Sensitive thermal microsensor with pn junction for heat measurement of a single cell

NASA Astrophysics Data System (ADS)

Yamada, Taito; Inomata, Naoki; Ono, Takahito

2016-02-01

A sensitive thermal microsensor based on a pn junction diode for heat measurements of biological single cells is developed and evaluated. Using a fabricated device, we demonstrated the heat measurement of a single brown fat cell. The principle of the sensor relies on the temperature dependence of the pn junction diode resistance. This method has a capability of the highly thermal sensitivity by downsizing and the advantage of a simple experimental setup using electrical circuits without any special equipment. To achieve highly sensitive heat measurement of single cells, downsizing of the sensor is necessary to reduce the heat capacity of the sensor itself. The sensor with the pn junction diode can be downsized by microfabrication. A bridge beam structure with the pn junction diode as a thermal sensor is placed in vacuum using a microfludic chip to decrease the heat loss to the surroundings. A temperature coefficient of resistance of 1.4%/K was achieved. The temperature and thermal resolutions of the fabricated device are 1.1 mK and 73.6 nW, respectively. The heat measurements of norepinephrine stimulated and nonstimulated single brown fat cells were demonstrated, and different behaviors in heat generation were observed.

Current-voltage characteristics of n-AlMgZnO/p-GaN junction diodes

NASA Astrophysics Data System (ADS)

Hsueh, Kuang-Po; Cheng, Po-Wei; Cheng, Yi-Chang; Sheu, Jinn-Kong; Yeh, Yu-Hsiang; Chiu, Hsien-Chin; Wang, Hsiang-Chun

2013-03-01

This study investigates the temperature dependence of the current-voltage (I-V) characteristics of Al-doped MgxZn1-xO/p-GaN junction diodes. Specifically, this study reports the deposition of n-type Al-doped MgxZn1-xO (AMZO) films on p-GaN using a radio-frequency (RF) magnetron sputtering system followed by annealing at 700, 800, 900, and 1000 °C in a nitrogen ambient for 60 seconds, respectively. The AMZO/GaN films were thereafter analyzed using Hall measurement and the x-ray diffraction (XRD) patterns. The XRD results show that the diffraction angles of the annealed AMZO films remain the same as that of GaN without shifting. The n-AMZO/p-GaN diode with 900 °C annealing had the lowest leakage current in forward and reverse bias. However, the leakage current of the diodes did not change significantly with an increase in annealing temperatures. These findings show that the n-AMZO/p-GaN junction diode is feasible for GaN-based heterojunction bipolar transistors (HBTs) and UV light-emitting diodes (LEDs).

Electrical characterization of ZnO/NiO p-n junction prepared by the sol-gel method

NASA Astrophysics Data System (ADS)

Merih Akyuzlu, A.; Dagdelen, Fethi; Gultek, Ahmet; Hendi, A. A.; Yakuphanoglu, Fahrettin

2017-04-01

ZnO and NiO films were synthesized on fluourine-doped tin oxide (FTO) glass substrate by the sol-gel method. The surface morphology of the films was investigated by atomic force microscopy. The optical band gaps of the ZnO and NiO films were found to be 3.198 and 3.827eV, respectively. A ZnO/NiO p-n junction diode was prepared and electrical charge transport mechanism of the diode was analyzed using thermionic emission and Norde functions. The ideality factor, barrier height and series resistance of the diode were determined to be 6.46, 1.036eV and 39.1 M {Ω} , respectively. The obtained results indicate that ZnO/NiO p-n junction can be used as transparent diode for optic communications.

InGaN/GaN tunnel junctions for hole injection in GaN light emitting diodes

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

Krishnamoorthy, Sriram, E-mail: krishnamoorthy.13@osu.edu, E-mail: rajan@ece.osu.edu; Akyol, Fatih; Rajan, Siddharth, E-mail: krishnamoorthy.13@osu.edu, E-mail: rajan@ece.osu.edu

InGaN/GaN tunnel junction contacts were grown using plasma assisted molecular beam epitaxy (MBE) on top of a metal-organic chemical vapor deposition (MOCVD)-grown InGaN/GaN blue (450 nm) light emitting diode. A voltage drop of 5.3 V at 100 mA, forward resistance of 2 × 10{sup −2} Ω cm{sup 2}, and a higher light output power compared to the reference light emitting diodes (LED) with semi-transparent p-contacts were measured in the tunnel junction LED (TJLED). A forward resistance of 5 × 10{sup −4} Ω cm{sup 2} was measured in a GaN PN junction with the identical tunnel junction contact as the TJLED, grown completely by MBE. Themore » depletion region due to the impurities at the regrowth interface between the MBE tunnel junction and the MOCVD-grown LED was hence found to limit the forward resistance measured in the TJLED.« less

Deep diode arrays for X-ray detection

NASA Technical Reports Server (NTRS)

Zemel, J. N.

1984-01-01

Temperature gradient zone melting process was used to form p-n junctions in bulk of high purity silicon wafers. These diodes were patterned to form arrays for X-ray spectrometers. The whole fabrication processes for these X-ray detectors are reviewed in detail. The p-n junctions were evaluated by (1) the dark diode I-V measurements, (2) the diode C sub I - V measurements, and (3) the MOS C-V measurements. The results showed that these junctions were linearly graded in charge distribution with low reverse bias leakage current flowing through them (few nA at -10 volts). The X-ray detection experiments showed that an FWHM of 500 eV was obtained from these diodes with a small bias of just -5 volts (for X-ray source Fe55). A theoretical model was proposed to explain the extra peaks found in the energy spectra and a very interesting point - cross talk effect was pointed out. This might be a solution to the problem of making really high resolution X-ray spectrometers.

Coupling characteristics of thin-film metal-oxide-metal diodes at 10.6 microns

NASA Technical Reports Server (NTRS)

Wang, S. Y.; Gustafson, T. K.; Izawa, T.

1975-01-01

Direct detection experiments have demonstrated the coherent coupling of 10.6 micrometer radiation into photolithographically fabricated metal-oxide-metal tunnel junctions. A CO2 laser beam mechanically chopped at 1 KHz was focused at a variable angle of incidence with a power density of about 10 W/sq cm at the diodes. Diodes in which the junction resistance was much greater than the lead resistance displayed angular characteristics dominated by coherent antenna coupling.

Investigation on a radiation tolerant betavoltaic battery based on Schottky barrier diode.

PubMed

Liu, Yebing; Hu, Rui; Yang, Yuqing; Wang, Guanquan; Luo, Shunzhong; Liu, Ning

2012-03-01

An Au-Si Schottky barrier diode was studied as the energy conversion device of betavoltaic batteries. Its electrical performance under radiation of Ni-63 and H-3 sources and radiation degradation under Am-241 were investigated and compared with those of the p-n junction. The results show that the Schottky diode had a higher I(sc) and harder radiation tolerance but lower V(oc) than the p-n junction. The results indicated that the Schottky diode can be a promising candidate for energy conversion of betavoltaic batteries. Copyright © 2011 Elsevier Ltd. All rights reserved.

Achievement of high diode sensitivity via spin torque-induced resonant expulsion in vortex magnetic tunnel junction

NASA Astrophysics Data System (ADS)

Tsunegi, Sumito; Taniguchi, Tomohiro; Yakushiji, Kay; Fukushima, Akio; Yuasa, Shinji; Kubota, Hitoshi

2018-05-01

We investigated the spin-torque diode effect in a magnetic tunnel junction with FeB free layer. Vortex-core expulsion was observed near the boundary between vortex and uniform states. A high diode voltage of 24 mV was obtained with alternative input power of 0.3 µW, corresponding to huge diode sensitivity of 80,000 mV/mW. In the expulsion region, a broad peak in the high frequency region was observed, which is attributed to the weak excitation of uniform magnetization by thermal noise. The high diode sensitivity is of great importance for device applications such as telecommunications, radar detectors, and high-speed magnetic-field sensors.

High sensitivity Schottky junction diode based on monolithically grown aligned polypyrrole nanofibers: Broad range detection of m-dihydroxybenzene.

PubMed

Ameen, Sadia; Akhtar, M Shaheer; Seo, Hyung-Kee; Shin, Hyung Shik

2015-07-30

Aligned p-type polypyrrole (PPy) nanofibers (NFs) thin film was grown on n-type silicon (100) substrate by an electrochemical technique to fabricate Schottky junction diode for the efficient detection of m-dihydroxybenzene chemical. The highly dense and well aligned PPy NFs with the average diameter (∼150-200 nm) were grown on n-type Si substrate. The formation of aligned PPy NFs was confirmed by elucidating the structural, compositional and the optical properties. The electrochemical behavior of the fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode was evaluated by cyclovoltametry (CV) and current (I)-voltage (V) measurements with the variation of m-dihydroxybenzene concentration in the phosphate buffer solution (PBS). The fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode exhibited the rectifying behavior of I-V curve with the addition of m-dihydroxybenzene chemical, while a weak rectifying I-V behavior was observed without m-dihydroxybenzene chemical. This non-linear I-V behavior suggested the formation of Schottky barrier at the interface of Pt layer and p-aligned PPy NFs/n-silicon thin film layer. By analyzing the I-V characteristics, the fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode displayed reasonably high sensitivity ∼23.67 μAmM(-1)cm(-2), good detection limit of ∼1.51 mM with correlation coefficient (R) of ∼0.9966 and short response time (10 s). Copyright © 2015 Elsevier B.V. All rights reserved.

Fabrication and characterization of magnetically tunable metal-semiconductor schottky diode using barium hexaferrite thin film on gold

NASA Astrophysics Data System (ADS)

Kaur, Jotinder; Sharma, Vinay; Sharma, Vipul; Veerakumar, V.; Kuanr, Bijoy K.

2016-05-01

Barium Hexaferrite (BaM) is an extensively studied magnetic material due to its potential device application. In this paper, we study Schottky junction diodes fabricated using gold and BaM and demonstrate the function of a spintronic device. Gold (50 nm)/silicon substrate was used to grow the BaM thin films (100-150 nm) using pulsed laser deposition. I-V characteristics were measured on the Au/BaM structure sweeping the voltage from ±5 volts. The forward and reverse bias current-voltage curves show diode like rectifying characteristics. The threshold voltage decreases while the output current increases with increase in the applied external magnetic field showing that the I-V characteristics of the BaM based Schottky junction diodes can be tuned by external magnetic field. It is also demonstrated that, the fabricated Schottky diode can be used as a half-wave rectifier, which could operate at high frequencies in the range of 1 MHz compared to the regular p-n junction diodes, which rectify below 10 kHz. In addition, it is found that above 1 MHz, Au/BaM diode can work as a rectifier as well as a capacitor filter, making the average (dc) voltage much larger.

Leakage current reduction of vertical GaN junction barrier Schottky diodes using dual-anode process

NASA Astrophysics Data System (ADS)

Hayashida, Tetsuro; Nanjo, Takuma; Furukawa, Akihiko; Watahiki, Tatsuro; Yamamuka, Mikio

2018-04-01

The origin of the leakage current of a trench-type vertical GaN diode was discussed. We found that the edge of p-GaN is the main leakage spot. To reduce the reverse leakage current at the edge of p-GaN, a dual-anode process was proposed. As a result, the reverse blocking voltage defined at the leakage current density of 1 mA/cm2 of a vertical GaN junction barrier Schottky (JBS) diode was improved from 780 to 1,190 V, which is the highest value ever reported for vertical GaN Schottky barrier diodes (SBDs).

Nitride-based stacked laser diodes with a tunnel junction

NASA Astrophysics Data System (ADS)

Okawara, Satoru; Aoki, Yuta; Kuwabara, Masakazu; Takagi, Yasufumi; Maeda, Junya; Yoshida, Harumasa

2018-01-01

We report on nitride-based two-stack laser diodes with a tunnel junction for the first time. The stacked laser diode was monolithically grown by metalorganic vapor phase epitaxy. It was confirmed that the two-stack InGaN/GaN multiple-quantum-well laser diode with an emission wavelength of 394 nm exhibited laser oscillation up to a peak output power of over 10 W in the pulsed current mode. The upper and lower emitters of the device were capable of lasing at different threshold currents of 2.4 and 5.2 A with different slope efficiencies of 0.8 and 0.3 W/A, respectively.

InGaP alpha voltaic batteries: Synthesis, modeling, and radiation tolerance

NASA Astrophysics Data System (ADS)

Cress, Cory D.; Landi, Brian J.; Raffaelle, Ryne P.; Wilt, David M.

2006-12-01

The viability of InGaP diodes coupled with α-particle sources as radioisotope power supplies is investigated both theoretically and experimentally. The electrical power output of epitaxially grown InGaP p-type/n-type (p/n) junction diodes coupled with Am241 and Po210 α-particle sources was measured. A theoretical model was developed that determines the α-particle energy deposition profile within an InGaP diode when irradiated by an omnidirectional α-particle source. The results of the model illustrate the dramatic influence the radiation source/diode configuration has on the α-particle energy deposition profile within a device. Progress has been shown towards increasing the radiation tolerance of the InGaP devices, which included utilizing an intrinsic region and reducing the junction thickness. Introduction of the intrinsic region within a conventional n /p diode to form a n-type/intrinsic/p-type diode enabled the device to withstand a ten times greater fluence of 4.2MeV α particles before decreasing to 50% of its original power output under simulated air mass zero illumination, when compared to an abrupt junction device with the same active region thickness.

Towards molecular electronics with large-area molecular junctions.

PubMed

Akkerman, Hylke B; Blom, Paul W M; de Leeuw, Dago M; de Boer, Bert

2006-05-04

Electronic transport through single molecules has been studied extensively by academic and industrial research groups. Discrete tunnel junctions, or molecular diodes, have been reported using scanning probes, break junctions, metallic crossbars and nanopores. For technological applications, molecular tunnel junctions must be reliable, stable and reproducible. The conductance per molecule, however, typically varies by many orders of magnitude. Self-assembled monolayers (SAMs) may offer a promising route to the fabrication of reliable devices, and charge transport through SAMs of alkanethiols within nanopores is well understood, with non-resonant tunnelling dominating the transport mechanism. Unfortunately, electrical shorts in SAMs are often formed upon vapour deposition of the top electrode, which limits the diameter of the nanopore diodes to about 45 nm. Here we demonstrate a method to manufacture molecular junctions with diameters up to 100 microm with high yields (> 95 per cent). The junctions show excellent stability and reproducibility, and the conductance per unit area is similar to that obtained for benchmark nanopore diodes. Our technique involves processing the molecular junctions in the holes of a lithographically patterned photoresist, and then inserting a conducting polymer interlayer between the SAM and the metal top electrode. This simple approach is potentially low-cost and could pave the way for practical molecular electronics.

Graded junction termination extensions for electronic devices

NASA Technical Reports Server (NTRS)

Merrett, J. Neil (Inventor); Isaacs-Smith, Tamara (Inventor); Sheridan, David C. (Inventor); Williams, John R. (Inventor)

2006-01-01

A graded junction termination extension in a silicon carbide (SiC) semiconductor device and method of its fabrication using ion implementation techniques is provided for high power devices. The properties of silicon carbide (SiC) make this wide band gap semiconductor a promising material for high power devices. This potential is demonstrated in various devices such as p-n diodes, Schottky diodes, bipolar junction transistors, thyristors, etc. These devices require adequate and affordable termination techniques to reduce leakage current and increase breakdown voltage in order to maximize power handling capabilities. The graded junction termination extension disclosed is effective, self-aligned, and simplifies the implementation process.

Graded junction termination extensions for electronic devices

NASA Technical Reports Server (NTRS)

Merrett, J. Neil (Inventor); Isaacs-Smith, Tamara (Inventor); Sheridan, David C. (Inventor); Williams, John R. (Inventor)

2007-01-01

A graded junction termination extension in a silicon carbide (SiC) semiconductor device and method of its fabrication using ion implementation techniques is provided for high power devices. The properties of silicon carbide (SiC) make this wide band gap semiconductor a promising material for high power devices. This potential is demonstrated in various devices such as p-n diodes, Schottky diodes, bipolar junction transistors, thyristors, etc. These devices require adequate and affordable termination techniques to reduce leakage current and increase breakdown voltage in order to maximize power handling capabilities. The graded junction termination extension disclosed is effective, self-aligned, and simplifies the implementation process.

Electrical isolation of component cells in monolithically interconnected modules

DOEpatents

Wanlass, Mark W.

2001-01-01

A monolithically interconnected photovoltaic module having cells which are electrically connected which comprises a substrate, a plurality of cells formed over the substrate, each cell including a primary absorber layer having a light receiving surface and a p-region, formed with a p-type dopant, and an n-region formed with an n-type dopant adjacent the p-region to form a single pn-junction, and a cell isolation diode layer having a p-region, formed with a p-type dopant, and an n-region formed with an n-type dopant adjacent the p-region to form a single pn-junction, the diode layer intervening the substrate and the absorber layer wherein the absorber and diode interfacial regions of a same conductivity type orientation, the diode layer having a reverse-breakdown voltage sufficient to prevent inter-cell shunting, and each cell electrically isolated from adjacent cells with a vertical trench trough the pn-junction of the diode layer, interconnects disposed in the trenches contacting the absorber regions of adjacent cells which are doped an opposite conductivity type, and electrical contacts.

Process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction

DOEpatents

Toet, Daniel; Sigmon, Thomas W.

