear full-wave-hydrodynamic numerical solver is also developed using a finite difference time domain algorithm. The developed analytical solutions are validated via the numerical solution. We also verify previous observations that were based on a simplified transmission line model. Itmore » is shown that at high levels of negative differential conductance, plasmon amplification is indeed possible. The proposed rigorous models can enable accurate design and optimization of practical resonant tunnel diode-based plasma-wave devices for terahertz sources, mixers, and detectors, by allowing a precise representation of their coupling when integrated with other electromagnetic structures.« less

Study of the enhancement-mode AlGaN/GaN high electron mobility transistor with split floating gates

NASA Astrophysics Data System (ADS)

Wang, Hui; Wang, Ning; Jiang, Ling-Li; Zhao, Hai-Yue; Lin, Xin-Peng; Yu, Hong-Yu

2017-11-01

In this work, the charge storage based split floating gates (FGs) enhancement mode (E-mode) AlGaN/GaN high electron mobility transistors (HEMTs) are studied. The simulation results reveal that under certain density of two dimensional electron gas, the variation tendency of the threshold voltage (Vth) with the variation of the blocking dielectric thickness depends on the FG charge density. It is found that when the length sum and isolating spacing sum of the FGs both remain unchanged, the Vth shall decrease with the increasing FGs number but maintaining the device as E-mode. It is also reported that for the FGs HEMT, the failure of a FG will lead to the decrease of Vth as well as the increase of drain current, and the failure probability can be improved significantly with the increase of FGs number.

Naphthodipyrrolidone (NDP) based conjugated polymers with high electron mobility and ambipolar transport properties

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

Zhang, Haichang; Zhang, Shuo; Mao, Yifan

Two novel donor–acceptor π-conjugated polymers based on naphthodipyrrolidone (NDP) were synthesized and characterized. The polymers possess low band gaps and suitable molecular orbital levels as ambipolar semiconductors. The thin film organic field effect transistor of NDP polymers exhibited ambipolar transport properties with a high electron mobility up to 0.67 cm 2 V –1 s –1. The grazing-incidence wide-angle X-ray scattering (GIWAXS) studies demonstrated that the polymer molecules pack into a long-range-ordered lamellar structure with isotropically oriented crystalline domains. Thermal annealing promoted edge-on lamellar stacking as evidenced by the increased diffraction intensity along the out-of-plane direction. In conclusion, the polymer withmore » NDP and bithiophene units achieved the best edge-on lamellar stacking after thermal annealing, which yielded the best electron transport performance in this work.« less

Naphthodipyrrolidone (NDP) based conjugated polymers with high electron mobility and ambipolar transport properties

DOE PAGES

Zhang, Haichang; Zhang, Shuo; Mao, Yifan; ...

2017-05-12

Two novel donor–acceptor π-conjugated polymers based on naphthodipyrrolidone (NDP) were synthesized and characterized. The polymers possess low band gaps and suitable molecular orbital levels as ambipolar semiconductors. The thin film organic field effect transistor of NDP polymers exhibited ambipolar transport properties with a high electron mobility up to 0.67 cm 2 V –1 s –1. The grazing-incidence wide-angle X-ray scattering (GIWAXS) studies demonstrated that the polymer molecules pack into a long-range-ordered lamellar structure with isotropically oriented crystalline domains. Thermal annealing promoted edge-on lamellar stacking as evidenced by the increased diffraction intensity along the out-of-plane direction. In conclusion, the polymer withmore » NDP and bithiophene units achieved the best edge-on lamellar stacking after thermal annealing, which yielded the best electron transport performance in this work.« less

Tuning the Two-Dimensional Electron Liquid at Oxide Interfaces by Buffer-Layer-Engineered Redox Reactions.

PubMed

Chen, Yunzhong; Green, Robert J; Sutarto, Ronny; He, Feizhou; Linderoth, Søren; Sawatzky, George A; Pryds, Nini

2017-11-08

Polar discontinuities and redox reactions provide alternative paths to create two-dimensional electron liquids (2DELs) at oxide interfaces. Herein, we report high mobility 2DELs at interfaces involving SrTiO 3 (STO) achieved using polar La 7/8 Sr 1/8 MnO 3 (LSMO) buffer layers to manipulate both polarities and redox reactions from disordered overlayers grown at room temperature. Using resonant X-ray reflectometry experiments, we quantify redox reactions from oxide overlayers on STO as well as polarity induced electronic reconstruction at epitaxial LSMO/STO interfaces. The analysis reveals how these effects can be combined in a STO/LSMO/disordered film trilayer system to yield high mobility modulation doped 2DELs, where the buffer layer undergoes a partial transformation from perovskite to brownmillerite structure. This uncovered interplay between polar discontinuities and redox reactions via buffer layers provides a new approach for the design of functional oxide interfaces.

Quinoline-Flanked Diketopyrrolopyrrole Copolymers Breaking through Electron Mobility over 6 cm2 V-1 s-1 in Flexible Thin Film Devices.

PubMed

Ni, Zhenjie; Dong, Huanli; Wang, Hanlin; Ding, Shang; Zou, Ye; Zhao, Qiang; Zhen, Yonggang; Liu, Feng; Jiang, Lang; Hu, Wenping

2018-03-01

Herein, the design and synthesis of novel π-extended quinoline-flanked diketopyrrolopyrrole (DPP) [abbreviated as QDPP] motifs and corresponding copolymers named PQDPP-T and PQDPP-2FT for high performing n-type organic field-effect transistors (OFETs) in flexible organic thin film devices are reported. Serving as DPP-flankers in backbones, quinoline is found to effectively tune copolymer optoelectric properties. Compared with TDPP and pyridine-flanked DPP (PyDPP) analogs, widened bandgaps and strengthened electron deficiency are achieved. Moreover, both hole and electron mobility are improved two orders of magnitude compared to those of PyDPP analogs (PPyDPP-T and PPyDPP-2FT). Notably, featuring an all-acceptor-incorporated backbone, PQDPP-2FT exhibits electron mobility of 6.04 cm 2 V -1 s -1 , among the highest value in OFETs fabricated on flexible substrates to date. Moreover, due to the widened bandgap and strengthened electron deficiency of PQDPP, n-channel on/off ratio over 10 5 with suppressed hole transport is first realized in the ambipolar DPP-based copolymers. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A thermodynamic model to predict electron mobility in superfluid helium.

PubMed

Aitken, Frédéric; Volino, Ferdinand; Mendoza-Luna, Luis Guillermo; Haeften, Klaus von; Eloranta, Jussi

2017-06-21

Electron mobility in superfluid helium is modeled between 0.1 and 2.2 K by a van der Waals-type thermodynamic equation of state, which relates the free volume of solvated electrons to temperature, density, and phase dependent internal pressure. The model is first calibrated against known electron mobility reference data along the saturated vapor pressure line and then validated to reproduce the existing mobility literature values as a function of pressure and temperature with at least 10% accuracy. Four different electron mobility regimes are identified: (1) Landau critical velocity limit (T ≈ 0), (2) mobility limited by thermal phonons (T < 0.6 K), (3) thermal phonon and discrete roton scattering ("roton gas") limited mobility (0.6 K < T < 1.2 K), and (4) the viscous liquid ("roton continuum") limit (T > 1.2 K) where the ion solvation structure directly determines the mobility. In the latter regime, the Stokes equation can be used to estimate the hydrodynamic radius of the solvated electron based on its mobility and fluid viscosity. To account for the non-continuum behavior appearing below 1.2 K, the temperature and density dependent Millikan-Cunningham factor is introduced. The hydrodynamic electron bubble radii predicted by the present model appear generally larger than the solvation cavity interface barycenter values obtained from density functional theory (DFT) calculations. Based on the classical Stokes law, this difference can arise from the variation of viscosity and flow characteristics around the electron. The calculated DFT liquid density profiles show distinct oscillations at the vacuum/liquid interface, which increase the interface rigidity.

Electronic transport in graphene-based heterostructures

NASA Astrophysics Data System (ADS)

Tan, J. Y.; Avsar, A.; Balakrishnan, J.; Koon, G. K. W.; Taychatanapat, T.; O'Farrell, E. C. T.; Watanabe, K.; Taniguchi, T.; Eda, G.; Castro Neto, A. H.; Özyilmaz, B.

2014-05-01

While boron nitride (BN) substrates have been utilized to achieve high electronic mobilities in graphene field effect transistors, it is unclear how other layered two dimensional (2D) crystals influence the electronic performance of graphene. In this Letter, we study the surface morphology of 2D BN, gallium selenide (GaSe), and transition metal dichalcogenides (tungsten disulfide (WS2) and molybdenum disulfide (MoS2)) crystals and their influence on graphene's electronic quality. Atomic force microscopy analysis shows that these crystals have improved surface roughness (root mean square value of only ˜0.1 nm) compared to conventional SiO2 substrate. While our results confirm that graphene devices exhibit very high electronic mobility (μ) on BN substrates, graphene devices on WS2 substrates (G/WS2) are equally promising for high quality electronic transport (μ ˜ 38 000 cm2/V s at room temperature), followed by G/MoS2 (μ ˜ 10 000 cm2/V s) and G/GaSe (μ ˜ 2200 cm2/V s). However, we observe a significant asymmetry in electron and hole conduction in G/WS2 and G/MoS2 heterostructures, most likely due to the presence of sulphur vacancies in the substrate crystals. GaSe crystals are observed to degrade over time even under ambient conditions, leading to a large hysteresis in graphene transport making it a less suitable substrate.

Effect of Energy Alignment, Electron Mobility, and Film Morphology of Perylene Diimide Based Polymers as Electron Transport Layer on the Performance of Perovskite Solar Cells.

PubMed

Guo, Qiang; Xu, Yingxue; Xiao, Bo; Zhang, Bing; Zhou, Erjun; Wang, Fuzhi; Bai, Yiming; Hayat, Tasawar; Alsaedi, Ahmed; Tan, Zhan'ao

2017-03-29

For organic-inorganic perovskite solar cells (PerSCs), the electron transport layer (ETL) plays a crucial role in efficient electron extraction and transport for high performance PerSCs. Fullerene and its derivatives are commonly used as ETL for p-i-n structured PerSCs. However, these spherical small molecules are easy to aggregate with high annealing temperature and thus induce morphology stability problems. N-type conjugated polymers are promising candidates to overcome these problems due to the tunable energy levels, controllable aggregation behaviors, and good film formation abilities. Herein, a series of perylene diimide (PDI) based polymers (PX-PDIs), which contain different copolymeried units (X), including vinylene (V), thiophene (T), selenophene (Se), dibenzosilole (DBS), and cyclopentadithiophene (CPDT), are introduced as ETL for p-i-n structured PerSCs. The effect of energy alignment, electron mobility, and film morphology of these ETLs on the photovoltaic performance of the PerSCs are fully investigated. Among the PX-PDIs, PV-PDI demonstrates the deeper LUMO energy level, the highly delocalized LUMO electron density, and a better planar structure, making it the best electron transport material for PerSCs. The planar heterojunction PerSC with PV-PDI as ETL achieves a power conversion efficiency (PCE) of 10.14%, among the best values for non-fullerene based PerSCs.

A study on agent-based secure scheme for electronic medical record system.

PubMed

Chen, Tzer-Long; Chung, Yu-Fang; Lin, Frank Y S

2012-06-01

Patient records, including doctors' diagnoses of diseases, trace of treatments and patients' conditions, nursing actions, and examination results from allied health profession departments, are the most important medical records of patients in medical systems. With patient records, medical staff can instantly understand the entire medical information of a patient so that, according to the patient's conditions, more accurate diagnoses and more appropriate in-depth treatments can be provided. Nevertheless, in such a modern society with booming information technologies, traditional paper-based patient records have faced a lot of problems, such as lack of uniform formats, low data mobility, slow data transfer, illegible handwritings, enormous and insufficient storage space, difficulty of conservation, being easily damaged, and low transferability. To improve such drawbacks, reduce medical costs, and advance medical quality, paper-based patient records are modified into electronic medical records and reformed into electronic patient records. However, since electronic patient records used in various hospitals are diverse and different, in consideration of cost, it is rather difficult to establish a compatible and complete integrated electronic patient records system to unify patient records from heterogeneous systems in hospitals. Moreover, as the booming of the Internet, it is no longer necessary to build an integrated system. Instead, doctors can instantly look up patients' complete information through the Internet access to electronic patient records as well as avoid the above difficulties. Nonetheless, the major problem of accessing to electronic patient records cross-hospital systems exists in the security of transmitting and accessing to the records in case of unauthorized medical personnels intercepting or stealing the information. This study applies the Mobile Agent scheme to cope with the problem. Since a Mobile Agent is a program, which can move among hosts and automatically disperse arithmetic processes, and moves from one host to another in heterogeneous network systems with the characteristics of autonomy and mobility, decreasing network traffic, reducing transfer lag, encapsulating protocol, availability on heterogeneous platforms, fault-tolerance, high flexibility, and personalization. However, since a Mobile Agent contacts and exchanges information with other hosts or agents on the Internet for rapid exchange and access to medical information, the security is threatened. In order to solve the problem, this study proposes a key management scheme based on Lagrange interpolation formulas and hierarchical management structure to make Mobile Agents a more secure and efficient access control scheme for electronic patient record systems when applied to the access of patients' personal electronic patient records cross hospitals. Meanwhile, with the comparison of security and efficacy analyses being the feasibility of validation scheme and the basis of better efficiency, the security of Mobile Agents in the process of operation can be guaranteed, key management efficacy can be advanced, and the security of the Mobile Agent system can be protected.

Influence of charge carrier mobility and morphology on solar cell parameters in devices of mono- and bis-fullerene adducts.

PubMed

Muth, Mathis-Andreas; Mitchell, William; Tierney, Steven; Lada, Thomas A; Xue, Xiang; Richter, Henning; Carrasco-Orozco, Miguel; Thelakkat, Mukundan

2013-12-06

Herein, we analyze charge carrier mobility and morphology of the active blend layer in thin film organic solar cells and correlate them with device parameters. A low band gap donor-acceptor copolymer in combination with phenyl-C61-butyric acid methyl ester (PCBM) or two bis-adduct fullerenes, bis-PCBM and bis-o-quino-dimethane C60 (bis-oQDMC), is investigated. We study the charge transport of polymer:fullerene blends in hole- and electron-only devices using the space-charge limited current method. Lower electron mobilities are observed in both bis-adduct fullerene blends. Hole mobility, however, is decreased only in the blend containing bis-oQDMC. Both bis-adduct fullerene blends show very high open circuit voltage in solar cell devices, but poor photocurrent compared to the standard PCBM blend for an active layer thickness of 200 nm. Therefore, a higher short circuit current is feasible for the polymer:bis-PCBM blend by reducing the active layer thickness in order to compensate for the low electron mobility, which results in a PCE of 4.3%. For the polymer:bis-oQDMC blend, no such improvement is achieved due to an unfavorable morphology in this particular blend system. The results are supported by external quantum efficiency measurements, atomic force microscopy, transmission electron microscopy and UV/vis spectroscopy. Based on these results, the investigations presented herein give a more scientific basis for the optimization of solar cells.

Electrical instability of high-mobility zinc oxynitride thin-film transistors upon water exposure

NASA Astrophysics Data System (ADS)

Kim, Dae-Hwan; Jeong, Hwan-Seok; Kwon, Hyuck-In

2017-03-01

We investigate the effects of water absorption on the electrical performance and stability in high-mobility zinc oxynitride (ZnON) thin-film transistors (TFTs). The ZnON TFT exhibits a smaller field-effect mobility, lower turn-on voltage, and higher subthreshold slope with a deteriorated electrical stability under positive gate bias stresses after being exposed to water. From the Hall measurements, an increase of the electron concentration and a decrease of the Hall mobility are observed in the ZnON thin film after water absorption. The observed phenomena are mainly attributed to the water molecule-induced increase of the defective ZnXNY bond and the oxygen vacancy inside the ZnON thin film based on the x-ray photoelectron spectroscopy analysis.

Influence of the electron-cation interaction on electron mobility in dye-sensitized ZnO and TiO2 nanocrystals: a study using ultrafast terahertz spectroscopy.

PubMed

Nemec, H; Rochford, J; Taratula, O; Galoppini, E; Kuzel, P; Polívka, T; Yartsev, A; Sundström, V

2010-05-14

Charge transport and recombination in nanostructured semiconductors are poorly understood key processes in dye-sensitized solar cells. We have employed time-resolved spectroscopies in the terahertz and visible spectral regions supplemented with Monte Carlo simulations to obtain unique information on these processes. Our results show that charge transport in the active solar cell material can be very different from that in nonsensitized semiconductors, due to strong electrostatic interaction between injected electrons and dye cations at the surface of the semiconductor nanoparticle. For ZnO, this leads to formation of an electron-cation complex which causes fast charge recombination and dramatically decreases the electron mobility even after the dissociation of the complex. Sensitized TiO2 does not suffer from this problem due to its high permittivity efficiently screening the charges.

Shutterless ion mobility spectrometer with fast pulsed electron source

NASA Astrophysics Data System (ADS)

Bunert, E.; Heptner, A.; Reinecke, T.; Kirk, A. T.; Zimmermann, S.

2017-02-01

Ion mobility spectrometers (IMS) are devices for fast and very sensitive trace gas analysis. The measuring principle is based on an initial ionization process of the target analyte. Most IMS employ radioactive electron sources, such as 63Ni or 3H. These radioactive materials have the disadvantage of legal restrictions and the electron emission has a predetermined intensity and cannot be controlled or disabled. In this work, we replaced the 3H source of our IMS with 100 mm drift tube length with our nonradioactive electron source, which generates comparable spectra to the 3H source. An advantage of our emission current controlled nonradioactive electron source is that it can operate in a fast pulsed mode with high electron intensities. By optimizing the geometric parameters and developing fast control electronics, we can achieve very short electron emission pulses for ionization with high intensities and an adjustable pulse width of down to a few nanoseconds. This results in small ion packets at simultaneously high ion densities, which are subsequently separated in the drift tube. Normally, the required small ion packet is generated by a complex ion shutter mechanism. By omitting the additional reaction chamber, the ion packet can be generated directly at the beginning of the drift tube by our pulsed nonradioactive electron source with only slight reduction in resolving power. Thus, the complex and costly shutter mechanism and its electronics can also be omitted, which leads to a simple low-cost IMS-system with a pulsed nonradioactive electron source and a resolving power of 90.

Hot electron generation under large-signal radio frequency operation of GaN high-electron-mobility transistors

NASA Astrophysics Data System (ADS)

Latorre-Rey, Alvaro D.; Sabatti, Flavio F. M.; Albrecht, John D.; Saraniti, Marco

2017-07-01

In order to assess the underlying physical mechanisms of hot carrier-related degradation such as defect generation in millimeter-wave GaN power amplifiers, we have simulated the electron energy distribution function under large-signal radio frequency conditions in AlGaN/GaN high-electron-mobility transistors. Our results are obtained through a full band Monte Carlo particle-based simulator self-consistently coupled to a harmonic balance circuit solver. At lower frequency, simulations of a Class AB power amplifier at 10 GHz show that the peak hot electron generation is up to 43% lower under RF drive than it is under DC conditions, regardless of the input power or temperature of operation. However, at millimeter-wave operation up to 40 GHz, RF hot carrier generation reaches that from DC biasing and even exceeds it up to 75% as the amplifier is driven into compression. Increasing the temperature of operation also shows that degradation of DC and RF characteristics are tightly correlated and mainly caused by increased phonon scattering. The accurate determination of the electron energy mapping is demonstrated to be a powerful tool for the extraction of compact models used in lifetime and reliability analysis.

Use and acceptance of electronic communication by patients with multiple sclerosis: a multicenter questionnaire study.

PubMed

Haase, Rocco; Schultheiss, Thorsten; Kempcke, Raimar; Thomas, Katja; Ziemssen, Tjalf

2012-10-15

The number of multiple sclerosis (MS) information websites, online communities, and Web-based health education programs has been increasing. However, MS patients' willingness to use new ways of communication, such as websites, mobile phone application, short message service, or email with their physician, remains unknown. We designed a questionnaire to evaluate the a priori use of electronic communication methods by MS patients and to assess their acceptance of such tools for communication with their health care providers. We received complete data from 586 MS patients aged between 17 and 73 years. Respondents were surveyed in outpatient clinics across Germany using a novel paper-and-pencil questionnaire. In addition to demographics, the survey items queried frequency of use of, familiarity with, and comfort with using computers, websites, email, and mobile phones. About 90% of all MS patients used a personal computer (534/586) and the Internet (527/586) at least once a week, 87.0% (510/586) communicated by email, and 85.6% (488/570) communicated by mobile phone. When asked about their comfort with using electronic communication methods for communication with health care providers, 20.5% (120/586) accepted communication by mobile Internet application or short message service via mobile phone, 41.0% (240/586) by websites, 54.3% (318/586) by email service, and 67.8% (397/586) by at least one type of electronic communication. The level of a priori use was the best predictor for the acceptance of electronic communication with health care providers. Patients who reported already searching online for health information (odds ratio 2.4, P < .001) and who had already communicated with a physician through a website (odds ratio 3.3, P = .03) reported higher acceptance for Web-based communication. Patients who already scheduled appointments with their mobile phones (odds ratio 2.1, P = .002) were more likely to accept the use of mobile phone applications or short message service for communicating with their physician. The majority of MS patients seen at specialist centers already use modern communication technology regularly. New forms of electronic communication appear to have high levels of acceptance for exchanging information about MS between patients and health care providers. Such methods should be integrated into eHealth services such as electronic health records and patient relationship management systems.

Impact of rounded electrode corners on breakdown characteristics of AlGaN/GaN high-electron mobility transistors

NASA Astrophysics Data System (ADS)

Yamazaki, Taisei; Asubar, Joel T.; Tokuda, Hirokuni; Kuzuhara, Masaaki

2018-05-01

We investigated the impact of rounded electrode corners on the breakdown characteristics of AlGaN/GaN high-electron mobility transistors. For standard reference devices, catastrophic breakdown occurred predominantly near the sharp electrode corners. By introducing a rounded-electrode architecture, premature breakdown at the corners was mitigated. Moreover, the rate of breakdown voltage (V BR) degradation with an increasing gate width (W G) was significantly lower for devices with rounded corners. When W G was increased from 100 µm to 10 mm, the V BR of the reference device dropped drastically, from 1,200 to 300 V, whereas that of the rounded-electrode device only decreased to a respectable value of 730 V.

Recessed Slant Gate AlGaN/GaN High Electron Mobility Transistors with 20.9 W/mm at 10 GHz

NASA Astrophysics Data System (ADS)

Pei, Yi; Chu, Rongming; Fichtenbaum, Nicholas A.; Chen, Zhen; Brown, David; Shen, Likun; Keller, Stacia; DenBaars, Steven P.; Mishra, Umesh K.

2007-12-01

A recessed slant gate processing has been used in AlGaN/GaN high electron mobility transistors (HEMTs) to mitigate the electric field, minimize the dispersion and increase the breakdown voltage. More than one order of magnitude of decrease in gate leakage has been observed by recessing the slant gate. For a 0.65 μm gate-length device, an extrinsic fT of 18 GHz and extrinsic fMAX of 52 GHz at a drain bias of 25 V were achieved. At 10 GHz, a state-of-the-art power density of 20.9 W/mm, with a power-added efficiency (PAE) of 40% at a drain bias of 83 V, was demonstrated.

Interpretation of transport measurements in ZnO-thin films

NASA Astrophysics Data System (ADS)

Petukhov, Vladimir; Stoemenos, John; Rothman, Johan; Bakin, Andrey; Waag, Andreas

2011-01-01

In order to interpret results of temperature dependent Hall measurements in heteroepitaxial ZnO-thin films, we adopted a multilayer conductivity model considering carrier-transport through the interfacial layer with degenerate electron gas as well as the upper part of ZnO layers with lower conductivity. This model was applied to the temperature dependence of the carrier concentration and mobility measured by Hall effect in a ZnO-layer grown on c-sapphire with conventional high-temperature MgO and low-temperature ZnO buffer. We also compared our results with the results of maximum entropy mobility-spectrum analysis (MEMSA). The formation of the highly conductive interfacial layer was explained by analysis of transmission electron microscopy (TEM) images taken from similar layers.

155- and 213-GHz AlInAs/GaInAs/InP HEMT MMIC oscillators

NASA Technical Reports Server (NTRS)

Rosenbaum, Steven E.; Kormanyos, Brian K.; Jelloian, Linda M.; Matloubian, Mehran; Brown, April S.; Larson, Lawrence E.; Nguyen, Loi D.; Thompson, Mark A.; Katehi, Linda P. B.; Rebeiz, Gabriel M.

1995-01-01

We report on the design and measurement of monolithic 155- and 213-GHz quasi-optical oscillators using AlInAs/GaInAs/InP HEMTs (high-electron mobility transistors). These results are believed to be the highest frequency three-terminal oscillators reported to date. The indium concentration in the channel was 80% for high sheet charge and mobility. The HEMT gates were fabricated with self-aligned sub-tenth-micrometer electron-beam techniques to achieve gate lengths on the order of 50 nm and drain-source spacing of 0.25 micron. Planar antennas were integrated into the fabrication process resulting in a compact and efficient quasi-optical Monolithic Millimeter-wave Integrated Circuit (MMIC) oscillator.

High mobility and high stability glassy metal-oxynitride materials and devices

NASA Astrophysics Data System (ADS)

Lee, Eunha; Kim, Taeho; Benayad, Anass; Hur, Jihyun; Park, Gyeong-Su; Jeon, Sanghun

2016-04-01

In thin film technology, future semiconductor and display products with high performance, high density, large area, and ultra high definition with three-dimensional functionalities require high performance thin film transistors (TFTs) with high stability. Zinc oxynitride, a composite of zinc oxide and zinc nitride, has been conceded as a strong substitute to conventional semiconductor film such as silicon and indium gallium zinc oxide due to high mobility value. However, zinc oxynitride has been suffered from poor reproducibility due to relatively low binding energy of nitrogen with zinc, resulting in the instability of composition and its device performance. Here we performed post argon plasma process on zinc oxynitride film, forming nano-crystalline structure in stable amorphous matrix which hampers the reaction of oxygen with zinc. Therefore, material properties and device performance of zinc oxynitride are greatly enhanced, exhibiting robust compositional stability even exposure to air, uniform phase, high electron mobility, negligible fast transient charging and low noise characteristics. Furthermore, We expect high mobility and high stability zinc oxynitride customized by plasma process to be applicable to a broad range of semiconductor and display devices.

Electron mobility limited by optical phonons in wurtzite InGaN/GaN core-shell nanowires

NASA Astrophysics Data System (ADS)

Liu, W. H.; Qu, Y.; Ban, S. L.

2017-09-01

Based on the force-balance and energy-balance equations, the optical phonon-limited electron mobility in InxGa1-xN/GaN core-shell nanowires (CSNWs) is discussed. It is found that the electrons tend to distribute in the core of the CSNWs due to the strong quantum confinement. Thus, the scattering from first kind of the quasi-confined optical (CO) phonons is more important than that from the interface (IF) and propagating (PR) optical phonons. Ternary mixed crystal and size effects on the electron mobility are also investigated. The results show that the PR phonons exist while the IF phonons disappear when the indium composition x < 0.047, and vice versa. Accordingly, the total electron mobility μ first increases and then decreases with indium composition x, and reaches a peak value of approximately 3700 cm2/(V.s) when x = 0.047. The results also show that the mobility μ increases as increasing the core radius of CSNWs due to the weakened interaction between the electrons and CO phonons. The total electron mobility limited by the optical phonons exhibits an obvious enhancement as decreasing temperature or increasing line electron density. Our theoretical results are expected to be helpful to develop electronic devices based on CSNWs.

Securing electronic health records with novel mobile encryption schemes.

PubMed

Weerasinghe, Dasun; Elmufti, Kalid; Rajarajan, Muttukrishnan; Rakocevic, Veselin

2007-01-01

Mobile devices have penetrated the healthcare sector due to their increased functionality, low cost, high reliability and easy-to-use nature. However, in healthcare applications the privacy and security of the transmitted information must be preserved. Therefore applications require a concrete security framework based on long-term security keys, such as the security key that can be found in a mobile Subscriber Identity Module (SIM). The wireless nature of communication links in mobile networks presents a major challenge in this respect. This paper presents a novel protocol that will send the information securely while including the access privileges to the authorized recipient.

Wide-bandwidth high-resolution search for extraterrestrial intelligence

NASA Technical Reports Server (NTRS)

Horowitz, Paul

1993-01-01

Research accomplished during the third 6-month period is summarized. Research covered the following: dual-horn antenna performance; high electron mobility transistors (HEMT) low-noise amplifiers; downconverters; fast Fourier transform (FFT) array; and backend 'feature recognizer' array.

Optically transparent semiconducting polymer nanonetwork for flexible and transparent electronics

PubMed Central

Yu, Kilho; Park, Byoungwook; Kim, Geunjin; Kim, Chang-Hyun; Park, Sungjun; Kim, Jehan; Jung, Suhyun; Jeong, Soyeong; Kwon, Sooncheol; Kang, Hongkyu; Kim, Junghwan; Yoon, Myung-Han; Lee, Kwanghee

2016-01-01

Simultaneously achieving high optical transparency and excellent charge mobility in semiconducting polymers has presented a challenge for the application of these materials in future “flexible” and “transparent” electronics (FTEs). Here, by blending only a small amount (∼15 wt %) of a diketopyrrolopyrrole-based semiconducting polymer (DPP2T) into an inert polystyrene (PS) matrix, we introduce a polymer blend system that demonstrates both high field-effect transistor (FET) mobility and excellent optical transparency that approaches 100%. We discover that in a PS matrix, DPP2T forms a web-like, continuously connected nanonetwork that spreads throughout the thin film and provides highly efficient 2D charge pathways through extended intrachain conjugation. The remarkable physical properties achieved using our approach enable us to develop prototype high-performance FTE devices, including colorless all-polymer FET arrays and fully transparent FET-integrated polymer light-emitting diodes. PMID:27911774

GaN-on-silicon high-electron-mobility transistor technology with ultra-low leakage up to 3000 V using local substrate removal and AlN ultra-wide bandgap

NASA Astrophysics Data System (ADS)

Dogmus, Ezgi; Zegaoui, Malek; Medjdoub, Farid

2018-03-01

We report on extremely low off-state leakage current in AlGaN/GaN-on-silicon metal–insulator–semiconductor high-electron-mobility transistors (MISHEMTs) up to a high blocking voltage. Remarkably low off-state gate and drain leakage currents below 1 µA/mm up to 3 kV have been achieved owing to the use of a thick in situ SiN gate dielectric under the gate, and a local Si substrate removal technique combined with a cost effective 15-µm-thick AlN dielectric layer followed by a Cu deposition. This result establishes a manufacturable state-of-the-art high-voltage GaN-on-silicon power transistors while maintaining a low specific on-resistance of approximately 10 mΩ·cm2.

High electric field conduction in low-alkali boroaluminosilicate glass

NASA Astrophysics Data System (ADS)

Dash, Priyanka; Yuan, Mengxue; Gao, Jun; Furman, Eugene; Lanagan, Michael T.