2004-12-07

A process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction for use in advanced magnetic random access memory (MRAM) cells for high performance, non-volatile memory arrays. The process is based on pulsed laser processing for the fabrication of vertical polycrystalline silicon electronic device structures, in particular p-n junction diodes, on films of metals deposited onto low temperature-substrates such as ceramics, dielectrics, glass, or polymers. The process preserves underlayers and structures onto which the devices are typically deposited, such as silicon integrated circuits. The process involves the low temperature deposition of at least one layer of silicon, either in an amorphous or a polycrystalline phase on a metal layer. Dopants may be introduced in the silicon film during or after deposition. The film is then irradiated with short pulse laser energy that is efficiently absorbed in the silicon, which results in the crystallization of the film and simultaneously in the activation of the dopants via ultrafast melting and solidification. The silicon film can be patterned either before or after crystallization.

Process For Direct Integration Of A Thin-Film Silicon P-N Junction Diode With A Magnetic Tunnel Junction

DOEpatents

Toet, Daniel; Sigmon, Thomas W.

2005-08-23

A process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction for use in advanced magnetic random access memory (MRAM) cells for high performance, non-volatile memory arrays. The process is based on pulsed laser processing for the fabrication of vertical polycrystalline silicon electronic device structures, in particular p-n junction diodes, on films of metals deposited onto low temperature-substrates such as ceramics, dielectrics, glass, or polymers. The process preserves underlayers and structures onto which the devices are typically deposited, such as silicon integrated circuits. The process involves the low temperature deposition of at least one layer of silicon, either in an amorphous or a polycrystalline phase on a metal layer. Dopants may be introduced in the silicon film during or after deposition. The film is then irradiated with short pulse laser energy that is efficiently absorbed in the silicon, which results in the crystallization of the film and simultaneously in the activation of the dopants via ultrafast melting and solidification. The silicon film can be patterned either before or after crystallization.

Process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction

DOEpatents

Toet, Daniel; Sigmon, Thomas W.

2003-01-01

A process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction for use in advanced magnetic random access memory (MRAM) cells for high performance, non-volatile memory arrays. The process is based on pulsed laser processing for the fabrication of vertical polycrystalline silicon electronic device structures, in particular p-n junction diodes, on films of metals deposited onto low temperature-substrates such as ceramics, dielectrics, glass, or polymers. The process preserves underlayers and structures onto which the devices are typically deposited, such as silicon integrated circuits. The process involves the low temperature deposition of at least one layer of silicon, either in an amorphous or a polycrystalline phase on a metal layer. Dopants may be introduced in the silicon film during or after deposition. The film is then irradiated with short pulse laser energy that is efficiently absorbed in the silicon, which results in the crystallization of the film and simultaneously in the activation of the dopants via ultrafast melting and solidification. The silicon film can be patterned either before or after crystallization.

Hybrid tunnel junction contacts to III-nitride light-emitting diodes

NASA Astrophysics Data System (ADS)

Young, Erin C.; Yonkee, Benjamin P.; Wu, Feng; Oh, Sang Ho; DenBaars, Steven P.; Nakamura, Shuji; Speck, James S.

2016-02-01

In this work, we demonstrate highly doped GaN p-n tunnel junction (TJ) contacts on III-nitride heterostructures where the active region of the device and the top p-GaN layers were grown by metal organic chemical vapor deposition and highly doped n-GaN was grown by NH3 molecular beam epitaxy to form the TJ. The regrowth interface in these hybrid devices was found to have a high concentration of oxygen, which likely enhanced tunneling through the diode. For optimized regrowth, the best tunnel junction device had a total differential resistivity of 1.5 × 10-4 Ω cm2, including contact resistance. As a demonstration, a blue-light-emitting diode on a (20\\bar{2}\\bar{1}) GaN substrate with a hybrid tunnel junction and an n-GaN current spreading layer was fabricated and compared with a reference sample with a transparent conducting oxide (TCO) layer. The tunnel junction LED showed a lower forward operating voltage and a higher efficiency at a low current density than the TCO LED.

Thermal characterization of GaN-based laser diodes by forward-voltage method

NASA Astrophysics Data System (ADS)

Feng, M. X.; Zhang, S. M.; Jiang, D. S.; Liu, J. P.; Wang, H.; Zeng, C.; Li, Z. C.; Wang, H. B.; Wang, F.; Yang, H.

2012-05-01

An expression of the relation between junction temperature and forward voltage common for both GaN-based laser diodes (LDs) and light emitting diodes is derived. By the expression, the junction temperature of GaN-based LDs emitting at 405 nm was measured at different injection current and compared with the result of micro-Raman spectroscopy, showing that the expression is reasonable. In addition, the activation energy of Mg in AlGaN/GaN superlattice layers is obtained based on the temperature dependence of forward voltage.

The dependence of Schottky junction (I-V) characteristics on the metal probe size in nano metal-semiconductor contacts

NASA Astrophysics Data System (ADS)

Rezeq, Moh'd.; Ali, Ahmed; Patole, Shashikant P.; Eledlebi, Khouloud; Dey, Ripon Kumar; Cui, Bo

2018-05-01

We have studied the dependence of Schottky junction (I-V) characteristics on the metal contact size in metal-semiconductor (M-S) junctions using different metal nanoprobe sizes. The results show strong dependence of (I-V) characteristics on the nanoprobe size when it is in contact with a semiconductor substrate. The results show the evolution from sub-10 nm reversed Schottky diode behavior to the normal diode behavior at 100 nm. These results also indicate the direct correlation between the electric field at the M-S interface and the Schottky rectification behavior. The effect of the metal contact size on nano-Schottky diode structure is clearly demonstrated, which would help in designing a new type of nano-devices at sub-10 nm scale.

Research and Development of Silicon Carbide (SiC) Junction Recovery Diodes for Picosecond Range, High Power Opening Switches

NASA Astrophysics Data System (ADS)

Grekhov, Igor V.

2002-07-01

This report results from a contract tasking Ioffe Institute as follows: The purpose of the proposed project is to develop, fabricate, test, and characterize silicon carbide power semiconductor opening switches operating in the picosecond range of switch time. Special SiC diode structures will be fabricated and investigated, including Junction Recovery Diodes (JRD). The operation of such diodes is founded on the superfast recovery of the junction's blocking ability after switching the device from forward to reverse bias conditions. Our estimations show that the parameters of JRD devices can be substantially improved in case of SiC devices, compared to both Si and GaAs capabilities. We expect i) to increase the speed of switch operation, the specific commutated power, and the operation frequency repetition; ii) to reduce the weight and size of pulse devices; and iii) to achieve better reliability of the devices due to the unique thermal conductivity and radiation hardness of SiC.

Coupling Two-Dimensional MoTe2 and InGaZnO Thin-Film Materials for Hybrid PN Junction and CMOS Inverters.

PubMed

Lee, Han Sol; Choi, Kyunghee; Kim, Jin Sung; Yu, Sanghyuck; Ko, Kyeong Rok; Im, Seongil

2017-05-10

We report the fabrication of hybrid PN junction diode and complementary (CMOS) inverters, where 2D p-type MoTe 2 and n-type thin film InGaZnO (IGZO) are coupled for each device process. IGZO thin film was initially patterned by conventional photolithography either for n-type material in a PN diode or for n-channel of top-gate field-effect transistors (FET) in CMOS inverter. The hybrid PN junction diode shows a good ideality factor of 1.57 and quite a high ON/OFF rectification ratio of ∼3 × 10 4 . Under photons, our hybrid PN diode appeared somewhat stable only responding to high-energy photons of blue and ultraviolet. Our 2D nanosheet-oxide film hybrid CMOS inverter exhibits voltage gains as high as ∼40 at 5 V, low power consumption less than around a few nW at 1 V, and ∼200 μs switching dynamics.

Electrical properties of epitaxial 3C- and 6H-SiC p-n junction diodes produced side-by-side on 6H-SiC substrates

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Larkin, David J.; Starr, Jonathan E.; Powell, J. Anthony; Salupo, Carl S.; Matus, Lawrence G.

1994-01-01

3C-SiC (beta-SiC) and 6H-SiC p-n junction diodes have been fabricated in regions of both 3C-SiC and 6H-SiC epitaxial layers which were grown side-by-side on low-tilt-angle 6H-SiC substrates via a chemical vapor deposition (CVD) process. Several runs of diodes exhibiting state-of-the-art electrical characteristics were produced, and performance characteristics were measured and compared as a function of doping, temperature, and polytype. The first 3C-SiC diodes which rectify to reverse voltages in excess of 300 V were characterized, representing a six-fold blocking voltage improvement over experimental 3C-SiC diodes produced by previous techniques. When placed under sufficient forward bias, the 3C-SiC diodes emit significantly bright green-yellow light while the 6H-SiC diodes emit in the blue-violet. The 6H-SiC p-n junction diodes represent the first reported high-quality 6H-SiC devices to be grown by CVD on very low-tilt-angle (less than 0.5 deg off the (0001) silicon face) 6H substrates. The reverse leakage current of a 200 micron diameter circular device at 1100 V reverse bias was less than 20 nA at room temperature, and excellent rectification characteristics were demonstrated at the peak characterization temperature of 400 C.

Investigating Bandgap Energies, Materials, and Design of Light-Emitting Diodes

ERIC Educational Resources Information Center

Wagner, Eugene P., II

2016-01-01

A student laboratory experiment to investigate the intrinsic and extrinsic bandgaps, dopant materials, and diode design in light-emitting diodes (LEDs) is presented. The LED intrinsic bandgap is determined by passing a small constant current through the diode and recording the junction voltage variation with temperature. A second visible…

Reconfigurable p-n junction diodes and the photovoltaic effect in exfoliated MoS{sub 2} films

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

Sutar, Surajit; Agnihotri, Pratik; Comfort, Everett

2014-03-24

Realizing basic semiconductor devices such as p-n junctions are necessary for developing thin-film and optoelectronic technologies in emerging planar materials such as MoS{sub 2}. In this work, electrostatic doping by buried gates is used to study the electronic and optoelectronic properties of p-n junctions in exfoliated MoS{sub 2} flakes. Creating a controllable doping gradient across the device leads to the observation of the photovoltaic effect in monolayer and bilayer MoS{sub 2} flakes. For thicker flakes, strong ambipolar conduction enables realization of fully reconfigurable p-n junction diodes with rectifying current-voltage characteristics, and diode ideality factors as low as 1.6. The spectralmore » response of the photovoltaic effect shows signatures of the predicted band gap transitions. For the first excitonic transition, a shift of >4{sub kB}T is observed between monolayer and bulk devices, indicating a thickness-dependence of the excitonic coulomb interaction.« less

Electrical and optical characteristics of n-Zno/p-GaN hetero-junction diode fabricated by ultra-high vacuum sputter.

PubMed

Cho, Seong Gook; Lee, Dong Uk; Kim, Eun Kyu

2013-09-01

We investigated the electrical and optical properties of n-ZnO/p-GaN hetero-junction diode fabricated by an ultra-high vacuum radio frequency magnetron sputter. A physical relationship between the rotation rate during deposition process and post annealing conditions after deposited ZnO layer on p-GaN layer was discussed. When the rotation rates during deposition process of n-ZnO layer were 5 rpm and 15 rpm, the full width at half maximum of photoluminescence spectra of ZnO layer on the p-GaN layer was about 106 and 133 meV, respectively. Also, the ratio of deep level emission to near band edge emission was dramatically increased as increasing the rotation rate from 5 to 15 rpm. The n-ZnO/p-GaN hetero-junction diode grown at 5 rpm has a higher ratio of forward to reverse currents than the diode grown at 15 rpm. Also, the 600 degrees C-annealed diodes with 5 rpm showed good rectifying behavior with the barrier height of 0.74 eV, the ideality factor of 12.2, and the forward to reverse current ratio of 614 at +/- 8 V.

Graphene-based vertical-junction diodes and applications

NASA Astrophysics Data System (ADS)

Choi, Suk-Ho

2017-09-01

In the last decade, graphene has received extreme attention as an intriguing building block for electronic and photonic device applications. This paper provides an overview of recent progress in the study of vertical-junction diodes based on graphene and its hybrid systems by combination of graphene and other materials. The review is especially focused on tunnelling and Schottky diodes produced by chemical doping of graphene or combination of graphene with various semiconducting/ insulating materials such as hexagonal boron nitrides, Si-quantum-dots-embedded SiO2 multilayers, Si wafers, compound semiconductors, Si nanowires, and porous Si. The uniqueness of graphene enables the application of these convergence structures in high-efficient devices including photodetectors, solar cells, resonant tunnelling diodes, and molecular/DNA sensors.

Current rectification in a single molecule diode: the role of electrode coupling.

PubMed

Sherif, Siya; Rubio-Bollinger, Gabino; Pinilla-Cienfuegos, Elena; Coronado, Eugenio; Cuevas, Juan Carlos; Agraït, Nicolás

2015-07-24

We demonstrate large rectification ratios (> 100) in single-molecule junctions based on a metal-oxide cluster (polyoxometalate), using a scanning tunneling microscope (STM) both at ambient conditions and at low temperature. These rectification ratios are the largest ever observed in a single-molecule junction, and in addition these junctions sustain current densities larger than 10(5) A cm(-2). By following the variation of the I-V characteristics with tip-molecule separation we demonstrate unambiguously that rectification is due to asymmetric coupling to the electrodes of a molecule with an asymmetric level structure. This mechanism can be implemented in other type of molecular junctions using both organic and inorganic molecules and provides a simple strategy for the rational design of molecular diodes.

Current rectification in a single molecule diode: the role of electrode coupling

NASA Astrophysics Data System (ADS)

Sherif, Siya; Rubio-Bollinger, Gabino; Pinilla-Cienfuegos, Elena; Coronado, Eugenio; Cuevas, Juan Carlos; Agraït, Nicolás

2015-07-01

We demonstrate large rectification ratios (\\gt 100) in single-molecule junctions based on a metal-oxide cluster (polyoxometalate), using a scanning tunneling microscope (STM) both at ambient conditions and at low temperature. These rectification ratios are the largest ever observed in a single-molecule junction, and in addition these junctions sustain current densities larger than 105 A cm-2. By following the variation of the I-V characteristics with tip-molecule separation we demonstrate unambiguously that rectification is due to asymmetric coupling to the electrodes of a molecule with an asymmetric level structure. This mechanism can be implemented in other type of molecular junctions using both organic and inorganic molecules and provides a simple strategy for the rational design of molecular diodes.

Modulation of Quantum Tunneling via a Vertical Two-Dimensional Black Phosphorus and Molybdenum Disulfide p-n Junction.

PubMed

Liu, Xiaochi; Qu, Deshun; Li, Hua-Min; Moon, Inyong; Ahmed, Faisal; Kim, Changsik; Lee, Myeongjin; Choi, Yongsuk; Cho, Jeong Ho; Hone, James C; Yoo, Won Jong

2017-09-26

Diverse diode characteristics were observed in two-dimensional (2D) black phosphorus (BP) and molybdenum disulfide (MoS 2 ) heterojunctions. The characteristics of a backward rectifying diode, a Zener diode, and a forward rectifying diode were obtained from the heterojunction through thickness modulation of the BP flake or back gate modulation. Moreover, a tunnel diode with a precursor to negative differential resistance can be realized by applying dual gating with a solid polymer electrolyte layer as a top gate dielectric material. Interestingly, a steep subthreshold swing of 55 mV/dec was achieved in a top-gated 2D BP-MoS 2 junction. Our simple device architecture and chemical doping-free processing guaranteed the device quality. This work helps us understand the fundamentals of tunneling in 2D semiconductor heterostructures and shows great potential in future applications in integrated low-power circuits.

n-ZnO/p-GaN heterojunction light-emitting diodes featuring a buried polarization-induced tunneling junction

NASA Astrophysics Data System (ADS)

Li, Ling; Zhang, Yuantao; Yan, Long; Jiang, Junyan; Han, Xu; Deng, Gaoqiang; Chi, Chen; Song, Junfeng

2016-12-01

n-ZnO/p-GaN heterojunction light-emitting diodes with a p-GaN/Al0.1Ga0.9N/n+-GaN polarization-induced tunneling junction (PITJ) were fabricated by metal-organic chemical vapor deposition. An intense and sharp ultraviolet emission centered at ˜396 nm was observed under forward bias. Compared with the n-ZnO/p-GaN reference diode without PITJ, the light intensity of the proposed diode is increased by ˜1.4-folds due to the improved current spreading. More importantly, the studied diode operates continuously for eight hours with the decay of only ˜3.5% under 20 mA, suggesting a remarkable operating stability. The results demonstrate the feasibility of using PITJ as hole injection layer for high-performance ZnO-based light-emitting devices.

P-n junction diodes with polarization induced p-type graded InxGa1-xN layer

NASA Astrophysics Data System (ADS)

Enatsu, Yuuki; Gupta, Chirag; Keller, Stacia; Nakamura, Shuji; Mishra, Umesh K.

2017-10-01

In this study, p-n junction diodes with polarization induced p-type layer are demonstrated on Ga polar (0001) bulk GaN substrates. A quasi-p-type region is obtained by linearly grading the indium composition in un-doped InxGa1-xN layers from 0% to 5%, taking advantage of the piezoelectric and spontaneous polarization fields which exist in group III-nitride heterostructures grown in the typical (0001) or c-direction. The un-doped graded InxGa1-xN layers needed to be capped with a thin Mg-doped InxGa1-xN layer to make good ohmic contacts and to reduce the on-resistance of the p-n diodes. The Pol-p-n junction diodes exhibited similar characteristics compared to reference samples with traditional p-GaN:Mg layers. A rise in breakdown voltage from 30 to 110 V was observed when the thickness of the graded InGaN layer was increased from 100 to 600 nm at the same grade composition.