2018-02-01

Electrical conduction in silica-based glasses under a low electric field is dominated by high mobility ions such as sodium, and there is a transition from ionic transport to electronic transport as the electric field exceeds 108 V/m at low temperatures. Electrical conduction under a high electric field was investigated in thin low-alkali boroaluminosilicate glass samples, showing nonlinear conduction with the current density scaling approximately with E1/2, where E is the electric field. In addition, thermally stimulated depolarization current (TSDC) characterization was carried out on room-temperature electrically poled glass samples, and an anomalous discharging current flowing in the same direction as the charging current was observed. High electric field conduction and TSDC results led to the conclusion that Poole-Frenkel based electronic transport occurs in the mobile-cation-depleted region adjacent to the anode, and accounts for the observed anomalous current.

High-performance enhancement-mode Al2O3/InAlGaN/GaN MOS high-electron mobility transistors with a self-aligned gate recessing technology

NASA Astrophysics Data System (ADS)

Zhang, Kai; Kong, Cen; Zhou, Jianjun; Kong, Yuechan; Chen, Tangsheng

2017-02-01

The paper reports high-performance enhancement-mode MOS high-electron mobility transistors (MOS-HEMTs) based on a quaternary InAlGaN barrier. Self-aligned gate technology is used for gate recessing, dielectric deposition, and gate electrode formation. An improved digital recessing process is developed, and an Al2O3 gate dielectric grown with O2 plasma is used. Compared to results with AlGaN barrier, the fabricated E-mode MOS-HEMT with InAlGaN barrier delivers a record output current density of 1.7 A/mm with a threshold voltage (V TH) of 1.5 V, and a small on-resistance (R on) of 2.0 Ω·mm. Excellent V TH hysteresis and greatly improved gate leakage characteristics are also demonstrated.

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Federal Register 2010, 2011, 2012, 2013, 2014

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Origin of the different transport properties of electron and hole polarons in an ambipolar polyselenophene-based conjugated polymer

NASA Astrophysics Data System (ADS)

Chen, Zhuoying; Bird, Matthew; Lemaur, Vincent; Radtke, Guillaume; Cornil, Jérôme; Heeney, Martin; McCulloch, Iain; Sirringhaus, Henning

2011-09-01

Understanding the mechanisms limiting ambipolar transport in conjugated polymer field-effect transistors (FETs) is of both fundamental and practical interest. Here, we present a systematic study comparing hole and electron charge transport in an ambipolar conjugated polymer, semicrystalline poly(3,3''-di-n-decylterselenophene) (PSSS). Starting from a detailed analysis of the device characteristics and temperature/charge-density dependence of the mobility, we interpret the difference between hole and electron transport through both the Vissenberg-Matters and the mobility-edge model. To obtain microscopic insight into the quantum mechanical wave function of the charges at a molecular level, we combine charge modulation spectroscopy (CMS) measuring the charge-induced absorption signatures from positive and negative polarons in these ambipolar FETs with corresponding density functional theory (DFT) calculations. We observe a significantly higher switch-on voltage for electrons than for holes due to deep electron trap states, but also a higher activation energy of the mobility for mobile electrons. The CMS spectra reveal that the electrons that remain mobile and contribute to the FET current have a wave function that is more localized onto a single polymer chain than that of holes, which is extended over several polymer chains. We interpret this as evidence that the transport properties of the mobile electrons in PSSS are still affected by the presence of deep electron traps. The more localized electron state could be due to the mobile electrons interacting with shallow trap states in the vicinity of a chemical, potentially water-related, impurity that might precede the capture of the electron into a deeply trapped state.

Novel Iron-based ternary amorphous oxide semiconductor with very high transparency, electronic conductivity, and mobility

DOE PAGES

Malasi, A.; Taz, H.; Farah, A.; ...

2015-12-16

We report that ternary metal oxides of type (Me) 2O 3 with the primary metal (Me) constituent being Fe (66 atomic (at.) %) along with the two Lanthanide elements Tb (10 at.%) and Dy (24 at.%) can show excellent semiconducting transport properties. Thin films prepared by pulsed laser deposition at room temperature followed by ambient oxidation showed very high electronic conductivity (>5 × 10 4 S/m) and Hall mobility (>30 cm 2/V-s). These films had an amorphous microstructure which was stable to at least 500 °C and large optical transparency with a direct band gap of 2.85 ± 0.14 eV.more » This material shows emergent semiconducting behavior with significantly higher conductivity and mobility than the constituent insulating oxides. In conclusion, since these results demonstrate a new way to modify the behaviors of transition metal oxides made from unfilled d- and/or f-subshells, a new class of functional transparent conducting oxide materials could be envisioned.« less

Method for extracting relevant electrical parameters from graphene field-effect transistors using a physical model

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

Boscá, A., E-mail: alberto.bosca@upm.es; Dpto. de Ingeniería Electrónica, E.T.S.I. de Telecomunicación, Universidad Politécnica de Madrid, Madrid 28040; Pedrós, J.

2015-01-28

Due to its intrinsic high mobility, graphene has proved to be a suitable material for high-speed electronics, where graphene field-effect transistor (GFET) has shown excellent properties. In this work, we present a method for extracting relevant electrical parameters from GFET devices using a simple electrical characterization and a model fitting. With experimental data from the device output characteristics, the method allows to calculate parameters such as the mobility, the contact resistance, and the fixed charge. Differentiated electron and hole mobilities and direct connection with intrinsic material properties are some of the key aspects of this method. Moreover, the method outputmore » values can be correlated with several issues during key fabrication steps such as the graphene growth and transfer, the lithographic steps, or the metalization processes, providing a flexible tool for quality control in GFET fabrication, as well as a valuable feedback for improving the material-growth process.« less

Rational In Silico Design of an Organic Semiconductor with Improved Electron Mobility.

PubMed

Friederich, Pascal; Gómez, Verónica; Sprau, Christian; Meded, Velimir; Strunk, Timo; Jenne, Michael; Magri, Andrea; Symalla, Franz; Colsmann, Alexander; Ruben, Mario; Wenzel, Wolfgang

2017-11-01

Organic semiconductors find a wide range of applications, such as in organic light emitting diodes, organic solar cells, and organic field effect transistors. One of their most striking disadvantages in comparison to crystalline inorganic semiconductors is their low charge-carrier mobility, which manifests itself in major device constraints such as limited photoactive layer thicknesses. Trial-and-error attempts to increase charge-carrier mobility are impeded by the complex interplay of the molecular and electronic structure of the material with its morphology. Here, the viability of a multiscale simulation approach to rationally design materials with improved electron mobility is demonstrated. Starting from one of the most widely used electron conducting materials (Alq 3 ), novel organic semiconductors with tailored electronic properties are designed for which an improvement of the electron mobility by three orders of magnitude is predicted and experimentally confirmed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

NOTE: Calibration of low-energy electron beams from a mobile linear accelerator with plane-parallel chambers using both TG-51 and TG-21 protocols

NASA Astrophysics Data System (ADS)

Beddar, A. S.; Tailor, R. C.

2004-04-01

A new approach to intraoperative radiation therapy led to the development of mobile linear electron accelerators that provide lower electron energy beams than the usual conventional accelerators commonly encountered in radiotherapy. Such mobile electron accelerators produce electron beams that have nominal energies of 4, 6, 9 and 12 MeV. This work compares the absorbed dose output calibrations using both the AAPM TG-51 and TG-21 dose calibration protocols for two types of ion chambers: a plane-parallel (PP) ionization chamber and a cylindrical ionization chamber. Our results indicate that the use of a 'Markus' PP chamber causes 2 3% overestimation in dose output determination if accredited dosimetry-calibration laboratory based chamber factors \\big(N_{{\\rm D},{\\rm w}}^{{}^{60}{\\rm Co}}, N_x\\big) are used. However, if the ionization chamber factors are derived using a cross-comparison at a high-energy electron beam, then a good agreement is obtained (within 1%) with a calibrated cylindrical chamber over the entire energy range down to 4 MeV. Furthermore, even though the TG-51 does not recommend using cylindrical chambers at the low energies, our results show that the cylindrical chamber has a good agreement with the PP chamber not only at 6 MeV but also down to 4 MeV electron beams.

Effects of p-(Trifluoromethoxy)benzyl and p-(Trifluoromethoxy)phenyl Molecular Architecture on the Performance of Naphthalene Tetracarboxylic Diimide-Based Air-Stable n-Type Semiconductors.

PubMed

Zhang, Dongwei; Zhao, Liang; Zhu, Yanan; Li, Aiyuan; He, Chao; Yu, Hongtao; He, Yaowu; Yan, Chaoyi; Goto, Osamu; Meng, Hong

2016-07-20

N,N'-Bis(4-trifluoromethoxyphenyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-POCF3) and N,N'-bis(4-trifluoromethoxybenzyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-BOCF3) have similar optical and electrochemical properties with a deep LUMO level of approximately 4.2 eV, but exhibit significant differences in electron mobility and molecular packing. NDI-POCF3 exhibits nondetectable charge mobility. Interestingly, NDI-BOCF3 shows air-stable electron transfer performance with enhanced mobility by increasing the deposition temperature onto the octadecyltrichlorosilane (OTS)-modified SiO2/Si substrates and achieves electron mobility as high as 0.7 cm(2) V(-1) s(-1) in air. The different mobilities of those two materials can be explained by several factors including thin-film morphology and crystallinity. In contrast to the poor thin-film morphology and crystallinity of NDI-POCF3, NDI-BOCF3 exhibits larger grain sizes and improved crystallinities due to the higher deposition temperature. In addition, the theoretical calculated transfer integrals of the intermolecular lowest unoccupied molecular orbital (LUMO) of the two materials further show that a large intermolecular orbital overlap of NDI-BOCF3 can transfer electron more efficiently than NDI-POCF3 in thin-film transistors. On the basis of fact that the theoretical calculations are consistent with the experimental results, it can be concluded that the p-(trifluoromethoxy) benzyl (BOCF3) molecular architecture on the former position of the naphthalene tetracarboxylic diimides (NDI) core provides a more effective way to enhance the intermolecular electron transfer property than the p-(trifluoromethoxy) phenyl (POCF3) group for the future design of NDI-related air-stable n-channel semiconductor.

Electrical characteristics of high-power AlGaN-GaN high electron mobility transistors irradiated with protons and heavy ions

NASA Astrophysics Data System (ADS)

Sin, Yongkun; Bonsall, Jeremy; Lingley, Zachary; Brodie, Miles; Mason, Maribeth

2017-02-01

High electron mobility transistors (HEMTs) based on AlGaN-GaN hetero-structures are finding an increasing number of commercial and military applications that require high voltage, high power, and high efficiency operation. In recent years, leading GaN HEMT manufacturers have reported excellent RF power characteristics and encouraging reliability, but long-term reliability in the space environment still remains a major concern due to a large number of defects and traps present both in the bulk as well as at the surface, leading to undesirable characteristics including current collapse. Furthermore, degradation mechanisms in GaN HEMTs are still not well understood. Thus, reliability and radiation effects of GaN HEMTs should be studied before solid state power amplifiers (SSPAs) based on GaN HEMT technology are successfully deployed in space satellite systems. For the present study, we investigated electrical characteristics of high-power GaN HEMTs irradiated with protons and heavy ions under various irradiation and biasing conditions.

Collaborative designing and job satisfaction of airplane manufacturing engineers: A case study

NASA Astrophysics Data System (ADS)

Johnson, Michael David, Sr.

The group III-nitride system of materials has had considerable commercial success in recent years in the solid state lighting (SSL) and power electronics markets. The need for high efficient general lighting applications has driven research into InGaN based blue light emitting diodes (LEDs), and demand for more efficient power electronics for telecommunications has driven research into AlGaN based high electron mobility transistors (HEMTs). However, the group III-nitrides material properties make them attractive for several other applications that have not received as much attention. This work focuses on developing group III-nitride based devices for novel applications. GaN is a robust, chemically inert, piezoelectric material, making it an ideal candidate for surface acoustic wave (SAW) devices designed for high temperature and/or harsh environment sensors. In this work, SAW devices based on GaN are developed for use in high temperature gas or chemical sensor applications. To increase device sensitivity, while maintaining a simple one-step photolithography fabrication process, devices were designed to operate at high harmonic frequencies. This allows for GHz regime operation without sub-micron fabrication. One potential market for this technology is continuous emissions monitoring of combustion gas vehicles. In addition to SAW devices, high electron mobility transistors (HEMTs) were developed. The epitaxial structure was characterized and the 2-D electron gas concentrations were simulated and compared to experimental results. Device fabrication processes were developed and are outlined. Fabricated devices were electrically measured and device performance is discussed.

Development of III-V p-MOSFETs with high-kappa gate stack for future CMOS applications

NASA Astrophysics Data System (ADS)

Nagaiah, Padmaja

As the semiconductor industry approaches the limits of traditional silicon CMOS scaling, non-silicon materials and new device architectures are gradually being introduced to improve Si integrated circuit performance and continue transistor scaling. Recently, the replacement of SiO2 with a high-k material (HfO2) as gate dielectric has essentially removed one of the biggest advantages of Si as channel material. As a result, alternate high mobility materials are being considered to replace Si in the channel to achieve higher drive currents and switching speeds. III-V materials in particular have become of great interest as channel materials, owing to their superior electron transport properties. However, there are several critical challenges that need to be addressed before III-V based CMOS can replace Si CMOS technology. Some of these challenges include development of a high quality, thermally stable gate dielectric/III-V interface, and improvement in III-V p-channel hole mobility to complement the n-channel mobility, low source/drain resistance and integration onto Si substrate. In this thesis, we would be addressing the first two issues i.e. the development high performance III-V p-channels and obtaining high quality III-V/high-k interface. We start with using the device architecture of the already established InGaAs n-channels as a baseline to understand the effect of remote scattering from the high-k oxide and oxide/semiconductor interface on channel transport properties such as electron mobility and channel electron concentration. Temperature dependent Hall electron mobility measurements were performed to separate various scattering induced mobility limiting factors. Dependence of channel mobility on proximity of the channel to the oxide interface, oxide thickness, annealing conditions are discussed. The results from this work will be used in the design of the p-channel MOSFETs. Following this, InxGa1-xAs (x>0.53) is chosen as channel material for developing p-channel MOSFETs. Band engineering, strain induced valence band splitting and quantum confinement is used to improve channel hole mobility. Experimental results on the Hall hole mobility is presented for InxGa1-xAs channels with varying In content, thickness of the quantum well and temperature. Then, high mobility InxGa 1-xAs heterostructure thus obtained are integrated with in-situ deposited high-k gate oxide required for high performance p-MOSFET and discuss the challenges associated with the gated structure and draw conclusions on this material system. Antimonide based channel materials such as GaSb and InxGa 1-xSb are explored for III-V based p-MOSFETs in last two chapters. Options for Sb based strained QW channels to obtain maximum hole mobility by varying the strain, channel and barrier material, thickness of the layers etc. is discussed followed by the growth of these Sb channels on GaAs and InP substrates using molecular beam epitaxy. The physical properties of the structures such as the heterostructure quality, alloy content and surface roughness are examined via TEM, XRD and AFM. Following this, electrical measurement results on Hall hole mobility is presented. The effect of strain, alloy content, temperature and thickness on channel mobility and concentration is reported. Development of GaSb n- and p-MOS capacitor structures with in-situ deposited HfO2 gate oxide dielectric using in-situ deposited amorphous Si (a-Si) interface passivation layer (IPL) to improve the interface quality of high-k oxide and (In)GaSb surface is presented. In-situ deposited gate oxides such as Al2O3 and combination oxide of Al 2O3 and HfO2 with and without the a-Si IPL are also explored as alternate gate dielectrics. Subsequently, MOS capacitor structures using buried InGaSb QWs are demonstrated. Development of an inversion type bulk GaSb with implanted source-drain contacts and in-situ deposited gate oxide HfO2 gate oxide is discussed. The merits of biaxial compressive strain is demonstrated on strained surface and buried channel In0.36 Ga0.64Sb QW MOSFETs with thin top barrier and in-situ deposited a-Si IPL and high-k HfO2 as well as combination Al 2O3+HfO2 gate stacks and ex-situ atomic layer deposited (ALD) combination gate oxide and with thin 2 nm InAs surface passivation layer is presented. Finally, summary of the salient results from the different chapters is provided with recommendations for future research.

SLS complementary logic devices with increase carrier mobility

DOEpatents

Chaffin, R.J.; Osbourn, G.C.; Zipperian, T.E.

1991-07-09

In an electronic device comprising a semiconductor material and having at least one performance characteristic which is limited by the mobility of holes in the semiconductor material, said mobility being limited because of a valence band degeneracy among high-mobility and low-mobility energy levels accessible to said holes at the energy-momentum space maximum, an improvement is provided wherein the semiconductor material is a strained layer superlattice (SLS) whose layer compositions and layer thicknesses are selected so that the strain on the layers predominantly containing said at least one carrier type splits said degeneracy and modifies said energy levels around said energy-momentum space maximum in a manner whereby said limitation on the mobility of said holes is alleviated. 5 figures.

SLS complementary logic devices with increase carrier mobility

DOEpatents

Chaffin, Roger J.; Osbourn, Gordon C.; Zipperian, Thomas E.

1991-01-01

In an electronic device comprising a semiconductor material and having at least one performance characteristic which is limited by the mobility of holes in the semiconductor material, said mobility being limited because of a valence band degeneracy among high-mobility and low-mobility energy levels accessible to said holes at the energy-momentum space maximum, an improvement is provided wherein the semiconductor material is a strained layer superlattice (SLS) whose layer compositions and layer thicknesses are selected so that the strain on the layers predominantly containing said at least one carrier type splits said degeneracy and modifies said energy levels around said energy-momentum space maximum in a manner whereby said limitation on the mobility of said holes is alleviated.

Dynamics driving function: new insights from electron transferring flavoproteins and partner complexes.

PubMed

Toogood, Helen S; Leys, David; Scrutton, Nigel S

2007-11-01

Electron transferring flavoproteins (ETFs) are soluble heterodimeric FAD-containing proteins that function primarily as soluble electron carriers between various flavoprotein dehydrogenases. ETF is positioned at a key metabolic branch point, responsible for transferring electrons from up to 10 primary dehydrogenases to the membrane-bound respiratory chain. Clinical mutations of ETF result in the often fatal disease glutaric aciduria type II. Structural and biophysical studies of ETF in complex with partner proteins have shown that ETF partitions the functions of partner binding and electron transfer between (a) a 'recognition loop', which acts as a static anchor at the ETF-partner interface, and (b) a highly mobile redox-active FAD domain. Together, this enables the FAD domain of ETF to sample a range of conformations, some compatible with fast interprotein electron transfer. This 'conformational sampling' enables ETF to recognize structurally distinct partners, whilst also maintaining a degree of specificity. Complex formation triggers mobility of the FAD domain, an 'induced disorder' mechanism contrasting with the more generally accepted models of protein-protein interaction by induced fit mechanisms. We discuss the implications of the highly dynamic nature of ETFs in biological interprotein electron transfer. ETF complexes point to mechanisms of electron transfer in which 'dynamics drive function', a feature that is probably widespread in biology given the modular assembly and flexible nature of biological electron transfer systems.

The effect of charged quantum dots on the mobility of a two-dimensional electron gas: How important is the Coulomb scattering?

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

Kurzmann, A., E-mail: annika.kurzmann@uni-due.de; Beckel, A.; Lorke, A.

2015-02-07

We have investigated the influence of a layer of charged self-assembled quantum dots (QDs) on the mobility of a nearby two-dimensional electron gas (2DEG). Time-resolved transconductance spectroscopy was used to separate the two contributions of the change in mobility, which are: (i) The electrons in the QDs act as Coulomb scatterers for the electrons in the 2DEG. (ii) The screening ability and, hence, the mobility of the 2DEG decreases when the charge carrier density is reduced by the charged QDs, i.e., the mobility itself depends on the charge carrier concentration. Surprisingly, we find a negligible influence of the Coulomb scatteringmore » on the mobility for a 2DEG, separated by a 30 nm tunneling barrier to the layer of QDs. This means that the mobility change is completely caused by depletion, i.e., reduction of the charge carrier density in the 2DEG, which indirectly influences the mobility.« less

High-mobility ultrathin semiconducting films prepared by spin coating.

PubMed

Mitzi, David B; Kosbar, Laura L; Murray, Conal E; Copel, Matthew; Afzali, Ali

2004-03-18

The ability to deposit and tailor reliable semiconducting films (with a particular recent emphasis on ultrathin systems) is indispensable for contemporary solid-state electronics. The search for thin-film semiconductors that provide simultaneously high carrier mobility and convenient solution-based deposition is also an important research direction, with the resulting expectations of new technologies (such as flexible or wearable computers, large-area high-resolution displays and electronic paper) and lower-cost device fabrication. Here we demonstrate a technique for spin coating ultrathin (approximately 50 A), crystalline and continuous metal chalcogenide films, based on the low-temperature decomposition of highly soluble hydrazinium precursors. We fabricate thin-film field-effect transistors (TFTs) based on semiconducting SnS(2-x)Se(x) films, which exhibit n-type transport, large current densities (>10(5) A cm(-2)) and mobilities greater than 10 cm2 V(-1) s(-1)--an order of magnitude higher than previously reported values for spin-coated semiconductors. The spin-coating technique is expected to be applicable to a range of metal chalcogenides, particularly those based on main group metals, as well as for the fabrication of a variety of thin-film-based devices (for example, solar cells, thermoelectrics and memory devices).

High-mobility ultrathin semiconducting films prepared by spin coating

NASA Astrophysics Data System (ADS)

Mitzi, David B.; Kosbar, Laura L.; Murray, Conal E.; Copel, Matthew; Afzali, Ali

2004-03-01

The ability to deposit and tailor reliable semiconducting films (with a particular recent emphasis on ultrathin systems) is indispensable for contemporary solid-state electronics. The search for thin-film semiconductors that provide simultaneously high carrier mobility and convenient solution-based deposition is also an important research direction, with the resulting expectations of new technologies (such as flexible or wearable computers, large-area high-resolution displays and electronic paper) and lower-cost device fabrication. Here we demonstrate a technique for spin coating ultrathin (~50Å), crystalline and continuous metal chalcogenide films, based on the low-temperature decomposition of highly soluble hydrazinium precursors. We fabricate thin-film field-effect transistors (TFTs) based on semiconducting SnS2-xSex films, which exhibit n-type transport, large current densities (>105Acm-2) and mobilities greater than 10cm2V-1s-1-an order of magnitude higher than previously reported values for spin-coated semiconductors. The spin-coating technique is expected to be applicable to a range of metal chalcogenides, particularly those based on main group metals, as well as for the fabrication of a variety of thin-film-based devices (for example, solar cells, thermoelectrics and memory devices).

H and Au diffusion in high mobility a-InGaZnO thin-film transistors via low temperature KrF excimer laser annealing

NASA Astrophysics Data System (ADS)

Bermundo, Juan Paolo S.; Ishikawa, Yasuaki; Fujii, Mami N.; Ikenoue, Hiroshi; Uraoka, Yukiharu

2017-03-01

We report the fabrication of high mobility amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) irradiated by a single shot of a 248 nm KrF excimer laser. Very high mobilities (μ) of up to 43.5 cm2/V s were obtained after the low temperature excimer laser annealing (ELA) process. ELA induces high temperatures primarily in the upper layers and maintains very low temperatures of less than 50 °C in the substrate region. Scanning Transmission Electron micrographs show no laser induced damage and clear interfaces after the laser irradiation. In addition, several characterization studies were performed to determine the μ improvement mechanism. The analysis of Secondary Ion Mass Spectrometry and X-ray Photoelectron Spectroscopy suggests incorporation of H mainly from the hybrid passivation layer into the channel. Moreover, Energy-dispersive X-ray Spectroscopy results show that Au diffused into the channel after ELA. Both KrF ELA-induced H and Au diffusion contributed to the higher μ. These results demonstrate that ELA can greatly enhance the electrical properties of a-IGZO TFTs for promising applications in large area, transparent, and flexible electronics.

D-region positive and negative ion concentration and mobilities during the February 1979 eclipse

NASA Astrophysics Data System (ADS)

Conley, T. D.; Narcisi, R. S.; Hegblom, E. R.

1983-07-01

Positive and negative ion concentrations and mobilities have been obtained from an analysis of Gerdien condenser measurements on rocket flights, A10.802-1 and A10.802-2, during and after eclipse totality. The aerodynamic instrument calibration and the data analysis techniques are discussed. The measured concentrations on both flights were about 10,000/cu cm in the altitudes range, 45-80 km. These high concentrations at very low altitudes suggest that a relativistic electron precipitation event was occurring during the measurements. The ion concentration measurements along with electron density measurements made by other groups during the eclipse were used to calculate the negative ion/ electron ratio, and the lumped parameter detachment rate. These results are compared with prior measurements during eclipse and solar proton events and code results. The analysis shows that the present negative ion model is incomplete. The reduced mobilities were also determined. The mobility distributions show that the heavy ions of both the positive and negative species dominate from 45 to 70 km. The data reveal more massive ions at higher altitudes than at low altitudes (1000 vs 300 a.m.u.) as well as possible evidence for multiply charged ions below about 60 km.

Air-stable solution-processed n-channel organic thin film transistors with polymerenhanced morphology

DOE PAGES

He, Zhengran; Shaik, Shoieb; Bi, Sheng; ...

2015-05-04

N,N 0-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN 2) is an n-type semiconductor exhibiting high electron mobility and excellent air stability. However, the reported electron mobility based on spin-coated PDIF-CN 2 film is much lower than the value of PDIF-CN 2 single crystals made from vapor phase deposition, indicating significant room for mobility enhancement. In this study, various insulating polymers, including poly(vinyl alcohol), poly(methyl methacrylate) (PMMA), and poly(alpha-methylstyrene) (PaMS), are pre-coated on silicon substrate aiming to enhance the morphology of the PDIF-CN 2 thin film, thereby improving the charge transport and air stability. Atomic force microscopy images reveal that with the pre-deposition of PaMSmore » or PMMA polymers, the morphology of the PDIF-CN 2 polycrystalline films is optimized in semiconducting crystal connectivity, domain size, and surface roughness, which leads to significant improvement of organic thin-film transistor (OTFT) performance. Particularly, an electron mobility of up to 0.55 cm 2/V s has been achieved from OTFTs based on the PDIF-CN 2 film with the pre-deposition of PaMS polymer.« less

Quantifying electronic band interactions in van der Waals materials using angle-resolved reflected-electron spectroscopy

PubMed Central

Jobst, Johannes; van der Torren, Alexander J. H.; Krasovskii, Eugene E.; Balgley, Jesse; Dean, Cory R.; Tromp, Rudolf M.; van der Molen, Sense Jan

2016-01-01

High electron mobility is one of graphene's key properties, exploited for applications and fundamental research alike. Highest mobility values are found in heterostructures of graphene and hexagonal boron nitride, which consequently are widely used. However, surprisingly little is known about the interaction between the electronic states of these layered systems. Rather pragmatically, it is assumed that these do not couple significantly. Here we study the unoccupied band structure of graphite, boron nitride and their heterostructures using angle-resolved reflected-electron spectroscopy. We demonstrate that graphene and boron nitride bands do not interact over a wide energy range, despite their very similar dispersions. The method we use can be generally applied to study interactions in van der Waals systems, that is, artificial stacks of layered materials. With this we can quantitatively understand the ‘chemistry of layers' by which novel materials are created via electronic coupling between the layers they are composed of. PMID:27897180

Single-electron random-number generator (RNG) for highly secure ubiquitous computing applications

NASA Astrophysics Data System (ADS)

Uchida, Ken; Tanamoto, Tetsufumi; Fujita, Shinobu

2007-11-01

Since the security of all modern cryptographic techniques relies on unpredictable and irreproducible digital keys generated by random-number generators (RNGs), the realization of high-quality RNG is essential for secure communications. In this report, a new RNG, which utilizes single-electron phenomena, is proposed. A room-temperature operating silicon single-electron transistor (SET) having nearby an electron pocket is used as a high-quality, ultra-small RNG. In the proposed RNG, stochastic single-electron capture/emission processes to/from the electron pocket are detected with high sensitivity by the SET, and result in giant random telegraphic signals (GRTS) on the SET current. It is experimentally demonstrated that the single-electron RNG generates extremely high-quality random digital sequences at room temperature, in spite of its simple configuration. Because of its small-size and low-power properties, the single-electron RNG is promising as a key nanoelectronic device for future ubiquitous computing systems with highly secure mobile communication capabilities.

Phonon-limited carrier mobility and resistivity from carbon nanotubes to graphene

NASA Astrophysics Data System (ADS)

Li, Jing; Miranda, Henrique Pereira Coutada; Niquet, Yann-Michel; Genovese, Luigi; Duchemin, Ivan; Wirtz, Ludger; Delerue, Christophe

2015-08-01

Under which conditions do the electrical transport properties of one-dimensional (1D) carbon nanotubes (CNTs) and 2D graphene become equivalent? We have performed atomistic calculations of the phonon-limited electrical mobility in graphene and in a wide range of CNTs of different types to address this issue. The theoretical study is based on a tight-binding method and a force-constant model from which all possible electron-phonon couplings are computed. The electrical resistivity of graphene is found in very good agreement with experiments performed at high carrier density. A common methodology is applied to study the transition from one to two dimensions by considering CNTs with diameter up to 16 nm. It is found that the mobility in CNTs of increasing diameter converges to the same value, i.e., the mobility in graphene. This convergence is much faster at high temperature and high carrier density. For small-diameter CNTs, the mobility depends strongly on chirality, diameter, and the existence of a band gap.

Dependence of mobility on shallow localized gap states in single-crystal organic field-effect-transistors

NASA Astrophysics Data System (ADS)

Butko, V. Y.; So, W.; Lang, D. V.; Chi, X.; Lashley, J. C.; Ramirez, A. P.

2009-12-01

In order to optimize the performance of molecular organic electronic devices it is important to study the intermolecular density of states and charge transport mechanisms in the environment of crystalline organic material. Using this approach in Field Effect Transistors (FETs) we show that material purification improves carrier mobility and decreases density of the deep localized electronic state. We also report a general exponential energy dependence of the density of localized states in a vicinity of the mobility edge (Fermi energies up to ∼7 times higher than the thermal energy (kT)) in a variety of the extensively purified molecular organic crystal FETs. This observation and the low activation energy of the order of ∼kT suggest that molecular structural misplacements of the sizes that are comparable with thermal molecular modes rather than impurity deep traps play a role in formation of these shallow states. We find that the charge carrier mobility in the FET nanochannels, μeff, is parameterized by two factors, the free-carrier mobility, μ0, and the ratio of the free carrier density to the total carrier density induced by gate bias. Crystalline FETs fabricated from rubrene, pentacene, and tetracene have a high free-carrier mobility, μ0∼50 cm2/Vs, at 300 K with lower device μeff dominated by localized shallow gap states. This relationship suggests that further improvements in electronic performance could be possible with enhanced device quality.

78 FR 32689 - Certain Portable Electronic Communications Devices, Including Mobile Phones and Components...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-31

..., Including Mobile Phones and Components Thereof Notice of Receipt of Complaint; Solicitation of Comments... Certain Portable Electronic Communications Devices, Including Mobile Phones and Components Thereof, DN... mobile phones and components thereof. The complaint names as respondents HTC Corporation of China and HTC...

Comparative investigation of surface transfer doping of hydrogen terminated diamond by high electron affinity insulators

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

Verona, C.; Marinelli, Marco; Verona-Rinati, G.

We report on a comparative study of transfer doping of hydrogenated single crystal diamond surface by insulators featured by high electron affinity, such as Nb{sub 2}O{sub 5}, WO{sub 3}, V{sub 2}O{sub 5}, and MoO{sub 3}. The low electron affinity Al{sub 2}O{sub 3} was also investigated for comparison. Hole transport properties were evaluated in the passivated hydrogenated diamond films by Hall effect measurements, and were compared to un-passivated diamond films (air-induced doping). A drastic improvement was observed in passivated samples in terms of conductivity, stability with time, and resistance to high temperatures. The efficiency of the investigated insulators, as electron acceptingmore » materials in hydrogenated diamond surface, is consistent with their electronic structure. These surface acceptor materials generate a higher hole sheet concentration, up to 6.5 × 10{sup 13} cm{sup −2}, and a lower sheet resistance, down to 2.6 kΩ/sq, in comparison to the atmosphere-induced values of about 1 × 10{sup 13} cm{sup −2} and 10 kΩ/sq, respectively. On the other hand, hole mobilities were reduced by using high electron affinity insulator dopants. Hole mobility as a function of hole concentration in a hydrogenated diamond layer was also investigated, showing a well-defined monotonically decreasing trend.« less

Tuning the Electronic Properties, Effective Mass and Carrier Mobility of MoS2 Monolayer by Strain Engineering: First-Principle Calculations

NASA Astrophysics Data System (ADS)

Phuc, Huynh V.; Hieu, Nguyen N.; Hoi, Bui D.; Hieu, Nguyen V.; Thu, Tran V.; Hung, Nguyen M.; Ilyasov, Victor V.; Poklonski, Nikolai A.; Nguyen, Chuong V.

2018-01-01

In this paper, we studied the electronic properties, effective masses, and carrier mobility of monolayer MoS_2 using density functional theory calculations. The carrier mobility was considered by means of ab initio calculations using the Boltzmann transport equation coupled with deformation potential theory. The effects of mechanical biaxial strain on the electronic properties, effective mass, and carrier mobility of monolayer MoS_2 were also investigated. It is demonstrated that the electronic properties, such as band structure and density of state, of monolayer MoS_2 are very sensitive to biaxial strain, leading to a direct-indirect transition in semiconductor monolayer MoS_2. Moreover, we found that the carrier mobility and effective mass can be enhanced significantly by biaxial strain and by lowering temperature. The electron mobility increases over 12 times with a biaxial strain of 10%, while the carrier mobility gradually decreases with increasing temperature. These results are very useful for the future nanotechnology, and they make monolayer MoS_2 a promising candidate for application in nanoelectronic and optoelectronic devices.

75 FR 32984 - Policy on the Retention of Supporting Documents and the Use of Electronic Mobile Communication...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-10

...-0168] Policy on the Retention of Supporting Documents and the Use of Electronic Mobile Communication/Tracking Technology in Assessing Motor Carriers' and Commercial Motor Vehicle Drivers' Compliance With the... changes regarding the retention of supporting documents and the use of electronic mobile communication...

Orion Service Module Umbilical (OSMU) Lift & Preparation for Ins

NASA Image and Video Library

2017-03-13

A view from below the mobile launcher shows a crane positioning the bracket for the Orion Service Module Umbilical (OSMU) high up for installation on the mobile launcher tower at NASA's Kennedy Space Center in Florida. The mobile launcher tower will be equipped with a number of lines, called umbilicals, that will connect to the Space Launch System rocket and Orion spacecraft for Exploration Mission-1 (EM-1). The OSMU will be located high on the mobile launcher tower and, prior to launch, will transfer liquid coolant for the electronics and air for the Environmental Control System to the Orion service module that houses these critical systems to support the spacecraft. EM-1 is scheduled to launch in 2018. The Ground Systems Development and Operations Program is overseeing installation of the umbilicals.

Orion Service Module Umbilical (OSMU) Lift & Preparation for Ins

NASA Image and Video Library

2017-03-13

In this view looking down from high up on the mobile launcher, a crane positions the bracket for the Orion Service Module Umbilical (OSMU) for installation on the mobile launcher tower at NASA's Kennedy Space Center in Florida. The mobile launcher tower will be equipped with a number of lines, called umbilicals, that will connect to the Space Launch System rocket and Orion spacecraft for Exploration Mission-1 (EM-1). The OSMU will be located high on the mobile launcher tower and, prior to launch, will transfer liquid coolant for the electronics and air for the Environmental Control System to the Orion service module that houses these critical systems to support the spacecraft. EM-1 is scheduled to launch in 2018. The Ground Systems Development and Operations Program is overseeing installation of the umbilicals.

Epitaxial Growth of Cubic Crystalline Semiconductor Alloys on Basal Plane of Trigonal or Hexagonal Crystal

NASA Technical Reports Server (NTRS)

Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor)

2011-01-01

Hetero-epitaxial semiconductor materials comprising cubic crystalline semiconductor alloys grown on the basal plane of trigonal and hexagonal substrates, in which misfit dislocations are reduced by approximate lattice matching of the cubic crystal structure to underlying trigonal or hexagonal substrate structure, enabling the development of alloyed semiconductor layers of greater thickness, resulting in a new class of semiconductor materials and corresponding devices, including improved hetero-bipolar and high-electron mobility transistors, and high-mobility thermoelectric devices.

Spin relaxation in n-type GaAs quantum wells from a fully microscopic approach

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

Zhou, J.; Wu, M. W.; Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026

2007-01-15

We perform a full microscopic investigation on the spin relaxation in n-type (001) GaAs quantum wells with an Al{sub 0.4}Ga{sub 0.6}As barrier due to the D'yakonov-Perel' mechanism from nearly 20 K to room temperature by constructing and numerically solving the kinetic spin Bloch equations. We consider all the relevant scattering such as the electron-acoustic-phonon, the electron-longitudinal-optical-phonon, the electron-nonmagnetic-impurity, and the electron-electron Coulomb scattering to the spin relaxation. The spin relaxation times calculated from our theory with a fitting spin splitting parameter are in good agreement with the experimental data by Ohno et al. [Physica E (Amsterdam) 6, 817 (2000)] overmore » the whole temperature regime (from 20 to 300 K). The value of the fitted spin splitting parameter agrees with many experiments and theoretical calculations. We further show the temperature dependence of the spin relaxation time under various conditions such as electron density, impurity density, and well width. We predict a peak solely due to the Coulomb scattering in the spin relaxation time at low temperature (<50 K) in samples with low electron density (e.g., density less than 1x10{sup 11} cm{sup -2}) but high mobility. This peak disappears in samples with high electron density (e.g., 2x10{sup 11} cm{sup -2}) and/or low mobility. The hot-electron spin kinetics at low temperature is also addressed with many features quite different from the high-temperature case predicted.« less

Printed indium gallium zinc oxide transistors. Self-assembled nanodielectric effects on low-temperature combustion growth and carrier mobility.

PubMed

Everaerts, Ken; Zeng, Li; Hennek, Jonathan W; Camacho, Diana I; Jariwala, Deep; Bedzyk, Michael J; Hersam, Mark C; Marks, Tobin J

2013-11-27

Solution-processed amorphous oxide semiconductors (AOSs) are emerging as important electronic materials for displays and transparent electronics. We report here on the fabrication, microstructure, and performance characteristics of inkjet-printed, low-temperature combustion-processed, amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) grown on solution-processed hafnia self-assembled nanodielectrics (Hf-SANDs). TFT performance for devices processed below 300 °C includes >4× enhancement in electron mobility (μFE) on Hf-SAND versus SiO2 or ALD-HfO2 gate dielectrics, while other metrics such as subthreshold swing (SS), current on:off ratio (ION:IOFF), threshold voltage (Vth), and gate leakage current (Ig) are unchanged or enhanced. Thus, low voltage IGZO/SAND TFT operation (<2 V) is possible with ION:IOFF = 10(7), SS = 125 mV/dec, near-zero Vth, and large electron mobility, μFE(avg) = 20.6 ± 4.3 cm(2) V(-1) s(-1), μFE(max) = 50 cm(2) V(-1) s(-1). Furthermore, X-ray diffraction analysis indicates that the 300 °C IGZO combustion processing leaves the underlying Hf-SAND microstructure and capacitance intact. This work establishes the compatibility and advantages of all-solution, low-temperature fabrication of inkjet-printed, combustion-derived high-mobility IGZO TFTs integrated with self-assembled hybrid organic-inorganic nanodielectrics.

Intrinsic phonon-limited charge carrier mobilities in thermoelectric SnSe

NASA Astrophysics Data System (ADS)

Ma, Jinlong; Chen, Yani; Li, Wu

2018-05-01

Within the past few years, tin selenide (SnSe) has attracted intense interest due to its remarkable thermoelectric potential for both n - and p -type crystals. In this work, the intrinsic phonon-limited electron/hole mobilities of SnSe are investigated using a Boltzmann transport equation based on first-principles calculated electron-phonon interactions. We find that the electrons have much larger mobilities than the holes. At room temperature, the mobilities of electrons along the a , b , and c axes are 325, 801, and 623 cm2/V s, respectively, whereas those of holes are 100, 299, and 291 cm2/V s, respectively. The anisotropy of mobilities is consistent with the reciprocal effective mass at band edges. The mode-specific analysis shows that the highest longitudinal optical phonons, rather than previously assumed acoustic phonons, dominate the scattering processes and consequently the mobilities in SnSe. The room-temperature largest mean free paths of electrons and holes in SnSe are about 21 and 13 nm, respectively.

Intrinsically stretchable and healable semiconducting polymer for organic transistors

DOE PAGES

Oh, Jin Young; Rondeau-Gagné, Simon; Chiu, Yu-Cheng; ...

2016-11-16

Developing a molecular design paradigm for conjugated polymers applicable to intrinsically stretchable semiconductors is crucial toward the next generation of wearable electronics. Current molecular design rules for high charge carrier mobility semiconducting polymers are unable to render the fabricated devices simultaneously stretchable and mechanically robust. Here in this paper, we present a new design concept to address the above challenge, while maintaining excellent electronic performance. This concept involves introducing chemical moieties to promote dynamic non-covalent crosslinking of the conjugated polymers. These non-covalent covalent crosslinking moieties are able to undergo an energy dissipation mechanism through breakage of bonds when strain ismore » applied, while retaining its high charge transport ability. As a result, our polymer is able to recover its high mobility performance (>1 cm 2/Vs) even after 100 cycles at 100% applied strain. Furthermore, we observed that the polymer can be efficiently repaired and/or healed with a simple heat and solvent treatment. These improved mechanical properties of our fabricated stretchable semiconductor enabled us to fabricate highly stretchable and high performance wearable organic transistors. This material design concept should illuminate and advance the pathways for future development of fully stretchable and healable skin-inspired wearable electronics.« less

Intrinsically stretchable and healable semiconducting polymer for organic transistors

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

Oh, Jin Young; Rondeau-Gagné, Simon; Chiu, Yu-Cheng

Developing a molecular design paradigm for conjugated polymers applicable to intrinsically stretchable semiconductors is crucial toward the next generation of wearable electronics. Current molecular design rules for high charge carrier mobility semiconducting polymers are unable to render the fabricated devices simultaneously stretchable and mechanically robust. Here in this paper, we present a new design concept to address the above challenge, while maintaining excellent electronic performance. This concept involves introducing chemical moieties to promote dynamic non-covalent crosslinking of the conjugated polymers. These non-covalent covalent crosslinking moieties are able to undergo an energy dissipation mechanism through breakage of bonds when strain ismore » applied, while retaining its high charge transport ability. As a result, our polymer is able to recover its high mobility performance (>1 cm 2/Vs) even after 100 cycles at 100% applied strain. Furthermore, we observed that the polymer can be efficiently repaired and/or healed with a simple heat and solvent treatment. These improved mechanical properties of our fabricated stretchable semiconductor enabled us to fabricate highly stretchable and high performance wearable organic transistors. This material design concept should illuminate and advance the pathways for future development of fully stretchable and healable skin-inspired wearable electronics.« less

Boost the electron mobility of solution-grown organic single crystals via reducing the amount of polar solvent residues

DOE PAGES

Xue, Guobiao; Xin, Huolin L.; Wu, Jiake; ...

2015-10-29

Enhancing electron transport to match with the development in hole transport is critical for organic electronics in the future. As electron motion is susceptible to extrinsic factors, seeking these factors and avoiding their negative effects have become the central challenge. Here, the existence of polar solvent residues in solution-grown single-crystals of 6,13-bis(triisopropylsilylethynyl)-5,7,12,14-tetraazapentacene is identified as a factor detrimental to electron motion. Field-effect transistors of the crystals exhibit electron mobility boosted by about 60% after the residues are removed. The average electron mobility reaches up to 8.0 ± 2.2 cm 2 V –1 s –1 with a highest value of 13.3more » cm 2 V –1 s –1; these results are significantly higher than those obtained previously for the same molecule (1.0–5.0 cm 2 V –1 s –1). Furthermore, the achieved mobility is also higher than the maximum reported electron mobility for organic materials (11 cm 2 V –1 s –1). As a result, this work should greatly accelerate the advancement of organic electron-transporting materials.« less

Terahertz spin current pulses controlled by magnetic heterostructures

NASA Astrophysics Data System (ADS)

Kampfrath, T.; Battiato, M.; Maldonado, P.; Eilers, G.; Nötzold, J.; Mährlein, S.; Zbarsky, V.; Freimuth, F.; Mokrousov, Y.; Blügel, S.; Wolf, M.; Radu, I.; Oppeneer, P. M.; Münzenberg, M.

2013-04-01

In spin-based electronics, information is encoded by the spin state of electron bunches. Processing this information requires the controlled transport of spin angular momentum through a solid, preferably at frequencies reaching the so far unexplored terahertz regime. Here, we demonstrate, by experiment and theory, that the temporal shape of femtosecond spin current bursts can be manipulated by using specifically designed magnetic heterostructures. A laser pulse is used to drive spins from a ferromagnetic iron thin film into a non-magnetic cap layer that has either low (ruthenium) or high (gold) electron mobility. The resulting transient spin current is detected by means of an ultrafast, contactless amperemeter based on the inverse spin Hall effect, which converts the spin flow into a terahertz electromagnetic pulse. We find that the ruthenium cap layer yields a considerably longer spin current pulse because electrons are injected into ruthenium d states, which have a much lower mobility than gold sp states. Thus, spin current pulses and the resulting terahertz transients can be shaped by tailoring magnetic heterostructures, which opens the door to engineering high-speed spintronic devices and, potentially, broadband terahertz emitters.

Dislocation blocking by AlGaN hot electron injecting layer in the epitaxial growth of GaN terahertz Gunn diode

NASA Astrophysics Data System (ADS)

Li, Liang; Yang, Lin'an; Zhang, Jincheng; Hao, Yue

2013-09-01

This paper reports an efficient method to improve the crystal quality of GaN Gunn diode with AlGaN hot electron injecting layer (HEI). An evident reduction of screw dislocation and edge dislocation densities is achieved by the strain management and the enhanced lateral growth in high temperature grown AlGaN HEI layer. Compared with the top hot electron injecting layer (THEI) structure, the bottom hot electron injecting layer (BHEI) structure enhances the crystal quality of transit region due to the growth sequence modulation of HEI layer. A high Hall mobility of 2934 cm2/Vs at 77 K, a nearly flat downtrend of Hall mobility at the temperature ranging from 300 to 573 K, a low intensity of ratio of yellow luminescence band to band edge emission, a narrow band edge emission line-width, and a smooth surface morphology are observed for the BHEI structural epitaxy of Gunn diode, which indicates that AlGaN BHEI structure is a promising candidate for fabrication of GaN Gunn diodes in terahertz regime.

Extremely large magnetoresistance induced by Zeeman effect-driven electron-hole compensation and topological protection in MoSi2

NASA Astrophysics Data System (ADS)

Matin, M.; Mondal, Rajib; Barman, N.; Thamizhavel, A.; Dhar, S. K.

2018-05-01

Here, we report an extremely large positive magnetoresistance (XMR) in a single-crystal sample of MoSi2, approaching almost 107% at 2 K in a 14-T magnetic field without appreciable saturation. Hall resistivity data reveal an uncompensated nature of MoSi2 with an electron-hole compensation level sufficient enough to expect strong saturation of magnetoresistance in the high-field regime. Magnetotransport and the complementary de Haas-van Alphen (dHvA) oscillations results, however, suggest that strong Zeeman effect causes a magnetic field-induced modulation of the Fermi pockets and drives the system towards perfect electron-hole compensation condition in the high-field regime. Thus, the nonsaturating XMR of this semimetal arises under the unconventional situation of Zeeman effect-driven electron-hole compensation, whereas its huge magnitude is decided solely by the ultralarge value of the carrier mobility. Intrinsic ultralarge carrier mobility, strong suppression of backward scattering of the charge carriers, and nontrivial Berry phase in dHvA oscillations attest to the topological character of MoSi2. Therefore, this semimetal represents another material hosting combination of topological and conventional electronic phases.

Improved mobility in InAlN/AlGaN two-dimensional electron gas heterostructures with an atomically smooth heterointerface

NASA Astrophysics Data System (ADS)

Hosomi, Daiki; Miyachi, Yuta; Egawa, Takashi; Miyoshi, Makoto

2018-04-01

We attempted to improve the mobility of InAlN/AlGaN two-dimensional electron gas (2DEG) heterostructures by achieving an atomically smooth heterointerface in metalorganic chemical vapor deposition processes. In the result, it was confirmed that the high-growth-rate AlGaN layer was very effective to improve the surface morphology. The atomically smooth surface morphology with a root-mean-square roughness of 0.26 nm was achieved for an Al0.15Ga0.85N layer under the growth rate of approximately 6 µm/h. Furthermore, nearly lattice-matched In0.17Al0.83N/Al0.15Ga0.85N 2DEG heterostructures with the atomically smooth heterointerface exhibited a 2DEG mobility of 242 cm2 V-1 s-1 with a 2DEG density of 2.6 × 1013/cm2, which was approximately 1.5 times larger than the mobility in a sample grown under original conditions.

Thickness-dependent electron mobility of single and few-layer MoS{sub 2} thin-film transistors

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

Kim, Ji Heon; Kim, Tae Ho; Lee, Hyunjea

We investigated the dependence of electron mobility on the thickness of MoS{sub 2} nanosheets by fabricating bottom-gate single and few-layer MoS{sub 2} thin-film transistors with SiO{sub 2} gate dielectrics and Au electrodes. All the fabricated MoS{sub 2} transistors showed on/off-current ratio of ∼10{sup 7} and saturated output characteristics without high-k capping layers. As the MoS{sub 2} thickness increased from 1 to 6 layers, the field-effect mobility of the fabricated MoS{sub 2} transistors increased from ∼10 to ∼18 cm{sup 2}V{sup −1}s{sup −1}. The increased subthreshold swing of the fabricated transistors with MoS{sub 2} thickness suggests that the increase of MoS{sub 2}more » mobility with thickness may be related to the dependence of the contact resistance and the dielectric constant of MoS{sub 2} layer on its thickness.« less

Open-source mobile digital platform for clinical trial data collection in low-resource settings.

PubMed

van Dam, Joris; Omondi Onyango, Kevin; Midamba, Brian; Groosman, Nele; Hooper, Norman; Spector, Jonathan; Pillai, Goonaseelan Colin; Ogutu, Bernhards

2017-02-01

Governments, universities and pan-African research networks are building durable infrastructure and capabilities for biomedical research in Africa. This offers the opportunity to adopt from the outset innovative approaches and technologies that would be challenging to retrofit into fully established research infrastructures such as those regularly found in high-income countries. In this context we piloted the use of a novel mobile digital health platform, designed specifically for low-resource environments, to support high-quality data collection in a clinical research study. Our primary aim was to assess the feasibility of a using a mobile digital platform for clinical trial data collection in a low-resource setting. Secondarily, we sought to explore the potential benefits of such an approach. The investigative site was a research institute in Nairobi, Kenya. We integrated an open-source platform for mobile data collection commonly used in the developing world with an open-source, standard platform for electronic data capture in clinical trials. The integration was developed using common data standards (Clinical Data Interchange Standards Consortium (CDISC) Operational Data Model), maximising the potential to extend the approach to other platforms. The system was deployed in a pharmacokinetic study involving healthy human volunteers. The electronic data collection platform successfully supported conduct of the study. Multidisciplinary users reported high levels of satisfaction with the mobile application and highlighted substantial advantages when compared with traditional paper record systems. The new system also demonstrated a potential for expediting data quality review. This pilot study demonstrated the feasibility of using a mobile digital platform for clinical research data collection in low-resource settings. Sustainable scientific capabilities and infrastructure are essential to attract and support clinical research studies. Since many research structures in Africa are being developed anew, stakeholders should consider implementing innovative technologies and approaches.

Recovery in dc and rf performance of off-state step-stressed AlGaN/GaN high electron mobility transistors with thermal annealing

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

Kim, Byung-Jae; Hwang, Ya-Hsi; Ahn, Shihyun

The recovery effects of thermal annealing on dc and rf performance of off-state step-stressed AlGaN/GaN high electron mobility transistors were investigated. After stress, reverse gate leakage current and sub-threshold swing increased and drain current on-off ratio decreased. However, these degradations were completely recovered after thermal annealing at 450 °C for 10 mins for devices stressed either once or twice. The trap densities, which were estimated by temperature-dependent drain-current sub-threshold swing measurements, increased after off-state step-stress and were reduced after subsequent thermal annealing. In addition, the small signal rf characteristics of stressed devices were completely recovered after thermal annealing.

Enhancement mode GaN-based multiple-submicron channel array gate-recessed fin metal-oxide-semiconductor high-electron mobility transistors

NASA Astrophysics Data System (ADS)

Lee, Ching-Ting; Wang, Chun-Chi

2018-04-01

To study the function of channel width in multiple-submicron channel array, we fabricated the enhancement mode GaN-based gate-recessed fin metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs) with a channel width of 450 nm and 195 nm, respectively. In view of the enhanced gate controllability in a narrower fin-channel structure, the transconductance was improved from 115 mS/mm to 151 mS/mm, the unit gain cutoff frequency was improved from 6.2 GHz to 6.8 GHz, and the maximum oscillation frequency was improved from 12.1 GHz to 13.1 GHz of the devices with a channel width of 195 nm, compared with the devices with a channel width of 450 nm.

Charge carrier mobility and electronic properties of Al(Op)3: impact of excimer formation

PubMed Central

Friederich, Pascal; Schäfer, Bernhard; Fattori, Valeria; Sun, Xiangnan; Strunk, Timo; Meded, Velimir; Hueso, Luis E; Wenzel, Wolfgang; Ruben, Mario

2015-01-01

Summary We have studied the electronic properties and the charge carrier mobility of the organic semiconductor tris(1-oxo-1H-phenalen-9-olate)aluminium(III) (Al(Op)3) both experimentally and theoretically. We experimentally estimated the HOMO and LUMO energy levels to be −5.93 and −3.26 eV, respectively, which were close to the corresponding calculated values. Al(Op)3 was successfully evaporated onto quartz substrates and was clearly identified in the absorption spectra of both the solution and the thin film. A structured steady state fluorescence emission was detected in solution, whereas a broad, red-shifted emission was observed in the thin film. This indicates the formation of excimers in the solid state, which is crucial for the transport properties. The incorporation of Al(Op)3 into organic thin film transistors (TFTs) was performed in order to measure the charge carrier mobility. The experimental setup detected no electron mobility, while a hole mobility between 0.6 × 10−6 and 2.1 × 10−6 cm2·V−1·s−1 was measured. Theoretical simulations, on the other hand, predicted an electron mobility of 9.5 × 10−6 cm2·V−1·s−1 and a hole mobility of 1.4 × 10−4 cm2·V−1·s−1. The theoretical simulation for the hole mobility predicted an approximately one order of magnitude higher hole mobility than was observed in the experiment, which is considered to be in good agreement. The result for the electron mobility was, on the other hand, unexpected, as both the calculated electron mobility and chemical common sense (based on the capability of extended aromatic structures to efficiently accept and delocalize additional electrons) suggest more robust electron charge transport properties. This discrepancy is explained by the excimer formation, whose inclusion in the multiscale simulation workflow is expected to bring the theoretical simulation and experiment into agreement. PMID:26171287

High resolution X-ray CT for advanced electronics packaging

NASA Astrophysics Data System (ADS)

Oppermann, M.; Zerna, T.

2017-02-01

Advanced electronics packaging is a challenge for non-destructive Testing (NDT). More, smaller and mostly hidden interconnects dominate modern electronics components and systems. To solve the demands of customers to get products with a high functionality by low volume, weight and price (e.g. mobile phones, personal medical monitoring systems) often the designers use System-in-Package solutions (SiP). The non-destructive testing of such devices is a big challenge. So our paper will impart fundamentals and applications for non-destructive evaluation of inner structures of electronics packaging for quality assurance and reliability investigations with a focus on X-ray methods, especially on high resolution X-ray computed tomography (CT).

LaTiO₃/KTaO₃ interfaces: A new two-dimensional electron gas system

DOE PAGES

Zou, K.; Ismail-Beigi, Sohrab; Kisslinger, Kim; ...

2015-03-01

We report a new 2D electron gas (2DEG) system at the interface between a Mott insulator, LaTiO₃, and a band insulator, KTaO₃. For LaTiO₃/KTaO₃ interfaces, we observe metallic conduction from 2 K to 300 K. One serious technological limitation of SrTiO₃-based conducting oxide interfaces for electronics applications is the relatively low carrier mobility (0.5-10 cm²/V s) of SrTiO₃ at room temperature. By using KTaO₃, we achieve mobilities in LaTiO₃/KTaO₃ interfaces as high as 21 cm²/V s at room temperature, over a factor of 3 higher than observed in doped bulk SrTiO₃. By density functional theory, we attribute the higher mobilitymore » in KTaO₃ 2DEGs to the smaller effective mass for electrons in KTaO₃.« less

Determination of Charge-Carrier Mobility in Disordered Thin-Film Solar Cells as a Function of Current Density

NASA Astrophysics Data System (ADS)

Mäckel, Helmut; MacKenzie, Roderick C. I.

2018-03-01

Charge-carrier mobility is a fundamental material parameter, which plays an important role in determining solar-cell efficiency. The higher the mobility, the less time a charge carrier will spend in a device and the less likely it is that it will be lost to recombination. Despite the importance of this physical property, it is notoriously difficult to measure accurately in disordered thin-film solar cells under operating conditions. We, therefore, investigate a method previously proposed in the literature for the determination of mobility as a function of current density. The method is based on a simple analytical model that relates the mobility to carrier density and transport resistance. By revising the theoretical background of the method, we clearly demonstrate what type of mobility can be extracted (constant mobility or effective mobility of electrons and holes). We generalize the method to any combination of measurements that is able to determine the mean electron and hole carrier density, and the transport resistance at a given current density. We explore the robustness of the method by simulating typical organic solar-cell structures with a variety of physical properties, including unbalanced mobilities, unbalanced carrier densities, and for high or low carrier trapping rates. The simulations reveal that near VOC and JSC , the method fails due to the limitation of determining the transport resistance. However, away from these regions (and, importantly, around the maximum power point), the method can accurately determine charge-carrier mobility. In the presence of strong carrier trapping, the method overestimates the effective mobility due to an underestimation of the carrier density.

Estimation of retired mobile phones generation in China: A comparative study on methodology.

PubMed

Li, Bo; Yang, Jianxin; Lu, Bin; Song, Xiaolong

2015-01-01

Due to the rapid development of economy and technology, China has the biggest production and possession of mobile phones around the world. In general, mobile phones have relatively short life time because the majority of users replace their mobile phones frequently. Retired mobile phones represent the most valuable electrical and electronic equipment (EEE) in the main waste stream because of such characteristics as large quantity, high reuse/recovery value and fast replacement frequency. Consequently, the huge amount of retired mobile phones in China calls for a sustainable management system. The generation estimation can provide fundamental information to construct the sustainable management system of retired mobile phones and other waste electrical and electronic equipment (WEEE). However, the reliable estimation result is difficult to get and verify. The priority aim of this paper is to provide proper estimation approach for the generation of retired mobile phones in China, by comparing some relevant methods. The results show that the sales&new method is in the highest priority in estimation of the retired mobile phones. The result of sales&new method shows that there are 47.92 million mobile phones retired in 2002, and it reached to 739.98 million in China in 2012. It presents an increasing tendency with some fluctuations clearly. Furthermore, some discussions on methodology, such as the selection of improper approach and error in the input data, are also conducted in order to improve generation estimation of retired mobile phones and other WEEE. Copyright © 2014 Elsevier Ltd. All rights reserved.

Tuning on-off current ratio and field-effect mobility in a MoS(2)-graphene heterostructure via Schottky barrier modulation.

PubMed

Shih, Chih-Jen; Wang, Qing Hua; Son, Youngwoo; Jin, Zhong; Blankschtein, Daniel; Strano, Michael S

2014-06-24

Field-effect transistor (FET) devices composed of a MoS2-graphene heterostructure can combine the advantages of high carrier mobility in graphene with the permanent band gap of MoS2 for digital applications. Herein, we investigate the electron transfer, photoluminescence, and gate-controlled carrier transport in such a heterostructure. We show that the junction is a Schottky barrier, whose height can be artificially controlled by gating or doping graphene. When the applied gate voltage (or the doping level) is zero, the photoexcited electron-hole pairs in monolayer MoS2 can be split by the heterojunction, significantly reducing the photoluminescence. By applying negative gate voltage (or p-doping) in graphene, the interlayer impedance formed between MoS2 and graphene exhibits an 100-fold increase. For the first time, we show that the gate-controlled interlayer Schottky impedance can be utilized to modulate carrier transport in graphene, significantly depleting the hole transport, but preserving the electron transport. Accordingly, we demonstrate a new type of FET device, which enables a controllable transition from NMOS digital to bipolar characteristics. In the NMOS digital regime, we report a very high room temperature on/off current ratio (ION/IOFF ∼ 36) in comparison to graphene-based FET devices without sacrificing the field-effect electron mobilities in graphene. By engineering the source/drain contact area, we further estimate that a higher value of ION/IOFF up to 100 can be obtained in the device architecture considered. The device architecture presented here may enable semiconducting behavior in graphene for digital and analogue electronics.

Rogue waves lead to the instability in GaN semiconductors

PubMed Central

Yahia, M. E.; Tolba, R. E.; El-Bedwehy, N. A.; El-Labany, S. K.; Moslem, W. M.

2015-01-01

A new approach to understand the electron/hole interfaced plasma in GaN high electron mobility transistors (HEMTs). A quantum hydrodynamic model is constructed to include electrons/holes degenerate pressure, Bohm potential, and the exchange/correlation effect and then reduced to the nonlinear Schrödinger equation (NLSE). Numerical analysis of the latter predicts the rough (in)stability domains, which allow for the rogue waves to occur. Our results might give physical solution rather than the engineering one to the intrinsic problems in these high frequency/power transistors. PMID:26206731

76 FR 23923 - Hazardous Materials: Restricting the Use of Cellular Phones by Drivers of Commercial Motor...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-29

... associated with the use of cellular (mobile) phones and electronic devices while operating a commercial motor... mobile communication device that falls under or uses any commercial mobile radio service, as defined in... restricting the use of mobile telephones and other distracting electronic devices by railroad operating...

Suppression of surface-originated gate lag by a dual-channel AlN/GaN high electron mobility transistor architecture

NASA Astrophysics Data System (ADS)

Deen, David A.; Storm, David F.; Scott Katzer, D.; Bass, R.; Meyer, David J.