Charge Transport in 2D DNA Tunnel Junction Diodes.

PubMed

Yoon, Minho; Min, Sung-Wook; Dugasani, Sreekantha Reddy; Lee, Yong Uk; Oh, Min Suk; Anthopoulos, Thomas D; Park, Sung Ha; Im, Seongil

2017-12-01

Recently, deoxyribonucleic acid (DNA) is studied for electronics due to its intrinsic benefits such as its natural plenitude, biodegradability, biofunctionality, and low-cost. However, its applications are limited to passive components because of inherent insulating properties. In this report, a metal-insulator-metal tunnel diode with Au/DNA/NiO x junctions is presented. Through the self-aligning process of DNA molecules, a 2D DNA nanosheet is synthesized and used as a tunneling barrier, and semitransparent conducting oxide (NiO x ) is applied as a top electrode for resolving metal penetration issues. This molecular device successfully operates as a nonresonant tunneling diode, and temperature-variable current-voltage analysis proves that Fowler-Nordheim tunneling is a dominant conduction mechanism at the junctions. DNA-based tunneling devices appear to be promising prototypes for nanoelectronics using biomolecules. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of silicide-induced-dopant-activation for steep tunnel junction in tunnel field effect transistor (TFET)

NASA Astrophysics Data System (ADS)

Kim, Sihyun; Kwon, Dae Woong; Park, Euyhwan; Lee, Junil; Lee, Roongbin; Lee, Jong-Ho; Park, Byung-Gook

2018-02-01

Numerous researches for making steep tunnel junction within tunnel field-effect transistor (TFET) have been conducted. One of the ways to make an abrupt junction is source/drain silicidation, which uses the phenomenon often called silicide-induced-dopant-segregation. It is revealed that the silicide process not only helps dopants to pile up adjacent to the metal-silicon alloy, also induces the dopant activation, thereby making it possible to avoid additional high temperature process. In this report, the availability of dopant activation induced by metal silicide process was thoroughly investigated by diode measurement and device simulation. Metal-silicon (MS) diodes having p+ and n+ silicon formed on the p- substrate exhibit the characteristics of ohmic and pn diodes respectively, for both the samples with and without high temperature annealing. The device simulation for TFETs with dopant-segregated source was also conducted, which verified enhanced DC performance.

Single crystalline ZnO radial homojunction light-emitting diodes fabricated by metalorganic chemical vapour deposition

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

Yoo, Jinkyoung; Ahmed, Towfiq; Tang, Wei

ZnO radial p–n junction architecture has the potential for forward-leap of light-emitting diode (LED) technology in terms of higher efficacy and economical production. Here, we report on ZnO radial p–n junction-based light emitting diodes prepared by full metalorganic chemical vapour deposition (MOCVD) with hydrogen-assisted p-type doping approach. The p-type ZnO(P) thin films were prepared by MOCVD with the precursors of dimethylzinc, tert-butanol, and tertiarybutylphosphine. Controlling the precursor flow for dopant results in the systematic change of doping concentration, Hall mobility, and electrical conductivity. Moreover, the approach of hydrogen-assisted phosphorous doping in ZnO expands the understanding of doping behaviour in ZnO.more » Ultraviolet and visible electroluminescence of ZnO radial p–n junction was demonstrated through a combination of position-controlled nano/microwire and crystalline p-type ZnO(P) radial shell growth on the wires. Lastly, the reported research opens a pathway of realisation of production-compatible ZnO p–n junction LEDs.« less

Single crystalline ZnO radial homojunction light-emitting diodes fabricated by metalorganic chemical vapour deposition

DOE PAGES

Yoo, Jinkyoung; Ahmed, Towfiq; Tang, Wei; ...

2017-09-05

ZnO radial p–n junction architecture has the potential for forward-leap of light-emitting diode (LED) technology in terms of higher efficacy and economical production. Here, we report on ZnO radial p–n junction-based light emitting diodes prepared by full metalorganic chemical vapour deposition (MOCVD) with hydrogen-assisted p-type doping approach. The p-type ZnO(P) thin films were prepared by MOCVD with the precursors of dimethylzinc, tert-butanol, and tertiarybutylphosphine. Controlling the precursor flow for dopant results in the systematic change of doping concentration, Hall mobility, and electrical conductivity. Moreover, the approach of hydrogen-assisted phosphorous doping in ZnO expands the understanding of doping behaviour in ZnO.more » Ultraviolet and visible electroluminescence of ZnO radial p–n junction was demonstrated through a combination of position-controlled nano/microwire and crystalline p-type ZnO(P) radial shell growth on the wires. Lastly, the reported research opens a pathway of realisation of production-compatible ZnO p–n junction LEDs.« less

Extension of the ADC Charge-Collection Model to Include Multiple Junctions

NASA Technical Reports Server (NTRS)

Edmonds, Larry D.

2011-01-01

The ADC model is a charge-collection model derived for simple p-n junction silicon diodes having a single reverse-biased p-n junction at one end and an ideal substrate contact at the other end. The present paper extends the model to include multiple junctions, and the goal is to estimate how collected charge is shared by the different junctions.

Monolithic stacked blue light-emitting diodes with polarization-enhanced tunnel junctions.

PubMed

Kuo, Yen-Kuang; Shih, Ya-Hsuan; Chang, Jih-Yuan; Lai, Wei-Chih; Liu, Heng; Chen, Fang-Ming; Lee, Ming-Lun; Sheu, Jinn-Kong

2017-08-07

Monolithic stacked InGaN light-emitting diode (LED) connected by a polarization-enhanced GaN/AlN-based tunnel junction is demonstrated experimentally in this study. The typical stacked LEDs exhibit 80% enhancement in output power compared with conventional single LEDs because of the repeated use of electrons and holes for photon generation. The typical operation voltage of stacked LEDs is higher than twice the operation voltage of single LEDs. This high operation voltage can be attributed to the non-optimal tunneling junction in stacked LEDs. In addition to the analyses of experimental results, theoretical analysis of different schemes of tunnel junctions, including diagrams of energy bands, diagrams of electric fields, and current-voltage relation curves, are investigated using numerical simulation. The results shown in this paper demonstrate the feasibility in developing cost-effective and highly efficient tunnel-junction LEDs.

Semiconductor laser devices having lateral refractive index tailoring

DOEpatents

Ashby, Carol I. H.; Hadley, G. Ronald; Hohimer, John P.; Owyoung, Adelbert

1990-01-01

A broad-area semiconductor laser diode includes an active lasing region interposed between an upper and a lower cladding layer, the laser diode further comprising structure for controllably varying a lateral refractive index profile of the diode to substantially compensate for an effect of junction heating during operation. In embodiments disclosed the controlling structure comprises resistive heating strips or non-radiative linear junctions disposed parallel to the active region. Another embodiment discloses a multi-layered upper cladding region selectively disordered by implanted or diffused dopant impurities. Still another embodiment discloses an upper cladding layer of variable thickness that is convex in shape and symmetrically disposed about a central axis of the active region. The teaching of the invention is also shown to be applicable to arrays of semiconductor laser diodes.

InP tunnel junctions for InP/InGaAs tandem solar cells

NASA Technical Reports Server (NTRS)

Vilela, Mauro F.; Freundlich, Alex; Renaud, P.; Medelci, N.; Bensaoula, A.

1996-01-01

We report, for the first time, an epitaxially grown InP p(+)/n(++) tunnel junction. A diode with peak current densities up to 1600 A/cm and maximum specific resistivities (Vp/Ip - peak voltage to peak current ratio) in the range of 10(exp -4)Omega cm(exp 2) is obtained. This peak current density is comparable to the highest results previously reported for lattice matched In(0.53)Ga(0.47)As tunnel junctions. Both results were obtained using chemical beam epitaxy (CBE). In this paper we discuss the electrical characteristics of these tunnel diodes and how the growth conditions influence them.

InP Tunnel Junctions for InP/InGaAs Tandem Solar Cells

NASA Technical Reports Server (NTRS)

Vilela, M. F.; Medelci, N.; Bensaoula, A.; Freundlich, A.; Renaud, P.

1995-01-01

We report, for the first time, an epitaxially grown InP p(+)/n(++) tunnel junction. A diode with peak current densities up to 1600 Al/sq cm and maximum specific resistivities (Vp/lp - peak voltage to peak current ratio) in the range of 10(exp -4)Om sq cm is obtained. This peak current density is comparable to the highest results previously reported for lattice matched In(0.53)Ga(0.47)As tunnel junctions. Both results were obtained using chemical beam epitaxy (CBE). In this paper we discuss the electrical characteristics of these tunnel diodes and how the growth conditions influence them.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: A super junction SiGe low-loss fast switching power diode

NASA Astrophysics Data System (ADS)

Ma, Li; Gao, Yong

2009-01-01

This paper proposes a novel super junction (SJ) SiGe switching power diode which has a columnar structure of alternating p- and n- doped pillar substituting conventional n- base region and has far thinner strained SiGe p+ layer to overcome the drawbacks of existing Si switching power diode. The SJ SiGe diode can achieve low specific on-resistance, high breakdown voltages and fast switching speed. The results indicate that the forward voltage drop of SJ SiGe diode is much lower than that of conventional Si power diode when the operating current densities do not exceed 1000 A/cm2, which is very good for getting lower operating loss. The forward voltage drop of the Si diode is 0.66 V whereas that of the SJ SiGe diode is only 0.52 V at operating current density of 10 A/cm2. The breakdown voltages are 203 V for the former and 235 V for the latter. Compared with the conventional Si power diode, the reverse recovery time of SJ SiGe diode with 20 per cent Ge content is shortened by above a half and the peak reverse current is reduced by over 15%. The SJ SiGe diode can remarkably improve the characteristics of power diode by combining the merits of both SJ structure and SiGe material.

Trap assisted space charge conduction in p-NiO/n-ZnO heterojunction diode

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

Tyagi, Manisha; Tomar, Monika; Gupta, Vinay, E-mail: drguptavinay@gmail.com

2015-06-15

Highlights: • p-NiO/n-ZnO heterojunction diode with enhanced junction parameters has been prepared. • Temperature dependent I–V throw insight into the involved conduction mechanism. • SCLC with exponential trap distribution was found to be the dominant mechanism. • C–V measurement at different frequencies support the presence of traps. - Abstract: The development of short-wavelength p–n junction is essentially important for the realization of transparent electronics for next-generation optoelectronic devices. In the present work, a p–n heterojunction diode based on p-NiO/n-ZnO has been prepared under the optimised growth conditions exhibiting improved electrical and junction parameters. The fabricated heterojunction gives typical current–voltage (I–V)more » characteristics with good rectifying behaviour (rectification ratio ≈ 10{sup 4} at 2 V). The temperature dependent current–voltage characteristics of heterojunction diode have been studied and origin of conduction mechanism is identified. The space-charge limited conduction with exponential trap distribution having deep level trap is found to be the dominant conduction mechanism in the fabricated p–n heterojunction diode. The conduction and valence band discontinuities for NiO/ZnO heterostructure have been determined from the capacitance–voltage (C–V) measurements.« less

Neutron Detection using Amorphous Boron-Carbide Hetero-Junction Diodes

DTIC Science & Technology

2012-03-22

Parameter Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 B.1.1 UMKC Built-in Voltage...Electronic properties of boron carbide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2. Diode Material/Geometric Parameters ...42 6. Material parameters for Davinci model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 x List of

Radial tunnel diodes based on InP/InGaAs core-shell nanowires

NASA Astrophysics Data System (ADS)

Tizno, Ofogh; Ganjipour, Bahram; Heurlin, Magnus; Thelander, Claes; Borgström, Magnus T.; Samuelson, Lars

2017-03-01

We report on the fabrication and characterization of radial tunnel diodes based on InP(n+)/InGaAs(p+) core-shell nanowires, where the effect of Zn-dopant precursor flow on the electrical properties of the devices is evaluated. Selective and local etching of the InGaAs shell is employed to access the nanowire core in the contact process. Devices with an n+-p doping profile show normal diode rectification, whereas n+-p+ junctions exhibit typical tunnel diode characteristics with peak-to-valley current ratios up to 14 at room temperature and 100 at 4.2 K. A maximum peak current density of 28 A/cm2 and a reverse current density of 7.3 kA/cm2 at VSD = -0.5 V are extracted at room temperature after normalization with the effective junction area.

High-Field Fast-Risetime Pulse Failures in 4H- and 6H-SiC pn Junction Diodes

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Fazi, Christian

1996-01-01

We report the observation of anomalous reverse breakdown behavior in moderately doped (2-3 x 10(exp 17 cm(exp -3)) small-area micropipe-free 4H- and 6H-SiC pn junction diodes. When measured with a curve tracer, the diodes consistently exhibited very low reverse leakage currents and sharp repeatable breakdown knees in the range of 140-150 V. However, when subjected to single-shot reverse bias pulses (200 ns pulsewidth, 1 ns risetime), the diodes failed catastrophically at pulse voltages of less than 100 V. We propose a possible mechanism for this anomalous reduction in pulsed breakdown voltage relative to dc breakdown voltage. This instability must be removed so that SiC high-field devices can operate with the same high reliability as silicon power devices.

Bypass Diode Temperature Tests of a Solar Array Coupon Under Space Thermal Environment Conditions

NASA Technical Reports Server (NTRS)

Wright, Kenneth H., Jr.; Schneider, Todd A.; Vaughn, Jason A.; Hoang, Bao; Wong, Frankie; Wu, Gordon

2016-01-01

Tests were performed on a 56-cell Advanced Triple Junction solar array coupon whose purpose was to determine margin available for bypass diodes integrated with new, large multi-junction solar cells that are manufactured from a 4-inch wafer. The tests were performed under high vacuum with coupon back side thermal conditions of both cold and ambient. The bypass diodes were subjected to a sequence of increasing discrete current steps from 0 Amp to 2.0 Amp in steps of 0.25 Amp. At each current step, a temperature measurement was obtained via remote viewing by an infrared camera. This paper discusses the experimental methodology, experiment results, and the thermal model.

By-Pass Diode Temperature Tests of a Solar Array Coupon Under Space Thermal Environment Conditions

NASA Technical Reports Server (NTRS)

Wright, Kenneth H., Jr.; Schneider, Todd A.; Vaughn, Jason A.; Hoang, Bao; Wong, Frankie

2016-01-01

Tests were performed on a 56-cell Advanced Triple Junction solar array coupon whose purpose was to determine margin available for bypass diodes integrated with new, large multi-junction solar cells that are manufactured from a 4-inch wafer. The tests were performed under high vacuum with cold and ambient coupon back-side. The bypass diodes were subjected to a sequence of increasing discrete current steps from 0 Amp to 2.0 Amp in steps of 0.25 Amp. At each current step, a temperature measurement was obtained via remote viewing by an infrared camera. This paper discusses the experimental methodology, including the calibration of the thermal imaging system, and the results.

High transmittance hetero junctions based on n-ITO/p-CuO bilayer thin films

NASA Astrophysics Data System (ADS)

Jaya, T. P.; Pradyumnan, P. P.

2016-12-01

Oxide based bilayered n-ITO/p-CuO crystalline diodes were fabricated by plasma vapor deposition using radio frequency magnetron sputtering. The p-n hetero junction diodes were highly transparent in the visible region and exhibits rectifying I-V characteristics. The substrate temperature during fabrication of p-layer CuO was found to have a profound influence on I-V characteristics. The films deposited at substrate temperature of 150 °C and 230 °C exhibited diode ideality factors of (η value) 1.731 and 1.862 respectively. This high ideality factor, combined with an optical transparency of above 70% suggests the potential use of these bi-layers in optoelectronic applications.

Tunnel junction enhanced nanowire ultraviolet light emitting diodes

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

Sarwar, A. T. M. Golam; May, Brelon J.; Deitz, Julia I.

Polarization engineered interband tunnel junctions (TJs) are integrated in nanowire ultraviolet (UV) light emitting diodes (LEDs). A ∼6 V reduction in turn-on voltage is achieved by the integration of tunnel junction at the base of polarization doped nanowire UV LEDs. Moreover, efficient hole injection into the nanowire LEDs leads to suppressed efficiency droop in TJ integrated nanowire LEDs. The combination of both reduced bias voltage and increased hole injection increases the wall plug efficiency in these devices. More than 100 μW of UV emission at ∼310 nm is measured with external quantum efficiency in the range of 4–6 m%. The realization of tunnel junctionmore » within the nanowire LEDs opens a pathway towards the monolithic integration of cascaded multi-junction nanowire LEDs on silicon.« less

Optical response at 10.6 microns in tungsten silicide Schottky barrier diodes

NASA Technical Reports Server (NTRS)

Kumar, Sandeep; Boyd, Joseph T.; Jackson, Howard E.

1987-01-01

Optical response to radiation at a wavelength of 10.6 microns in tungsten silicide-silicon Schottky barrier diodes has been observed. Incident photons excite electrons by means of junction plasmon assisted inelastic electron tunneling. At 78 K, a peak in the second derivative of current versus junction bias voltage was observed at a voltage corresponding to the energy of photons having a wavelength of 10.6 microns. This peak increased with increasing incident laser power, saturating at the highest laser powers investigated.

Application of the SEM to the measurement of solar cell parameters

NASA Technical Reports Server (NTRS)

Weizer, V. G.; Andrews, C. W.

1977-01-01

Techniques are described which make use of the SEM to measure the minority carrier diffusion length and the metallurgical junction depth in silicon solar cells. The former technique permits the measurement of the true bulk diffusion length through the application of highly doped field layers to the back surfaces of the cells being investigated. It is shown that the secondary emission contrast observed in the SEM on a reverse-biased diode can depict the location of the metallurgical junction if the diode has been prepared with the proper beveled geometry. The SEM provides the required contrast and the option of high magnification, permitting the measurement of extremely shallow junction depths.

Integral bypass diodes in an amorphous silicon alloy photovoltaic module

NASA Technical Reports Server (NTRS)

Hanak, J. J.; Flaisher, H.

1991-01-01

Thin-film, tandem-junction, amorphous silicon (a-Si) photovoltaic modules were constructed in which a part of the a-Si alloy cell material is used to form bypass protection diodes. This integral design circumvents the need for incorporating external, conventional diodes, thus simplifying the manufacturing process and reducing module weight.

Fully porous GaN p-n junction diodes fabricated by chemical vapor deposition.

PubMed

Bilousov, Oleksandr V; Carvajal, Joan J; Geaney, Hugh; Zubialevich, Vitaly Z; Parbrook, Peter J; Martínez, Oscar; Jiménez, Juan; Díaz, Francesc; Aguiló, Magdalena; O'Dwyer, Colm

2014-10-22

Porous GaN based LEDs produced by corrosion etching techniques demonstrated enhanced light extraction efficiency in the past. However, these fabrication techniques require further postgrown processing steps, which increases the price of the final system. Also, the penetration depth of these etching techniques is limited, and affects not only the semiconductor but also the other elements constituting the LED when applied to the final device. In this paper, we present the fabrication of fully porous GaN p-n junctions directly during growth, using a sequential chemical vapor deposition (CVD) process to produce the different layers that form the p-n junction. We characterized their diode behavior from room temperature to 673 K and demonstrated their ability as current rectifiers, thus proving the potential of these fully porous p-n junctions for diode and LEDs applications. The electrical and luminescence characterization confirm that high electronic quality porous structures can be obtained by this method, and we believe this investigation can be extended to other III-N materials for the development of white light LEDs, or to reduce reflection losses and narrowing the output light cone for improved LED external quantum efficiencies.

Multicolor (UV-IR) Photodetectors Based on Lattice-Matched 6.1 A II/VI and III/V Semiconductors

DTIC Science & Technology

2015-08-27

photodiodes with different cutoff wavelengths connected in series with tunnel diodes between adjacent photodiodes. The LEDs optically bias the inactive...perfectly conductive n-CdTe/p-InSb tunnel junction. 15. SUBJECT TERMS optical biasing; multi-junction photodetectors; triple-junction solar cell...during this project, including initial demonstrations of optical addressing, tunnel junction studies and multicolor device characterization

Study of Bulk and Elementary Screw Dislocation Assisted Reverse Breakdown in Low-Voltage (< 250 V) 4H-SiC p(sup +)n Junction Diodes--Part II: Dynamic Breakdown Properties. Part 2; Dynamic Breakdown Properties

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Fazi, Christian

1999-01-01

This paper outlines the dynamic reverse-breakdown characteristics of low-voltage (<250 V) small-area <5 x 10(exp -4) sq cm 4H-SiC p(sup +)n diodes subjected to nonadiabatic breakdown-bias pulsewidths ranging from 0.1 to 20 microseconds. 4H-SiC diodes with and without elementary screw dislocations exhibited positive temperature coefficient of breakdown voltage and high junction failure power densities approximately five times larger than the average failure power density of reliable silicon pn rectifiers. This result indicates that highly reliable low-voltage SiC rectifiers may be attainable despite the presence of elementary screw dislocations. However, the impact of elementary screw dislocations on other more useful 4H-SiC power device structures, such as high-voltage (>1 kV) pn junction and Schottky rectifiers, and bipolar gain devices (thyristors, IGBT's, etc.) remains to be investigated.

Aging behavior of Au-based ohmic contacts to GaAs

NASA Technical Reports Server (NTRS)

Fatemi, Navid S.

1989-01-01

Gold based alloys, commonly used as ohmic contacts for solar cells, are known to react readily with GaAs. It is shown that the contact interaction with the underlying GaAs can continue even at room temperature upon aging, altering both the electrical characteristics of the contacts and the nearby pn junction. Au-Ge-Ni as-deposited (no heat-treatment) contacts made to thin emitter (0.15 microns) GaAs diodes have shown severe shunting of the pn junction upon aging for several months at room temperature. The heat-treated contacts, despite showing degradation in contact resistance, did not affect the underlying pn junction. Au-Zn-Au contacts to p-GaAs emitter (0.2 microns) diodes, however, showed slight improvement in contact resistance upon 200 C isothermal annealing for several months, without degrading the pn junction. The effect of aging on electrical characteristics of the as-deposited and heat-treated contacts and the nearby pn junction, as well as on the surface morphology of the contacts are presented.

Aging behavior of Au-based ohmic contacts to GaAs

NASA Technical Reports Server (NTRS)

Fatemi, Navid S.

1988-01-01

Gold based alloys, commonly used as ohmic contacts for solar cells, are known to react readily with GaAs. It is shown that the contact interaction with the underlying GaAs can continue even at room temperature upon aging, altering both the electrical characteristics of the contacts and the nearby pn junction. Au-Ge-Ni as-deposited (no heat treatment) contacts made to thin emitter (0.15 micrometer) GaAs diodes have shown severe shunting of the pn junction upon aging for several months at room temperature. The heat-treated contacts, despite showing degradation in contact resistance did not affect the underlying pn junction. Au-Zn-Au contacts to p-GaAs emitter (0.2 micrometer) diodes, however, showed slight improvement in contact resistance upon 200 C isothermal annealing for several months, without degrading the pn junction. The effect of aging on electrical characteristics of the as-deposited and heat-treated contacts and the nearby pn junction, as well as on the surface morphology of the contacts are presented.

Polarization-enhanced InGaN/GaN-based hybrid tunnel junction contacts to GaN p-n diodes and InGaN LEDs

NASA Astrophysics Data System (ADS)

Mughal, Asad J.; Young, Erin C.; Alhassan, Abdullah I.; Back, Joonho; Nakamura, Shuji; Speck, James S.; DenBaars, Steven P.

2017-12-01

Improved turn-on voltages and reduced series resistances were realized by depositing highly Si-doped n-type GaN using molecular beam epitaxy on polarization-enhanced p-type InGaN contact layers grown using metal-organic chemical vapor deposition. We compared the effects of different Si doping concentrations and the addition of p-type InGaN on the forward voltages of p-n diodes and light-emitting diodes, and found that increasing the Si concentrations from 1.9 × 1020 to 4.6 × 1020 cm-3 and including a highly doped p-type InGaN at the junction both contributed to reductions in the depletion width, the series resistance of 4.2 × 10-3-3.4 × 10-3 Ω·cm2, and the turn-on voltages of the diodes.

IR detection and energy harvesting using antenna coupled MIM tunnel diodes

NASA Astrophysics Data System (ADS)

Yesilkoy, Filiz

The infrared (IR) spectrum lies between the microwave and optical frequency ranges, which are well suited for communication and energy harvesting purposes, respectively. The long wavelength IR (LWIR) spectrum, corresponding to wavelengths from 8microm to 15microm, includes the thermal radiation emitted by objects at room temperature and the Earth's terrestrial radiation. Therefore, LWIR detectors are very appealing for thermal imaging purposes. Thermal detectors developed so far either demand cryogenic operation for fast detection, or they rely on the accumulation of thermal energy in their mass and subsequent measurable changes in material properties. Therefore, they are relatively slow. Quantum detectors allow for tunable and instantaneous detection but are expensive and require complex processes for fabrication. Bolometer detectors are simple and cheap but do not allow for tunability or for rapid detection. Harvesting the LWIR radiation energy sourced by the Earth's heating/cooling cycle is very important for the development of mobile energy resources. While speed is not as significant an issue here, conversion efficiency is an eminent problem for cheap, large area energy transduction. This dissertation addresses the development of tunable, fast, and low cost wave detectors that can operate at room temperature and, when produced in large array format, can harvest Earth's terrestrial radiation energy. This dissertation demonstrates the design, fabrication and testing of Antenna Coupled Metal-Insulator-Metal (ACMIM) tunnel diodes optimized for 10microm wavelength radiation detection. ACMIM tunnel diodes operate as electromagnetic wave detectors: the incident radiation is coupled by an antenna and converted into a 30 terahertz signal that is rectified by a fast tunneling MIM diode. For efficient IR radiation coupling, the antenna geometry and its critical dimensions are studied using a commercial finite-element based multi-physics simulation tool, and the half-wave dipole-like bow-tie antennas are fabricated using simulation-optimized geometries. The major challenge of this work is designing and fabricating MIM diodes and coupled antennas with internal capacitances and resistances small enough to allow response in the desired frequency range (˜30 THz) and yet capable of efficiently coupling to the incident radiation. It is crucial to keep the RC time constant of the tunnel junction small to achieve the requisite cut-off frequency and adequate rectification efficiency. Moreover, a low junction resistance is necessary to load the coupled AC power across the MIM junction. For energy harvesting applications, the device has to operate without an external bias, which requires asymmetry at the zero bias operation point. To address these requirements, the MIM tunnel junction is established so that one electrode has a field enhancing sharp tip (cathode) and the other is a rectangular patch. This asymmetric geometry not only offers asymmetric current-voltage behavior at the zero bias point, but also it decouples the junction resistance and capacitance by concentrating the charge transport in a small volume around the tip. Various fabrication methods are developed in order to create small junction area (= low parasitic capacitance), low junction resistance (= effective power coupling through antenna), asymmetry (= zero bias operation), high fabrication yield and low cost ACMIM tunnel diodes. High resolution fabrication needs are accomplished by electron beam lithography and nano-accuracy in the junction area is achieved by employing dose modifying proximity effect correction and critical alignment methods. Our Ni/NiOx/Ni ACMIM diodes with an optimized insulation layer created with O2 plasma oxidation are the most successful devices presented to date. A novel fabrication technique called "strain assisted self lift-off process" is used to achieve small junction area devices without relying on lithographic resolution. This technique eliminates the rival parasitic capacitance issue of today's ACMIM tunnel diodes and does not rely on extreme-high resolution lithography technologies.

Maximizing ion current rectification in a bipolar conical nanopore fluidic diode using optimum junction location.

PubMed

Singh, Kunwar Pal

2016-10-12

The ion current rectification has been obtained as a function of the location of a heterojunction in a bipolar conical nanopore fluidic diode for different parameters to determine the junction location for maximum ion current rectification using numerical simulations. Forward current peaks for a specific location of the junction and reverse current decreases with the junction location due to a change in ion enrichment/depletion in the pore. The optimum location of the heterojunction shifts towards the tip with base/tip diameter and surface charge density, and towards the base with the electrolyte concentration. The optimum location of the heterojunction has been approximated by an equation as a function of pore length, base/tip diameter, surface charge density and electrolyte concentration. The study is useful to design a rectifier with maximum ion current rectification for practical purposes.

Fast Risetime Reverse Bias Pulse Failures in SiC PN Junction Diodes

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Fazi, Christian; Parsons, James D.

1996-01-01

SiC-based high temperature power devices are being developed for aerospace systems which will require high reliability. One behavior crucial to power device reliability. To date, it has necessarily been assumed to date is that the breakdown behavior of SiC pn junctions will be similar to highly reliable silicon-based pn junctions. Challenging this assumption, we report the observation of anomalous unreliable reverse breakdown behavior in moderately doped (2-3 x 10(exp 17) cm(exp -3)) small-area 4H- and 6H-SiC pn junction diodes at temperatures ranging from 298 K (25 C) to 873 K (600 C). We propose a mechanism in which carrier emission from un-ionized dopants and deep level defects leads to this unstable behavior. The fundamental instability mechanism is applicable to all wide bandgap semiconductors whose dopants are significantly un-ionized at typical device operating temperatures.

Performance tradeoff between lateral and interdigitated doping patterns for high speed carrier-depletion based silicon modulators.

PubMed

Yu, Hui; Pantouvaki, Marianna; Van Campenhout, Joris; Korn, Dietmar; Komorowska, Katarzyna; Dumon, Pieter; Li, Yanlu; Verheyen, Peter; Absil, Philippe; Alloatti, Luca; Hillerkuss, David; Leuthold, Juerg; Baets, Roel; Bogaerts, Wim

2012-06-04

Carrier-depletion based silicon modulators with lateral and interdigitated PN junctions are compared systematically on the same fabrication platform. The interdigitated diode is shown to outperform the lateral diode in achieving a low VπLπ of 0.62 V∙cm with comparable propagation loss at the expense of a higher depletion capacitance. The low VπLπ of the interdigitated PN junction is employed to demonstrate 10 Gbit/s modulation with 7.5 dB extinction ration from a 500 µm long device whose static insertion loss is 2.8 dB. In addition, up to 40 Gbit/s modulation is demonstrated for a 3 mm long device comprising a lateral diode and a co-designed traveling wave electrode.

Diode/magnetic tunnel junction cell for fully scalable matrix-based biochip

NASA Astrophysics Data System (ADS)

Cardoso, F. A.; Ferreira, H. A.; Conde, J. P.; Chu, V.; Freitas, P. P.; Vidal, D.; Germano, J.; Sousa, L.; Piedade, M. S.; Costa, B. A.; Lemos, J. M.

2006-04-01

Magnetoresistive biochips have been recently introduced for the detection of biomolecular recognition. In this work, the detection site incorporates a thin-film diode in series with a magnetic tunnel junction (MTJ), leading to a matrix-based biochip that can be easily scaled up to screen large numbers of different target analytes. The fabricated 16×16 cell matrix integrates hydrogenated amorphous silicon (a-Si:H) diodes with aluminum oxide barrier MTJ. Each detection site also includes a U-shaped current line for magnetically assisted target concentration at probe sites. The biochip is being integrated in a portable, credit card size electronics control platform. Detection of 250 nm diameter magnetic nanoparticles by one of the matrix cells is demonstrated.

Electron transport in doped fullerene molecular junctions

NASA Astrophysics Data System (ADS)

Kaur, Milanpreet; Sawhney, Ravinder Singh; Engles, Derick

The effect of doping on the electron transport of molecular junctions is analyzed in this paper. The doped fullerene molecules are stringed to two semi-infinite gold electrodes and analyzed at equilibrium and nonequilibrium conditions of these device configurations. The contemplation is done using nonequilibrium Green’s function (NEGF)-density functional theory (DFT) to evaluate its density of states (DOS), transmission coefficient, molecular orbitals, electron density, charge transfer, current, and conductance. We conclude from the elucidated results that Au-C16Li4-Au and Au-C16Ne4-Au devices behave as an ordinary p-n junction diode and a Zener diode, respectively. Moreover, these doped fullerene molecules do not lose their metallic nature when sandwiched between the pair of gold electrodes.

Single n-GaN microwire/p-Silicon thin film heterojunction light-emitting diode.

PubMed

Ahn, Jaehui; Mastro, Michael A; Klein, Paul B; Hite, Jennifer K; Feigelson, Boris; Eddy, Charles R; Kim, Jihyun

2011-10-24

The emission and waveguiding properties of individual GaN microwires as well as devices based on an n-GaN microwire/p-Si (100) junction were studied for relevance in optoelectronics and optical circuits. Pulsed photoluminescence of the GaN microwire excited in the transverse or longitudinal direction demonstrated gain. These n-type GaN microwires were positioned mechanically or by dielectrophoretic force onto pre-patterned electrodes on a p-type Si (100) substrate. Electroluminescence from this p-n point junction was characteristic of a heterostructure light-emitting diode. Additionally, waveguiding was observed along the length of the microwire for light originating from photoluminescence as well as from electroluminescence generated at the p-n junction. © 2011 Optical Society of America

Room temperature polariton light emitting diode with integrated tunnel junction.

PubMed

Brodbeck, S; Jahn, J-P; Rahimi-Iman, A; Fischer, J; Amthor, M; Reitzenstein, S; Kamp, M; Schneider, C; Höfling, S

2013-12-16

We present a diode incorporating a large number (12) of GaAs quantum wells that emits light from exciton-polariton states at room temperature. A reversely biased tunnel junction is placed in the cavity region to improve current injection into the device. Electroluminescence studies reveal two polariton branches which are spectrally separated by a Rabi splitting of 6.5 meV. We observe an anticrossing of the two branches when the temperature is lowered below room temperature as well as a Stark shift of both branches in a bias dependent photoluminescence measurement.

Carbon-Nanotube Schottky Diodes

NASA Technical Reports Server (NTRS)

Manohara, Harish; Wong, Eric; Schlecht, Erich; Hunt, Brian; Siegel, Peter

2006-01-01

Schottky diodes based on semiconducting single-walled carbon nanotubes are being developed as essential components of the next generation of submillimeter-wave sensors and sources. Initial performance predictions have shown that the performance characteristics of these devices can exceed those of the state-of-the-art solid-state Schottky diodes that have been the components of choice for room-temperature submillimeter-wave sensors for more than 50 years. For state-of-the-art Schottky diodes used as detectors at frequencies above a few hundred gigahertz, the inherent parasitic capacitances associated with their semiconductor junction areas and the resistances associated with low electron mobilities limit achievable sensitivity. The performance of such a detector falls off approximately exponentially with frequency above 500 GHz. Moreover, when used as frequency multipliers for generating signals, state-of-the-art solid-state Schottky diodes exhibit extremely low efficiencies, generally putting out only micro-watts of power at frequencies up to 1.5 THz. The shortcomings of the state-of-the-art solid-state Schottky diodes can be overcome by exploiting the unique electronic properties of semiconducting carbon nanotubes. A single-walled carbon nanotube can be metallic or semiconducting, depending on its chirality, and exhibits high electron mobility (recently reported to be approx.= 2x10(exp 5)sq cm/V-s) and low parasitic capacitance. Because of the narrowness of nanotubes, Schottky diodes based on carbon nanotubes have ultra-small junction areas (of the order of a few square nanometers) and consequent junction capacitances of the order of 10(exp -18) F, which translates to cutoff frequency >5 THz. Because the turn-on power levels of these devices are very low (of the order of nano-watts), the input power levels needed for pumping local oscillators containing these devices should be lower than those needed for local oscillators containing state-of-the-art solid-state Schottky diodes.