2016-08-01

A dual-channel AlN/GaN high electron mobility transistor (HEMT) architecture is demonstrated that leverages ultra-thin epitaxial layers to suppress surface-related gate lag. Two high-density two-dimensional electron gas (2DEG) channels are utilized in an AlN/GaN/AlN/GaN heterostructure wherein the top 2DEG serves as a quasi-equipotential that screens potential fluctuations resulting from distributed surface and interface states. The bottom channel serves as the transistor's modulated channel. Dual-channel AlN/GaN heterostructures were grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. HEMTs fabricated with 300 nm long recessed gates demonstrated a gate lag ratio (GLR) of 0.88 with no degradation in drain current after bias stressed in subthreshold. These structures additionally achieved small signal metrics ft/fmax of 27/46 GHz. These performance results are contrasted with the non-recessed gate dual-channel HEMT with a GLR of 0.74 and 82 mA/mm current collapse with ft/fmax of 48/60 GHz.

Basic Equations for the Modeling of Gallium Nitride (gan) High Electron Mobility Transistors (hemts)

NASA Technical Reports Server (NTRS)

Freeman, Jon C.

2003-01-01

Gallium nitride (GaN) is a most promising wide band-gap semiconductor for use in high-power microwave devices. It has functioned at 320 C, and higher values are well within theoretical limits. By combining four devices, 20 W has been developed at X-band. GaN High Electron Mobility Transistors (HEMTs) are unique in that the two-dimensional electron gas (2DEG) is supported not by intentional doping, but instead by polarization charge developed at the interface between the bulk GaN region and the AlGaN epitaxial layer. The polarization charge is composed of two parts: spontaneous and piezoelectric. This behavior is unlike other semiconductors, and for that reason, no commercially available modeling software exists. The theme of this document is to develop a self-consistent approach to developing the pertinent equations to be solved. A Space Act Agreement, "Effects in AlGaN/GaN HEMT Semiconductors" with Silvaco Data Systems to implement this approach into their existing software for III-V semiconductors, is in place (summer of 2002).

An AlN/Al 0.85Ga 0.15N high electron mobility transistor

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

Baca, Albert G.; Armstrong, Andrew M.; Allerman, Andrew A.

2016-07-22

An AlN barrier high electron mobility transistor (HEMT) based on the AlN/Al 0.85Ga 0.15N heterostructure was grown, fabricated, and electrically characterized, thereby extending the range of Al composition and bandgap for AlGaN channel HEMTs. An etch and regrowth procedure was implemented for source and drain contact formation. A breakdown voltage of 810 V was achieved without a gate insulator or field plate. Excellent gate leakage characteristics enabled a high I on/I off current ratio greater than 10 7 and an excellent subthreshold slope of 75 mV/decade. A large Schottky barrier height of 1.74 eV contributed to these results. In conclusion,more » the room temperature voltage-dependent 3-terminal off-state drain current was adequately modeled with Frenkel-Poole emission.« less

An AlN/Al{sub 0.85}Ga{sub 0.15}N high electron mobility transistor

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

Baca, Albert G.; Armstrong, Andrew M.; Allerman, Andrew A.

2016-07-18

An AlN barrier high electron mobility transistor (HEMT) based on the AlN/Al{sub 0.85}Ga{sub 0.15}N heterostructure was grown, fabricated, and electrically characterized, thereby extending the range of Al composition and bandgap for AlGaN channel HEMTs. An etch and regrowth procedure was implemented for source and drain contact formation. A breakdown voltage of 810 V was achieved without a gate insulator or field plate. Excellent gate leakage characteristics enabled a high I{sub on}/I{sub off} current ratio greater than 10{sup 7} and an excellent subthreshold slope of 75 mV/decade. A large Schottky barrier height of 1.74 eV contributed to these results. The room temperature voltage-dependent 3-terminalmore » off-state drain current was adequately modeled with Frenkel-Poole emission.« less

Characterization of gate recessed GaN/AlGaN/GaN high electron mobility transistors fabricated using a SiCl4/SF6 dry etch recipe

NASA Astrophysics Data System (ADS)

Green, R. T.; Luxmoore, I. J.; Lee, K. B.; Houston, P. A.; Ranalli, F.; Wang, T.; Parbrook, P. J.; Uren, M. J.; Wallis, D. J.; Martin, T.

2010-07-01

Incorporating GaN capping layers in conjunction with recessing has been identified as a means to maximize the high frequency performance of AlGaN/GaN high electron mobility transistors (HEMTs). Doping the cap heavily n-type is required in order to ensure minimal loss of carriers from the channel. Using a SiCl4/SF6 dry etch plasma recipe, 250 nm gate length HEMTs with recess lengths varying from 300 nm to 5 μm are fabricated. Heavily doped n+GaN caps enabled contact resistances of 0.3 Ω mm to be achieved. Recessing using a SiCl4/SF6 recipe does not introduce significant numbers of bulk traps. Gate recessing in conjunction with Si3N4 passivation reduces rf dispersion to negligible levels.

Wafer-Scale and Wrinkle-Free Epitaxial Growth of Single-Orientated Multilayer Hexagonal Boron Nitride on Sapphire.

PubMed

Jang, A-Rang; Hong, Seokmo; Hyun, Chohee; Yoon, Seong In; Kim, Gwangwoo; Jeong, Hu Young; Shin, Tae Joo; Park, Sung O; Wong, Kester; Kwak, Sang Kyu; Park, Noejung; Yu, Kwangnam; Choi, Eunjip; Mishchenko, Artem; Withers, Freddie; Novoselov, Kostya S; Lim, Hyunseob; Shin, Hyeon Suk

2016-05-11

Large-scale growth of high-quality hexagonal boron nitride has been a challenge in two-dimensional-material-based electronics. Herein, we present wafer-scale and wrinkle-free epitaxial growth of multilayer hexagonal boron nitride on a sapphire substrate by using high-temperature and low-pressure chemical vapor deposition. Microscopic and spectroscopic investigations and theoretical calculations reveal that synthesized hexagonal boron nitride has a single rotational orientation with AA' stacking order. A facile method for transferring hexagonal boron nitride onto other target substrates was developed, which provides the opportunity for using hexagonal boron nitride as a substrate in practical electronic circuits. A graphene field effect transistor fabricated on our hexagonal boron nitride sheets shows clear quantum oscillation and highly improved carrier mobility because the ultraflatness of the hexagonal boron nitride surface can reduce the substrate-induced degradation of the carrier mobility of two-dimensional materials.

Small-signal modeling with direct parameter extraction for impact ionization effect in high-electron-mobility transistors

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

Guan, He; Lv, Hongliang; Guo, Hui, E-mail: hguan@stu.xidian.edu.cn

2015-11-21

Impact ionization affects the radio-frequency (RF) behavior of high-electron-mobility transistors (HEMTs), which have narrow-bandgap semiconductor channels, and this necessitates complex parameter extraction procedures for HEMT modeling. In this paper, an enhanced small-signal equivalent circuit model is developed to investigate the impact ionization, and an improved method is presented in detail for direct extraction of intrinsic parameters using two-step measurements in low-frequency and high-frequency regimes. The practicability of the enhanced model and the proposed direct parameter extraction method are verified by comparing the simulated S-parameters with published experimental data from an InAs/AlSb HEMT operating over a wide frequency range. The resultsmore » demonstrate that the enhanced model with optimal intrinsic parameter values that were obtained by the direct extraction approach can effectively characterize the effects of impact ionization on the RF performance of HEMTs.« less

Conductors and semiconductors for advanced organic electronics

NASA Astrophysics Data System (ADS)

Meyer-Friedrichsen, Timo; Elschner, Andreas; Keohan, Frank; Lövenich, Wilfried; Ponomarenko, Sergei A.

2009-08-01

The development of suitable materials for organic electronics is still one of the key points to access new application areas with this promising technology. Semiconductors based on thiophene chemistry show very high charge carrier mobilities. The functionalization with linker groups provided materials that built monomolecular layers of the semiconductors on the hydrolyzed oxide surface of a silicon-wafer. This approach lead to self-assembled mono-layer field-effect transistors (SAM-FETs) with mobilities of up to 0.04 cm2/Vs, which is comparable to the values of the respective bulk thin film. Transparent inorganic conductors like ITO are highly conductive but the costly processing and the brittleness hamper their use in cost-sensitive and/or flexible devices. Highly conductive PEDOT-grades have been developed with conductivities of up to 1000 S/cm which are easily applicable by printing techniques and can be used as ITO replacement in devices such as touch panels or organic photovoltaics.

Electrical characteristics of proton-irradiated Sc2O3 passivated AlGaN/GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Luo, B.; Kim, Jihyun; Ren, F.; Gillespie, J. K.; Fitch, R. C.; Sewell, J.; Dettmer, R.; Via, G. D.; Crespo, A.; Jenkins, T. J.; Gila, B. P.; Onstine, A. H.; Allums, K. K.; Abernathy, C. R.; Pearton, S. J.; Dwivedi, R.; Fogarty, T. N.; Wilkins, R.

2003-03-01

Sc2O3-passivated AlGaN/GaN high electron mobility transistors (HEMTs) were irradiated with 40 MeV protons to a fluence corresponding to approximately 10 years in low-earth orbit (5×109 cm-2). Devices with an AlGaN cap layer showed less degradation in dc characteristics than comparable GaN-cap devices, consistent with differences in average band energy. The changes in device performance could be attributed completely to bulk trapping effects, demonstrating that the effectiveness of the Sc2O3 layers in passivating surface states in the drain-source region was undiminished by the proton irradiation. Sc2O3-passivated AlGaN/HEMTs appear to be attractive candidates for space and terrestrial applications where resistance to high fluxes of ionizing radiation is a criteria.

Microwave-induced resistance oscillations on a high-mobility two-dimensional electron gas: Exact waveform, absorption/reflection and temperature damping

NASA Astrophysics Data System (ADS)

Studenikin, S. A.; Potemski, M.; Sachrajda, A.; Hilke, M.; Pfeiffer, L. N.; West, K. W.

2005-06-01

In this work we address experimentally a number of unresolved issues related to microwave induced resistance oscillations (MIROs) leading to the zero-resistance states observed recently on 2D electron gases in GaAs/AlGaAs heterostructures. We stress the importance of the electrodynamic effects detected in both reflection and absorption experiments, although they are not revealed in transport experiments on very high mobility samples. We also study the exact waveform of MIROs and their damping due to temperature. A simple equation is given, which can be considered as phenomenological, which describes precisely the experimental MIROs waveform. The waveform depends only on a single parameter—the width of the Landau levels, which is related to the quantum lifetime. A very good correlation was found between the temperature dependencies of the quantum lifetime from MIROs and the transport scattering time from the electron mobility with a ratio τtr/τq≃20 . It is found that the prefactor in the equation for MIROs decays as 1/T2 with the temperature which can be explained within the distribution function model suggested by Dmitriev . The results are compared with measurements of the Shubnikov-de Haas oscillations down to 30mK on the same sample.

Orion Service Module Umbilical (OSMU) Installation

NASA Image and Video Library

2017-03-16

A crane lifts the Orion Service Module Umbilical (OSMU) high up for installation on the mobile launcher tower at NASA's Kennedy Space Center in Florida. The mobile launcher tower will be equipped with a number of lines, called umbilicals, that will connect to the Space Launch System rocket and Orion spacecraft for Exploration Mission-1 (EM-1). The OSMU will be located high on the mobile launcher tower and, prior to launch, will transfer liquid coolant for the electronics and air for the Environmental Control System to the Orion service module that houses these critical systems to support the spacecraft. EM-1 is scheduled to launch in 2018. The Ground Systems Development and Operations Program is overseeing installation of the umbilicals.

Atom probe tomography of lithium-doped network glasses.

PubMed

Greiwe, Gerd-Hendrik; Balogh, Zoltan; Schmitz, Guido

2014-06-01

Li-doped silicate and borate glasses are electronically insulating, but provide considerable ionic conductivity. Under measurement conditions of laser-assisted atom probe tomography, mobile Li ions are redistributed in response to high electric fields. In consequence, the direct interpretation of measured composition profiles is prevented. It is demonstrated that composition profiles are nevertheless well understood by a complex model taking into account the electronic structure of dielectric materials, ionic mobility and field screening. Quantitative data on band bending and field penetration during measurement are derived which are important in understanding laser-assisted atom probe tomography of dielectric materials. Copyright © 2014 Elsevier B.V. All rights reserved.

Far-infrared-induced magnetoresistance oscillations in GaAs/AlxGa1-xAs -based two-dimensional electron systems

NASA Astrophysics Data System (ADS)

Wirthmann, André; McCombe, Bruce D.; Heitmann, Detlef; Holland, Steffen; Friedland, Klaus-Jürgen; Hu, Can-Ming

2007-11-01

We report on photoresistance and magnetotransport measurements in a moderate mobility two-dimensional electron system subject to far-infrared (terahertz) radiation. The photoresistance shows radiation induced 1/B -periodic oscillations, which we identify as the terahertz analog of microwave-induced resistance oscillations (MIROs). The MIRO-analog oscillations show a sign reversal in the low-field, high current regime. We simultaneously observe magnetoplasmons and MIRO-analog oscillations with no apparent coupling between them. Using a meandering Hall-bar geometry allows us to greatly enhance sensitivity and detect these oscillations even at elevated temperatures and moderate mobilities.

High transport and excellent optical property of a two-dimensional single-layered hybrid perovskite (C4H9NH3)2PbBr4: a theoretical study.

PubMed

Lei, Jun-Hui; Zhao, Yu-Qing; Tang, Qiong; Lin, Jian-Guo; Cai, Meng-Qiu

2018-05-16

Organic-inorganic hybrid perovskites are developed to pursue high charge carrier mobility and light absorption coefficient. In this study, we present a detailed comparative research of the atomic and electronic structures of single-layered perovskites (C4H9NH3)2PbBr4 with two-dimensional/three-dimensional (2D/3D) spatial arrangement to predict the in plane charge carrier mobility along with the charge effective mass, elastic constant, and deformation potential. The calculated results reveal that the intrinsic in plane carrier mobilities of 2D single-layered hybrid perovskite (C4H9NH3)2PbBr4 along the 100 and 010 directions are superior to those of the 3D structure. Furthermore, the optical properties are calculated from the electronic structure; it is found that the light absorption spectrum of 2D single-layered perovskite (C4H9NH3)2PbBr4 with a high absorption coefficient is wider than that of the 3D phase. We speculate that the superior mobility and wider absorption spectrum of the 2D mono-layered perovskite are due to high charge density and ferroelectricity originating from structure distortion upon 3D-to-2D structure transformation. These results indicate that the 2D single-layered hybrid perovskite (C4H9NH3)2PbBr4 is a potential candidate for application in the optoelectronic and photovoltaic fields.

Terahertz cyclotron resonance spectroscopy of an AlGaN/GaN heterostructure using a high-field pulsed magnet and an asynchronous optical sampling technique

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

Spencer, B. F., E-mail: Ben.Spencer@manchester.ac.uk; Smith, W. F.; Hibberd, M. T.

2016-05-23

The effective mass, sheet carrier concentration, and mobility of electrons within a two-dimensional electron gas in an AlGaN/GaN heterostructure were determined using a laboratory-based terahertz cyclotron resonance spectrometer. The ability to perform terahertz cyclotron resonance spectroscopy with magnetic fields of up to 31 T was enabled by combining a high-field pulsed magnet with a modified asynchronous optical sampling terahertz detection scheme. This scheme allowed around 100 transmitted terahertz waveforms to be recorded over the 14 ms magnetic field pulse duration. The sheet density and mobility were measured to be 8.0 × 10{sup 12 }cm{sup −2} and 9000 cm{sup 2} V{sup −1} s{sup −1} at 77 K. The in-planemore » electron effective mass at the band edge was determined to be 0.228 ± 0.002m{sub 0}.« less

A universal self-charging system driven by random biomechanical energy for sustainable operation of mobile electronics

NASA Astrophysics Data System (ADS)

Niu, Simiao; Wang, Xiaofeng; Yi, Fang; Zhou, Yu Sheng; Wang, Zhong Lin

2015-12-01

Human biomechanical energy is characterized by fluctuating amplitudes and variable low frequency, and an effective utilization of such energy cannot be achieved by classical energy-harvesting technologies. Here we report a high-efficient self-charging power system for sustainable operation of mobile electronics exploiting exclusively human biomechanical energy, which consists of a high-output triboelectric nanogenerator, a power management circuit to convert the random a.c. energy to d.c. electricity at 60% efficiency, and an energy storage device. With palm tapping as the only energy source, this power unit provides a continuous d.c. electricity of 1.044 mW (7.34 W m-3) in a regulated and managed manner. This self-charging unit can be universally applied as a standard `infinite-lifetime' power source for continuously driving numerous conventional electronics, such as thermometers, electrocardiograph system, pedometers, wearable watches, scientific calculators and wireless radio-frequency communication system, which indicates the immediate and broad applications in personal sensor systems and internet of things.

Semiconducting polymers with nanocrystallites interconnected via boron-doped carbon nanotubes.

PubMed

Yu, Kilho; Lee, Ju Min; Kim, Junghwan; Kim, Geunjin; Kang, Hongkyu; Park, Byoungwook; Ho Kahng, Yung; Kwon, Sooncheol; Lee, Sangchul; Lee, Byoung Hun; Kim, Jehan; Park, Hyung Il; Kim, Sang Ouk; Lee, Kwanghee

2014-12-10

Organic semiconductors are key building blocks for future electronic devices that require unprecedented properties of low-weight, flexibility, and portability. However, the low charge-carrier mobility and undesirable processing conditions limit their compatibility with low-cost, flexible, and printable electronics. Here, we present significantly enhanced field-effect mobility (μ(FET)) in semiconducting polymers mixed with boron-doped carbon nanotubes (B-CNTs). In contrast to undoped CNTs, which tend to form undesired aggregates, the B-CNTs exhibit an excellent dispersion in conjugated polymer matrices and improve the charge transport between polymer chains. Consequently, the B-CNT-mixed semiconducting polymers enable the fabrication of high-performance FETs on plastic substrates via a solution process; the μFET of the resulting FETs reaches 7.2 cm(2) V(-1) s(-1), which is the highest value reported for a flexible FET based on a semiconducting polymer. Our approach is applicable to various semiconducting polymers without any additional undesirable processing treatments, indicating its versatility, universality, and potential for high-performance printable electronics.

A universal self-charging system driven by random biomechanical energy for sustainable operation of mobile electronics.

PubMed

Niu, Simiao; Wang, Xiaofeng; Yi, Fang; Zhou, Yu Sheng; Wang, Zhong Lin

2015-12-11

Human biomechanical energy is characterized by fluctuating amplitudes and variable low frequency, and an effective utilization of such energy cannot be achieved by classical energy-harvesting technologies. Here we report a high-efficient self-charging power system for sustainable operation of mobile electronics exploiting exclusively human biomechanical energy, which consists of a high-output triboelectric nanogenerator, a power management circuit to convert the random a.c. energy to d.c. electricity at 60% efficiency, and an energy storage device. With palm tapping as the only energy source, this power unit provides a continuous d.c. electricity of 1.044 mW (7.34 W m(-3)) in a regulated and managed manner. This self-charging unit can be universally applied as a standard 'infinite-lifetime' power source for continuously driving numerous conventional electronics, such as thermometers, electrocardiograph system, pedometers, wearable watches, scientific calculators and wireless radio-frequency communication system, which indicates the immediate and broad applications in personal sensor systems and internet of things.

Emptying Dirac valleys in bismuth using high magnetic fields

DOE PAGES

Zhu, Zengwei; Wang, Jinhua; Zuo, Huakun; ...

2017-05-19

The Fermi surface of elemental bismuth consists of three small rotationally equivalent electron pockets, offering a valley degree of freedom to charge carriers. A relatively small magnetic field can confine electrons to their lowest Landau level. This is the quantum limit attained in other dilute metals upon application of sufficiently strong magnetic field. Here in this paper we report on the observation of another threshold magnetic field never encountered before in any other solid. Above this field, B empty, one or two valleys become totally empty. Drying up a Fermi sea by magnetic field in the Brillouin zone leads tomore » a manyfold enhancement in electric conductance. We trace the origin of the large drop in magnetoresistance across B empty to transfer of carriers between valleys with highly anisotropic mobilities. The non-interacting picture of electrons with field-dependent mobility explains most results but the Coulomb interaction may play a role in shaping the fine details.« less

Electron-polar optical phonon scattering suppression and mobility enhancement in wurtzite heterostructures

NASA Astrophysics Data System (ADS)

Pokatilov, E. P.; Nika, D. L.; Zincenco, N. D.; Balandin, A. A.

2007-12-01

We have shown theoretically that the electron mobility in wurtzite AlN/GaN/AlN heterostructures can be enhanced by compensating the built-in electric field with the externally applied perpendicular electric field and by introducing a shallow InxGa1-xN channel in the center of GaN potential well. It was found that two- to fivefold increase of the room temperature electron mobility can be achieved. The tuning of the electron mobility with the external electric field or InxGa1-xN channel can be useful for the design of GaN-based field-effect transistors and optoelectronic devices.

Browsing the Real World using Organic Electronics, Si-Chips, and a Human Touch.

PubMed

Berggren, Magnus; Simon, Daniel T; Nilsson, David; Dyreklev, Peter; Norberg, Petronella; Nordlinder, Staffan; Ersman, Peter Andersson; Gustafsson, Göran; Wikner, J Jacob; Hederén, Jan; Hentzell, Hans

2016-03-09

Organic electronics have been developed according to an orthodox doctrine advocating "all-printed'', "all-organic'' and "ultra-low-cost'' primarily targeting various e-paper applications. In order to harvest from the great opportunities afforded with organic electronics potentially operating as communication and sensor outposts within existing and future complex communication infrastructures, high-quality computing and communication protocols must be integrated with the organic electronics. Here, we debate and scrutinize the twinning of the signal-processing capability of traditional integrated silicon chips with organic electronics and sensors, and to use our body as a natural local network with our bare hand as the browser of the physical world. The resulting platform provides a body network, i.e., a personalized web, composed of e-label sensors, bioelectronics, and mobile devices that together make it possible to monitor and record both our ambience and health-status parameters, supported by the ubiquitous mobile network and the resources of the "cloud". © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phase separation of electrons strongly coupled with phonons in cuprates and manganites

NASA Astrophysics Data System (ADS)

Alexandrov, Sasha

2009-03-01

Recent advanced Monte Carlo simulations have not found superconductivity and phase separation in the Hubbard model with on-site repulsive electron-electron correlations. I argue that microscopic phase separations in cuprate superconductors and colossal magnetoresistance (CMR) manganites originate from a strong electron-phonon interaction (EPI) combined with unavoidable disorder. Attractive electron correlations, caused by an almost unretarded EPI, are sufficient to overcome the direct inter-site Coulomb repulsion in these charge-transfer Mott-Hubbard insulators, so that low energy physics is that of small polarons and small bipolarons. They form clusters localized by disorder below the mobility edge, but propagate as the Bloch states above the mobility edge. I identify the Froehlich EPI as the most essential for pairing and phase separation in superconducting layered cuprates. The pairing of oxygen holes into heavy bipolarons in the paramagnetic phase (current-carrier density collapse (CCDC)) explains also CMR and high and low-resistance phase coexistence near the ferromagnetic transition of doped manganites.

Electronic transport in smectic liquid crystals

NASA Astrophysics Data System (ADS)

Shiyanovskaya, I.; Singer, K. D.; Twieg, R. J.; Sukhomlinova, L.; Gettwert, V.

2002-04-01

Time-of-flight measurements of transient photoconductivity have revealed bipolar electronic transport in phenylnaphthalene and biphenyl liquid crystals (LC), which exhibit several smectic mesophases. In the phenylnaphthalene LC, the hole mobility is significantly higher than the electron mobility and exhibits different temperature and phase behavior. Electron mobility in the range ~10-5 cm2/V s is temperature activated and remains continuous at the phase transitions. However, hole mobility is nearly temperature independent within the smectic phases, but is very sensitive to smectic order, 10-3 cm2/V s in the smectic-B (Sm-B) and 10-4 cm2/V s in the smectic-A (Sm-A) mesophases. The different behavior for holes and electron transport is due to differing transport mechanisms. The electron mobility is apparently controlled by rate-limiting multiple shallow trapping by impurities, but hole mobility is not. To explain the lack of temperature dependence for hole mobility within the smectic phases we consider two possible polaron transport mechanisms. The first mechanism is based on the hopping of Holstein small polarons in the nonadiabatic limit. The polaron binding energy and transfer integral values, obtained from the model fit, turned out to be sensitive to the molecular order in smectic mesophases. A second possible scenario for temperature-independent hole mobility involves the competion between two different polaron mechanisms involving so-called nearly small molecular polarons and small lattice polarons. Although the extracted transfer integrals and binding energies are reasonable and consistent with the model assumptions, the limited temperature range of the various phases makes it difficult to distinguish between any of the models. In the biphenyl LCs both electron and hole mobilities exhibit temperature activated behavior in the range of 10-5 cm2/V s without sensitivity to the molecular order. The dominating transport mechanism is considered as multiple trapping in the impurity sites. Temperature-activated mobility was treated within the disorder formalism, and activation energy and width of density of states have been calculated.

Channel length dependence of field-effect mobility of c-axis-aligned crystalline In-Ga-Zn-O field-effect transistors

NASA Astrophysics Data System (ADS)

Matsuda, Shinpei; Kikuchi, Erumu; Yamane, Yasumasa; Okazaki, Yutaka; Yamazaki, Shunpei

2015-04-01

Field-effect transistors (FETs) with c-axis-aligned crystalline In-Ga-Zn-O (CAAC-IGZO) active layers have extremely low off-state leakage current. Exploiting this feature, we investigated the application of CAAC-IGZO FETs to LSI memories. A high on-state current is required for the high-speed operation of these LSI memories. The field-effect mobility μFE of a CAAC-IGZO FET is relatively low compared with the electron mobility of single-crystal Si (sc-Si). In this study, we measured and calculated the channel length L dependence of μFE for CAAC-IGZO and sc-Si FETs. For CAAC-IGZO FETs, μFE remains almost constant, particularly when L is longer than 0.3 µm, whereas that of sc-Si FETs decreases markedly as L shortens. Thus, the μFE difference between both FET types is reduced by miniaturization. This difference in μFE behavior is attributed to the different susceptibilities of electrons to phonon scattering. On the basis of this result and the extremely low off-state leakage current of CAAC-IGZO FETs, we expect high-speed LSI memories with low power consumption.

Dual-wavelength photo-Hall effect spectroscopy of deep levels in high resistive CdZnTe with negative differential photoconductivity

NASA Astrophysics Data System (ADS)

Musiienko, A.; Grill, R.; Moravec, P.; Korcsmáros, G.; Rejhon, M.; Pekárek, J.; Elhadidy, H.; Šedivý, L.; Vasylchenko, I.

2018-04-01

Photo-Hall effect spectroscopy was used in the study of deep levels in high resistive CdZnTe. The monochromator excitation in the photon energy range 0.65-1.77 eV was complemented by a laser diode high-intensity excitation at selected photon energies. A single sample characterized by multiple unusual features like negative differential photoconductivity and anomalous depression of electron mobility was chosen for the detailed study involving measurements at both the steady and dynamic regimes. We revealed that the Hall mobility and photoconductivity can be both enhanced and suppressed by an additional illumination at certain photon energies. The anomalous mobility decrease was explained by an excitation of the inhomogeneously distributed deep level at the energy Ev + 1.0 eV, thus enhancing potential non-uniformities. The appearance of negative differential photoconductivity was interpreted by an intensified electron occupancy of that level by a direct valence band-to-level excitation. Modified Shockley-Read-Hall theory was used for fitting experimental results by a model comprising five deep levels. Properties of the deep levels and their impact on the device performance were deduced.

Electrical Conductivity of Rocks and Dominant Charge Carriers. Part 1; Thermally Activated Positive Holes

NASA Technical Reports Server (NTRS)

Freund, Friedemann T.; Freund, Minoru M.

2012-01-01

The prevailing view in the geophysics community is that the electrical conductivity structure of the Earth's continental crust over the 5-35 km depth range can best be understood by assuming the presence of intergranular fluids and/or of intragranular carbon films. Based on single crystal studies of melt-grown MgO, magma-derived sanidine and anorthosite feldspars and upper mantle olivine, we present evidence for the presence of electronic charge carriers, which derive from peroxy defects that are introduced during cooling, under non-equilibrium conditions, through a redox conversion of pairs of solute hydroxyl arising from dissolution of H2O.The peroxy defects become thermally activated in a 2-step process, leading to the release of defect electrons in the oxygen anion sublattice. Known as positive holes and symbolized by h(dot), these electronic charge carriers are highly mobile. Chemically equivalent to O(-) in a matrix of O(2-) they are highly oxidizing. Being metastable they can exist in the matrix of minerals, which crystallized in highly reduced environments. The h(dot) are highly mobile. They appear to control the electrical conductivity of crustal rocks in much of the 5-35 km depth range.

17 CFR 23.202 - Daily trading records.

Code of Federal Regulations, 2014 CFR

2014-04-01

..., instant messaging, chat rooms, electronic mail, mobile device, or other digital or electronic media. Such...; (ii) Moneys borrowed and moneys loaned; (iii) The daily calculation of the value of each outstanding... rooms, electronic mail, mobile device, or other digital or electronic media; (2) Reliable timing data...

17 CFR 23.202 - Daily trading records.

Code of Federal Regulations, 2013 CFR

2013-04-01

..., instant messaging, chat rooms, electronic mail, mobile device, or other digital or electronic media. Such...; (ii) Moneys borrowed and moneys loaned; (iii) The daily calculation of the value of each outstanding... rooms, electronic mail, mobile device, or other digital or electronic media; (2) Reliable timing data...

Electrospun Polymer Fibers for Electronic Applications

PubMed Central

Luzio, Alessandro; Canesi, Eleonora Valeria; Bertarelli, Chiara; Caironi, Mario

2014-01-01

Nano- and micro- fibers of conjugated polymer semiconductors are particularly interesting both for applications and for fundamental research. They allow an investigation into how electronic properties are influenced by size confinement and chain orientation within microstructures that are not readily accessible within thin films. Moreover, they open the way to many applications in organic electronics, optoelectronics and sensing. Electro-spinning, the technique subject of this review, is a simple method to effectively form and control conjugated polymer fibers. We provide the basics of the technique and its recent advancements for the formation of highly conducting and high mobility polymer fibers towards their adoption in electronic applications. PMID:28788493

Magnetic field induced strong valley polarization in the three-dimensional topological semimetal LaBi

NASA Astrophysics Data System (ADS)

Kumar, Nitesh; Shekhar, Chandra; Klotz, J.; Wosnitza, J.; Felser, Claudia

2017-10-01

LaBi is a three-dimensional rocksalt-type material with a surprisingly quasi-two-dimensional electronic structure. It exhibits excellent electronic properties such as the existence of nontrivial Dirac cones, extremely large magnetoresistance, and high charge-carrier mobility. The cigar-shaped electron valleys make the charge transport highly anisotropic when the magnetic field is varied from one crystallographic axis to another. We show that the electrons can be polarized effectively in these electron valleys under a rotating magnetic field. We achieved a polarization of 60% at 2 K despite the coexistence of three-dimensional hole pockets. The valley polarization in LaBi is compared to the sister compound LaSb where it is found to be smaller. The performance of LaBi is comparable to the highly efficient bismuth.