Semiconductor diode with external field modulation

DOEpatents

Nasby, Robert D.

2000-01-01

A non-destructive-readout nonvolatile semiconductor diode switching device that may be used as a memory element is disclosed. The diode switching device is formed with a ferroelectric material disposed above a rectifying junction to control the conduction characteristics therein by means of a remanent polarization. The invention may be used for the formation of integrated circuit memories for the storage of information.

The Novel Preparation of P-N Junction Mesa Diodes by Silicon-Wafer Direct Bonding (SDB)

NASA Astrophysics Data System (ADS)

Yeh, Ching-Fa; Hwangleu, Shyang

1992-05-01

The key processes of silicon-wafer direct bonding (SDB), including hydrophilic surface formation and optimal two-step heat treatment, have been developed However, H2SO4/H2O2 solution being a strong oxidized acid solution, native oxide is found to have grown on the wafer surface as soon as a wafer is treated in this solution. In the case of a wafer further treated in diluted HF solution after hydrophilic surface formation, it is shown that the wafer surface can not only be cleaned of its native oxide but also remains hydrophilic, and can provide excellent voidless bonding. The N+/P and N/P combination junction mesa diodes fabricated on the wafers prepared by these novel SDB technologies are examined. The ideality factor n of the N/P mesa diode is 2.4˜2.8 for the voltage range 0.2˜0.3 V; hence, the lowering of the ideality factor n is evidently achieved. As for the N+/P mesa diode, the ideality factor n shows a value of 1.10˜1.30 for the voltage range 0.2˜0.6 V; the low value of n is attributed to an autodoping phenomenon which has caused the junction interface to form in the P-silicon bulk. However, the fact that the sustaining voltage of the N/P mesa diode showed a value greater than 520 V reveals the effectiveness of our novel SDB processes.

Electrical characterization of n/p-type nickel silicide/silicon junctions by Sb segregation.

PubMed

Jun, Myungsim; Park, Youngsam; Hyun, Younghoon; Choi, Sung-Jin; Zyung, Taehyung; Jang, Moongyu

2011-08-01

In this paper, n/p-type nickel-silicided Schottky diodes were fabricated by incorporating antimony atoms near the nickel silicide/Si junction interface and the electrical characteristics were studied through measurements and simulations. The effective Schottky barrier height (SBH) for electron, extracted from the thermionic emission model, drastically decreased from 0.68 to less than 0.1 eV while that for hole slightly increased from 0.43 to 0.53 eV. In order to identify the current conduction mechanisms, the experimental current-temperature-voltage characteristics for the n-type diode were fitted based on various models for transport of charge carrier in Schottky diodes. As the result, the large change in effective SBH for electron is ascribed to trap-assisted tunneling rather than barrier height inhomogeneity.

Switchable diode effect in oxygen vacancy-modulated SrTiO3 single crystal

NASA Astrophysics Data System (ADS)

Pan, Xinqiang; Shuai, Yao; Wu, Chuangui; Luo, Wenbo; Sun, Xiangyu; Zeng, Huizhong; Bai, Xiaoyuan; Gong, Chaoguan; Jian, Ke; Zhang, Lu; Guo, Hongliang; Tian, Benlang; Zhang, Wanli

2017-09-01

SrTiO3 (STO) single crystal wafer was annealed in vacuum, and co-planar metal-insulator-metal structure of Pt/Ti/STO/Ti/Pt were formed by sputtering Pt/Ti electrodes onto the surface of STO after annealing. The forming-free resistive switching behavior with self-compliance property was observed in the sample. The sample showed switchable diode effect, which is explained by a simple model that redistribution of oxygen vacancies (OVs) under the external electric field results in the formation of n-n+ junction or n+-n junction (n donated n-type semiconductor; n+ donated heavily doped n-type semiconductor). The self-compliance property is also interpreted by the formation of n-n+/n+-n junction caused by the migration of the OVs under the electric field.

Black Phosphorus-Zinc Oxide Nanomaterial Heterojunction for p-n Diode and Junction Field-Effect Transistor.

PubMed

Jeon, Pyo Jin; Lee, Young Tack; Lim, June Yeong; Kim, Jin Sung; Hwang, Do Kyung; Im, Seongil

2016-02-10

Black phosphorus (BP) nanosheet is two-dimensional (2D) semiconductor with distinct band gap and attracting recent attention from researches because it has some similarity to gapless 2D semiconductor graphene in the following two aspects: single element (P) for its composition and quite high mobilities depending on its fabrication conditions. Apart from several electronic applications reported with BP nanosheet, here we report for the first time BP nanosheet-ZnO nanowire 2D-1D heterojunction applications for p-n diodes and BP-gated junction field effect transistors (JFETs) with n-ZnO channel on glass. For these nanodevices, we take advantages of the mechanical flexibility of p-type conducting of BP and van der Waals junction interface between BP and ZnO. As a result, our BP-ZnO nanodimension p-n diode displays a high ON/OFF ratio of ∼10(4) in static rectification and shows kilohertz dynamic rectification as well while ZnO nanowire channel JFET operations are nicely demonstrated by BP gate switching in both electrostatics and kilohertz dynamics.

Observation of radiative surface plasmons in metal-oxide-metal tunnel junctions

NASA Technical Reports Server (NTRS)

Donohue, J. F.; Yang, E. Y.

1986-01-01

A peak in the UV region of the spectrum of light emitted from metal-oxide-metal (MOM) tunnel junctions has been observed at room temperature. Both the amplitude and wavelength of the peak are sensitive to applied junction bias. The UV peak corresponds to the normal or radiative surface plasmon mode while a visible peak, also present in the present spectra and reported in past MOM literature, is due to the tangential or nonradiative mode. The radiative mode requires no surface roughness or gratings for photon coupling. The results show that it is possible to obtain radiative surface plasmon production followed by a direct decay into photons with MOM tunnel diodes. A MOM diode with a double anode structure is found to emit light associated only with the nonradiative mode. The thickness dependence of the UV peak, along with the experimental results of the double anode MOM diode and the ratio of the UV peak to visible peak, support the contention that the UV light emission is indeed due to the radiative surface plasmon.

Temperature issues with white laser diodes, calculation and approach for new packages

NASA Astrophysics Data System (ADS)

Lachmayer, Roland; Kloppenburg, Gerolf; Stephan, Serge

2015-01-01

Bright white light sources are of significant importance for automotive front lighting systems. Today's upper class systems mainly use HID or LED light sources. As a further step laser diode based systems offer a high luminance, efficiency and allow the realization of new dynamic and adaptive light functions and styling concepts. The use of white laser diode systems in automotive applications is still limited to laboratories and prototypes even though announcements of laser based front lighting systems have been made. But the environment conditions for vehicles and other industry sectors differ from laboratory conditions. Therefor a model of the system's thermal behavior is set up. The power loss of a laser diode is transported as thermal flux from the junction layer to the diode's case and on to the environment. Therefor its optical power is limited by the maximum junction temperature (for blue diodes typically 125 - 150 °C), the environment temperature and the diode's packaging with its thermal resistances. In a car's headlamp the environment temperature can reach up to 80 °C. While the difference between allowed case temperature and environment temperature is getting small or negative the relevant heat flux also becomes small or negative. In early stages of LED development similar challenges had to be solved. Adapting LED packages to the conditions in a vehicle environment lead to today's efficient and bright headlights. In this paper the need to transfer these results to laser diodes is shown by calculating the diodes lifetimes based on the presented model.

Silicon carbide semiconductor device fabrication and characterization

NASA Technical Reports Server (NTRS)

Davis, R. F.; Das, K.

1990-01-01

A number of basic building blocks i.e., rectifying and ohmic contacts, implanted junctions, MOS capacitors, pnpn diodes and devices, such as, MESFETs on both alpha and beta SiC films were fabricated and characterized. Gold forms a rectifying contact on beta SiC. Since Au contacts degrade at high temperatures, these are not considered to be suitable for high temperature device applications. However, it was possible to utilize Au contact diodes for electrically characterizing SiC films. Preliminary work indicates that sputtered Pt or Pt/Si contacts on beta SiC films are someways superior to Au contacts. Sputtered Pt layers on alpha SiC films form excellent rectifying contacts, whereas Ni layers following anneal at approximately 1050 C provide an ohmic contact. It has demonstrated that ion implantation of Al in substrates held at 550 C can be successfully employed for the fabrication of rectifying junction diodes. Feasibility of fabricating pnpn diodes and platinum gated MESFETs on alpha SiC films was also demonstrated.

5.0 kV breakdown-voltage vertical GaN p-n junction diodes

NASA Astrophysics Data System (ADS)

Ohta, Hiroshi; Hayashi, Kentaro; Horikiri, Fumimasa; Yoshino, Michitaka; Nakamura, Tohru; Mishima, Tomoyoshi

2018-04-01

A high breakdown voltage of 5.0 kV has been achieved for the first time in vertical GaN p-n junction diodes by using our newly developed guard-ring structures. A resistance device was inserted between the main diode portion and the guard-ring portion in a ring-shaped p-n diode to generate a voltage drop over the resistance device by leakage current flowing through the guard-ring portion under negatively biased conditions before breakdown. The voltage at the outer mesa edge of the guard-ring portion, where the electric field intensity is highest and the destructive breakdown usually occurs, is decreased by the voltage drop, so the electric field concentration in the portion is reduced. By adopting this structure, the breakdown voltage (V B) is raised by about 200 V. Combined with a low measured on-resistance (R on) of 1.25 mΩ cm2, Baliga’s figure of merit (V\\text{B}2/R\\text{on}) was as high as 20 GW/cm2.

Manipulating Ion Migration for Highly Stable Light-Emitting Diodes with Single-Crystalline Organometal Halide Perovskite Microplatelets.

PubMed

Chen, Mingming; Shan, Xin; Geske, Thomas; Li, Junqiang; Yu, Zhibin

2017-06-27

Ion migration has been commonly observed as a detrimental phenomenon in organometal halide perovskite semiconductors, causing the measurement hysteresis in solar cells and ultrashort operation lifetimes in light-emitting diodes. In this work, ion migration is utilized for the formation of a p-i-n junction at ambient temperature in single-crystalline organometal halide perovskites. The junction is subsequently stabilized by quenching the ionic movement at a low temperature. Such a strategy of manipulating the ion migration has led to efficient single-crystalline light-emitting diodes that emit 2.3 eV photons starting at 1.8 V and sustain a continuous operation for 54 h at ∼5000 cd m -2 without degradation of brightness. In addition, a whispering-gallery-mode cavity and exciton-exciton interaction in the perovskite microplatelets have both been observed that can be potentially useful for achieving electrically driven laser diodes based on single-crystalline organometal halide perovskite semiconductors.

p - n junction diodes fabricated from isolated electrospun fibers of (P(NDI2ODT2)) and an inorganic p-doped semiconductor

NASA Astrophysics Data System (ADS)

Rosado, Alexander; Pinto, Nicholas

2013-03-01

A simple method to fabricate, under ambient conditions and within seconds, p - n diodes using an individual electrospun poly{[N, N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)}-(P(NDI2ODT2)) fiber and a commercially available p-doped Si/SiO2 substrate is presented. Band bending at the fiber/Si+ interface leads to asymmetric I-V characteristic curves resembling that of a diode. The diode turn-on voltage was in the range 1V and was unaffected via UV light irradiation. The rectification ratio however could be tuned reversibly thereby making this device multifunctional. In addition to being a rectifier, the advantage of our design is the complete exposure of the rectifying junction to the surrounding environment. This has the advantage of making them attractive candidates in the potential fabrication of low power, sensitive and rapid response photo-sensors. NSF

Development of reverse biased p-n junction electron emission

NASA Technical Reports Server (NTRS)

Fowler, P.; Muly, E. C.

1971-01-01

A cold cathode emitter of hot electrons for use as a source of electrons in vacuum gauges and mass spectrometers was developed using standard Norton electroluminescent silicon carbide p-n diodes operated under reverse bias conditions. Continued development including variations in the geometry of these emitters was carried out such that emitters with an emission efficiency (emitted current/junction current) as high as 3 x 10-0.00001 were obtained. Pulse measurements of the diode characteristics were made and showed that higher efficiency can be attained under pulse conditions probably due to the resulting lower temperatures resulting from such operation.

Semiconductor tunnel junction with enhancement layer

DOEpatents

Klem, John F.; Zolper, John C.

1997-01-01

The incorporation of a pseudomorphic GaAsSb layer in a runnel diode structure affords a new degree of freedom in designing runnel junctions for p-n junction device interconnects. Previously only doping levels could be varied to control the tunneling properties. This invention uses the valence band alignment band of the GaAsSb with respect to the surrounding materials to greatly relax the doping requirements for tunneling.

On the Relationship Between Schottky Barrier Capacitance and Mixer Performance at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Romanofsky, Robert R.

1996-01-01

The flat-band voltage is the Schottky junction voltage required to shrink the depletion width to zero. At cryogenic temperatures, mixer diodes are generally biased and/or pumped beyond the flat-band condition to minimize conversion loss and noise figure. This occurs despite the presumed sharp increase in junction capacitance near flat-band, which should instead limit mixer performance. Past moderate forward bias, the diode C-V relationship is difficult to measure. A simple analytic expression for C(V) is usually used to model and predict mixer performance. This letter provides experimental data on C(V) at 77 K based on a microwave measurement and modeling technique. Data is also provided on the conversion loss of a singly balanced mixer optimized for 77 K operation. The connection between junction capacitance, flat-band potential, and conversion loss is examined. It is shown that the analytic expression greatly overestimates the junction capacitance that occurs as flat-band is approached.

Electrochemical Formation of a p-n Junction on Thin Film Silicon Deposited in Molten Salt.

PubMed

Zou, Xingli; Ji, Li; Yang, Xiao; Lim, Taeho; Yu, Edward T; Bard, Allen J

2017-11-15

Herein we report the demonstration of electrochemical deposition of silicon p-n junctions all in molten salt. The results show that a dense robust silicon thin film with embedded junction formation can be produced directly from inexpensive silicates/silicon oxide precursors by a two-step electrodeposition process. The fabricated silicon p-n junction exhibits clear diode rectification behavior and photovoltaic effects, indicating promise for application in low-cost silicon thin film solar cells.

p-n Junction Diodes Fabricated on Si-Si/Ge Heteroepitaxial Films

NASA Technical Reports Server (NTRS)

Das, K.; Mazumder, M. D. A.; Hall, H.; Alterovitz, Samuel A. (Technical Monitor)

2000-01-01

A set of photolithographic masks was designed for the fabrication of diodes in the Si-Si/Ge material system. Fabrication was performed on samples obtained from two different wafers: (1) a complete HBT structure with an n (Si emitter), p (Si/Ge base), and an n/n+ (Si collector/sub-collector) deposited epitaxially (MBE) on a high resistivity p-Si substrate, (2) an HBT structure where epitaxial growth was terminated after the p-type base (Si/Ge) layer deposition. Two different process runs were attempted for the fabrication of Si-Si/Ge (n-p) and Si/Ge-Si (p-n) junction diodes formed between the emitter-base and base-collector layers, respectively, of the Si-Si/Ge-Si HBT structure. One of the processes employed a plasma etching step to expose the p-layer in the structure (1) and to expose the e-layer in structure (2). The Contact metallization used for these diodes was a Cu-based metallization scheme that was developed during the first year of the grant. The plasma-etched base-collector diodes on structure (2) exhibited well-behaved diode-like characteristics. However, the plasma-etched emitter-base diodes demonstrated back-to-back diode characteristics. These back-to back characteristics were probably due to complete etching of the base-layer, yielding a p-n-p diode. The deep implantation process yielded rectifying diodes with asymmetric forward and reverse characteristics. The ideality factor of these diodes were between 1.6 -2.1, indicating that the quality of the MBE grown epitaxial films was not sufficiently high, and also incomplete annealing of the implantation damage. Further study will be conducted on CVD grown films, which are expected to have higher epitaxial quality.

Fabrication and electrical characterizations of graphene nanocomposite thin film based heterojunction diode

NASA Astrophysics Data System (ADS)

Rahim, Ishrat; Shah, Mutabar; Iqbal, Mahmood; Wahab, Fazal; Khan, Afzal; Khan, Shah Haider

2017-11-01

The use of graphene in electronic devices is becoming attractive due to its inherent scalability and is thus well suited for flexible electronic devices. Here we present the electrical characterization of heterojunction diode, based on the nanocomposite of graphene (G) with silver nanoparticles (Ag NPs), at room temperature. The diode was fabricated by depositing nanocomposite on the n-Si substrate. The current - voltage (I - V) characteristic of the fabricated junction shows rectifying behavior similar to a Schottky junction. The junction parameters such as ideality factor (n), series resistance (Rs), and barrier height (ϕb) has been extracted, using various methods, from the experimentally obtained I - V data. The measured values of n, Rs and ϕb are 3.86, 45 Ω and 0.367 eV, respectively, as calculated from the I - V curve. The numerical values of these parameters calculated by different methods are in good agreement with each other showing the consistency of the applied calculating techniques. The conduction mechanism of the fabricated diode seems to have been dominated by the Trap Charge Limited Conduction (TCLC) behavior. The energy distribution of interface states density determined from forward bias I - V characteristic shows an exponential decrease with bias from 27 × 1013 cm-2 eV-1 at (Ec - 0.345) eV to 3 × 1013 cm-2 eV-1at (Ec - 0.398) eV.

Application of the SEM to the measurement of solar cell parameters

NASA Technical Reports Server (NTRS)

Weizer, V. G.; Andrews, C. W.

1977-01-01

A pair of techniques are described which make use of the SEM to measure, respectively, the minority carrier diffusion length and the metallurgical junction depth in silicon solar cells. The former technique permits the measurement of the true bulk diffusion length through the application of highly doped field layers to the back surfaces of the cells being investigated. The technique yields an absolute value of the diffusion length from a knowledge of the collected fraction of the injected carriers and the cell thickness. It is shown that the secondary emission contrast observed in the SEM on a reverse-biased diode can depict the location of the metallurgical junction if the diode has been prepared with the proper beveled geometry. The SEM provides the required contrast and the option of high magnification, permitting the measurement of extremely shallow junction depths.

Lateral Hydrogen Diffusion at p-GaN Layers in Nitride-Based Light Emitting Diodes with Tunnel Junctions

NASA Astrophysics Data System (ADS)

Kuwano, Yuka; Kaga, Mitsuru; Morita, Takatoshi; Yamashita, Kouji; Yagi, Kouta; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu

2013-08-01

We demonstrated lateral Mg activation along p-GaN layers underneath n-GaN surface layers in nitride-based light emitting diodes (LEDs) with GaInN tunnel junctions. A high temperature thermal annealing was effective for the lateral Mg activation when the p-GaN layers were partly exposed to an oxygen ambient as etched sidewalls. The activated regions gradually extended from the etched sidewalls to the centers with an increase of annealing time, observed as emission regions with current injection. These results suggest that hydrogen diffuses not vertically thorough the above n-GaN but laterally through the exposed portions of the p-GaN. The lowest voltage drop at the GaInN tunnel junction was estimated to be 0.9 V at 50 mA with the optimized annealing condition.

Semiconductor tunnel junction with enhancement layer

DOEpatents

Klem, J.F.; Zolper, J.C.

1997-10-21

The incorporation of a pseudomorphic GaAsSb layer in a runnel diode structure affords a new degree of freedom in designing runnel junctions for p-n junction device interconnects. Previously only doping levels could be varied to control the tunneling properties. This invention uses the valence band alignment band of the GaAsSb with respect to the surrounding materials to greatly relax the doping requirements for tunneling. 5 figs.

I-V and C-V Characterization of a High-Responsivity Graphene/Silicon Photodiode with Embedded MOS Capacitor.

PubMed

Luongo, Giuseppe; Giubileo, Filippo; Genovese, Luca; Iemmo, Laura; Martucciello, Nadia; Di Bartolomeo, Antonio

2017-06-27

We study the effect of temperature and light on the I-V and C-V characteristics of a graphene/silicon Schottky diode. The device exhibits a reverse-bias photocurrent exceeding the forward current and achieves a photoresponsivity as high as 2.5 A / W . We show that the enhanced photocurrent is due to photo-generated carriers injected in the graphene/Si junction from the parasitic graphene/SiO₂/Si capacitor connected in parallel to the diode. The same mechanism can occur with thermally generated carriers, which contribute to the high leakage current often observed in graphene/Si junctions.

GUARD RING SEMICONDUCTOR JUNCTION

DOEpatents

Goulding, F.S.; Hansen, W.L.

1963-12-01

A semiconductor diode having a very low noise characteristic when used under reverse bias is described. Surface leakage currents, which in conventional diodes greatly contribute to noise, are prevented from mixing with the desired signal currents. A p-n junction is formed with a thin layer of heavily doped semiconductor material disposed on a lightly doped, physically thick base material. An annular groove cuts through the thin layer and into the base for a short distance, dividing the thin layer into a peripheral guard ring that encircles the central region. Noise signal currents are shunted through the guard ring, leaving the central region free from such currents. (AEC)

Transparent indium-tin oxide/indium-gallium-zinc oxide Schottky diodes formed by gradient oxygen doping

NASA Astrophysics Data System (ADS)

Ho, Szuheng; Yu, Hyeonggeun; So, Franky

2017-11-01

Amorphous InGaZnO (a-IGZO) is promising for transparent electronics due to its high carrier mobility and optical transparency. However, most metal/a-IGZO junctions are ohmic due to the Fermi-level pinning at the interface, restricting their device applications. Here, we report that indium-tin oxide/a-IGZO Schottky diodes can be formed by gradient oxygen doping in the a-IGZO layer that would otherwise form an ohmic contact. Making use of back-to-back a-IGZO Schottky junctions, a transparent IGZO permeable metal-base transistor is also demonstrated with a high common-base gain.

High reliability and high performance of 9xx-nm single emitter laser diodes

NASA Astrophysics Data System (ADS)

Bao, L.; Leisher, P.; Wang, J.; Devito, M.; Xu, D.; Grimshaw, M.; Dong, W.; Guan, X.; Zhang, S.; Bai, C.; Bai, J. G.; Wise, D.; Martinsen, R.

2011-03-01

Improved performance and reliability of 9xx nm single emitter laser diodes are presented. To date, over 15,000 hours of accelerated multi-cell lifetest reliability data has been collected, with drive currents from 14A to 18A and junction temperatures ranging from 60°C to 110°C. Out of 208 devices, 14 failures have been observed so far. Using established accelerated lifetest analysis techniques, the effects of temperature and power acceleration are assessed. The Mean Time to Failure (MTTF) is determined to be >30 years, for use condition 10W and junction temperature 353K (80°C), with 90% statistical confidence.

Sensor fabrication method for in situ temperature and humidity monitoring of light emitting diodes.

PubMed

Lee, Chi-Yuan; Su, Ay; Liu, Yin-Chieh; Chan, Pin-Cheng; Lin, Chia-Hung

2010-01-01

In this work micro temperature and humidity sensors are fabricated to measure the junction temperature and humidity of light emitting diodes (LED). The junction temperature is frequently measured using thermal resistance measurement technology. The weakness of this method is that the timing of data capture is not regulated by any standard. This investigation develops a device that can stably and continually measure temperature and humidity. The device is light-weight and can monitor junction temperature and humidity in real time. Using micro-electro-mechanical systems (MEMS), this study minimizes the size of the micro temperature and humidity sensors, which are constructed on a stainless steel foil substrate (40 μm-thick SS-304). The micro temperature and humidity sensors can be fixed between the LED chip and frame. The sensitivities of the micro temperature and humidity sensors are 0.06±0.005 (Ω/°C) and 0.033 pF/%RH, respectively.

Laser diode with thermal conducting, current confining film

NASA Technical Reports Server (NTRS)

Hawrylo, Frank Z. (Inventor)

1980-01-01

A laser diode formed of a rectangular parallelopiped body of single crystalline semiconductor material includes regions of opposite conductivity type indium phosphide extending to opposite surfaces of the body. Within the body is a PN junction at which light can be generated. A stripe of a conductive material is on the surface of the body to which the P type region extends and forms an ohmic contact with the P type region. The stripe is spaced from the side surfaces of the body and extends to the end surfaces of the body. A film of germanium is on the portions of the surface of the P type region which is not covered by the conductive stripe. The germanium film serves to conduct heat from the body and forms a blocking junction with the P type region so as to confine the current through the body, across the light generating PN junction, away from the side surfaces of the body.

Ultralow-voltage-drop GaN/InGaN/GaN tunnel junctions with 12% indium content

NASA Astrophysics Data System (ADS)

Akyol, Fatih; Zhang, Yuewei; Krishnamoorthy, Sriram; Rajan, Siddharth

2017-12-01

We report a combination of highly doped layers and polarization engineering that achieves highly efficient blue-transparent GaN/InGaN/GaN tunnel junctions (In content = 12%). NPN diode structures with a low voltage drop of 4.04 V at 5 kA/cm2 and a differential resistance of 6.51 × 10-5 Ω·cm2 at 3 kA/cm2 were obtained. The tunnel junction design with n++-GaN (Si: 5 × 1020 cm-3)/3 nm p++-In0.12Ga0.88N (Mg: 1.5 × 1020 cm-3)/p++-GaN (Mg: 5 × 1020 cm-3) showed the best device performance. Device simulations agree well with the experimentally determined optimal design. The combination of low In composition and high doping can facilitate lower tunneling resistance for blue-transparent light-emitting diodes.

High efficiency single Ag nanowire/p-GaN substrate Schottky junction-based ultraviolet light emitting diodes

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

Wu, Y.; Li, X.; Xu, P.

2015-02-02

We report a high efficiency single Ag nanowire (NW)/p-GaN substrate Schottky junction-based ultraviolet light emitting diode (UV-LED). The device demonstrates deep UV free exciton electroluminescence at 362.5 nm. The dominant emission, detectable at ultralow (<1 μA) forward current, does not exhibit any shifts when the forward current is increased. External quantum efficiency (EQE) as high as 0.9% is achieved at 25 μA current at room temperature. Experiments and simulation analysis show that devices fabricated with thinner Ag NWs have higher EQE. However, for very thin Ag NWs (diameter < 250 nm), this trend breaks down due to heat accumulation in the NWs. Our simple device architecturemore » offers a potentially cost-effective scheme to fabricate high efficiency Schottky junction-based UV-LEDs.« less

Solar-energy conversion and light emission in an atomic monolayer p-n diode.

PubMed

Pospischil, Andreas; Furchi, Marco M; Mueller, Thomas

2014-04-01

The limitations of the bulk semiconductors currently used in electronic devices-rigidity, heavy weight and high costs--have recently shifted the research efforts to two-dimensional atomic crystals such as graphene and atomically thin transition-metal dichalcogenides. These materials have the potential to be produced at low cost and in large areas, while maintaining high material quality. These properties, as well as their flexibility, make two-dimensional atomic crystals attractive for applications such as solar cells or display panels. The basic building blocks of optoelectronic devices are p-n junction diodes, but they have not yet been demonstrated in a two-dimensional material. Here, we report a p-n junction diode based on an electrostatically doped tungsten diselenide (WSe2) monolayer. We present applications as a photovoltaic solar cell, a photodiode and a light-emitting diode, and obtain light-power conversion and electroluminescence efficiencies of ∼ 0.5% and ∼ 0.1%, respectively. Given recent advances in the large-scale production of two-dimensional crystals, we expect them to profoundly impact future developments in solar, lighting and display technologies.

Many-junction photovoltaic device performance under non-uniform high-concentration illumination

NASA Astrophysics Data System (ADS)

Valdivia, Christopher E.; Wilkins, Matthew M.; Chahal, Sanmeet S.; Proulx, Francine; Provost, Philippe-Olivier; Masson, Denis P.; Fafard, Simon; Hinzer, Karin

2017-09-01

A parameterized 3D distributed circuit model was developed to calculate the performance of III-V solar cells and photonic power converters (PPC) with a variable number of epitaxial vertically-stacked pn junctions. PPC devices are designed with many pn junctions to realize higher voltages and to operate under non-uniform illumination profiles from a laser or LED. Performance impacts of non-uniform illumination were greatly reduced with increasing number of junctions, with simulations comparing PPC devices with 3 to 20 junctions. Experimental results using Azastra Opto's 12- and 20-junction PPC illuminated by an 845 nm diode laser show high performance even with a small gap between the PPC and optical fiber output, until the local tunnel junction limit is reached.

Unveiling the composite structures of emissive consolidated p-i-n junction nanocells for white light emission.

PubMed

Lee, Kyu Seung; Shim, Jaeho; Lee, Hyunbok; Yim, Sang-Youp; Angadi, Basavaraj; Lim, Byungkwon; Son, Dong Ick

2018-06-08

Hybrid organic-Red-Green-Blue (RGB) color quantum dots were incorporated into consolidated p(polymer)-i(RGB quantum dots)-n(small molecules) junction structures to fabricate a single active layer for a light emitting diode device for white electroluminescence. The semiconductor RGB quantum dots, as an intrinsic material, were electrostatically bonded between functional groups of the p-type polymer organic material core surface and the n-type small molecular organic material shell surface. The ZnCdSe/ZnS and CdSe/ZnS quantum dots distributed uniformly and isotropically surrounding the polymer core which in turn was surrounded by small molecular organic materials. In the present study, we have identified the mechanisms of chemical synthesis and interactions of the p-i-n junction nanocell structure through modeling studies by DFT calculations. We have also investigated optical, structural and electrical properties along with the carrier transport mechanism of the light emitting diodes which have a single active layer of consolidated p-i-n junction nanocells for white electroluminescence.

Method of making diode structures

DOEpatents

Compaan, Alvin D.; Gupta, Akhlesh

2006-11-28

A method of making a diode structure includes the step of depositing a transparent electrode layer of any one or more of the group ZnO, ZnS and CdO onto a substrate layer, and depositing an active semiconductor junction having an n-type layer and a p-type layer onto the transparent electrode layer under process conditions that avoid substantial degradation of the electrode layer. A back electrode coating layer is applied to form a diode structure.

Unclassified Publications of Lincoln Laboratory. Volume 5

DTIC Science & Technology

1975-12-15

10 TN-1974-36 LIGHT - EMITTING DIODES (LED) JA-4295 LIGHT SCATTERING JA-4456 LINCOLN DIGITAL VOICE TERMINAL TN-1975-53, TN-1975-65 LINCOLN...Hinkley J. O. Sample G. Dresselhaus T. C. Harman J. P. McVittie J. Filson p-n Junction PbSi_xSex Photo- J. P. Donnelly diodes Fabricated by Se...Room-Temperature Operation of GalnAsP/lnP Double- Heterostructure Diode Lasers Emitting at 1.1 (im Transparent Heat Mirrors for Solar-Energy

Performance analysis of high-concentrated multi-junction solar cells in hot climate

NASA Astrophysics Data System (ADS)

Ghoneim, Adel A.; Kandil, Kandil M.; Alzanki, Talal H.; Alenezi, Mohammad R.

2018-03-01

Multi-junction concentrator solar cells are a promising technology as they can fulfill the increasing energy demand with renewable sources. Focusing sunlight upon the aperture of multi-junction photovoltaic (PV) cells can generate much greater power densities than conventional PV cells. So, concentrated PV multi-junction solar cells offer a promising way towards achieving minimum cost per kilowatt-hour. However, these cells have many aspects that must be fixed to be feasible for large-scale energy generation. In this work, a model is developed to analyze the impact of various atmospheric factors on concentrator PV performance. A single-diode equivalent circuit model is developed to examine multi-junction cells performance in hot weather conditions, considering the impacts of both temperature and concentration ratio. The impacts of spectral variations of irradiance on annual performance of various high-concentrated photovoltaic (HCPV) panels are examined, adapting spectra simulations using the SMARTS model. Also, the diode shunt resistance neglected in the existing models is considered in the present model. The present results are efficiently validated against measurements from published data to within 2% accuracy. Present predictions show that the single-diode model considering the shunt resistance gives accurate and reliable results. Also, aerosol optical depth (AOD) and air mass are most important atmospheric parameters having a significant impact on HCPV cell performance. In addition, the electrical efficiency (η) is noticed to increase with concentration to a certain concentration degree after which it decreases. Finally, based on the model predictions, let us conclude that the present model could be adapted properly to examine HCPV cells' performance over a broad range of operating conditions.

On-chip very low junction temperature GaN-based light emitting diodes by selective ion implantation

NASA Astrophysics Data System (ADS)

Cheng, Yun-Wei; Chen, Hung-Hsien; Ke, Min-Yung; Chen, Cheng-Pin; Huang, JianJang

2008-08-01

We propose an on-wafer heat relaxation technology by selectively ion-implanted in part of the p-type GaN to decrease the junction temperature in the LED structure. The Si dopant implantation energy and concentration are characterized to exhibit peak carrier density 1×1018 cm-3 at the depth of 137.6 nm after activation in nitrogen ambient at 750 °C for 30 minutes. The implantation schedule is designed to neutralize the selected region or to create a reverse p-n diode in the p-GaN layer, which acts as the cold zone for heat dissipation. The cold zone with lower effective carrier concentration and thus higher resistance is able to divert the current path. Therefore, the electrical power consumption through the cold zone was reduced, resulting in less optical power emission from the quantum well under the cold zone. Using the diode forward voltage method to extract junction temperature, when the injection current increases from 10 to 60 mA, the junction temperature of the ion-implanted LED increases from 34.3 °C to 42.3 °C, while that of the conventional one rises from 30.3 °C to 63.6 °C. At 100 mA, the output power of the ion-implanted device is 6.09 % higher than that of the conventional device. The slight increase of optical power is due to the increase of current density outside the cold zone region of the implanted device and reduced junction temperature. The result indicates that our approach improves thermal dissipation and meanwhile maintains the linearity of L-I curves.