Modulation doping at BaSnO3LaInO3

NASA Astrophysics Data System (ADS)

Char, Kookrin; Shin, Juyeon; Kim, Young Mo; Kim, Youjung

We recently reported on the conductance enhancement at the interface between two band insulators: LaInO3 (LIO) and BaSnO3 (BSO). These two-dimensional electron gas-like (2DEG) states at the LIO/Ba1-xLaxSnO3 (BLSO) polar interface display the stability, the controllability of the local carrier concentration, and the high electron mobility of BLSO. Search for the origin of enhanced conductance at the interface has been carried out, and one of the findings is that the doping level of BSO is a critical parameter for the polar charge contribution . We have also investigated a new modulated heterostructure by inserting an undoped BSO spacer layer at the LIO/BLSO interface. As increasing the thickness of the spacer layer, the carrier concentration and the mobility continually decreased. We attribute the results to the modified band bending as the thickness of the spacer layer varies and to the dislocation-limited transport. However, when we controlled the band bending by field effect, improved mobility was observed in these modulated heterostructures. This new modulated heterostructures of the LIO/BSO polar interface look promising not only for higher electron mobility devices but also for elucidating the mechanism of the 2DEG-like behavior. Samsung science and technology foundation.

Theoretical Characterization of Charge Transport in Chromia (α-Cr2O3)

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

Iordanova, Nellie I.; Dupuis, Michel; Rosso, Kevin M.

2005-08-15

Transport of conduction electrons and holes through the lattice of ?-Cr2O3 (chromia) is modeled as a valence alternation of chromium cations using ab initio electronic structure calculations and electron transfer theory. In the context of the small polaron model, a cluster approach was used to compute quantities controlling the mobility of localized electrons and holes, i.e. the reorganization energy and the electronic coupling matrix element that enter Marcus? theory. The calculation of the electronic coupling followed the Generalized Mulliken-Hush approach and the quasi-diabatic method using the complete active space self-consistent field (CASSCF) method. Our findings indicate that hole mobility ismore » more than three orders of magnitude larger than electron mobility in both (001) and [001] lattice directions. The difference arises mainly from the larger internal reorganization energy calculated for electron transport relative to hole transport processes while electronic couplings have similar magnitudes. The much larger hole mobility vs electron mobility in ?-Cr2O3 is in contrast to similar hole and electron mobility in hematite ?-Fe2O3 previously calculated. Our calculations also indicate that the electronic coupling for all charge transfer processes of interest is smaller than for the corresponding processes in hematite. This variation is attributed to weaker interaction between the metal 3d states and the O(2p) states in chromia than in hematite, leading to smaller overlap between the charge transfer donor and acceptor wavefunctions and smaller super-exchange coupling in chromia. Nevertheless, the weaker coupling in chromia is still sufficiently large to suggest that charge transport processes in chromia are adiabatic in nature. The electronic coupling is found to depend on both the superexchange interaction through the bridging oxygen atoms and the d-shell electron spin coupling within the Cr-Cr donor-acceptor pair, while the reorganization energy is essentially independent of the electron spin coupling.« less

Theoretical characterization of charge transport in chromia (α-Cr2O3)

NASA Astrophysics Data System (ADS)

Iordanova, N.; Dupuis, M.; Rosso, K. M.

2005-08-01

Transport of conduction electrons and holes through the lattice of α-Cr2O3 (chromia) is modeled as a valence alternation of chromium cations using ab initio electronic structure calculations and electron-transfer theory. In the context of the small polaron model, a cluster approach was used to compute quantities controlling the mobility of localized electrons and holes, i.e., the reorganization energy and the electronic coupling matrix element that enter Marcus' theory. The calculation of the electronic coupling followed the generalized Mulliken-Hush approach using the complete active space self-consistent-field (CASSCF) method and the quasidiabatic method. Our findings indicate that hole mobility is more than three orders of magnitude larger than electron mobility in both (001) and [001] lattice directions. The difference arises mainly from the larger internal reorganization energy calculated for electron-transport relative to hole-transport processes while electronic couplings have similar magnitudes. The much larger hole mobility versus electron mobility in α-Cr2O3 is in contrast to similar hole and electron mobilities in hematite α-Fe2O3 previously calculated. Our calculations also indicate that the electronic coupling for all charge-transfer processes of interest is smaller than for the corresponding processes in hematite. This variation is attributed to the weaker interaction between the metal 3d states and the O(2p ) states in chromia than in hematite, leading to a smaller overlap between the charge-transfer donor and acceptor wave functions and smaller superexchange coupling in chromia. Nevertheless, the weaker coupling in chromia is still sufficiently large to suggest that charge-transport processes in chromia are adiabatic in nature. The electronic coupling is found to depend on both the superexchange interaction through the bridging oxygen atoms and the d-shell electron-spin coupling within the Cr-Cr donor-acceptor pair, while the reorganization energy is essentially independent of the electron-spin coupling.

Modeling charge transport in organic photovoltaic materials.

PubMed

Nelson, Jenny; Kwiatkowski, Joe J; Kirkpatrick, James; Frost, Jarvist M

2009-11-17

The performance of an organic photovoltaic cell depends critically on the mobility of charge carriers within the constituent molecular semiconductor materials. However, a complex combination of phenomena that span a range of length and time scales control charge transport in disordered organic semiconductors. As a result, it is difficult to rationalize charge transport properties in terms of material parameters. Until now, efforts to improve charge mobilities in molecular semiconductors have proceeded largely by trial and error rather than through systematic design. However, recent developments have enabled the first predictive simulation studies of charge transport in disordered organic semiconductors. This Account describes a set of computational methods, specifically molecular modeling methods, to simulate molecular packing, quantum chemical calculations of charge transfer rates, and Monte Carlo simulations of charge transport. Using case studies, we show how this combination of methods can reproduce experimental mobilities with few or no fitting parameters. Although currently applied to material systems of high symmetry or well-defined structure, further developments of this approach could address more complex systems such anisotropic or multicomponent solids and conjugated polymers. Even with an approximate treatment of packing disorder, these computational methods simulate experimental mobilities within an order of magnitude at high electric fields. We can both reproduce the relative values of electron and hole mobility in a conjugated small molecule and rationalize those values based on the symmetry of frontier orbitals. Using fully atomistic molecular dynamics simulations of molecular packing, we can quantitatively replicate vertical charge transport along stacks of discotic liquid crystals which vary only in the structure of their side chains. We can reproduce the trends in mobility with molecular weight for self-organizing polymers using a cheap, coarse-grained structural simulation method. Finally, we quantitatively reproduce the field-effect mobility in disordered C60 films. On the basis of these results, we conclude that all of the necessary building blocks are in place for the predictive simulation of charge transport in macromolecular electronic materials and that such methods can be used as a tool toward the future rational design of functional organic electronic materials.

Enhancing mHealth Technology in the PCMH Environment to Activate Chronic Care Patients

DTIC Science & Technology

2017-09-01

AVAILABILITY STATEMENT Approved for Public Release; Distribution Unlimited 13. SUPPLEMENTARY NOTES - 14. ABSTRACT - The potential of mobile health (mHealth...biometric data, electronic coaching, electronic-based health education, secure e-mail communication between visits, and electronic collection of lifestyle...influence patient activation and self-care activities. 15. SUBJECT TERMS MHCE, Mobile Health Care Environment mHealth, mobile health MHS, Military Health

Design, synthesis, and structure-property relationships of isoindigo-based conjugated polymers.

PubMed

Lei, Ting; Wang, Jie-Yu; Pei, Jian

2014-04-15

Conjugated polymers have developed rapidly due to their promising applications in low-cost, lightweight, and flexible electronics. The development of the third-generation donor-acceptor (D-A) polymers greatly improved the device performance in organic solar cells (OSCs) and field-effect transistors (FETs). However, for further improvement of device performance, scientists need to develop new building blocks, in particular electron-deficient aromatics, and gain an in-depth understanding of the structure-property relationships. Recently, isoindigo has been used as a new acceptor of D-A conjugated polymers. An isomer of indigo, isoindigo is a less well-known dye and can be isolated as a by-product from certain biological processes. It has two lactam rings and exhibits strong electron-withdrawing character. This electron deficiency gives isoindigo-based polymers intriguing properties, such as broad absorption and high open circuit voltage in OSCs, as well as high mobility and good ambient stability in FETs. In this Account, we review our recent progress on the design, synthesis, and structure-property relationship study of isoindigo-based polymers for FETs. Starting with some discussion on carrier transport in polymer films, we provide some basic strategies towards high-performance polymer FETs. We discuss the stability issue of devices, the impediment of the alkyl side chains, and the choice of the donor part of conjugated polymers. We demonstrate that introducing the isoindigo core effectively lowers the HOMO levels of polymers and provides FETs with long-time stability. In addition, we have found that when we use inappropriate alkyl side chains or non-centrosymmetric donors, the device performance of isoindigo polymers suffers. To further improve device performance and ambient stability, we propose several design strategies, such as using farther branched alkyl chains, modulating polymer energy levels, and extending π-conjugated backbones. We have found that using farther branched alkyl chains can effectively decrease interchain π-π stacking distance and improve carrier mobility. When we introduce electron-deficient functional groups on the isoindigo core, the LUMO levels of the polymers markedly decrease, which significantly improves the electron mobility and device stability. In addition, we present a new polymer system called BDOPV, which is based on the concept of π-extended isoindigo. By application of some strategies successfully used in isoindigo-based polymers, BDOPV-based polymers exhibit high mobility and good stability both in n-type and in ambipolar FETs. We believe that a synergy of molecular engineering strategies towards the isoindigo core, donor units, and side chains may further improve the performance and broaden the application of isoindigo-based polymers.

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.

Effect of atomic layer deposition temperature on the performance of top-down ZnO nanowire transistors

PubMed Central

2014-01-01

This paper studies the effect of atomic layer deposition (ALD) temperature on the performance of top-down ZnO nanowire transistors. Electrical characteristics are presented for 10-μm ZnO nanowire field-effect transistors (FETs) and for deposition temperatures in the range 120°C to 210°C. Well-behaved transistor output characteristics are obtained for all deposition temperatures. It is shown that the maximum field-effect mobility occurs for an ALD temperature of 190°C. This maximum field-effect mobility corresponds with a maximum Hall effect bulk mobility and with a ZnO film that is stoichiometric. The optimized transistors have a field-effect mobility of 10 cm2/V.s, which is approximately ten times higher than can typically be achieved in thin-film amorphous silicon transistors. Furthermore, simulations indicate that the drain current and field-effect mobility extraction are limited by the contact resistance. When the effects of contact resistance are de-embedded, a field-effect mobility of 129 cm2/V.s is obtained. This excellent result demonstrates the promise of top-down ZnO nanowire technology for a wide variety of applications such as high-performance thin-film electronics, flexible electronics, and biosensing. PMID:25276107

Fourier-domain Mobility Spectrum Analysis (FMSA) for Characterizing Semiconductors with Multi-Electron/Hole Species

NASA Astrophysics Data System (ADS)

Cui, Boya; Kielb, Edward; Luo, Jiajun; Tang, Yang; Grayson, Matthew

Superlattices and narrow gap semiconductors often host multiple conducting species, such as electrons and holes, requiring a mobility spectral analysis (MSA) method to separate contributions to the conductivity. Here, a least-squares MSA method is introduced: the QR-algorithm Fourier-domain MSA (FMSA). Like other MSA methods, the FMSA sorts the conductivity contributions of different carrier species from magnetotransport measurements, arriving at a best fit to the experimentally measured longitudinal and Hall conductivities σxx and σxy, respectively. This method distinguishes itself from other methods by using the so-called QR-algorithm of linear algebra to achieve rapid convergence of the mobility spectrum as the solution to an eigenvalue problem, and by alternately solving this problem in both the mobility domain and its Fourier reciprocal-space. The result accurately fits a mobility range spanning nearly four orders of magnitude (μ = 300 to 1,000,000 cm2/V .s). This method resolves the mobility spectra as well as, or better than, competing MSA methods while also achieving high computational efficiency, requiring less than 30 second on average to converge to a solution on a standard desktop computer. Acknowledgement: Funded by AFOSR FA9550-15-1-0377 and AFOSR FA9550-15-1-0247.

N-Functionalized MXenes: ultrahigh carrier mobility and multifunctional properties.

PubMed

Shao, Yangfan; Zhang, Fang; Shi, Xingqiang; Pan, Hui

2017-11-01

Two dimensional (2D) nanomaterials have demonstrated huge potential in wide applications from nanodevices to energy harvesting/storage. In this work, we propose a new class of 2D monolayers, nitrogen-functionalized MXenes (Nb 2 CN 2 and Ta 2 CN 2 ), based on density-functional theory (DFT). We find that these monolayers are direct semiconductors with near linear energy dispersions at the Γ point. M 2 CN 2 monolayers have significant small effective mass and show an ultra-high mobility of up to 10 6 cm 2 V -1 s -1 . We show that the electronic structures of the M 2 CN 2 monolayers can be easily controlled by biaxial and uniaxial strains. Importantly, the carrier mobility and direct band gap can be dramatically increased within a certain range of strain. A direct-indirect band gap transition can be triggered and the band gap can be tuned under strain. The tunable electronic properties are attributed to the structural changes and charge redistribution under stain. Our findings demonstrate that N-functionalized MXenes are promising materials for nanodevices with high speed and low power.

Synthesis of one-dimensional metal-containing insulated molecular wire with versatile properties directed toward molecular electronics materials.

PubMed

Masai, Hiroshi; Terao, Jun; Seki, Shu; Nakashima, Shigeto; Kiguchi, Manabu; Okoshi, Kento; Fujihara, Tetsuaki; Tsuji, Yasushi

2014-02-05

We report, herein, the design, synthesis, and properties of new materials directed toward molecular electronics. A transition metal-containing insulated molecular wire was synthesized through the coordination polymerization of a Ru(II) porphyrin with an insulated bridging ligand of well-defined structure. The wire displayed not only high linearity and rigidity, but also high intramolecular charge mobility. Owing to the unique properties of the coordination bond, the interconversion between the monomer and polymer states was realized under a carbon monoxide atmosphere or UV irradiation. The results demonstrated a high potential of the metal-containing insulated molecular wire for applications in molecular electronics.

Electron Transporting Semiconductor Dielectric Intramolecular

DTIC Science & Technology

2012-04-27

gate dielectric, and the capacitance times mobility was 80 nS/V (10x typical pentacene /oxide), stable to heating to 70 °C in air. Remarkably...oxide/ Pentacene Bilayer Transistors: High Mobility n-Channel, Ambipolar and Nonvolatile Devices” Adv. Funct. Mater. 18, 1832-1839 (2008) Sun, J...case of layered OSC OFETs. This proposal is somewhat different from a model by deLeeuw for amorphous OFETs13 in which carriers would be locally

Microwave zero-resistance states in a bilayer electron system.

PubMed

Wiedmann, S; Gusev, G M; Raichev, O E; Bakarov, A K; Portal, J C

2010-07-09

Magnetotransport measurements on a high-mobility electron bilayer system formed in a wide GaAs quantum well reveal vanishing dissipative resistance under continuous microwave irradiation. Profound zero-resistance states (ZRS) appear even in the presence of additional intersubband scattering of electrons. We study the dependence of photoresistance on frequency, microwave power, and temperature. Experimental results are compared with a theory demonstrating that the conditions for absolute negative resistivity correlate with the appearance of ZRS.

Relieved kink effects in symmetrically graded In0.45Al0.55As/InxGa1-xAs metamorphic high-electron-mobility transistors

NASA Astrophysics Data System (ADS)

Lee, Ching-Sung; Liao, Chen-Hsian

2007-12-01

Kink effects in an In-rich InxGa1-xAs (x=0.53-0.63) linearly graded channel of an In0.45Al0.55As/InxGa1-xAs metamorphic high-electron-mobility transistor have been effectively relieved by depositing a high-barrier Ni /Au gate with the silicon nitride passivation. Complete physical investigations for the relieved kink effects have been made by comparing identical devices with/without a high-barrier Schottky gate or the surface passivation. After successfully suppressing the kink effects, the proposed device has shown a superior voltage gain of 173.8, low output conductance of 2.09mS/mm, and excellent power-added efficiency of 54.1% with high output power (power gain) of 14.87dBm (14.53dB). Improved linearity and excellent thermal threshold coefficient (∂Vth/∂T) of -0.14mV/K have also been achieved. The proposed design provides good potential for high-gain and high-linearity circuit applications.

Analysis of microscopic parameters of surface charging in polymer caused by defocused electron beam irradiation.

PubMed

Liu, Jing; Zhang, Hai-Bo

2014-12-01

The relationship between microscopic parameters and polymer charging caused by defocused electron beam irradiation is investigated using a dynamic scattering-transport model. The dynamic charging process of an irradiated polymer using a defocused 30 keV electron beam is conducted. In this study, the space charge distribution with a 30 keV non-penetrating e-beam is negative and supported by some existing experimental data. The internal potential is negative, but relatively high near the surface, and it decreases to a maximum negative value at z=6 μm and finally tend to 0 at the bottom of film. The leakage current and the surface potential behave similarly, and the secondary electron and leakage currents follow the charging equilibrium condition. The surface potential decreases with increasing beam current density, trap concentration, capture cross section, film thickness and electron-hole recombination rate, but with decreasing electron mobility and electron energy. The total charge density increases with increasing beam current density, trap concentration, capture cross section, film thickness and electron-hole recombination rate, but with decreasing electron mobility and electron energy. This study shows a comprehensive analysis of microscopic factors of surface charging characteristics in an electron-based surface microscopy and analysis. Copyright © 2014 Elsevier Ltd. All rights reserved.

Electron Mobility and Trapping in Ferrihydrite Nanoparticles

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

Soltis, Jennifer A.; Schwartzberg, Adam M.; Zarzycki, Piotr

Iron is the most abundant transition metal in the Earth’s crust, and naturally occurring iron oxide minerals play a commanding role in environmental redox reactions. Although iron oxide redox reactions are well-studied, their precise mechanisms are not fully understood. Recent work has shown that these involve electron transfer pathways within the solid, suggesting that overall reaction rates could be dependent upon electron mobility. Initial ultrafast spectroscopy studies of iron oxide nanoparticles sensitized by fluorescein derivatives supported a model for electron mobility based on polaronic hopping of electron charge carriers between iron sites, but the constitutive relationships between hopping mobilities andmore » interfacial charge transfer processes has remained obscured. In this paper, we developed a coarse-grained lattice Monte Carlo model to simulate the collective mobilities and lifetimes of these photoinjected electrons with respect to recombination with adsorbed dye molecules for essential nanophase ferrihydrite and tested predictions made by the simulations using pump–probe spectroscopy. We acquired optical transient absorption spectra as a function of the particle size and under a variety of solution conditions and used cryogenic transmission electron microscopy to determine the aggregation state of the nanoparticles. We observed biphasic electron recombination kinetics over time scales that spanned from picoseconds to microseconds, the slower regime of which was fit with a stretched exponential decay function. The recombination rates were weakly affected by the nanoparticle size and aggregation state, suspension pH, and injection of multiple electrons per nanoparticle. Finally, we conclude that electron mobility indeed limits the rate of interfacial electron transfer in these systems, with the slowest processes relating to escape from deep traps, the presence of which outweighs the influence of environmental factors, such as pH-dependent surface charge.« less

Electron Mobility and Trapping in Ferrihydrite Nanoparticles

DOE PAGES

Soltis, Jennifer A.; Schwartzberg, Adam M.; Zarzycki, Piotr; ...

2017-05-18

Iron is the most abundant transition metal in the Earth’s crust, and naturally occurring iron oxide minerals play a commanding role in environmental redox reactions. Although iron oxide redox reactions are well-studied, their precise mechanisms are not fully understood. Recent work has shown that these involve electron transfer pathways within the solid, suggesting that overall reaction rates could be dependent upon electron mobility. Initial ultrafast spectroscopy studies of iron oxide nanoparticles sensitized by fluorescein derivatives supported a model for electron mobility based on polaronic hopping of electron charge carriers between iron sites, but the constitutive relationships between hopping mobilities andmore » interfacial charge transfer processes has remained obscured. In this paper, we developed a coarse-grained lattice Monte Carlo model to simulate the collective mobilities and lifetimes of these photoinjected electrons with respect to recombination with adsorbed dye molecules for essential nanophase ferrihydrite and tested predictions made by the simulations using pump–probe spectroscopy. We acquired optical transient absorption spectra as a function of the particle size and under a variety of solution conditions and used cryogenic transmission electron microscopy to determine the aggregation state of the nanoparticles. We observed biphasic electron recombination kinetics over time scales that spanned from picoseconds to microseconds, the slower regime of which was fit with a stretched exponential decay function. The recombination rates were weakly affected by the nanoparticle size and aggregation state, suspension pH, and injection of multiple electrons per nanoparticle. Finally, we conclude that electron mobility indeed limits the rate of interfacial electron transfer in these systems, with the slowest processes relating to escape from deep traps, the presence of which outweighs the influence of environmental factors, such as pH-dependent surface charge.« less

A video processing method for convenient mobile reading of printed barcodes with camera phones

NASA Astrophysics Data System (ADS)

Bäckström, Christer; Södergård, Caj; Udd, Sture

2006-01-01

Efficient communication requires an appropriate choice and combination of media. The print media has succeeded to attract audiences also in our electronic age because of its high usability. However, the limitations of print are self evident. By finding ways of combining printed and electronic information into so called hybrid media, the strengths of both media can be obtained. In hybrid media, paper functions as an interface to the web, integrating printed products into the connected digital world. This is a "reinvention" of printed matter making it into a more communicative technology. Hybrid media means that printed products can be updated in real time. Multimedia clips, personalization and e-shopping can be added as a part of the interactive medium. The concept of enhancing print with interactive features has been around for years. However, the technology has been so far too restricting - people don't want to be tied in front of their PC's reading newspapers. Our solution is communicative and totally mobile. A code on paper or electronic media constitutes the link to mobility.

Ultra-high-throughput Production of III-V/Si Wafer for Electronic and Photonic Applications

PubMed Central

Geum, Dae-Myeong; Park, Min-Su; Lim, Ju Young; Yang, Hyun-Duk; Song, Jin Dong; Kim, Chang Zoo; Yoon, Euijoon; Kim, SangHyeon; Choi, Won Jun

2016-01-01

Si-based integrated circuits have been intensively developed over the past several decades through ultimate device scaling. However, the Si technology has reached the physical limitations of the scaling. These limitations have fuelled the search for alternative active materials (for transistors) and the introduction of optical interconnects (called “Si photonics”). A series of attempts to circumvent the Si technology limits are based on the use of III-V compound semiconductor due to their superior benefits, such as high electron mobility and direct bandgap. To use their physical properties on a Si platform, the formation of high-quality III-V films on the Si (III-V/Si) is the basic technology ; however, implementing this technology using a high-throughput process is not easy. Here, we report new concepts for an ultra-high-throughput heterogeneous integration of high-quality III-V films on the Si using the wafer bonding and epitaxial lift off (ELO) technique. We describe the ultra-fast ELO and also the re-use of the III-V donor wafer after III-V/Si formation. These approaches provide an ultra-high-throughput fabrication of III-V/Si substrates with a high-quality film, which leads to a dramatic cost reduction. As proof-of-concept devices, this paper demonstrates GaAs-based high electron mobility transistors (HEMTs), solar cells, and hetero-junction phototransistors on Si substrates. PMID:26864968

Investigation of high sensitivity radio-frequency readout circuit based on AlGaN/GaN high electron mobility transistor

NASA Astrophysics Data System (ADS)

Zhang, Xiao-Yu; Tan, Ren-Bing; Sun, Jian-Dong; Li, Xin-Xing; Zhou, Yu; Lü, Li; Qin, Hua

2015-10-01

An AlGaN/GaN high electron mobility transistor (HEMT) device is prepared by using a semiconductor nanofabrication process. A reflective radio-frequency (RF) readout circuit is designed and the HEMT device is assembled in an RF circuit through a coplanar waveguide transmission line. A gate capacitor of the HEMT and a surface-mounted inductor on the transmission line are formed to generate LC resonance. By tuning the gate voltage Vg, the variations of gate capacitance and conductance of the HEMT are reflected sensitively from the resonance frequency and the magnitude of the RF reflection signal. The aim of the designed RF readout setup is to develop a highly sensitive HEMT-based detector. Project supported by the National Natural Science Foundation of China (Grant No. 61107093), the Suzhou Science and Technology Project, China (Grant No. ZXG2012024), and the Youth Innovation Promotion Association, Chinese Academy of Sciences (Grant No. 2012243).

High performance thin film transistor with ZnO channel layer deposited by DC magnetron sputtering.

PubMed

Moon, Yeon-Keon; Moon, Dae-Yong; Lee, Sang-Ho; Jeong, Chang-Oh; Park, Jong-Wan

2008-09-01

Research in large area electronics, especially for low-temperature plastic substrates, focuses commonly on limitations of the semiconductor in thin film transistors (TFTs), in particular its low mobility. ZnO is an emerging example of a semiconductor material for TFTs that can have high mobility, while a-Si and organic semiconductors have low mobility (<1 cm2/Vs). ZnO-based TFTs have achieved high mobility, along with low-voltage operation low off-state current, and low gate leakage current. In general, ZnO thin films for the channel layer of TFTs are deposited with RF magnetron sputtering methods. On the other hand, we studied ZnO thin films deposited with DC magnetron sputtering for the channel layer of TFTs. After analyzing the basic physical and chemical properties of ZnO thin films, we fabricated a TFT-unit cell using ZnO thin films for the channel layer. The field effect mobility (micro(sat)) of 1.8 cm2/Vs and threshold voltage (Vth) of -0.7 V were obtained.

Pursuing High-Mobility n-Type Organic Semiconductors by Combination of "Molecule-Framework" and "Side-Chain" Engineering.

PubMed

Zhang, Cheng; Zang, Yaping; Zhang, Fengjiao; Diao, Ying; McNeill, Christopher R; Di, Chong-An; Zhu, Xiaozhang; Zhu, Daoben

2016-10-01

"Molecule-framework" and "side-chain" engineering is powerful for the design of high-performance organic semiconductors. Based on 2DQTTs, the relationship between molecular structure, film microstructure, and charge-transport property in organic thin-film transistors (OTFTs) is studied. 2DQTT-o-B exhibits outstanding electron mobilities of 5.2 cm 2 V -1 s -1 , which is a record for air-stable solution-processable n-channel small-molecule OTFTs to date. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of plasmonic resonances in the two-dimensional electron gas of an InGaAs/InP high electron mobility transistor

NASA Astrophysics Data System (ADS)

Cleary, Justin W.; Peale, Robert E.; Saxena, Himanshu; Buchwald, Walter R.

2011-05-01

The observation of THz regime transmission resonances in an InGaAs/InP high electron mobility transistor (HEMT) can be attributed to excitation of plasmons in its two-dimensional electron gas (2DEG). Properties of grating-based, gate-voltage tunable resonances are shown to be adequately modeled using commercial finite element method (FEM) software when the HEMT layer structure, gate geometry and sheet charge concentration are taken into account. The FEM results are shown to produce results consistent with standard analytical theories in the 10-100 cm-1 wavenumber range. An original analytic formula presented here describes how the plasmonic resonance may change in the presence of a virtual gate, or region of relatively high free charge carriers that lies in the HEMT between the physical grating gate and the 2DEG. The virtual gate and corresponding analytic formulation are able to account for the red-shifting experimentally observed in plasmonic resonances. The calculation methods demonstrated here have the potential to greatly aid in the design of future detection devices that require specifically tuned plasmonic modes in the 2DEG of a HEMT, as well as giving new insights to aid in the development of more complete analytic theories.

Bacteria, hypertolerant to arsenic in the rocks of an ancient gold mine, and their potential role in dissemination of arsenic pollution.

PubMed

Drewniak, Lukasz; Styczek, Aleksandra; Majder-Lopatka, Malgorzata; Sklodowska, Aleksandra

2008-12-01

The aim of the present study was to find out if bacteria present in ancient gold mine could transform immobilized arsenic into its mobile form and increase its dissemination in the environment. Twenty-two arsenic-hypertolerant cultivable bacterial strains were isolated. No chemolithoautotrophs, which could use arsenite as an electron donor as well as arsenate as an electron acceptor, were identified. Five isolates exhibited hypertolerance to arsenic: up to 500mM of arsenate. A correlation between the presence of siderophores and high resistance to arsenic was found. The results of this study show that detoxification processes based on arsenate reductase activity might be significant in dissemination of arsenic pollution. It was concluded that the activity of the described heterotrophic bacteria contributes to the mobilization of arsenic in the more toxic As(III) form and a new mechanism of arsenic mobilization from a scorodite was proposed.

Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method.

PubMed

Yuan, Yongbo; Giri, Gaurav; Ayzner, Alexander L; Zoombelt, Arjan P; Mannsfeld, Stefan C B; Chen, Jihua; Nordlund, Dennis; Toney, Michael F; Huang, Jinsong; Bao, Zhenan

2014-01-01

Organic semiconductors with higher carrier mobility and better transparency have been actively pursued for numerous applications, such as flat-panel display backplane and sensor arrays. The carrier mobility is an important figure of merit and is sensitively influenced by the crystallinity and the molecular arrangement in a crystal lattice. Here we describe the growth of a highly aligned meta-stable structure of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) from a blended solution of C8-BTBT and polystyrene by using a novel off-centre spin-coating method. Combined with a vertical phase separation of the blend, the highly aligned, meta-stable C8-BTBT films provide a significantly increased thin film transistor hole mobility up to 43 cm(2) Vs(-1) (25 cm(2) Vs(-1) on average), which is the highest value reported to date for all organic molecules. The resulting transistors show high transparency of >90% over the visible spectrum, indicating their potential for transparent, high-performance organic electronics.

Ultrawide electrical tuning of light matter interaction in a high electron mobility transistor structure

PubMed Central

Pal, Shovon; Nong, Hanond; Markmann, Sergej; Kukharchyk, Nadezhda; Valentin, Sascha R.; Scholz, Sven; Ludwig, Arne; Bock, Claudia; Kunze, Ulrich; Wieck, Andreas D.; Jukam, Nathan

2015-01-01

The interaction between intersubband resonances (ISRs) and metamaterial microcavities constitutes a strongly coupled system where new resonances form that depend on the coupling strength. Here we present experimental evidence of strong coupling between the cavity resonance of a terahertz metamaterial and the ISR in a high electron mobility transistor (HEMT) structure. The device is electrically switched from an uncoupled to a strongly coupled regime by tuning the ISR with epitaxially grown transparent gate. The asymmetric potential in the HEMT structure enables ultrawide electrical tuning of ISR, which is an order of magnitude higher as compared to an equivalent square well. For a single heterojunction with a triangular confinement, we achieve an avoided splitting of 0.52 THz, which is a significant fraction of the bare intersubband resonance at 2 THz. PMID:26578287

AlGaN/GaN High Electron Mobility Transistor-Based Biosensor for the Detection of C-Reactive Protein

PubMed Central

Lee, Hee Ho; Bae, Myunghan; Jo, Sung-Hyun; Shin, Jang-Kyoo; Son, Dong Hyeok; Won, Chul-Ho; Jeong, Hyun-Min; Lee, Jung-Hee; Kang, Shin-Won

2015-01-01

In this paper, we propose an AlGaN/GaN high electron mobility transistor (HEMT)-based biosensor for the detection of C-reactive protein (CRP) using a null-balancing circuit. A null-balancing circuit was used to measure the output voltage of the sensor directly. The output voltage of the proposed biosensor was varied by antigen-antibody interactions on the gate surface due to CRP charges. The AlGaN/GaN HFET-based biosensor with null-balancing circuit applied shows that CRP can be detected in a wide range of concentrations, varying from 10 ng/mL to 1000 ng/mL. X-ray photoelectron spectroscopy was carried out to verify the immobilization of self-assembled monolayer with Au on the gated region. PMID:26225981

High mobility back-gated InAs/GaSb double quantum well grown on GaSb substrate

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

Nguyen, Binh-Minh, E-mail: mbnguyen@hrl.com, E-mail: MSokolich@hrl.com; Yi, Wei; Noah, Ramsey

2015-01-19

We report a backgated InAs/GaSb double quantum well device grown on GaSb substrate. The use of the native substrate allows for high materials quality with electron mobility in excess of 500 000 cm{sup 2}/Vs at sheet charge density of 8 × 10{sup 11} cm{sup −2} and approaching 100 000 cm{sup 2}/Vs near the charge neutrality point. Lattice matching between the quantum well structure and the substrate eliminates the need for a thick buffer, enabling large back gate capacitance and efficient coupling with the conduction channels in the quantum wells. As a result, quantum Hall effects are observed in both electron and hole regimes across the hybridizationmore » gap.« less

Progressive failure site generation in AlGaN/GaN high electron mobility transistors under OFF-state stress: Weibull statistics and temperature dependence

NASA Astrophysics Data System (ADS)

Sun, Huarui; Bajo, Miguel Montes; Uren, Michael J.; Kuball, Martin

2015-01-01

Gate leakage degradation of AlGaN/GaN high electron mobility transistors under OFF-state stress is investigated using a combination of electrical, optical, and surface morphology characterizations. The generation of leakage "hot spots" at the edge of the gate is found to be strongly temperature accelerated. The time for the formation of each failure site follows a Weibull distribution with a shape parameter in the range of 0.7-0.9 from room temperature up to 120 °C. The average leakage per failure site is only weakly temperature dependent. The stress-induced structural degradation at the leakage sites exhibits a temperature dependence in the surface morphology, which is consistent with a surface defect generation process involving temperature-associated changes in the breakdown sites.

Proton irradiation of MgO- or Sc 2O 3 passivated AlGaN/GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Luo, B.; Ren, F.; Allums, K. K.; Gila, B. P.; Onstine, A. H.; Abernathy, C. R.; Pearton, S. J.; Dwivedi, R.; Fogarty, T. N.; Wilkins, R.; Fitch, R. C.; Gillespie, J. K.; Jenkins, T. J.; Dettmer, R.; Sewell, J.; Via, G. D.; Crespo, A.; Baca, A. G.; Shul, R. J.

2003-06-01

AlGaN/GaN high electron mobility transistors with either MgO or Sc 2O 3 surface passivation were irradiated with 40 MeV protons at a dose of 5×10 9 cm -2. While both forward and reverse bias current were decreased in the devices as a result of decreases in channel doping and introduction of generation-recombination centers, there was no significant change observed in gate lag measurements. By sharp contrast, unpassivated devices showed significant decreases in drain current under pulsed conditions for the same proton dose. These results show the effectiveness of the oxide passivation in mitigating the effects of surface states present in the as-grown structures and also of surface traps created by the proton irradiation.

Investigation of abrupt degradation of drain current caused by under-gate crack in AlGaN/GaN high electron mobility transistors during high temperature operation stress

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

Zeng, Chang; Liao, XueYang; Li, RuGuan

2015-09-28

In this paper, we investigate the degradation mode and mechanism of AlGaN/GaN based high electron mobility transistors (HEMTs) during high temperature operation (HTO) stress. It demonstrates that there was abrupt degradation mode of drain current during HTO stress. The abrupt degradation is ascribed to the formation of crack under the gate which was the result of the brittle fracture of epilayer based on failure analysis. The origin of the mechanical damage under the gate is further investigated and discussed based on top-down scanning electron microscope, cross section transmission electron microscope and energy dispersive x-ray spectroscopy analysis, and stress simulation. Basedmore » on the coupled analysis of the failure physical feature and stress simulation considering the coefficient of thermal expansion (CTE) mismatch in different materials in gate metals/semiconductor system, the mechanical damage under the gate is related to mechanical stress induced by CTE mismatch in Au/Ti/Mo/GaN system and stress concentration caused by the localized structural damage at the drain side of the gate edge. These results indicate that mechanical stress induced by CTE mismatch of materials inside the device plays great important role on the reliability of AlGaN/GaN HEMTs during HTO stress.« less

Electronic waste recovery in Finland: Consumers' perceptions towards recycling and re-use of mobile phones.

PubMed

Ylä-Mella, Jenni; Keiski, Riitta L; Pongrácz, Eva

2015-11-01

This paper examines consumers' awareness and perceptions towards mobile phone recycling and re-use. The results are based on a survey conducted in the city of Oulu, Finland, and analysed in the theoretical framework based on the theories of planned behaviour (TPB) and value-belief-norm (VBN). The findings indicate that consumers' awareness of the importance and existence of waste recovery system is high; however, awareness has not translated to recycling behaviour. The survey reveals that 55% of respondents have two or more unused mobile phones at homes. The more phones stored at homes, the more often reasons 'I don't know where to return' and/or 'have not got to do it yet' were mentioned. This indicates that proximity and the convenience of current waste management system are inadequate in promoting the return of small waste electrical and electronic equipment (WEEE). To facilitate re-use, and the highest level of recovery, consumers will need to be committed to return end-of-use electronics to WEEE collection centres without delays. Further, the supply and demand of refurbished mobile phones do not meet at this moment in Finland due to consumer's storing habits versus expectations of recent features under guarantee and unrealistic low prizes. The study also points out that, in order to change current storing habits of consumers, there is an explicit need for more information and awareness on mobile phone collection in Finland, especially on regarding retailers' take-back. Copyright © 2015 Elsevier Ltd. All rights reserved.

Carrier mobility in double-helix DNA and RNA: A quantum chemistry study with Marcus-Hush theory.

PubMed

Wu, Tao; Sun, Lei; Shi, Qi; Deng, Kaiming; Deng, Weiqiao; Lu, Ruifeng

2016-12-21

Charge mobilities of six DNAs and RNAs have been computed using quantum chemistry calculation combined with the Marcus-Hush theory. Based on this simulation model, we obtained quite reasonable results when compared with the experiment, and the obtained charge mobility strongly depends on the molecular reorganization and electronic coupling. Besides, we find that hole mobilities are larger than electron mobilities no matter in DNAs or in RNAs, and the hole mobility of 2L8I can reach 1.09 × 10 -1 cm 2 V -1 s -1 which can be applied in the molecular wire. The findings also show that our theoretical model can be regarded as a promising candidate for screening DNA- and RNA-based molecular electronic devices.

Carrier mobility in double-helix DNA and RNA: A quantum chemistry study with Marcus-Hush theory

NASA Astrophysics Data System (ADS)

Wu, Tao; Sun, Lei; Shi, Qi; Deng, Kaiming; Deng, Weiqiao; Lu, Ruifeng

2016-12-01

Charge mobilities of six DNAs and RNAs have been computed using quantum chemistry calculation combined with the Marcus-Hush theory. Based on this simulation model, we obtained quite reasonable results when compared with the experiment, and the obtained charge mobility strongly depends on the molecular reorganization and electronic coupling. Besides, we find that hole mobilities are larger than electron mobilities no matter in DNAs or in RNAs, and the hole mobility of 2L8I can reach 1.09 × 10-1 cm2 V-1 s-1 which can be applied in the molecular wire. The findings also show that our theoretical model can be regarded as a promising candidate for screening DNA- and RNA-based molecular electronic devices.

Polaron mobility obtained by a variational approach for lattice Fröhlich models

NASA Astrophysics Data System (ADS)

Kornjača, Milan; Vukmirović, Nenad

2018-04-01

Charge carrier mobility for a class of lattice models with long-range electron-phonon interaction was investigated. The approach for mobility calculation is based on a suitably chosen unitary transformation of the model Hamiltonian which transforms it into the form where the remaining interaction part can be treated as a perturbation. Relevant spectral functions were then obtained using Matsubara Green's functions technique and charge carrier mobility was evaluated using Kubo's linear response formula. Numerical results were presented for a wide range of electron-phonon interaction strengths and temperatures in the case of one-dimensional version of the model. The results indicate that the mobility decreases with increasing temperature for all electron-phonon interaction strengths in the investigated range, while longer interaction range leads to more mobile carriers.

Fundamental limits on the electron mobility of β-Ga2O3

NASA Astrophysics Data System (ADS)

Kang, Youngho; Krishnaswamy, Karthik; Peelaers, Hartwin; Van de Walle, Chris G.

2017-06-01

We perform first-principles calculations to investigate the electronic and vibrational spectra and the electron mobility of β-Ga2O3. We calculate the electron-phonon scattering rate of the polar optical phonon modes using the Vogl model in conjunction with Fermi’s golden rule; this enables us to fully take the anisotropic phonon spectra of the monoclinic lattice of β-Ga2O3 into account. We also examine the scattering rate due to ionized impurities or defects using a Yukawa-potential-based model. We consider scattering due to donor impurities, as well as the possibility of compensation by acceptors such as Ga vacancies. We then calculate the room-temperature mobility of β-Ga2O3 using the Boltzmann transport equation within the relaxation time approximation, for carrier densities in the range from 1017 to 1020 cm-3. We find that the electron-phonon interaction dominates the mobility for carrier densities of up to 1019 cm-3. We also find that the intrinsic anisotropy in the mobility is small; experimental findings of large anisotropy must therefore be attributed to other factors. We attribute the experimentally observed reduction of the mobility with increasing carrier density to increasing levels of compensation, which significantly affect the mobility.

Fundamental limits on the electron mobility of β-Ga2O3.

PubMed

Kang, Youngho; Krishnaswamy, Karthik; Peelaers, Hartwin; Van de Walle, Chris G

2017-06-14

We perform first-principles calculations to investigate the electronic and vibrational spectra and the electron mobility of β-Ga 2 O 3 . We calculate the electron-phonon scattering rate of the polar optical phonon modes using the Vogl model in conjunction with Fermi's golden rule; this enables us to fully take the anisotropic phonon spectra of the monoclinic lattice of β-Ga 2 O 3 into account. We also examine the scattering rate due to ionized impurities or defects using a Yukawa-potential-based model. We consider scattering due to donor impurities, as well as the possibility of compensation by acceptors such as Ga vacancies. We then calculate the room-temperature mobility of β-Ga 2 O 3 using the Boltzmann transport equation within the relaxation time approximation, for carrier densities in the range from 10 17 to 10 20 cm -3 . We find that the electron-phonon interaction dominates the mobility for carrier densities of up to 10 19 cm -3 . We also find that the intrinsic anisotropy in the mobility is small; experimental findings of large anisotropy must therefore be attributed to other factors. We attribute the experimentally observed reduction of the mobility with increasing carrier density to increasing levels of compensation, which significantly affect the mobility.

T-gate geometric (solution for submicrometer gate length) HEMT: Physical analysis, modeling and implementation as parasitic elements and its usage as dual gate for variable gain amplifiers

NASA Astrophysics Data System (ADS)

Gupta, Ritesh; Rathi, Servin; Kaur, Ravneet; Gupta, Mridula; Gupta, R. S.

2009-03-01

In order to achieve superior RF performance, short gate length is required for the compound semiconductor field effect transistors, but the limitation in lithography for submicrometer gate lengths leads to the formation of various metal-insulator geometries like T-gate [Sandeep R. Bahl, Jesus A. del Alamo, Physics of breakdown in InAlAs/ n +-InGaAs heterostructure field-effect transistors, IEEE Trans. Electron Devices 41 (12) (1994) 2268-2275]. These geometries are the combination of various Metal-Semiconductor (MS)/Metal-Air-Semiconductor (MAS) contacts. Moreover, field plates [S. Karmalkar, M.S. Shur, G. Simin, M. Asif Khan, Field-plate engineering for HFETs, IEEE Trans. Electron Devices 52 (2005) 2534-2540] are also being fabricated these days, mainly at the drain end ( Γ-gate) having Metal-Insulator-Semiconductor (MIS) instead of MAS contact with the intention of increasing the breakdown voltage of the device. To realize the effect of upper gate electrode in the T-gate structure and field plates, an analytical model has been proposed in the present article by dividing the whole structure into MS/MIS contact regions, applying current continuity among them and solving iteratively. The model proposed for Metal-Insulator Semiconductor High Electron Mobility Transistor (MISHEMT) [R. Gupta, S.K. Aggarwal, M. Gupta, R.S. Gupta, Analytical model for metal insulator semiconductor high electron mobility transistor (MISHEMT) for its high frequency and high power applications, J. Semicond. Technol. Sci. 6 (3) (2006) 189-198], is equally applicable to High Electron Mobility Transistors (HEMT) and has been used to formulate this model. In this paper, various structures and geometries have been compared to anticipate the need of T-gate modeling. The effect of MIS contacts has been implemented as parasitic resistance and capacitance and has also been studied to control the middle conventional gate as in dual gate technology by applying separate voltages across it. The results obtained using the proposed analytical scheme has been compared with simulated and experimental results, to prove the validity of our model.

Diverse carrier mobility of monolayer BNC_x: A combined density functional theory and Boltzmann transport theory study.

PubMed

Wu, Tao; Deng, Kaiming; Deng, Wei-Qiao; Lu, Ruifeng

2017-09-19

BNCX monolayer as a kind of two-dimensional material has numerous chemical atomic ratios and arrangements with different electronic structures. Via calculations on the basis of density functional theory and Boltzmann transport theory under deformation potential approximation, the band structures and carrier mobilities of BNCX (x=1,2,3,4) nanosheets are systematically investigated. The calculated results show that BNC2-1 is a material with very small band gap (0.02 eV) among all the structures while other BNCX monolayers are semiconductors with band gap ranging from 0.51 to 1.32 eV. The carrier mobility of BNCX varies considerably from tens to millions of cm2 V-1 s-1. For BNC2-1, the hole mobility and electron mobility along both x and y directions can reach 105 orders of magnitude, which is similar to the carrier mobility of graphene. Besides, all studied BNCX monolayers obviously have anisotropic hole mobility and electron mobility. In particular, for semiconductor BNC4, its hole mobility along y direction and electron mobility along x direction unexpectedly reach 106 orders of magnitude, even higher than that of graphene. Our findings suggest that BNCX layered materials with proper ratio and arrangement of carbon atoms will possess desirable charge transport properties, exhibiting potential applications in nanoelectronic devices. © 2017 IOP Publishing Ltd.

Damage effect and mechanism of the GaAs high electron mobility transistor induced by high power microwave

NASA Astrophysics Data System (ADS)

Yang, Liu; Chang-Chun, Chai; Yin-Tang, Yang; Jing, Sun; Zhi-Peng, Li

2016-04-01

In this paper, we present the damage effect and mechanism of high power microwave (HPM) on AlGaAs/GaAs pseudomorphic high-electron-mobility transistor (pHEMT) of low-noise amplifier (LNA). A detailed investigation is carried out by simulation and experiment study. A two-dimensional electro-thermal model of the typical GaAs pHEMT induced by HPM is established in this paper. The simulation result reveals that avalanche breakdown, intrinsic excitation, and thermal breakdown all contribute to damage process. Heat accumulation occurs during the positive half cycle and the cylinder under the gate near the source side is most susceptible to burn-out. Experiment is carried out by injecting high power microwave into GaAs pHEMT LNA samples. It is found that the damage to LNA is because of the burn-out at first stage pHEMT. The interiors of the damaged samples are observed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). Experimental results accord well with the simulation of our model. Project supported by the National Basic Research Program of China (Grant No. 2014CB339900) and the Open Fund of Key Laboratory of Complex Electromagnetic Environment Science and Technology, China Academy of Engineering Physics (Grant No. 2015-0214.XY.K).

Compact, Single-Stage MMIC InP HEMT Amplifier

NASA Technical Reports Server (NTRS)

Pukala, David; Samoska, Lorene; Fung, King Man; Gaier, Todd; Deal, W. R.; Mei, Gerry; Radisic, Vesna; Lai, Richard

2008-01-01

A monolithic micro - wave integrated-circuit (MMIC) singlestage amplifier containing an InP-based high-electron-mobility transistor (HEMT) plus coplanar-waveguide (CPW) transmission lines for impedance matching and input and output coupling, all in a highly miniaturized layout as needed for high performance at operating frequencies of hundreds of gigahertz is described.

Highly stretchable polymer semiconductor films through the nanoconfinement effect

NASA Astrophysics Data System (ADS)

Xu, Jie; Wang, Sihong; Wang, Ging-Ji Nathan; Zhu, Chenxin; Luo, Shaochuan; Jin, Lihua; Gu, Xiaodan; Chen, Shucheng; Feig, Vivian R.; To, John W. F.; Rondeau-Gagné, Simon; Park, Joonsuk; Schroeder, Bob C.; Lu, Chien; Oh, Jin Young; Wang, Yanming; Kim, Yun-Hi; Yan, He; Sinclair, Robert; Zhou, Dongshan; Xue, Gi; Murmann, Boris; Linder, Christian; Cai, Wei; Tok, Jeffery B.-H.; Chung, Jong Won; Bao, Zhenan

2017-01-01

Soft and conformable wearable electronics require stretchable semiconductors, but existing ones typically sacrifice charge transport mobility to achieve stretchability. We explore a concept based on the nanoconfinement of polymers to substantially improve the stretchability of polymer semiconductors, without affecting charge transport mobility. The increased polymer chain dynamics under nanoconfinement significantly reduces the modulus of the conjugated polymer and largely delays the onset of crack formation under strain. As a result, our fabricated semiconducting film can be stretched up to 100% strain without affecting mobility, retaining values comparable to that of amorphous silicon. The fully stretchable transistors exhibit high biaxial stretchability with minimal change in on current even when poked with a sharp object. We demonstrate a skinlike finger-wearable driver for a light-emitting diode.

Orion Service Module Umbilical (OSMU) Installation

NASA Image and Video Library

2017-03-16

Seeming to hang in midair, the Orion Service Module Umbilical (OSMU) is lifted high up by crane for installation on the mobile launcher tower at NASA's Kennedy Space Center in Florida. The mobile launcher tower will be equipped with a number of lines, called umbilicals, that will connect to the Space Launch System rocket and Orion spacecraft for Exploration Mission-1 (EM-1). The OSMU will be located high on the mobile launcher tower and, prior to launch, will transfer liquid coolant for the electronics and air for the Environmental Control System to the Orion service module that houses these critical systems to support the spacecraft. EM-1 is scheduled to launch in 2018. The Ground Systems Development and Operations Program is overseeing installation of the umbilicals.

Orion Service Module Umbilical (OSMU) Installation

NASA Image and Video Library

2017-03-16

A crane and rigging are used to position the Orion Service Module Umbilical (OSMU) for installation high up on the mobile launcher tower at NASA's Kennedy Space Center in Florida. The mobile launcher tower will be equipped with a number of lines, called umbilicals, that will connect to the Space Launch System rocket and Orion spacecraft for Exploration Mission-1 (EM-1). The OSMU will be located high on the mobile launcher tower and, prior to launch, will transfer liquid coolant for the electronics and air for the Environmental Control System to the Orion service module that houses these critical systems to support the spacecraft. EM-1 is scheduled to launch in 2018. The Ground Systems Development and Operations Program is overseeing installation of the umbilicals.

Orion Service Module Umbilical (OSMU) Installation

NASA Image and Video Library

2017-03-16

A crane and rigging are used to lift the Orion Service Module Umbilical (OSMU) high up for installation on the mobile launcher tower at NASA's Kennedy Space Center in Florida. The mobile launcher tower will be equipped with a number of lines, called umbilicals, that will connect to the Space Launch System rocket and Orion spacecraft for Exploration Mission-1 (EM-1). The OSMU will be located high on the mobile launcher tower and, prior to launch, will transfer liquid coolant for the electronics and air for the Environmental Control System to the Orion service module that houses these critical systems to support the spacecraft. EM-1 is scheduled to launch in 2018. The Ground Systems Development and Operations Program is overseeing installation of the umbilicals.

Orion Service Module Umbilical (OSMU) Lift & Preparation for Ins

NASA Image and Video Library

2017-03-13

A crane lifts the bracket for the Orion Service Module Umbilical (OSMU) high up for installation on the mobile launcher tower at NASA's Kennedy Space Center in Florida. The mobile launcher tower will be equipped with a number of lines, called umbilicals, that will connect to the Space Launch System rocket and Orion spacecraft for Exploration Mission-1 (EM-1). The OSMU will be located high on the mobile launcher tower and, prior to launch, will transfer liquid coolant for the electronics and air for the Environmental Control System to the Orion service module that houses these critical systems to support the spacecraft. EM-1 is scheduled to launch in 2018. The Ground Systems Development and Operations Program is overseeing installation of the umbilicals.

Carbon nanotube transistor based high-frequency electronics

NASA Astrophysics Data System (ADS)

Schroter, Michael

At the nanoscale carbon nanotubes (CNTs) have higher carrier mobility and carrier velocity than most incumbent semiconductors. Thus CNT based field-effect transistors (FETs) are being considered as strong candidates for replacing existing MOSFETs in digital applications. In addition, the predicted high intrinsic transit frequency and the more recent finding of ways to achieve highly linear transfer characteristics have inspired investigations on analog high-frequency (HF) applications. High linearity is extremely valuable for an energy efficient usage of the frequency spectrum, particularly in mobile communications. Compared to digital applications, the much more relaxed constraints for CNT placement and lithography combined with already achieved operating frequencies of at least 10 GHz for fabricated devices make an early entry in the low GHz HF market more feasible than in large-scale digital circuits. Such a market entry would be extremely beneficial for funding the development of production CNTFET based process technology. This talk will provide an overview on the present status and feasibility of HF CNTFET technology will be given from an engineering point of view, including device modeling, experimental results, and existing roadblocks. Carbon nanotube transistor based high-frequency electronics.

Doppler Velocimetry of Current Driven Spin Helices in a Two-Dimensional Electron Gas

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

Yang, Luyi

2013-05-17

Spins in semiconductors provide a pathway towards the development of spin-based electronics. The appeal of spin logic devices lies in the fact that the spin current is even under time reversal symmetry, yielding non-dissipative coupling to the electric field. To exploit the energy-saving potential of spin current it is essential to be able to control it. While recent demonstrations of electrical-gate control in spin-transistor configurations show great promise, operation at room temperature remains elusive. Further progress requires a deeper understanding of the propagation of spin polarization, particularly in the high mobility semiconductors used for devices. This dissertation presents the demonstrationmore » and application of a powerful new optical technique, Doppler spin velocimetry, for probing the motion of spin polarization at the level of 1 nm on a picosecond time scale. We discuss experiments in which this technique is used to measure the motion of spin helices in high mobility n-GaAs quantum wells as a function of temperature, in-plane electric field, and photoinduced spin polarization amplitude. We find that the spin helix velocity changes sign as a function of wave vector and is zero at the wave vector that yields the largest spin lifetime. This observation is quite striking, but can be explained by the random walk model that we have developed. We discover that coherent spin precession within a propagating spin density wave is lost at temperatures near 150 K. This finding is critical to understanding why room temperature operation of devices based on electrical gate control of spin current has so far remained elusive. We report that, at all temperatures, electron spin polarization co-propagates with the high-mobility electron sea, even when this requires an unusual form of separation of spin density from photoinjected electron density. Furthermore, although the spin packet co-propagates with the two-dimensional electron gas, spin diffusion is strongly suppressed by electron-electron interactions, leading to remarkable resistance to diffusive spreading of the drifting pulse of spin polarization. Finally, we show that spin helices continue propagate at the same speed as the Fermi sea even when the electron drift velocity exceeds the Fermi velocity of 107 cm s -1.« less

Tuning a circular p-n junction in graphene from quantum confinement to optical guiding

NASA Astrophysics Data System (ADS)

Jiang, Yuhang; Mao, Jinhai; Moldovan, Dean; Masir, Massoud Ramezani; Li, Guohong; Watanabe, Kenji; Taniguchi, Takashi; Peeters, Francois M.; Andrei, Eva Y.

2017-11-01

The photon-like propagation of the Dirac electrons in graphene, together with its record-high electronic mobility, can lead to applications based on ultrafast electronic response and low dissipation. However, the chiral nature of the charge carriers that is responsible for the high mobility also makes it difficult to control their motion and prevents electronic switching. Here, we show how to manipulate the charge carriers by using a circular p-n junction whose size can be continuously tuned from the nanometre to the micrometre scale. The junction size is controlled with a dual-gate device consisting of a planar back gate and a point-like top gate made by decorating a scanning tunnelling microscope tip with a gold nanowire. The nanometre-scale junction is defined by a deep potential well created by the tip-induced charge. It traps the Dirac electrons in quantum-confined states, which are the graphene equivalent of the atomic collapse states (ACSs) predicted to occur at supercritically charged nuclei. As the junction size increases, the transition to the optical regime is signalled by the emergence of whispering-gallery modes, similar to those observed at the perimeter of acoustic or optical resonators, and by the appearance of a Fabry-Pérot interference pattern for junctions close to a boundary.

Remarkable enhancement of charge carrier mobility of conjugated polymer field-effect transistors upon incorporating an ionic additive

PubMed Central

Luo, Hewei; Yu, Chenmin; Liu, Zitong; Zhang, Guanxin; Geng, Hua; Yi, Yuanping; Broch, Katharina; Hu, Yuanyuan; Sadhanala, Aditya; Jiang, Lang; Qi, Penglin; Cai, Zhengxu; Sirringhaus, Henning; Zhang, Deqing

2016-01-01

Organic semiconductors with high charge carrier mobilities are crucial for flexible electronic applications. Apart from designing new conjugated frameworks, different strategies have been explored to increase charge carrier mobilities. We report a new and simple approach to enhancing the charge carrier mobility of DPP-thieno[3,2-b]thiophene–conjugated polymer by incorporating an ionic additive, tetramethylammonium iodide, without extra treatments into the polymer. The resulting thin films exhibit a very high hole mobility, which is higher by a factor of 24 than that of thin films without the ionic additive under the same conditions. On the basis of spectroscopic grazing incidence wide-angle x-ray scattering and atomic force microscopy studies as well as theoretical calculations, the remarkable enhancement of charge mobility upon addition of tetramethylammonium iodide is attributed primarily to an inhibition of the torsion of the alkyl side chains by the presence of the ionic species, facilitating a more ordered lamellar packing of the alkyl side chains and interchain π-π interactions. PMID:27386541

Geometrical and band-structure effects on phonon-limited hole mobility in rectangular cross-sectional germanium nanowires

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

Tanaka, H., E-mail: tanaka@semicon.kuee.kyoto-u.ac.jp; Mori, S.; Morioka, N.

2014-12-21

We calculated the phonon-limited hole mobility in rectangular cross-sectional [001], [110], [111], and [112]-oriented germanium nanowires, and the hole transport characteristics were investigated. A tight-binding approximation was used for holes, and phonons were described by a valence force field model. Then, scattering probability of holes by phonons was calculated taking account of hole-phonon interaction atomistically, and the linearized Boltzmann's transport equation was solved to calculate the hole mobility at low longitudinal field. The dependence of the hole mobility on nanowire geometry was analyzed in terms of the valence band structure of germanium nanowires, and it was found that the dependencemore » was qualitatively reproduced by considering an average effective mass and the density of states of holes. The calculation revealed that [110] germanium nanowires with large height along the [001] direction show high hole mobility. Germanium nanowires with this geometry are also expected to exhibit high electron mobility in our previous work, and thus they are promising for complementary metal-oxide-semiconductor (CMOS) applications.« less

Electric microwave absorption for the study of GaAs/AlGaAs heterostructure systems

NASA Astrophysics Data System (ADS)

Zappe, Hans P.; Jantz, Wolfgang

1990-12-01

The use of magnetic-field-dependent microwave absorption as a nondestructive and contact-free means to study transport behavior in GaAs/AlGaAs devices is explored. This technique allows quick measurement of resistance, mobility, and carrier concentration in bulk substrates as well as in the two-dimensional electron gas of heterostructure quantum wells. The two- and three-dimensional conductivities may be separably evaluated, allowing detailed study of conduction in the active layer of high-electron-mobility devices. A brief theoretical foundation is provided, followed by application of the approach to examination of device structural dependencies, carrier-density conduction behavior, and the effects of etch processing on quantum-well integrity.

Electron scattering times in ZnO based polar heterostructures

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

Falson, J., E-mail: j.falson@fkf.mpg.de; Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561; Max Planck Institute for Solid State Research, D-70569 Stuttgart

2015-08-24

The remarkable historic advances experienced in condensed matter physics have been enabled through the continued exploration and proliferation of increasingly richer and cleaner material systems. In this work, we report on the scattering times of charge carriers confined in state-of-the-art MgZnO/ZnO heterostructures displaying electron mobilities in excess of 10{sup 6} cm{sup 2}/V s. Through an examination of low field quantum oscillations, we obtain the effective mass of charge carriers, along with the transport and quantum scattering times. These times compare favorably with high mobility AlGaAs/GaAs heterostructures, suggesting the quality of MgZnO/ZnO heterostructures now rivals that of traditional semiconductors.

A world of minerals in your mobile device

USGS Publications Warehouse

Jenness, Jane E.; Ober, Joyce A.; Wilkins, Aleeza M.; Gambogi, Joseph

2016-09-15

Mobile phones and other high-technology communications devices could not exist without mineral commodities. More than one-half of all components in a mobile device—including its electronics, display, battery, speakers, and more—are made from mined and semiprocessed materials (mineral commodities). Some mineral commodities can be recovered as byproducts during the production and processing of other commodities. As an example, bauxite is mined for its aluminum content, but gallium is recovered during the aluminum production process. The images show the ore minerals (sources) of some mineral commodities that are used to make components of a mobile device. On the reverse side, the map and table depict the major source countries producing these mineral commodities along with how these commodities are used in mobile devices. For more information on minerals, visit http://minerals.usgs.gov.

Evolution of subband structure with gate-tuning at LaAlO3/SrTiO3 interfaces

NASA Astrophysics Data System (ADS)

Tang, Lucas; Smink, Sander; van Heeringen, Linde; Geessinck, Jaap; Rana, Abimanuya; Rastogi, Ankur; Maan, Jan Kees; Brinkman, Alexander; Zeitler, Uli; Hilgenkamp, Hans; McCollam, Alix

The outstanding characteristic of LaAlO3/SrTiO3 heterostructures is the formation of a high mobility 2D electron gas (2DEG) at the interface. The additional presence of superconductivity, magnetism and large spin-orbit coupling in these systems suggests that strong correlations play an important role in the electronic properties, in contrast to conventional semiconductor-based 2DEGs. Knowledge of the electronic bandstructure, and the interdependence of conduction electron density and properties is therefore essential for our understanding of these materials. We present new results of low temperature transport measurements in a high mobility LaAlO3/SrTiO3-based heterostructure, in magnetic fields up to 33 T. Shubnikov de-Haas oscillations are observed, revealing several subbands with different carrier densities. By application of an electric field in the back gate geometry, the Fermi level is tuned and thus we are able to map the smooth evolution of the subbands and their properties with carrier density. These results are in good agreement with recent theoretical work, such that we can disentangle the complex band structure, and quantify aspects such as Rashba spin-splitting and the mixing of orbital character.

Present status of recycling waste mobile phones in China: a review.