Delayed avalanche breakdown of high-voltage silicon diodes: Various structures exhibit different picosecond-range switching behavior

NASA Astrophysics Data System (ADS)

Brylevskiy, Viktor; Smirnova, Irina; Gutkin, Andrej; Brunkov, Pavel; Rodin, Pavel; Grekhov, Igor

2017-11-01

We present a comparative study of silicon high-voltage diodes exhibiting the effect of delayed superfast impact-ionization breakdown. The effect manifests itself in a sustainable picosecond-range transient from the blocking to the conducting state and occurs when a steep voltage ramp is applied to the p+-n-n+ diode in the reverse direction. Nine groups of diodes with graded and abrupt pn-junctions have been specially fabricated for this study by different techniques from different Si substrates. Additionally, in two groups of these structures, the lifetime of nonequilibrium carriers was intentionally reduced by electron irradiation. All diodes have identical geometrical parameters and similar stationary breakdown voltages. Our experimental setup allows measuring both device voltage and current during the kilovolt switching with time resolution better than 50 ps. Although all devices are capable of forming a front with kilovolt amplitude and 100 ps risetime in the in-series load, the structures with graded pn-junctions have anomalously large residual voltage. The Deep Level Transient Spectroscopy study of all diode structures has been performed in order to evaluate the effect of deep centers on device performance. It was found that the presence of deep-level electron traps negatively correlates with parameters of superfast switching, whereas a large concentration of recombination centers created by electron irradiation has virtually no influence on switching characteristics.

Spin valve-like magnetic tunnel diode exhibiting giant positive junction magnetoresistance at low temperature in Co2MnSi/SiO2/p-Si heterostructure

NASA Astrophysics Data System (ADS)

Maji, Nilay; Kar, Uddipta; Nath, T. K.

2018-02-01

The rectifying magnetic tunnel diode has been fabricated by growing Co2MnSi (CMS) Heusler alloy film carefully on a properly cleaned p-Si (100) substrate with the help of electron beam physical vapor deposition technique and its structural, electrical and magnetic properties have been experimentally investigated in details. The electronic- and magneto-transport properties at various isothermal conditions have been studied in the temperature regime of 78-300 K. The current-voltage ( I- V) characteristics of the junction show an excellent rectifying magnetic tunnel diode-like behavior throughout that temperature regime. The current ( I) across the junction has been found to decrease with the application of a magnetic field parallel to the plane of the CMS film clearly indicating positive junction magnetoresistance (JMR) of the heterostructure. When forward dc bias is applied to the heterostructure, the I- V characteristics are highly influenced on turning on the field B = 0.5 T at 78 K, and the forward current reduces abruptly (99.2% current reduction at 3 V) which is nearly equal to the order of the magnitude of the current observed in the reverse bias. Hence, our Co2MnSi/SiO2/p-Si heterostructure can perform in off ( I off)/on ( I on) states with the application of non-zero/zero magnetic field like a spin valve at low temperature (78 K).

Gallium phosphide high temperature diodes

NASA Technical Reports Server (NTRS)

Chaffin, R. J.; Dawson, L. R.

1981-01-01

High temperature (300 C) diodes for geothermal and other energy applications were developed. A comparison of reverse leakage currents of Si, GaAs, and GaP was made. Diodes made from GaP should be usable to 500 C. A Liquid Phase Epitaxy (LPE) process for producing high quality, grown junction GaP diodes is described. This process uses low vapor pressure Mg as a dopant which allows multiple boat growth in the same LPE run. These LPE wafers were cut into die and metallized to make the diodes. These diodes produce leakage currents below ten to the -9th power A/sq cm at 400 C while exhibiting good high temperature rectification characteristics. High temperature life test data is presented which shows exceptional stability of the V-I characteristics.

Characterization of vertical GaN p-n diodes and junction field-effect transistors on bulk GaN down to cryogenic temperatures

NASA Astrophysics Data System (ADS)

Kizilyalli, I. C.; Aktas, O.

2015-12-01

There is great interest in wide-bandgap semiconductor devices and most recently in vertical GaN structures for power electronic applications such as power supplies, solar inverters and motor drives. In this paper the temperature-dependent electrical behavior of vertical GaN p-n diodes and vertical junction field-effect transistors fabricated on bulk GaN substrates of low defect density (104 to 106 cm-2) is described. Homoepitaxial MOCVD growth of GaN on its native substrate and the ability to control the doping in the drift layers in GaN have allowed the realization of vertical device architectures with drift layer thicknesses of 6 to 40 μm and net carrier electron concentrations as low as 1 × 1015 cm-3. This parameter range is suitable for applications requiring breakdown voltages of 1.2 kV to 5 kV. Mg, which is used as a p-type dopant in GaN, is a relatively deep acceptor (E A ≈ 0.18 eV) and susceptible to freeze-out at temperatures below 200 K. The loss of holes in p-GaN has a deleterious effect on p-n junction behavior, p-GaN contacts and channel control in junction field-effect transistors at temperatures below 200 K. Impact ionization-based avalanche breakdown (BV > 1200 V) in GaN p-n junctions is characterized between 77 K and 423 K for the first time. At higher temperatures the p-n junction breakdown voltage improves due to increased phonon scattering. A positive temperature coefficient in the breakdown voltage is demonstrated down to 77 K; however, the device breakdown characteristics are not as abrupt at temperatures below 200 K. On the other hand, contact resistance to p-GaN is reduced dramatically above room temperature, improving the overall device performance in GaN p-n diodes in all cases except where the n-type drift region resistance dominates the total forward resistance. In this case, the electron mobility can be deconvolved and is found to decrease with T -3/2, consistent with a phonon scattering model. Also, normally-on vertical junction field-effect transistors with BV = 1000 V and drain currents of 4 A are fabricated and characterized over the same temperature range. It is demonstrated that vertical GaN devices (diodes and transistors) utilizing p-n junctions are suitable for most practical applications including automotive ones (210 K < T < 423 K). While devices are functional at cryogenic temperatures (77 K) there may be some limitations to their performance due the freeze-out of Mg acceptors.

Simulation study on AlGaN/GaN diode with Γ-shaped anode for ultra-low turn-on voltage

NASA Astrophysics Data System (ADS)

Wang, Zeheng; Chen, Wanjun; Wang, Fangzhou; Cao, Jun; Sun, Ruize; Ren, Kailin; Luo, Yi; Guo, Songnan; Wang, Zirui; Jin, Xiaosheng; Yang, Lei; Zhang, Bo

2018-05-01

An ultra-low turn-on voltage (VT) Γ-shaped anode AlGaN/GaN Schottky barrier diode (GA-SBD) is proposed via modeling and simulation for the first time, in which a Γ-shaped anode consists of a metal-2DEG junction together with a metal-AlGaN junction beside a shallowly recessed MIS field plate (MFP). An analytic forward current-voltage model matching the simulation results well is presented where an ultra-low VT of 0.08 V is obtained. The turn-on and blocking mechanisms are investigated to reveal the GA-SBD's great potential for applications of highly efficient power ICs.

Reduced-droop green III-nitride light-emitting diodes utilizing GaN tunnel junction

NASA Astrophysics Data System (ADS)

Alhassan, Abdullah I.; Young, Erin C.; Alyamani, Ahmed Y.; Albadri, Abdulrahman; Nakamura, Shuji; DenBaars, Steven P.; Speck, James S.

2018-04-01

We report the fabrication of low-droop high-efficiency green c-plane light-emitting diodes (LEDs) utilizing GaN tunnel junction (TJ) contacts. The LED epitaxial layers with a top p-GaN layer were grown by metal organic chemical vapor deposition and an n++-GaN layer was deposited by molecular beam epitaxy to form a TJ. The TJ LEDs were then compared with equivalent LEDs having a tin-doped indium oxide (ITO) contact. The TJ LEDs exhibited a higher performance and a lower efficiency droop than did the ITO LEDs. At 35 A/cm2, the external quantum efficiencies for the TJ and ITO LEDs were 31.2 and 27%, respectively.

Van der Waals MoS2/VO2 heterostructure junction with tunable rectifier behavior and efficient photoresponse.

PubMed

Oliva, Nicoló; Casu, Emanuele Andrea; Yan, Chen; Krammer, Anna; Rosca, Teodor; Magrez, Arnaud; Stolichnov, Igor; Schueler, Andreas; Martin, Olivier J F; Ionescu, Adrian Mihai

2017-10-27

Junctions between n-type semiconductors of different electron affinity show rectification if the junction is abrupt enough. With the advent of 2D materials, we are able to realize thin van der Waals (vdW) heterostructures based on a large diversity of materials. In parallel, strongly correlated functional oxides have emerged, having the ability to show reversible insulator-to-metal (IMT) phase transition by collapsing their electronic bandgap under a certain external stimulus. Here, we report for the first time the electronic and optoelectronic characterization of ultra-thin n-n heterojunctions fabricated using deterministic assembly of multilayer molybdenum disulphide (MoS 2 ) on a phase transition material, vanadium dioxide (VO 2 ). The vdW MoS 2 /VO 2 heterojunction combines the excellent blocking capability of an n-n junction with a high conductivity in on-state, and it can be turned into a Schottky rectifier at high applied voltage or at temperatures higher than 68 °C, exploiting the metal state of VO 2 . We report tunable diode-like current rectification with a good diode ideality factor of 1.75 and excellent conductance swing of 120 mV/dec. Finally, we demonstrate unique tunable photosensitivity and excellent junction photoresponse in the 500/650 nm wavelength range.

Effect of temperature on series resistance of organic/inorganic semiconductor junction diode

NASA Astrophysics Data System (ADS)

Tripathi, Udbhav; Kaur, Ramneek; Bharti, Shivani

2016-05-01

The paper reports the fabrication and characterization of CuPc/n-Si organic/inorganic semiconductor diode. Copper phthalocyanine, a p-type organic semiconductor layer has been deposited on Si substrate by thermal evaporation technique. The detailed analysis of the forward and reverse bias current-voltage characteristics has been provided. Temperature dependence of the schottky diode parameters has been studied and discussed in the temperature range, 303 K to 353 K. Series resistance of the diode has been determined using Cheung's function method. Series resistance decreases with increase in temperature. The large value of series resistance at low temperature has been explained on the basis of barrier inhomogeneities in the diode.

Transport and Junction Physics of Semiconductor-Metal Eutectic Composites

DTIC Science & Technology

1988-06-01

eutectic junction and includes the method for making contacts as well as current-voltage (I-V), capacitance- voltage (C-V), and electron-beam-induced current...junction was performed with another RTA at 8000C to 9000C for 10 s. This technique also worked well to provide the necessary ohmic contact. The necessary...solid state diffusion of Ta and Si. The diode is well behaved, with an ideality factor n = 1.10 ± 0.05. Deviation from the straight line forward

Vertical GaN Devices for Power Electronics in Extreme Environments

DTIC Science & Technology

2016-03-31

electronics applications. In this paper vertical p-n diodes and transistors fabricated on pseudo bulk low defect density (104 to 106 cm-2) GaN substrates are...holes in p-GaN has deleterious effect on p-n junction behavior (Fig. 2), p-GaN contacts, and channel control in junction field-effect transistors at...and transistors ) utilizing p-n junctions are suitable for most practical applications including automotive (210K < T < 423K) but may have limitations

Manifestation of counteracting photovoltaic effect on IV characteristics in multi-junction solar cells

NASA Astrophysics Data System (ADS)

Mintairov, M. A.; Evstropov, V. V.; Mintairov, S. A.; Shvarts, M. Z.; Kozhukhovskaia, S. A.; Kalyuzhnyy, N. A.

2017-11-01

The existence within monolithic double- and triple-junction solar cells of a photoelectric source, which counteracts the basic photovoltaic p-n junctions, is proved. The paper presents a detailed analysis of the shape of the light IV-characteristics, as well as the dependence Voc-Jsc (open circuit voltage - short-circuit current). It is established that the counteracting source is tunnel p+-n+ junction. The photoelectric characteristics of samples with different tunnel diode peak current values were investigated, including the case of a zero value. When the tunnel p+-n+ junction is photoactive, the Voc-Jsc dependence has a dropping part, including a sharp jump. This undesirable effect decreases with increasing peak current.

Metal-Insulator-Semiconductor Diode Consisting of Two-Dimensional Nanomaterials.

PubMed

Jeong, Hyun; Oh, Hye Min; Bang, Seungho; Jeong, Hyeon Jun; An, Sung-Jin; Han, Gang Hee; Kim, Hyun; Yun, Seok Joon; Kim, Ki Kang; Park, Jin Cheol; Lee, Young Hee; Lerondel, Gilles; Jeong, Mun Seok

2016-03-09

We present a novel metal-insulator-semiconductor (MIS) diode consisting of graphene, hexagonal BN, and monolayer MoS2 for application in ultrathin nanoelectronics. The MIS heterojunction structure was fabricated by vertically stacking layered materials using a simple wet chemical transfer method. The stacking of each layer was confirmed by confocal scanning Raman spectroscopy and device performance was evaluated using current versus voltage (I-V) and photocurrent measurements. We clearly observed better current rectification and much higher current flow in the MIS diode than in the p-n junction and the metal-semiconductor diodes made of layered materials. The I-V characteristic curve of the MIS diode indicates that current flows mainly across interfaces as a result of carrier tunneling. Moreover, we observed considerably high photocurrent from the MIS diode under visible light illumination.

Controlled carrier screening in p-n NiO/GaN piezoelectric generators by an Al2O3 insertion layer

NASA Astrophysics Data System (ADS)

Johar, Muhammad Ali; Jeong, Dae Kyung; Afifi Hassan, Mostafa; Kang, Jin-Ho; Ha, Jun-Seok; Key Lee, June; Ryu, Sang-Wan

2017-12-01

The performance of a piezoelectric generator (PG) depends significantly on the internal screening process inside the device. As piezoelectric charges appear on both ends of the piezoelectric crystal, internal screening starts to decrease the piezoelectric bias. Therefore, the piezoelectric energy generated by external stress is not fully utilized by external circuit, which is the most challenging aspect of high-efficiency PGs. In this work, the internal screening effect of a NiO/GaN p-n PG was analyzed and controlled with an Al2O3 insertion layer. Internal screening in the p-n diode PG was categorized into free-carrier screening in neutral regions and junction screening due to charge drift across the junction. It was observed that junction screening could be significantly suppressed by inserting an Al2O3 layer and that effect was dominant in a leaky diode PG. With this implementation, the piezoelectric bias of the NiO/GaN PG was improved by a factor of ~100 for high-leakage diodes and a factor of ~1.6 for low-leakage diodes. Consequently, NiO/Al2O3/GaN PGs under a stress of 5 MPa provided a piezoelectric bias of 12.1 V and a current density of 2.25 µA cm-2. The incorporation of a highly resistive Al2O3 layer between p-NiO and n-GaN layers in NiO/GaN heterojunctions provides an efficient means of improving the piezoelectric performance by controlling the internal screening of the piezoelectric field.

Power degradation and reliability study of high-power laser bars at quasi-CW operation

NASA Astrophysics Data System (ADS)

Zhang, Haoyu; Fan, Yong; Liu, Hui; Wang, Jingwei; Zah, Chungen; Liu, Xingsheng

2017-02-01

The solid state laser relies on the laser diode (LD) pumping array. Typically for high peak power quasi-CW (QCW) operation, both energy output per pulse and long term reliability are critical. With the improved bonding technique, specially Indium-free bonded diode laser bars, most of the device failures were caused by failure within laser diode itself (wearout failure), which are induced from dark line defect (DLD), bulk failure, point defect generation, facet mirror damage and etc. Measuring the reliability of LD under QCW condition will take a rather long time. Alternatively, an accelerating model could be a quicker way to estimate the LD life time under QCW operation. In this report, diode laser bars were mounted on micro channel cooler (MCC) and operated under QCW condition with different current densities and junction temperature (Tj ). The junction temperature is varied by modulating pulse width and repetition frequency. The major concern here is the power degradation due to the facet failure. Reliability models of QCW and its corresponding failures are studied. In conclusion, QCW accelerated life-time model is discussed, with a few variable parameters. The model is compared with CW model to find their relationship.

Silicon Carbide Diodes Performance Characterization and Comparison With Silicon Devices

NASA Technical Reports Server (NTRS)

Lebron-Velilla, Ramon C.; Schwarze, Gene E.; Trapp, Scott

2003-01-01

Commercially available silicon carbide (SiC) Schottky diodes from different manufacturers were electrically tested and characterized at room temperature. Performed electrical tests include steady state forward and reverse I-V curves, as well as switching transient tests performed with the diodes operating in a hard switch dc-to-dc buck converter. The same tests were performed in current state of the art silicon (Si) and gallium arsenide (GaAs) Schottky and pn junction devices for evaluation and comparison purposes. The SiC devices tested have a voltage rating of 200, 300, and 600 V. The comparison parameters are forward voltage drop at rated current, reverse current at rated voltage and peak reverse recovery currents in the dc to dc converter. Test results show that steady state characteristics of the tested SiC devices are not superior to the best available Si Schottky and ultra fast pn junction devices. Transient tests reveal that the tested SiC Schottky devices exhibit superior transient behavior. This is more evident at the 300 and 600 V rating where SiC Schottky devices showed drastically lower reverse recovery currents than Si ultra fast pn diodes of similar rating.

Electrical transport characterization of PEDOT:PSS/n-Si Schottky diodes and their applications in solar cells.