PubMed

Li, Jingying; Ge, Zhongying; Liang, Changjin; An, Ni

2017-07-01

A large number of waste mobile phones have already been generated and are being generated. Various countries around the world have all been positively exploring the way of recycling and reuse when facing such a large amount of waste mobile phones. In some countries, processing waste mobile phones has been forming a complete industrial chain, which can not only recycle waste mobile phones to reduce their negative influence on the environment but also turn waste into treasure to acquire economic benefits dramatically. However, the situation of recycling waste mobile phones in China is not going well. Waste mobile phones are not formally covered by existing regulations and policies for the waste electric and electronic equipment in China. In order to explore an appropriate system to recover waste mobile phones, the mobile phone production and the amount of waste mobile phones are introduced in this paper, and status of waste mobile phones recycling is described; then, the disposal technology of electronic waste that would be most likely to be used for processing of electronic waste in industrial applications in the near future is reviewed. Finally, rationalization proposals are put forward based on the current recovery status of waste mobile phones for the purpose of promoting the development of recycling waste mobile phones in developing countries with a special emphasis on China.

Molecular design of photovoltaic materials for polymer solar cells: toward suitable electronic energy levels and broad absorption.

PubMed

Li, Yongfang

2012-05-15

Bulk heterojunction (BHJ) polymer solar cells (PSCs) sandwich a blend layer of conjugated polymer donor and fullerene derivative acceptor between a transparent ITO positive electrode and a low work function metal negative electrode. In comparison with traditional inorganic semiconductor solar cells, PSCs offer a simpler device structure, easier fabrication, lower cost, and lighter weight, and these structures can be fabricated into flexible devices. But currently the power conversion efficiency (PCE) of the PSCs is not sufficient for future commercialization. The polymer donors and fullerene derivative acceptors are the key photovoltaic materials that will need to be optimized for high-performance PSCs. In this Account, I discuss the basic requirements and scientific issues in the molecular design of high efficiency photovoltaic molecules. I also summarize recent progress in electronic energy level engineering and absorption spectral broadening of the donor and acceptor photovoltaic materials by my research group and others. For high-efficiency conjugated polymer donors, key requirements are a narrower energy bandgap (E(g)) and broad absorption, relatively lower-lying HOMO (the highest occupied molecular orbital) level, and higher hole mobility. There are three strategies to meet these requirements: D-A copolymerization for narrower E(g) and lower-lying HOMO, substitution with electron-withdrawing groups for lower-lying HOMO, and two-dimensional conjugation for broad absorption and higher hole mobility. Moreover, better main chain planarity and less side chain steric hindrance could strengthen π-π stacking and increase hole mobility. Furthermore, the molecular weight of the polymers also influences their photovoltaic performance. To produce high efficiency photovoltaic polymers, researchers should attempt to increase molecular weight while maintaining solubility. High-efficiency D-A copolymers have been obtained by using benzodithiophene (BDT), dithienosilole (DTS), or indacenodithiophene (IDT) donor unit and benzothiadiazole (BT), thienopyrrole-dione (TPD), or thiazolothiazole (TTz) acceptor units. The BDT unit with two thienyl conjugated side chains is a highly promising unit in constructing high-efficiency copolymer donor materials. The electron-withdrawing groups of ester, ketone, fluorine, or sulfonyl can effectively tune the HOMO energy levels downward. To improve the performance of fullerene derivative acceptors, researchers will need to strengthen absorption in the visible spectrum, upshift the LUMO (the lowest unoccupied molecular orbital) energy level, and increase the electron mobility. [6,6]-Phenyl-C(71)-butyric acid methyl ester (PC(70)BM) is superior to [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) because C(70) absorbs visible light more efficiently. Indene-C(60) bisadduct (ICBA) and Indene-C(70) bisadduct (IC(70)BA) show 0.17 and 0.19 eV higher LUMO energy levels, respectively, than PCBM, due to the electron-rich character of indene and the effect of bisadduct. ICBA and IC(70)BA are excellent acceptors for the P3HT-based PSCs.

Dramatic inversion of charge polarity in diketopyrrolopyrrole-based organic field-effect transistors via a simple nitrile group substitution.

PubMed

Yun, Hui-Jun; Kang, Seok-Ju; Xu, Yong; Kim, Seul Ong; Kim, Yun-Hi; Noh, Yong-Young; Kwon, Soon-Ki

2014-11-19

A record-breaking high electron mobility of 7.0 cm(2) V(-1) s(-1) for n-channel polymer OFETs is reported. By the incorporation of only one nitrile group as an electron-withdrawing function in the vinyl linkage of the DPP-based copolymer, a dramatic inversion of majority charge-carriers from holes to electrons is achieved. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Charge-transport anisotropy in black phosphorus: critical dependence on the number of layers.

PubMed

Banerjee, Swastika; Pati, Swapan K

2016-06-28

Phosphorene is a promising candidate for modern electronics because of the anisotropy associated with high electron-hole mobility. Additionally, superior mechanical flexibility allows the strain-engineering of various properties including the transport of charge carriers in phosphorene. In this work, we have shown the criticality of the number of layers to dictate the transport properties of black phosphorus. Trilayer black phosphorus (TBP) has been proposed as an excellent anisotropic material, based on the transport parameters using Boltzmann transport formalisms coupled with density functional theory. The mobilities of both the electron and the hole are found to be higher along the zigzag direction (∼10(4) cm(2) V(-1) s(-1) at 300 K) compared to the armchair direction (∼10(2) cm(2) V(-1) s(-1)), resulting in the intrinsic directional anisotropy. Application of strain leads to additional electron-hole anisotropy with 10(3) fold higher mobility for the electron compared to the hole. Critical strain for maximum anisotropic response has also been determined. Whether the transport anisotropy is due to the spatial or charge-carrier has been determined through analyses of the scattering process of electrons and holes, and their recombination as well as relaxation dynamics. In this context, we have derived two descriptors (S and F(k)), which are general enough for any 2D or quasi-2D systems. Information on the scattering involving purely the carrier states also helps to understand the layer-dependent photoluminescence and electron (hole) relaxation in black phosphorus. Finally, we justify trilayer black phosphorus (TBP) as the material of interest with excellent transport properties.

Electron transport in some transition metal di-chalcogenides: MoS2 and WS2

NASA Astrophysics Data System (ADS)

Ferry, D. K.

2017-08-01

The transition metal di-chalcogenides are promising single monolayer materials that hold promise for applications in several fields, including nanoelectronics. Here, I study the transport of electrons in two of these materials, MoS2 and WS2. While the low-field behavior shows very low mobility, due mostly to impurity scattering, the high-field behavior shows a relatively high saturated velocity and a high breakdown field. Complications arise due to the relative narrowness of the conduction band, and the effect of this on the transport is discussed.

Pre-Clinical and Clinical Evaluation of High Resolution, Mobile Gamma Camera and Positron Imaging Devices

DTIC Science & Technology

2007-11-01

accuracy. FPGA ADC data acquisition is controlled by distributed Java -based software. Java -based server application sits on each of the acquisition...JNI ( Java Native Interface) is used to allow Java indirect control of the USB driver. Fig. 5. Photograph of mobile electronics rack...supplies with the monitor and keyboard. The server application on each of these machines is controlled by a remote client Java -based application

Motion Simulation Research Related Short Term Training Attachment to TARDEC

DTIC Science & Technology

2013-04-01

CASSI group has five main areas of focus, which are, ground vehicle power and mobility , vehicle electronics and architecture, intelligent ground...control, steering as well as seats can all be changed to mock the necessary vehicle. Originally it was designed for a High Mobility Multipurpose Wheeled...necessary outputs to the motion base. SimCreator is a software package, similar to SimuLink. Most of the backend coding is done in C++. RTI accounts

Miniaturized Ion Mobility Spectrometer

NASA Technical Reports Server (NTRS)

Stimac, Robert M. (Inventor); Kaye, William J (Inventor)

2017-01-01

By utilizing the combination of a unique electronic ion injection control circuit in conjunction with a particularly designed drift cell construction, the instantly disclosed ion mobility spectrometer (IMS) achieves increased levels of sensitivity, while achieving significant reductions in size and weight. The instant IMS is of a much simpler and easy to manufacture design, rugged and hermetically sealed, capable of operation at high temperatures to at least 250 degrees Centigrade, and is uniquely sensitive, particularly to explosive chemicals.

Miniaturized Ion Mobility Spectrometer

NASA Technical Reports Server (NTRS)

Kaye, William J. (Inventor); Stimac, Robert M. (Inventor)

2015-01-01

By utilizing the combination of a unique electronic ion injection control circuit in conjunction with a particularly designed drift cell construction, the instantly disclosed ion mobility spectrometer achieves increased levels of sensitivity, while achieving significant reductions in size and weight. The instant IMS is of a much simpler and easy to manufacture design, rugged and hermetically sealed, capable of operation at high temperatures to at least 250.degree. C., and is uniquely sensitive, particularly to explosive chemicals.

Estimation of retired mobile phones generation in China: A comparative study on methodology

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

Li, Bo; Yang, Jianxin, E-mail: yangjx@rcees.ac.cn; Lu, Bin

Highlights: • The sales data of mobile phones in China was revised by considering the amount of smuggled and counterfeit mobile phones. • The estimation of retired mobile phones in China was made by comparing some relevant methods. • The advanced result of estimation can help improve the policy-making. • The method suggested in this paper can be also used in other countries. • Some discussions on methodology are also conducted in order for the improvement. - Abstract: Due to the rapid development of economy and technology, China has the biggest production and possession of mobile phones around the world.more » In general, mobile phones have relatively short life time because the majority of users replace their mobile phones frequently. Retired mobile phones represent the most valuable electrical and electronic equipment (EEE) in the main waste stream because of such characteristics as large quantity, high reuse/recovery value and fast replacement frequency. Consequently, the huge amount of retired mobile phones in China calls for a sustainable management system. The generation estimation can provide fundamental information to construct the sustainable management system of retired mobile phones and other waste electrical and electronic equipment (WEEE). However, the reliable estimation result is difficult to get and verify. The priority aim of this paper is to provide proper estimation approach for the generation of retired mobile phones in China, by comparing some relevant methods. The results show that the sales and new method is in the highest priority in estimation of the retired mobile phones. The result of sales and new method shows that there are 47.92 million mobile phones retired in 2002, and it reached to 739.98 million in China in 2012. It presents an increasing tendency with some fluctuations clearly. Furthermore, some discussions on methodology, such as the selection of improper approach and error in the input data, are also conducted in order to improve generation estimation of retired mobile phones and other WEEE.« less

A pilot study of an mHealth application for healthcare workers: poor uptake despite high reported acceptability at a rural South African community-based MDR-TB treatment program.

PubMed

Chaiyachati, Krisda H; Loveday, Marian; Lorenz, Stephen; Lesh, Neal; Larkan, Lee-Megan; Cinti, Sandro; Friedland, Gerald H; Haberer, Jessica E

2013-01-01

As the South African province of KwaZulu-Natal addresses a growing multidrug-resistant tuberculosis (MDR-TB) epidemic by shifting care and treatment from trained specialty centers to community hospitals, delivering and monitoring MDR-TB therapy has presented new challenges. In particular, tracking and reporting adverse clinical events have been difficult for mobile healthcare workers (HCWs), trained health professionals who travel daily to patient homes to administer and monitor therapy. We designed and piloted a mobile phone application (Mobilize) for mobile HCWs that electronically standardized the recording and tracking of MDR-TB patients on low-cost, functional phones. We assess the acceptability and feasibility of using Mobilize to record and submit adverse events forms weekly during the intensive phase of MDR-TB therapy and evaluate mobile HCW perceptions throughout the pilot period. All five mobile HCWs at one site were trained and provided with phones. Utilizing a mixed-methods evaluation, mobile HCWs' usage patterns were tracked electronically for seven months and analyzed. Qualitative focus groups and questionnaires were designed to understand the impact of mobile phone technology on the work environment. Mobile HCWs submitted nine of 33 (27%) expected adverse events forms, conflicting with qualitative results in which mobile HCWs stated that Mobilize improved adverse events communication, helped their daily workflow, and could be successfully expanded to other health interventions. When presented with the conflict between their expressed views and actual practice, mobile HCWs cited forgetfulness and believed patients should take more responsibility for their own care. This pilot experience demonstrated poor uptake by HCWs despite positive responses to using mHealth. Though our results should be interpreted cautiously because of the small number of mobile HCWs and MDR-TB patients in this study, we recommend carefully exploring the motivations of HCWs and technologic enhancements prior to scaling new mHealth initiatives in resource poor settings.

Low-Temperature Postfunctionalization of Highly Conductive Oxide Thin-Films toward Solution-Based Large-Scale Electronics.

PubMed

Ban, Seok-Gyu; Kim, Kyung-Tae; Choi, Byung Doo; Jo, Jeong-Wan; Kim, Yong-Hoon; Facchetti, Antonio; Kim, Myung-Gil; Park, Sung Kyu

2017-08-09

Although transparent conducting oxides (TCOs) have played a key role in a wide range of solid-state electronics from conventional optoelectronics to emerging electronic systems, the processing temperature and conductivity of solution-processed materials seem to be far exceeding the thermal limitations of soft materials and insufficient for high-perfomance large-area systems, respectively. Here, we report a strategy to form highly conductive and scalable solution-processed oxide materials and their successful translation into large-area electronic applications, which is enabled by photoassisted postfunctionalization at low temperature. The low-temperature fabrication of indium-tin-oxide (ITO) thin films was achieved by using photoignited combustion synthesis combined with photoassisted reduction process under hydrogen atmosphere. It was noteworthy that the photochemically activated hydrogens on ITO surface could be triggered to facilitate highly crystalline oxygen deficient structure allowing significant increase of carrier concentration and mobility through film microstructure modifications. The low-temperature postfunctionalized ITO films demonstrated conductivity of >1607 S/cm and sheet resistance of <104 Ω/□ under the process temperature of less than 300 °C, which are comparable to those of vacuum-deposited and high-temperature annealed ITO films. Based on the photoassisted postfunctionalization route, all-solution-processed transparent metal-oxide thin-film-transistors and large-area integrated circuits with the ITO bus lines were demonstrated, showing field-effect mobilities of >6.5 cm 2 V -1 s -1 with relatively good operational stability and oscillation frequency of more than 1 MHz in 7-stage ring oscillators, respectively.

Effects of macroscopic inhomogeneities on electron mobility in semi-insulating GaAs

NASA Technical Reports Server (NTRS)

Walukiewicz, W.; Wang, L.; Pawlowicz, L. M.; Lagowski, J.; Gatos, H. C.

1986-01-01

It is shown that defect inhomogeneities of sizes larger than the electron mean free path are responsible for the low values and anomalous temperature dependence of the electron mobility in semi-insulating (SI) GaAs. The room-temperature electron mobility values below about 6000 sq cm/V s cannot be uniquely used for the determination of the concentration of ionized defects, since the contribution from inhomogeneities usually exceeds that from scattering by ionized impurities. The effects of the macroscopically inhomogeneous distribution of residual acceptors and the major deep donor EL2 diminish at elevated temperatures between 600 and 900 K, which offers a means for identification of inhomogeneities, and furthermore explains recently reported steplike mobility versus temperature behavior in SI-GaAs.

Charge transport in metal oxides: A theoretical study of hematite α-Fe2O3

NASA Astrophysics Data System (ADS)

Iordanova, N.; Dupuis, M.; Rosso, K. M.

2005-04-01

Transport of conduction electrons and holes through the lattice of α-Fe2O3 (hematite) is modeled as a valence alternation of iron cations using ab initio electronic structure calculations and electron transfer theory. Experimental studies have shown that the conductivity along the (001) basal plane is four orders of magnitude larger than the conductivity along the [001] direction. In the context of the small polaron model, a cluster approach was used to compute quantities controlling the mobility of localized electrons and holes, i.e., the reorganization energy and the electronic coupling matrix element that enter Marcus' theory. The calculation of the electronic coupling followed the generalized Mulliken-Hush approach using the complete active space self-consistent field method. Our findings demonstrate an approximately three orders of magnitude anisotropy in both electron and hole mobility between directions perpendicular and parallel to the c axis, in good accord with experimental data. The anisotropy arises from the slowness of both electron and hole mobilities across basal oxygen planes relative to that within iron bilayers between basal oxygen planes. Interestingly, for elementary reaction steps along either of the directions considered, there is only less than one order of magnitude difference in mobility between electrons and holes, in contrast to accepted classical arguments. Our findings indicate that the most important quantity underlying mobility differences is the electronic coupling, albeit the reorganization energy contributes as well. The large values computed for the electronic coupling suggest that charge transport reactions in hematite are adiabatic in nature. The electronic coupling is found to depend on both the superexchange interaction through the bridging oxygen atoms and the d-shell electron spin coupling within the Fe-Fe donor-acceptor pair, while the reorganization energy is essentially independent of the electron spin coupling.

High performance unipolar MoTe2 field effect transistors enabled by doping and Al2O3 capping

NASA Astrophysics Data System (ADS)

Qu, Deshun; Liu, Xiaochi; Ahmed, Faisal; Yoo, Won Jong

We carry out the first systematic experiment on carrier type modulation of MoTe2 FET in this work. unipolar p- and n-type MoTe2 FETs with 105 and 106 on-off ratios are achieved through rapid thermal annealing (RTA) and Benzyl Viologen (BV) doping respectively. By varying the vacuum level in RTA chamber before annealing and BV dopant concentration, annealing condition, both hole and electron doping concentration can be modulated in a wide range from slight doping to degenerate like doping. Furthermore, Al2O3 is deposited onto the device surfaces for the mobility engineering. Hole and electron mobilities are improved to 62 cm2/Vs and 82 cm2/Vs respectively after Al2O3 capping; they are among the highest carrier mobilities of MoTe2 transistors ever obtained. A lateral homogeneous MoTe2 p-n diode is fabricated combining the electron and hole doping techniques, the device displays excellent diode properties with a high rectification ratio of 104 at 0 gate bias and an ideality factor of 1.2. This work was supported by the Global Research Laboratory and Global Frontier R&D Programs at the Center for Hybrid Interface Materials, both funded by the Ministry of Science, ICT & Future Planning via the National Research Foundation of Korea (NRF).

Theory for the anomalous electron transport in Hall-effect thrusters

NASA Astrophysics Data System (ADS)

Lafleur, Trevor; Baalrud, Scott; Chabert, Pascal

2016-09-01

Using insights from particle-in-cell (PIC) simulations, we develop a kinetic theory to explain the anomalous cross-field electron transport in Hall-effect thrusters (HETs). The large axial electric field in the acceleration region of HETs, together with the radially applied magnetic field, causes electrons to drift in the azimuthal direction with a very high velocity. This drives an electron cyclotron instability that produces large amplitude oscillations in the plasma density and azimuthal electric field, and which is convected downstream due to the large axial ion drift velocity. The frequency and wavelength of the instability are of the order of 5 MHz and 1 mm respectively, while the electric field amplitude can be of a similar magnitude to axial electric field itself. The instability leads to enhanced electron scattering many orders of magnitude higher than that from standard electron-neutral or electron-ion Coulomb collisions, and gives electron mobilities in good agreement with experiment. Since the instability is a strong function of almost all plasma properties, the mobility cannot in general be fitted with simple 1/B or 1/B2 scaling laws, and changes to the secondary electron emission coefficient of the HET channel walls are expected to play a role in the evolution of the instability. This work received financial support from a CNES postdoctoral research award.

Skutterudite Compounds For Power Semiconductor Devices

NASA Technical Reports Server (NTRS)

Fleurial, Jean-Pierre; Caillat, Thierry; Borshchevsky, Alexander; Vandersande, Jan

1996-01-01

New semiconducting materials with p-type carrier mobility values much higher than state-of-art semiconductors discovered. Nine compounds, antimonides CoSb(sub3), RhSb(sub3), IrSb(sub3), arsenides CoAs(sub3), RhAs(sub3), IrAs(sub3), and phosphides CoP(sub3), RhP(sub3) and IrP(sub3), exhibit same skutterudite crystallographic structure and form solid solutions of general composition Co(1-x-y)RH(x)Ir(y)P(1-w-z)As(w)Sb(z). Materials exhibit high hole mobilities, high doping levels, and high electronic figures of merit. Some compositions show great potential for application to thermoelectric devices.

Joint Services Electronics Program Research in Electronics (University of Southern California, Electronic Sciences Laboratory)

DTIC Science & Technology

1990-01-05

submitted). 3. 0. J. Kim, A. Madhukar, W. Chen, K. Z. Hu, "Realization of High Mobilities at Ultra Low Electron Density in GaAs-Al O.3GaO.7As Inverted...to-Coherent Optical Conversion", in Photorefractive Materials and Aplications , J. P. Huignard and P. Gunter, Eds., Springer-Verlag, New York (1989). 2...Schottky Barrier Epitaxial Structures," USC Ph.D. Thesis (May 1989). 2. E. Garmire, N. M. Jokerst, A. Kost, A. Dar,---, and P. D. Dapkus, "Optical

Polarization-mediated Debye-screening of surface potential fluctuations in dual-channel AlN/GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Deen, David A.; Miller, Ross A.; Osinsky, Andrei V.; Downey, Brian P.; Storm, David F.; Meyer, David J.; Scott Katzer, D.; Nepal, Neeraj

2016-12-01

A dual-channel AlN/GaN/AlN/GaN high electron mobility transistor (HEMT) architecture is proposed, simulated, and demonstrated that suppresses gate lag due to surface-originated trapped charge. Dual two-dimensional electron gas (2DEG) channels are utilized such that the top 2DEG serves as an equipotential that screens potential fluctuations resulting from surface trapped charge. The bottom channel serves as the transistor's modulated channel. Two device modeling approaches have been performed as a means to guide the device design and to elucidate the relationship between the design and performance metrics. The modeling efforts include a self-consistent Poisson-Schrodinger solution for electrostatic simulation as well as hydrodynamic three-dimensional device modeling for three-dimensional electrostatics, steady-state, and transient simulations. Experimental results validated the HEMT design whereby homo-epitaxial growth on free-standing GaN substrates and fabrication of the same-wafer dual-channel and recessed-gate AlN/GaN HEMTs have been demonstrated. Notable pulsed-gate performance has been achieved by the fabricated HEMTs through a gate lag ratio of 0.86 with minimal drain current collapse while maintaining high levels of dc and rf performance.

High-Throughput Fabrication of Flexible and Transparent All-Carbon Nanotube Electronics.

PubMed

Chen, Yong-Yang; Sun, Yun; Zhu, Qian-Bing; Wang, Bing-Wei; Yan, Xin; Qiu, Song; Li, Qing-Wen; Hou, Peng-Xiang; Liu, Chang; Sun, Dong-Ming; Cheng, Hui-Ming

2018-05-01

This study reports a simple and effective technique for the high-throughput fabrication of flexible all-carbon nanotube (CNT) electronics using a photosensitive dry film instead of traditional liquid photoresists. A 10 in. sized photosensitive dry film is laminated onto a flexible substrate by a roll-to-roll technology, and a 5 µm pattern resolution of the resulting CNT films is achieved for the construction of flexible and transparent all-CNT thin-film transistors (TFTs) and integrated circuits. The fabricated TFTs exhibit a desirable electrical performance including an on-off current ratio of more than 10 5 , a carrier mobility of 33 cm 2 V -1 s -1 , and a small hysteresis. The standard deviations of on-current and mobility are, respectively, 5% and 2% of the average value, demonstrating the excellent reproducibility and uniformity of the devices, which allows constructing a large noise margin inverter circuit with a voltage gain of 30. This study indicates that a photosensitive dry film is very promising for the low-cost, fast, reliable, and scalable fabrication of flexible and transparent CNT-based integrated circuits, and opens up opportunities for future high-throughput CNT-based printed electronics.

Suppression of surface-originated gate lag by a dual-channel AlN/GaN high electron mobility transistor architecture

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

Deen, David A., E-mail: david.deen@alumni.nd.edu; Storm, David F.; Scott Katzer, D.

A dual-channel AlN/GaN high electron mobility transistor (HEMT) architecture is demonstrated that leverages ultra-thin epitaxial layers to suppress surface-related gate lag. Two high-density two-dimensional electron gas (2DEG) channels are utilized in an AlN/GaN/AlN/GaN heterostructure wherein the top 2DEG serves as a quasi-equipotential that screens potential fluctuations resulting from distributed surface and interface states. The bottom channel serves as the transistor's modulated channel. Dual-channel AlN/GaN heterostructures were grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. HEMTs fabricated with 300 nm long recessed gates demonstrated a gate lag ratio (GLR) of 0.88 with no degradation in drain currentmore » after bias stressed in subthreshold. These structures additionally achieved small signal metrics f{sub t}/f{sub max} of 27/46 GHz. These performance results are contrasted with the non-recessed gate dual-channel HEMT with a GLR of 0.74 and 82 mA/mm current collapse with f{sub t}/f{sub max} of 48/60 GHz.« less

Electron attachment to toluene in n-hexane and 2,2-dimethylbutane at high pressure

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

Itoh, Kengo; Nishikawa, Masaru; Holroyd, R.

The effect of dilute concentration of toluene on the electron mobility in two isometric hexanes was studied as a function of pressure from 1 bar to 3 kbar and at selected temperatures between 9 and 60[degrees]C. The effect of toluene on the mobility is small at 1 bar but quite large at the higher pressures. The results are interpreted in terms of reversible electron attachment to a toluene species which is the monomer in n-hexane. For this reaction [triangle]H[sub r] is - 12.0 kcal /mol in n-hexane at 2.5 kbar. In 2,2-dimethylbutane attachment to a dimeric species is indicated. Themore » volume changes for these attachment reactions are large, between [minus]80 and [minus]100 cm[sup 3]/mol. In hexane the volume changes are attributed in part to the electrostriction of the solvent by the toluene anion and in part to a positive molar volume of the electron. 19 refs., 8 figs., 3 tabs.« less

Low-temperature high-mobility amorphous IZO for silicon heterojunction solar cells

DOE PAGES

Morales-Masis, Monica; Martin De Nicolas, Silvia; Holovsky, Jakub; ...

2015-07-13

Parasitic absorption in the transparent conductive oxide (TCO) front electrode is one of the limitations of silicon heterojunction (SHJ) solar cells efficiency. To avoid such absorption while retaining high conductivity, TCOs with high electron mobility are preferred over those with high carrier density. Here, we demonstrate improved SHJ solar cell efficiencies by applying high-mobility amorphous indium zinc oxide (a-IZO) as the front TCO. We sputtered a-IZO at low substrate temperature and low power density and investigated the optical and electrical properties, as well as subband tail formation-quantified by the Urbach energy (E U)-as a function of the sputtering oxygen partialmore » pressure. We obtain an E U as low as 128 meV for films with the highest Hall mobility of 60 cm 2/Vs. When comparing the performance of a-IZO films with indium tin oxide (ITO) and hydrogenated indium oxide (IO:H), we find that IO:H (115 cm 2/Vs) exhibits a similar E U of 130 meV, while ITO (25 cm 2/Vs) presents a much larger E U of up to 270 meV. The high film quality, indicated by the low E U, the high mobility, and low free carrier absorption of the developed a-IZO electrodes, result in a significant current improvement, achieving conversion efficiencies over 21.5%, outperforming those with standard ITO.« less

AlN Surface Passivation of GaN-Based High Electron Mobility Transistors by Plasma-Enhanced Atomic Layer Deposition.

PubMed

Tzou, An-Jye; Chu, Kuo-Hsiung; Lin, I-Feng; Østreng, Erik; Fang, Yung-Sheng; Wu, Xiao-Peng; Wu, Bo-Wei; Shen, Chang-Hong; Shieh, Jia-Ming; Yeh, Wen-Kuan; Chang, Chun-Yen; Kuo, Hao-Chung

2017-12-01

We report a low current collapse GaN-based high electron mobility transistor (HEMT) with an excellent thermal stability at 150 °C. The AlN was grown by N 2 -based plasma enhanced atomic layer deposition (PEALD) and shown a refractive index of 1.94 at 633 nm of wavelength. Prior to deposit AlN on III-nitrides, the H 2 /NH 3 plasma pre-treatment led to remove the native gallium oxide. The X-ray photoelectron spectroscopy (XPS) spectroscopy confirmed that the native oxide can be effectively decomposed by hydrogen plasma. Following the in situ ALD-AlN passivation, the surface traps can be eliminated and corresponding to a 22.1% of current collapse with quiescent drain bias (V DSQ ) at 40 V. Furthermore, the high temperature measurement exhibited a shift-free threshold voltage (V th ), corresponding to a 40.2% of current collapse at 150 °C. The thermal stable HEMT enabled a breakdown voltage (BV) to 687 V at high temperature, promising a good thermal reliability under high power operation.

Nucleation-controlled low-temperature solid-phase crystallization for Sn-doped polycrystalline-Ge film on insulator with high carrier mobility (˜550 cm2/V s)

NASA Astrophysics Data System (ADS)

Xu, Chang; Gao, Hongmiao; Sugino, Takayuki; Miyao, Masanobu; Sadoh, Taizoh

2018-06-01

High-speed thin-film transistors (TFTs) are required to develop the next generation of electronics, such as three-dimensional large-scale integrated circuits and advanced system-in-displays. For this purpose, high-carrier-mobility semiconductor films on insulator structures should be fabricated with low-temperature processing conditions (≤500 °C). To achieve this, we investigate solid-phase crystallization of amorphous-GeSn (a-GeSn) films (Sn concentration: 2% and thickness: 50-200 nm) on insulating substrates, where thin a-Si under-layers (thickness: 0-20 nm) are introduced between a-GeSn films and insulating substrates. The GeSn films are polycrystallized by annealing (450 °C, 20 h) for all samples irrespective of a-GeSn and a-Si thickness conditions, while the Si films remain amorphous. Analysis of crystal structures of GeSn films (thickness: 50 nm) reveals that grain sizes decrease from ˜10 μm to 2-3 μm by the introduction of a-Si under-layers (thickness: 3-20 nm). This phenomenon is attributed to the change in dominant nucleation sites from the interface to the bulk, which significantly decreases grain-boundary scattering of carriers through a decrease in the barrier heights at grain boundaries. Bulk-nucleation further becomes dominant by increasing the GeSn film thickness. As a result, a high carrier mobility of ˜550 cm2/V s is realized for GeSn films (thickness: 100 nm) grown with a-Si under-layers. This mobility is the largest among ever reported data for Ge and GeSn grown on an insulator. This technique will facilitate realization of high-speed TFTs for use in the next generation of electronics.

Intrinsically stretchable and healable semiconducting polymer for organic transistors

NASA Astrophysics Data System (ADS)

Oh, Jin Young; Rondeau-Gagné, Simon; Chiu, Yu-Cheng; Chortos, Alex; Lissel, Franziska; Wang, Ging-Ji Nathan; Schroeder, Bob C.; Kurosawa, Tadanori; Lopez, Jeffrey; Katsumata, Toru; Xu, Jie; Zhu, Chenxin; Gu, Xiaodan; Bae, Won-Gyu; Kim, Yeongin; Jin, Lihua; Chung, Jong Won; Tok, Jeffrey B.-H.; Bao, Zhenan

2016-11-01

Thin-film field-effect transistors are essential elements of stretchable electronic devices for wearable electronics. All of the materials and components of such transistors need to be stretchable and mechanically robust. Although there has been recent progress towards stretchable conductors, the realization of stretchable semiconductors has focused mainly on strain-accommodating engineering of materials, or blending of nanofibres or nanowires into elastomers. An alternative approach relies on using semiconductors that are intrinsically stretchable, so that they can be fabricated using standard processing methods. Molecular stretchability can be enhanced when conjugated polymers, containing modified side-chains and segmented backbones, are infused with more flexible molecular building blocks. Here we present a design concept for stretchable semiconducting polymers, which involves introducing chemical moieties to promote dynamic non-covalent crosslinking of the conjugated polymers. These non-covalent crosslinking moieties are able to undergo an energy dissipation mechanism through breakage of bonds when strain is applied, while retaining high charge transport abilities. As a result, our polymer is able to recover its high field-effect mobility performance (more than 1 square centimetre per volt per second) even after a hundred cycles at 100 per cent applied strain. Organic thin-film field-effect transistors fabricated from these materials exhibited mobility as high as 1.3 square centimetres per volt per second and a high on/off current ratio exceeding a million. The field-effect mobility remained as high as 1.12 square centimetres per volt per second at 100 per cent strain along the direction perpendicular to the strain. The field-effect mobility of damaged devices can be almost fully recovered after a solvent and thermal healing treatment. Finally, we successfully fabricated a skin-inspired stretchable organic transistor operating under deformations that might be expected in a wearable device.

Intrinsically stretchable and healable semiconducting polymer for organic transistors.

PubMed

Oh, Jin Young; Rondeau-Gagné, Simon; Chiu, Yu-Cheng; Chortos, Alex; Lissel, Franziska; Wang, Ging-Ji Nathan; Schroeder, Bob C; Kurosawa, Tadanori; Lopez, Jeffrey; Katsumata, Toru; Xu, Jie; Zhu, Chenxin; Gu, Xiaodan; Bae, Won-Gyu; Kim, Yeongin; Jin, Lihua; Chung, Jong Won; Tok, Jeffrey B-H; Bao, Zhenan

2016-11-17

Thin-film field-effect transistors are essential elements of stretchable electronic devices for wearable electronics. All of the materials and components of such transistors need to be stretchable and mechanically robust. Although there has been recent progress towards stretchable conductors, the realization of stretchable semiconductors has focused mainly on strain-accommodating engineering of materials, or blending of nanofibres or nanowires into elastomers. An alternative approach relies on using semiconductors that are intrinsically stretchable, so that they can be fabricated using standard processing methods. Molecular stretchability can be enhanced when conjugated polymers, containing modified side-chains and segmented backbones, are infused with more flexible molecular building blocks. Here we present a design concept for stretchable semiconducting polymers, which involves introducing chemical moieties to promote dynamic non-covalent crosslinking of the conjugated polymers. These non-covalent crosslinking moieties are able to undergo an energy dissipation mechanism through breakage of bonds when strain is applied, while retaining high charge transport abilities. As a result, our polymer is able to recover its high field-effect mobility performance (more than 1 square centimetre per volt per second) even after a hundred cycles at 100 per cent applied strain. Organic thin-film field-effect transistors fabricated from these materials exhibited mobility as high as 1.3 square centimetres per volt per second and a high on/off current ratio exceeding a million. The field-effect mobility remained as high as 1.12 square centimetres per volt per second at 100 per cent strain along the direction perpendicular to the strain. The field-effect mobility of damaged devices can be almost fully recovered after a solvent and thermal healing treatment. Finally, we successfully fabricated a skin-inspired stretchable organic transistor operating under deformations that might be expected in a wearable device.

Electron and proton transfer in chloroplasts in silico. 2: The effect of diffusion limitations on the process of photosynthesis in spatially inhomogeneous thylakoids

NASA Astrophysics Data System (ADS)

Vershubskii, A. V.; Tikhonov, A. N.

2017-07-01

The lateral mobility of protons and mobile electron carriers (plastoquinone and plastocyanin) is subjected to diffusion limitations; the effect of these limitations on the kinetics of photoinduced pH i changes has been investigated in the present work for metabolic states 3 (conditions of intensive ATP synthesis) and 4 (the state of photosynthetic control). Computer simulations were based on a mathematical model of electron and proton transport in chloroplasts developed earlier by the authors. Non-uniform distribution of electron carriers and ATP synthase complexes in the membranes of grana and intergranal thylakoids was taken into account in the model. The kinetics of intrathylakoid pH i changes and the lateral profiles of distribution of the mobile electron transporters in granal and intergranal thylakoids were studied. The formation of non-uniform pH i profiles (with lumen acidification in the central parts of the grana being substantially slower than in the stromal thylakoids) was shown to occur under the conditions of ATP synthesis. Variation of the diffusion coefficients of intrathylakoid hydrogen ions and mobile electron carriers (plastoquinone and plastocyanin) can have substantial effects on the lateral pH i profiles and the redox state of the mobile electron carriers.

Diverse carrier mobility of monolayer BNC x : a combined density functional theory and Boltzmann transport theory study.

PubMed

Wu, Tao; Deng, Kaiming; Deng, Weiqiao; Lu, Ruifeng

2017-10-19

BNC x monolayer as a kind of two-dimensional material has numerous chemical atomic ratios and arrangements with different electronic structures. Via calculations on the basis of density functional theory and Boltzmann transport theory under deformation potential approximation, the band structures and carrier mobilities of BNC x (x  =  1,2,3,4) nanosheets are systematically investigated. The calculated results show that BNC 2 -1 is a material with very small band gap (0.02 eV) among all the structures while other BNC x monolayers are semiconductors with band gap ranging from 0.51 eV to 1.32 eV. The carrier mobility of BNC x varies considerably from tens to millions of cm 2 V -1 s -1 . For BNC 2 -1, the hole mobility and electron mobility along both x and y directions can reach 10 5 orders of magnitude, which is similar to the carrier mobility of graphene. Besides, all studied BNC x monolayers obviously have anisotropic hole mobility and electron mobility. In particular, for semiconductor BNC 4 , its hole mobility along the y direction and electron mobility along the x direction unexpectedly reach 10 6 orders of magnitude, even higher than that of graphene. Our findings suggest that BNC x layered materials with the proper ratio and arrangement of carbon atoms will possess desirable charge transport properties, exhibiting potential applications in nanoelectronic devices.

Diverse carrier mobility of monolayer BNC x : a combined density functional theory and Boltzmann transport theory study

NASA Astrophysics Data System (ADS)

Wu, Tao; Deng, Kaiming; Deng, Weiqiao; Lu, Ruifeng

2017-11-01

BNC x monolayer as a kind of two-dimensional material has numerous chemical atomic ratios and arrangements with different electronic structures. Via calculations on the basis of density functional theory and Boltzmann transport theory under deformation potential approximation, the band structures and carrier mobilities of BNC x (x  =  1,2,3,4) nanosheets are systematically investigated. The calculated results show that BNC2-1 is a material with very small band gap (0.02 eV) among all the structures while other BNC x monolayers are semiconductors with band gap ranging from 0.51 eV to 1.32 eV. The carrier mobility of BNC x varies considerably from tens to millions of cm2 V-1 s-1. For BNC2-1, the hole mobility and electron mobility along both x and y directions can reach 105 orders of magnitude, which is similar to the carrier mobility of graphene. Besides, all studied BNC x monolayers obviously have anisotropic hole mobility and electron mobility. In particular, for semiconductor BNC4, its hole mobility along the y direction and electron mobility along the x direction unexpectedly reach 106 orders of magnitude, even higher than that of graphene. Our findings suggest that BNC x layered materials with the proper ratio and arrangement of carbon atoms will possess desirable charge transport properties, exhibiting potential applications in nanoelectronic devices.

Correlation between mobility collapse and carbon impurities in Si-doped GaN grown by low pressure metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Kaess, Felix; Mita, Seiji; Xie, Jingqiao; Reddy, Pramod; Klump, Andrew; Hernandez-Balderrama, Luis H.; Washiyama, Shun; Franke, Alexander; Kirste, Ronny; Hoffmann, Axel; Collazo, Ramón; Sitar, Zlatko

2016-09-01

In the low doping range below 1 × 1017 cm-3, carbon was identified as the main defect attributing to the sudden reduction of the electron mobility, the electron mobility collapse, in n-type GaN grown by low pressure metalorganic chemical vapor deposition. Secondary ion mass spectroscopy has been performed in conjunction with C concentration and the thermodynamic Ga supersaturation model. By controlling the ammonia flow rate, the input partial pressure of Ga precursor, and the diluent gas within the Ga supersaturation model, the C concentration in Si-doped GaN was controllable from 6 × 1019 cm-3 to values as low as 2 × 1015 cm-3. It was found that the electron mobility collapsed as a function of free carrier concentration, once the Si concentration closely approached the C concentration. Lowering the C concentration to the order of 1015 cm-3 by optimizing Ga supersaturation achieved controllable free carrier concentrations down to 5 × 1015 cm-3 with a peak electron mobility of 820 cm2/V s without observing the mobility collapse. The highest electron mobility of 1170 cm2/V s was obtained even in metalorganic vapor deposition-grown GaN on sapphire substrates by optimizing growth parameters in terms of Ga supersaturation to reduce the C concentration.

Organic Power Electronics: Transistor Operation in the kA/cm2 Regime

PubMed Central

Klinger, Markus P.; Fischer, Axel; Kaschura, Felix; Widmer, Johannes; Kheradmand-Boroujeni, Bahman; Ellinger, Frank; Leo, Karl

2017-01-01

In spite of interesting features as flexibility, organic thin-film transistors have commercially lagged behind due to the low mobilities of organic semiconductors associated with hopping transport. Furthermore, organic transistors usually have much larger channel lengths than their inorganic counterparts since high-resolution structuring is not available in low-cost production schemes. Here, we present an organic permeable-base transistor (OPBT) which, despite extremely simple processing without any high-resolution structuring, achieve a performance beyond what has so far been possible using organic semiconductors. With current densities above 1 kA cm−2 and switching speeds towards 100 MHz, they open the field of organic power electronics. Finding the physical limits and an effective mobility of only 0.06 cm2 V−1 s−1, this OPBT device architecture has much more potential if new materials optimized for its geometry will be developed. PMID:28303924

Impact of recess etching and surface treatments on ohmic contacts regrown by molecular-beam epitaxy for AlGaN/GaN high electron mobility transistors

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

Joglekar, S.; Azize, M.; Palacios, T.

Ohmic contacts fabricated by regrowth of n{sup +} GaN are favorable alternatives to metal-stack-based alloyed contacts in GaN-based high electron mobility transistors. In this paper, the influence of reactive ion dry etching prior to regrowth on the contact resistance in AlGaN/GaN devices is discussed. We demonstrate that the dry etch conditions modify the surface band bending, dangling bond density, and the sidewall depletion width, which influences the contact resistance of regrown contacts. The impact of chemical surface treatments performed prior to regrowth is also investigated. The sensitivity of the contact resistance to the surface treatments is found to depend uponmore » the dangling bond density of the sidewall facets exposed after dry etching. A theoretical model has been developed in order to explain the observed trends.« less

Progressive failure site generation in AlGaN/GaN high electron mobility transistors under OFF-state stress: Weibull statistics and temperature dependence

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

Sun, Huarui, E-mail: huarui.sun@bristol.ac.uk; Bajo, Miguel Montes; Uren, Michael J.

2015-01-26

Gate leakage degradation of AlGaN/GaN high electron mobility transistors under OFF-state stress is investigated using a combination of electrical, optical, and surface morphology characterizations. The generation of leakage “hot spots” at the edge of the gate is found to be strongly temperature accelerated. The time for the formation of each failure site follows a Weibull distribution with a shape parameter in the range of 0.7–0.9 from room temperature up to 120 °C. The average leakage per failure site is only weakly temperature dependent. The stress-induced structural degradation at the leakage sites exhibits a temperature dependence in the surface morphology, which ismore » consistent with a surface defect generation process involving temperature-associated changes in the breakdown sites.« less

Organic Power Electronics: Transistor Operation in the kA/cm2 Regime.

PubMed

Klinger, Markus P; Fischer, Axel; Kaschura, Felix; Widmer, Johannes; Kheradmand-Boroujeni, Bahman; Ellinger, Frank; Leo, Karl

2017-03-17

In spite of interesting features as flexibility, organic thin-film transistors have commercially lagged behind due to the low mobilities of organic semiconductors associated with hopping transport. Furthermore, organic transistors usually have much larger channel lengths than their inorganic counterparts since high-resolution structuring is not available in low-cost production schemes. Here, we present an organic permeable-base transistor (OPBT) which, despite extremely simple processing without any high-resolution structuring, achieve a performance beyond what has so far been possible using organic semiconductors. With current densities above 1 kA cm -2 and switching speeds towards 100 MHz, they open the field of organic power electronics. Finding the physical limits and an effective mobility of only 0.06 cm 2  V -1  s -1 , this OPBT device architecture has much more potential if new materials optimized for its geometry will be developed.

Properties of Ir-based Ohmic contacts to AlGaN/GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Fitch, R. C.; Gillespie, J. K.; Moser, N.; Jenkins, T.; Sewell, J.; Via, D.; Crespo, A.; Dabiran, A. M.; Chow, P. P.; Osinsky, A.; La Roche, J. R.; Ren, F.; Pearton, S. J.

2004-03-01

Measurement of the electrical characteristics of 250 devices on the same 2 in. diameter wafer shows that Ti/Al/Ir/Au Ohmic contacts on AlGaN/GaN high electron mobility transistors (HEMTs) have lower average specific contact resistance after annealing at 850 °C for 30 s (4.6×10-5 Ω cm2) compared to more standard Ti/Al/Ni/Au contacts (2×10-4 Ω cm2). HEMTs with these Ir-based contacts also show average interdevice isolation currents approximately a factor of 2 lower, higher peak transconductance (134 mS/mm compared to 121 mS/mm), and higher device breakdown voltage (31 V compared to 23 V) than the devices with Ni-based contacts. This Ir-based contact metallurgy looks promising for applications requiring extended thermal stability of the HEMTs.

Comparison of gate and drain current detection of hydrogen at room temperature with AlGaN /GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Wang, Hung-Ta; Kang, B. S.; Ren, F.; Fitch, R. C.; Gillespie, J. K.; Moser, N.; Jessen, G.; Jenkins, T.; Dettmer, R.; Via, D.; Crespo, A.; Gila, B. P.; Abernathy, C. R.; Pearton, S. J.

2005-10-01

Pt-gated AlGaN /GaN high electron mobility transistors can be used as room-temperature hydrogen gas sensors at hydrogen concentrations as low as 100ppm. A comparison of the changes in drain and gate current-voltage (I-V) characteristics with the introduction of 500ppm H2 into the measurement ambient shows that monitoring the change in drain-source current provides a wider gate voltage operation range for maximum detection sensitivity and higher total current change than measuring the change in gate current. However, over a narrow gate voltage range, the relative sensitivity of detection by monitoring the gate current changes is up to an order of magnitude larger than that of drain-source current changes. In both cases, the changes are fully reversible in <2-3min at 25°C upon removal of the hydrogen from the ambient.

Perylene Diimide Based ``Nanofabric'' Thin Films for Organic Photovoltaic Cells

NASA Astrophysics Data System (ADS)

Carter, Austin; Park, June Hyoung; Min, Yong; Epstein, Arthur

2011-03-01

We report progress in using a perylene diimide (PDI) nanofabric as an effective electron accepting nanostructure for organic photovoltaics (OPV). A key challenge in OPV continues to be the recovery of electrons after charge separation due to the relatively poor mobility of C60 and related materials. A series of PDI compounds and complexes have been synthesized and used to fabricate nanofibers and thin films using solution and vacuum deposition techniques. Overlaping PDI-based nanofibers form a fast electron-transporting ``nanofabric'' that has been characterized (AFM, PL, UV-vis, etc.) and can be blended with electron donating materials. A solution-processible OPV configuration containing a nanofabric heterojunction (FHJ) of poly(3-hexylthiophene) and the PDI nanofabric was investigated. We observed a significant improvement in power-conversion efficiency due in part to expansion of the interfacial area and the presence of high mobility electron pathways to the LiF/Al electrode. This work is supported by the Wright Center for Photovoltaic Innovation and Commercialization, the Institute for Materials Research and the Center for Affordable Nanoengineering of Polymeric Biomedical Devices.

Electron and hole transport in ambipolar, thin film pentacene transistors

NASA Astrophysics Data System (ADS)

Saudari, Sangameshwar R.; Kagan, Cherie R.

2015-01-01

Solution-processed, ambipolar, thin-film pentacene field-effect transistors were employed to study both electron and hole transport simultaneously in a single, organic solid-state device. Electron and hole mobilities were extracted from the respective unipolar saturation regimes and show thermally activated behavior and gate voltage dependence. We fit the gate voltage dependent saturation mobility to a power law to extract the characteristic Meyer-Neldel (MN) energy, a measure of the width of the exponential distribution of localized states extending into the energy gap of the organic semiconductor. The MN energy is ˜78 and ˜28 meV for electrons and holes, respectively, which reflects a greater density of localized tail states for electrons than holes. This is consistent with the lower measured electron than hole mobility. For holes, the well-behaved linear regime allows for four-point probe measurement of the contact resistance independent mobility and separate characterization of the width of the localized density of states, yielding a consistent MN energy of 28 meV.

Surface morphology of Al0.3Ga0.7N/Al2O3-high electron mobility transistor structure.

PubMed

Cörekçi, S; Usanmaz, D; Tekeli, Z; Cakmak, M; Ozçelik, S; Ozbay, E

2008-02-01

We present surface properties of buffer films (AIN and GaN) and Al0.3Gao.zN/Al2O3-High Electron Mobility Transistor (HEMT) structures with/without AIN interlayer grown on High Temperature (HT)-AIN buffer/Al2O3 substrate and Al2O3 substrate. We have found that the GaN surface morphology is step-flow in character and the density of dislocations was about 10(8)-10(9) cm(-2). The AFM measurements also exhibited that the presence of atomic steps with large lateral step dimension and the surface of samples was smooth. The lateral step sizes are in the range of 100-250 nm. The typical rms values of HEMT structures were found as 0.27, 0.30, and 0.70 nm. HT-AIN buffer layer can have a significant impact on the surface morphology of Al0.3Ga0.7N/Al2O3-HEMT structures.

Large linear magnetoresistance in heavily-doped Nb:SrTiO3 epitaxial thin films

PubMed Central

Jin, Hyunwoo; Lee, Keundong; Baek, Seung-Hyub; Kim, Jin-Sang; Cheong, Byung-ki; Park, Bae Ho; Yoon, Sungwon; Suh, B. J.; Kim, Changyoung; Seo, S. S. A.; Lee, Suyoun

2016-01-01

Interaction between electrons has long been a focused topic in condensed-matter physics since it has led to the discoveries of astonishing phenomena, for example, high-Tc superconductivity and colossal magnetoresistance (CMR) in strongly-correlated materials. In the study of strongly-correlated perovskite oxides, Nb-doped SrTiO3 (Nb:SrTiO3) has been a workhorse not only as a conducting substrate, but also as a host possessing high carrier mobility. In this work, we report the observations of large linear magnetoresistance (LMR) and the metal-to-insulator transition (MIT) induced by magnetic field in heavily-doped Nb:STO (SrNb0.2Ti0.8O3) epitaxial thin films. These phenomena are associated with the interplay between the large classical MR due to high carrier mobility and the electronic localization effect due to strong spin-orbit coupling, implying that heavily Nb-doped Sr(Nb0.2Ti0.8)O3 is promising for the application in spintronic devices. PMID:27703222

Heteroepitaxial growth of In{sub 0.30}Ga{sub 0.70}As high-electron mobility transistor on 200 mm silicon substrate using metamorphic graded buffer

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

Kohen, David, E-mail: david.kohen@asm.com; Nguyen, Xuan Sang; Made, Riko I

We report on the growth of an In{sub 0.30}Ga{sub 0.70}As channel high-electron mobility transistor (HEMT) on a 200 mm silicon wafer by metal organic vapor phase epitaxy. By using a 3 μm thick buffer comprising a Ge layer, a GaAs layer and an InAlAs compositionally graded strain relaxing buffer, we achieve threading dislocation density of (1.0 ± 0.3) × 10{sup 7} cm{sup −2} with a surface roughness of 10 nm RMS. No phase separation was observed during the InAlAs compositionally graded buffer layer growth. 1.4 μm long channel length transistors are fabricated from the wafer with I{sub DS} of 70more » μA/μm and g{sub m} of above 60 μS/μm, demonstrating the high quality of the grown materials.« less

High carrier mobility in ultrapure diamond measured by time-resolved cyclotron resonance

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

Akimoto, Ikuko, E-mail: akimoto@sys.wakayama-u.ac.jp; Handa, Yushi; Fukai, Katsuyuki

2014-07-21

We have performed time-resolved cyclotron resonance measurements in ultrapure diamond crystals for the temperature range of T=7.3–40 K and obtained the temperature-dependent momentum relaxation times based on the cyclotron resonance widths for optically generated electrons and holes. The relaxation time follows a T{sup −3/2} law down to 12 K, which is expected for acoustic-phonon scattering without impurity effect because of the high purity of our samples. The deviation from the law at lower temperatures is explained by the impurity scattering and the breakdown of the high-temperature approximation for the phonon scattering. We extract the carrier drift mobility by using the directly measuredmore » effective masses and the relaxation times. The mobility at 10 K for 600 ns delay time after optical injection is found to be μ{sub e}=1.5×10{sup 6} cm{sup 2}/V s for the electrons, and μ{sub lh}=2.3×10{sup 6} cm{sup 2}/V s and  μ{sub hh}=2.4×10{sup 5} cm{sup 2}/V s for the light and heavy holes, respectively. These high values are achieved by our high-sensitivity detection for low-density carriers (at <10{sup 11} cm{sup −3}) free from the carrier-carrier scattering as well as by the suppression of the impurity scattering in the high-purity samples.« less

Carrier mobility enhancement of nano-crystalline semiconductor films: Incorporation of redox -relay species into the grain boundary interface

NASA Astrophysics Data System (ADS)

Desilva, L. A.; Bandara, T. M. W. J.; Hettiarachchi, B. H.; Kumara, G. R. A.; Perera, A. G. U.; Rajapaksa, R. M. G.; Tennakone, K.

Dye-sensitized and perovskite solar cells and other nanostructured heterojunction electronic devices require securing intimate electronic contact between nanostructured surfaces. Generally, the strategy is solution phase coating of a hole -collector over a nano-crystalline high-band gap n-type oxide semiconductor film painted with a thin layer of the light harvesting material. The nano-crystallites of the hole - collector fills the pores of the painted oxide surface. Most ills of these devices are associated with imperfect contact and high resistance of the hole conducting layer constituted of nano-crystallites. Denaturing of the delicate light harvesting material forbid sintering at elevated temperatures to reduce the grain boundary resistance. It is found that the interfacial and grain boundary resistance can be significantly reduced via incorporation of redox species into the interfaces to form ultra-thin layers. Suitable redox moieties, preferably bonded to the surface, act as electron transfer relays greatly reducing the film resistance offerring a promising method of enhancing the effective hole mobility of nano-crystalline hole-collectors and developing hole conductor paints for application in nanostructured devices.

A universal self-charging system driven by random biomechanical energy for sustainable operation of mobile electronics

PubMed Central

Niu, Simiao; Wang, Xiaofeng; Yi, Fang; Zhou, Yu Sheng; Wang, Zhong Lin

2015-01-01

Human biomechanical energy is characterized by fluctuating amplitudes and variable low frequency, and an effective utilization of such energy cannot be achieved by classical energy-harvesting technologies. Here we report a high-efficient self-charging power system for sustainable operation of mobile electronics exploiting exclusively human biomechanical energy, which consists of a high-output triboelectric nanogenerator, a power management circuit to convert the random a.c. energy to d.c. electricity at 60% efficiency, and an energy storage device. With palm tapping as the only energy source, this power unit provides a continuous d.c. electricity of 1.044 mW (7.34 W m−3) in a regulated and managed manner. This self-charging unit can be universally applied as a standard ‘infinite-lifetime' power source for continuously driving numerous conventional electronics, such as thermometers, electrocardiograph system, pedometers, wearable watches, scientific calculators and wireless radio-frequency communication system, which indicates the immediate and broad applications in personal sensor systems and internet of things. PMID:26656252

Study of the effects of GaN buffer layer quality on the dc characteristics of AlGaN/GaN high electron mobility transistors

DOE PAGES

Ahn, Shihyun; Zhu, Weidi; Dong, Chen; ...

2015-04-21

Here we studied the effect of buffer layer quality on dc characteristics of AlGaN/GaN high electron mobility (HEMTs). AlGaN/GaN HEMT structures with 2 and 5 μm GaN buffer layers on sapphire substrates from two different vendors with the same Al concentration of AlGaN were used. The defect densities of HEMT structures with 2 and 5 μm GaN buffer layer were 7 × 10 9 and 5 × 10 8 cm ₋2, respectively, as measured by transmission electron microscopy. There was little difference in drain saturation current or in transfer characteristics in HEMTs on these two types of buffer. However, theremore » was no dispersion observed on the nonpassivated HEMTs with 5 μm GaN buffer layer for gate-lag pulsed measurement at 100 kHz, which was in sharp contrast to the 71% drain current reduction for the HEMT with 2 μm GaN buffer layer.« less

Highly Sensitive Detection of Deoxyribonucleic Acid Hybridization Using Au-Gated AlInN/GaN High Electron Mobility Transistor-Based Sensors

NASA Astrophysics Data System (ADS)

Zhan, Xiang-Mi; Hao, Mei-Lan; Wang, Quan; Li, Wei; Xiao, Hong-Ling; Feng, Chun; Jiang, Li-Juan; Wang, Cui-Mei; Wang, Xiao-Liang; Wang, Zhan-Guo

2017-03-01

Gallium nitride- (GaN) based high electron mobility transistors (HEMTs) provide a good platform for biological detection. In this work, both Au-gated AlInN/GaN HEMT and AlGaN/GaN HEMT biosensors are fabricated for the detection of deoxyribonucleic acid (DNA) hybridization. The Au-gated AlInN/GaN HEMT biosensor exhibits higher sensitivity in comparison with the AlGaN/GaN HEMT biosensor. For the former, the drain-source current ( {V}{DS}=0.5 V) shows a clear decrease of 69 μA upon the introduction of 1 μmolL {}-1 (μM) complimentary DNA to the probe DNA at the sensor area, while for the latter it is only 38 μA. This current reduction is a notable indication of the hybridization. The high sensitivity can be attributed to the thinner barrier of the AlInN/GaN heterostructure, which makes the two-dimensional electron gas channel more susceptible to a slight change of the surface charge. Supported by the National Key Research and Development Program of China under Grant Nos 2016YFB0400104 and 2016YFB0400301, the National Natural Sciences Foundation of China under Grant No 61334002, and the National Science and Technology Major Project.

75 FR 4583 - In the Matter of: Certain Electronic Devices, Including Mobile Phones, Portable Music Players...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-28

..., Including Mobile Phones, Portable Music Players, and Computers; Notice of Investigation AGENCY: U.S... music players, and computers, by reason of infringement of certain claims of U.S. Patent Nos. 6,714,091... importation of certain electronic devices, including mobile phones, portable music players, or computers that...

Elimination of columnar microstructure in N-face InAlN, lattice-matched to GaN, grown by plasma-assisted molecular beam epitaxy in the N-rich regime

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

Ahmadi, Elaheh; Wienecke, Steven; Keller, Stacia

2014-02-17

The microstructure of N-face InAlN layers, lattice-matched to GaN, was investigated by scanning transmission electron microscopy and atom probe tomography. These layers were grown by plasma-assisted molecular beam epitaxy (PAMBE) in the N-rich regime. Microstructural analysis shows an absence of the lateral composition modulation that was previously observed in InAlN films grown by PAMBE. A room temperature two-dimensional electron gas (2DEG) mobility of 1100 cm{sup 2}/V s and 2DEG sheet charge density of 1.9 × 10{sup 13} cm{sup −2} was measured for N-face GaN/AlN/GaN/InAlN high-electron-mobility transistors with lattice-matched InAlN back barriers.

Inkjet printing of single-crystal films.

PubMed

Minemawari, Hiromi; Yamada, Toshikazu; Matsui, Hiroyuki; Tsutsumi, Jun'ya; Haas, Simon; Chiba, Ryosuke; Kumai, Reiji; Hasegawa, Tatsuo

2011-07-13

The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science. Whether based on inorganic or organic materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has recently been focused on developing simple ways of producing electronic devices by means of printing technologies. 'Printed electronics' is being explored for the manufacture of large-area and flexible electronic devices by the patterned application of functional inks containing soluble or dispersed semiconducting materials. However, because of the strong self-organizing tendency of the deposited materials, the production of semiconducting thin films of high crystallinity (indispensable for realizing high carrier mobility) may be incompatible with conventional printing processes. Here we develop a method that combines the technique of antisolvent crystallization with inkjet printing to produce organic semiconducting thin films of high crystallinity. Specifically, we show that mixing fine droplets of an antisolvent and a solution of an active semiconducting component within a confined area on an amorphous substrate can trigger the controlled formation of exceptionally uniform single-crystal or polycrystalline thin films that grow at the liquid-air interfaces. Using this approach, we have printed single crystals of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C(8)-BTBT) (ref. 15), yielding thin-film transistors with average carrier mobilities as high as 16.4 cm(2) V(-1) s(-1). This printing technique constitutes a major step towards the use of high-performance single-crystal semiconductor devices for large-area and flexible electronics applications.

Imaging Gallium Nitride High Electron Mobility Transistors to Identify Point Defects

DTIC Science & Technology

2014-03-01

streamline the sample preparation procedure to maximize the yield of successful samples to be analyzed chemically in an energy dispersive spectrometry...transmission electron microscope (STEM), sample preparation 15. NUMBER OF PAGES 103 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT...Computer Engineering iii THIS PAGE INTENTIONALLY LEFT BLANK iv ABSTRACT The purpose of this thesis is to streamline the sample preparation

Magnetization processes and existence of reentrant phase transitions in coupled spin-electron model on doubly decorated planar lattices

NASA Astrophysics Data System (ADS)

Čenčariková, Hana; Strečka, Jozef; Gendiar, Andrej

2018-04-01

An alternative model for a description of magnetization processes in coupled 2D spin-electron systems has been introduced and rigorously examined using the generalized decoration-iteration transformation and the corner transfer matrix renormalization group method. The model consists of localized Ising spins placed on nodal lattice sites and mobile electrons delocalized over the pairs of decorating sites. It takes into account a hopping term for mobile electrons, the Ising coupling between mobile electrons and localized spins as well as the Zeeman term acting on both types of particles. The ground-state and finite-temperature phase diagrams were established and comprehensively analyzed. It was found that the ground-state phase diagrams are very rich depending on the electron hopping and applied magnetic field. The diversity of magnetization curves can be related to intermediate magnetization plateaus, which may be continuously tuned through the density of mobile electrons. In addition, the existence of several types of reentrant phase transitions driven either by temperature or magnetic field was proven.

Universal Correlation between Flatband Voltage and Electron Mobility in TiN/HfSiON Devices with MgO or La2O3 Incorporation and Stack Variation

NASA Astrophysics Data System (ADS)

Mise, Nobuyuki; Kadoshima, Masaru; Morooka, Tetsu; Eimori, Takahisa; Nara, Yasuo; Ohji, Yuzuru

2008-10-01

We investigated the controversial effective workfunction and electron mobility of TiN/HfSiON devices by intentionally adding MgO or La2O3 into HfSiON and by changing the material on TiN or the TiN thickness. As a result, we found a close relationship between the electron mobility at low effective field and the flatband voltage. This relationship is explained on the basis of the fixed charge in HfSiON and its neutralization. The intrinsic workfunction of TiN/HfSiON without charge is determined to be 4.3 eV from the flatband voltage when the electron mobility at low effective field is the highest.

Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics.

PubMed

Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Jaung, Jae Yun; Kim, Yong-Hoon; Park, Sung Kyu

2015-09-28

The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.

Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics

NASA Astrophysics Data System (ADS)

Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Yun Jaung, Jae; Kim, Yong-Hoon; Kyu Park, Sung

2015-09-01

The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.