PubMed

Khurelbaatar, Zagarzusem; Hyung, Jung-Hwan; Kim, Gil-Sung; Park, No-Won; Shim, Kyu-Hwan; Lee, Sang-Kwon

2014-06-01

We demonstrate locally contacted PEDOT:PSS Schottky diodes with excellent rectifying behavior, fabricated on n-type Si substrates using a spin-coating process and a reactive-ion etching process. Electrical transport characterizations of these Schottky diodes were investigated by both current-voltage (I-V) and capacitance-voltage (C-V) measurements. We found that these devices exhibit excellent modulation in the current with an on/off ratio of - 10(6). Schottky junction solar cells composed of PEDOT:PSS and n-Si structures were also examined. From the current density-voltage (J-V) measurement of a solar cell under illumination, the short circuit current (I(sc)), open circuit voltage (V(oc)), and conversion efficiency (eta) were - 19.7 mA/cm2, - 578.5 mV, and - 6.5%, respectively. The simple and low-cost fabrication process of the PEDOT:PSS/n-Si Schottky junctions makes them a promising candidate for further high performance solar cell applications.

Mo1-xWxSe2-Based Schottky Junction Photovoltaic Cells.

PubMed

Yi, Sum-Gyun; Kim, Sung Hyun; Park, Sungjin; Oh, Donggun; Choi, Hwan Young; Lee, Nara; Choi, Young Jai; Yoo, Kyung-Hwa

2016-12-14

We developed Schottky junction photovoltaic cells based on multilayer Mo 1-x W x Se 2 with x = 0, 0.5, and 1. To generate built-in potentials, Pd and Al were used as the source and drain electrodes in a lateral structure, and Pd and graphene were used as the bottom and top electrodes in a vertical structure. These devices exhibited gate-tunable diode-like current rectification and photovoltaic responses. Mo 0.5 W 0.5 Se 2 Schottky diodes with Pd and Al electrodes exhibited higher photovoltaic efficiency than MoSe 2 and WSe 2 devices with Pd and Al electrodes, likely because of the greater adjusted band alignment in Mo 0.5 W 0.5 Se 2 devices. Furthermore, we showed that Mo 0.5 W 0.5 Se 2 -based vertical Schottky diodes yield a power conversion efficiency of ∼16% under 532 nm light and ∼13% under a standard air mass 1.5 spectrum, demonstrating their remarkable potential for photovoltaic applications.

Temperature-dependent Schottky barrier in high-performance organic solar cells

PubMed Central

Li, Hui; He, Dan; Zhou, Qing; Mao, Peng; Cao, Jiamin; Ding, Liming; Wang, Jizheng

2017-01-01

Organic solar cells (OSCs) have attracted great attention in the past 30 years, and the power conversion efficiency (PCE) now reaches around 10%, largely owning to the rapid material developments. Meanwhile with the progress in the device performance, more and more interests are turning to understanding the fundamental physics inside the OSCs. In the conventional bulk-heterojunction architecture, only recently it is realized that the blend/cathode Schottky junction serves as the fundamental diode for the photovoltaic function. However, few researches have focused on such junctions, and their physical properties are far from being well-understood. In this paper based on PThBDTP:PC71BM blend, we fabricated OSCs with PCE exceeding 10%, and investigated temperature-dependent behaviors of the junction diodes by various characterization including current-voltage, capacitance-voltage and impedance measurements between 70 to 290 K. We found the Schottky barrier height exhibits large inhomogeneity, which can be described by two sets of Gaussian distributions. PMID:28071700

On the effect of N-GaN/P-GaN/N-GaN/P-GaN/N-GaN built-in junctions in the n-GaN layer for InGaN/GaN light-emitting diodes.

PubMed

Kyaw, Zabu; Zhang, Zi-Hui; Liu, Wei; Tan, Swee Tiam; Ju, Zhen Gang; Zhang, Xue Liang; Ji, Yun; Hasanov, Namig; Zhu, Binbin; Lu, Shunpeng; Zhang, Yiping; Sun, Xiao Wei; Demir, Hilmi Volkan

2014-01-13

N-GaN/P-GaN/N-GaN/P-GaN/N-GaN (NPNPN-GaN) junctions embedded between the n-GaN region and multiple quantum wells (MQWs) are systematically studied both experimentally and theoretically to increase the performance of InGaN/GaN light emitting diodes (LEDs) in this work. In the proposed architecture, each thin P-GaN layer sandwiched in the NPNPN-GaN structure is completely depleted due to the built-in electric field in the NPNPN-GaN junctions, and the ionized acceptors in these P-GaN layers serve as the energy barriers for electrons from the n-GaN region, resulting in a reduced electron over flow and enhanced the current spreading horizontally in the n- GaN region. These lead to increased optical output power and external quantum efficiency (EQE) from the proposed device.

By-Pass Diode Temperature Tests of a Solar Array Coupon under Space Thermal Environment Conditions

NASA Technical Reports Server (NTRS)

Wright, Kenneth H.; Schneider, Todd A.; Vaughn, Jason A.; Hoang, Bao; Wong, Frankie; Wu, Gordon

2016-01-01

By-Pass diodes are a key design feature of solar arrays and system design must be robust against local heating, especially with implementation of larger solar cells. By-Pass diode testing was performed to aid thermal model development for use in future array designs that utilize larger cell sizes that result in higher string currents. Testing was performed on a 56-cell Advanced Triple Junction solar array coupon provided by SSL. Test conditions were vacuum with cold array backside using discrete by-pass diode current steps of 0.25 A ranging from 0 A to 2.0 A.

An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band.

PubMed

Sadaf, S M; Zhao, S; Wu, Y; Ra, Y-H; Liu, X; Vanka, S; Mi, Z

2017-02-08

To date, semiconductor light emitting diodes (LEDs) operating in the deep ultraviolet (UV) spectral range exhibit very low efficiency due to the presence of large densities of defects and extremely inefficient p-type conduction of conventional AlGaN quantum well heterostructures. We have demonstrated that such critical issues can be potentially addressed by using nearly defect-free AlGaN tunnel junction core-shell nanowire heterostructures. The core-shell nanowire arrays exhibit high photoluminescence efficiency (∼80%) in the UV-C band at room temperature. With the incorporation of an epitaxial Al tunnel junction, the p-(Al)GaN contact-free nanowire deep UV LEDs showed nearly one order of magnitude reduction in the device resistance, compared to the conventional nanowire p-i-n device. The unpackaged Al tunnel junction deep UV LEDs exhibit an output power >8 mW and a peak external quantum efficiency ∼0.4%, which are nearly one to two orders of magnitude higher than previously reported AlGaN nanowire devices. Detailed studies further suggest that the maximum achievable efficiency is limited by electron overflow and poor light extraction efficiency due to the TM polarized emission.

Application of CaCu3Ti4O12 based quadruple perovskites as a promising candidate for optoelectronic devices

NASA Astrophysics Data System (ADS)

Pal, Kamalesh; Jana, Rajkumar; Dey, Arka; Ray, Partha P.; Seikh, Md Motin; Gayen, Arup

2018-05-01

We report the synthesis of nanosized (40-50 nm) CaCu3-xMnxTi4-xMnxO12 (x = 0, 0.5 and 1) quadruple perovskite (QP) semiconductor via a modified combustion method for use as Schottky barrier diode (SBD) at the Al/QP junction. The fabricated SBD is analysed on the basis of thermionic emission theory to observe its quality and some important diode parameters. For insight analysis of charge transport mechanism through metal-semiconductor junction, theory of space charge limited currents is applied and discussed in the light of parameters like carrier concentration, mobility-lifetime product and diffusion length. The Mn-doped exhibit better device performance compared to parent material.

True-blue laser diodes with tunnel junctions grown monolithically by plasma-assisted molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Skierbiszewski, Czeslaw; Muziol, Grzegorz; Nowakowski-Szkudlarek, Krzesimir; Turski, Henryk; Siekacz, Marcin; Feduniewicz-Zmuda, Anna; Nowakowska-Szkudlarek, Anna; Sawicka, Marta; Perlin, Piotr

2018-03-01

We demonstrate true-blue 450 nm tunnel junction (TJ) laser diodes (LDs) grown by plasma-assisted molecular beam epitaxy (PAMBE). The absence of hydrogen during PAMBE growth allows us to achieve TJs with low resistance. We compare TJ LDs with LDs of standard construction with p-type metal contact. For both types of LD, the threshold current density is around 3 kA/cm2 and the slope efficiency is 0.5 W/A. We do not observe any significant changes in optical losses and differential gain in TJ LDs compared with standard LDs. The differential resistivity of the TJs for current densities higher than 2 kA/cm2 is below 10-4 Ω·cm2.

Micro-light-emitting diodes with III-nitride tunnel junction contacts grown by metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Hwang, David; Mughal, Asad J.; Wong, Matthew S.; Alhassan, Abdullah I.; Nakamura, Shuji; DenBaars, Steven P.

2018-01-01

Micro-light-emitting diodes (µLEDs) with tunnel junction (TJ) contacts were grown entirely by metalorganic chemical vapor deposition. A LED structure was grown, treated with UV ozone and hydrofluoric acid, and reloaded into the reactor for TJ regrowth. The silicon doping level of the n++-GaN TJ was varied to examine its effect on voltage. µLEDs from 2.5 × 10-5 to 0.01 mm2 in area were processed, and the voltage penalty of the TJ for the smallest µLED at 20 A/cm2 was 0.60 V relative to that for a standard LED with indium tin oxide. The peak external quantum efficiency of the TJ LED was 34%.

Multiple negative differential resistance devices with ultra-high peak-to-valley current ratio for practical multi-valued logic and memory applications

NASA Astrophysics Data System (ADS)

Shin, Sunhae; Rok Kim, Kyung

2015-06-01

In this paper, we propose a novel multiple negative differential resistance (NDR) device with ultra-high peak-to-valley current ratio (PVCR) over 106 by combining tunnel diode with a conventional MOSFET, which suppresses the valley current with transistor off-leakage level. Band-to-band tunneling (BTBT) in tunnel junction provides the first peak, and the second peak and valley are generated from the suppression of diffusion current in tunnel diode by the off-state MOSFET. The multiple NDR curves can be controlled by doping concentration of tunnel junction and the threshold voltage of MOSFET. By using complementary multiple NDR devices, five-state memory is demonstrated only with six transistors.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Research on reverse recovery characteristics of SiGeC p-i-n diodes

NASA Astrophysics Data System (ADS)

Gao, Yong; Liu, Jing; Yang, Yuan

2008-12-01

This paper analyses the reverse recovery characteristics and mechanism of SiGeC p-i-n diodes. Based on the integrated systems engineering (ISE) data, the critical physical models of SiGeC diodes are proposed. Based on hetero-junction band gap engineering, the softness factor increases over six times, reverse recovery time is over 30% short and there is a 20% decrease in peak reverse recovery current for SiGeC diodes with 20% of germanium and 0.5% of carbon, compared to Si diodes. Those advantages of SiGeC p-i-n diodes are more obvious at high temperature. Compared to lifetime control, SiGeC technique is more suitable for improving diode properties and the tradeoff between reverse recovery time and forward voltage drop can be easily achieved in SiGeC diodes. Furthermore, the high thermal-stability of SiGeC diodes reduces the costs of further process steps and offers more freedoms to device design.

Contact Metallization and Packaging Technology Development for SiC Bipolar Junction Transistors, PiN Diodes, and Schottky Diodes Designed for Long-Term Operations at 350degreeC

DTIC Science & Technology

2006-05-01

switches that are used in power conditioning systems. Silicon carbide diodes are now available commercially, and transistors (JEFETs, MOSFETs, IGBTs ...in UHP Ar for 60s in a rapid thermal annealing (RTA) furnace to achieve a low contact resistance. Following the RTA step, photolithography was...with 20μm Au is shown in Figure 3-4. The brazing process was performed with an SST 3150 high vacuum furnace . The 3150 utilizes an oil-free roughing

In situ measurement of the junction temperature of light emitting diodes using a flexible micro temperature sensor.

PubMed

Lee, Chi-Yuan; Su, Ay; Liu, Yin-Chieh; Fan, Wei-Yuan; Hsieh, Wei-Jung

2009-01-01

This investigation aimed to fabricate a flexible micro resistive temperature sensor to measure the junction temperature of a light emitting diode (LED). The junction temperature is typically measured using a thermal resistance measurement approach. This approach is limited in that no standard regulates the timing of data capture. This work presents a micro temperature sensor that can measure temperature stably and continuously, and has the advantages of being lightweight and able to monitor junction temperatures in real time. Micro-electro-mechanical-systems (MEMS) technologies are employed to minimize the size of a temperature sensor that is constructed on a stainless steel foil substrate (SS-304 with 30 μm thickness). A flexible micro resistive temperature sensor can be fixed between the LED chip and the frame. The junction temperature of the LED can be measured from the linear relationship between the temperature and the resistance. The sensitivity of the micro temperature sensor is 0.059 ± 0.004 Ω/°C. The temperature of the commercial CREE(®) EZ1000 chip is 119.97 °C when it is thermally stable, as measured using the micro temperature sensor; however, it was 126.9 °C, when measured by thermal resistance measurement. The micro temperature sensor can be used to replace thermal resistance measurement and performs reliably.

Forward-bias diode parameters, electronic noise, and photoresponse of graphene/silicon Schottky junctions with an interfacial native oxide layer

NASA Astrophysics Data System (ADS)

An, Yanbin; Behnam, Ashkan; Pop, Eric; Bosman, Gijs; Ural, Ant

2015-09-01

Metal-semiconductor Schottky junction devices composed of chemical vapor deposition grown monolayer graphene on p-type silicon substrates are fabricated and characterized. Important diode parameters, such as the Schottky barrier height, ideality factor, and series resistance, are extracted from forward bias current-voltage characteristics using a previously established method modified to take into account the interfacial native oxide layer present at the graphene/silicon junction. It is found that the ideality factor can be substantially increased by the presence of the interfacial oxide layer. Furthermore, low frequency noise of graphene/silicon Schottky junctions under both forward and reverse bias is characterized. The noise is found to be 1/f dominated and the shot noise contribution is found to be negligible. The dependence of the 1/f noise on the forward and reverse current is also investigated. Finally, the photoresponse of graphene/silicon Schottky junctions is studied. The devices exhibit a peak responsivity of around 0.13 A/W and an external quantum efficiency higher than 25%. From the photoresponse and noise measurements, the bandwidth is extracted to be ˜1 kHz and the normalized detectivity is calculated to be 1.2 ×109 cm Hz1/2 W-1. These results provide important insights for the future integration of graphene with silicon device technology.

Studies of silicon p-n junction solar cells

NASA Technical Reports Server (NTRS)

Neugroschel, A.; Lindholm, F. A.

1979-01-01

To provide theoretical support for investigating different ways to obtain high open-circuit voltages in p-n junction silicon solar cells, an analytical treatment of heavily doped transparent-emitter devices is presented that includes the effects of bandgap narrowing, Fermi-Dirac statistics, a doping concentration gradient, and a finite surface recombination velocity at the emitter surface. Topics covered include: (1) experimental determination of bandgap narrowing in the emitter of silicon p-n junction devices; (2) heavily doped transparent regions in junction solar cells, diodes, and transistors; (3) high-low-emitter solar cell; (4) determination of lifetimes and recombination currents in p-n junction solar cells; (5) MOS and oxide-charged-induced BSF solar cells; and (6) design of high efficiency solar cells for space and terrestrial applications.

Light Emitting, Photovoltaic or Other Electronic Apparatus and System

NASA Technical Reports Server (NTRS)

Blanchard, Richard A. (Inventor); Lewandowski, Mark Allan (Inventor); Lowenthal, Mark D. (Inventor); Fuller, Kirk A. (Inventor); Frazier, Donald Odell (Inventor); Shotton, Neil O. (Inventor); Ray, William Johnstone (Inventor)

2016-01-01

The present invention provides an electronic apparatus, such as a lighting device comprised of light emitting diodes (LEDs) or a power generating apparatus comprising photovoltaic diodes, which may be created through a printing process, using a semiconductor or other substrate particle ink or suspension and using a lens particle ink or suspension. An exemplary apparatus comprises a base; at least one first conductor; a plurality of diodes coupled to the at least one first conductor; at least one second conductor coupled to the plurality of diodes; and a plurality of lenses suspended in a polymer deposited or attached over the diodes. The lenses and the suspending polymer have different indices of refraction. In some embodiments, the lenses and diodes are substantially spherical, and have a ratio of mean diameters or lengths between about 10:1 and 2:1. The diodes may be LEDs or photovoltaic diodes, and in some embodiments, have a junction formed at least partially as a hemispherical shell or cap.

Light Emitting, Photovoltaic or Other Electronic Apparatus and System

NASA Technical Reports Server (NTRS)

Shotton, Neil O. (Inventor); Lewandowski, Mark Allan (Inventor); Lowenthal, Mark D. (Inventor); Ray, William Johnstone (Inventor); Blanchard, Richard A. (Inventor); Fuller, Kirk A. (Inventor); Frazier, Donald Odell (Inventor)

2018-01-01

The present invention provides an electronic apparatus, such as a lighting device comprised of light emitting diodes (LEDs) or a power generating apparatus comprising photovoltaic diodes, which may be created through a printing process, using a semiconductor or other substrate particle ink or suspension and using a lens particle ink or suspension. An exemplary apparatus comprises a base; at least one first conductor; a plurality of diodes coupled to the at least one first conductor; at least one second conductor coupled to the plurality of diodes; and a plurality of lenses suspended in a polymer deposited or attached over the diodes. The lenses and the suspending polymer have different indices of refraction. In some embodiments, the lenses and diodes are substantially spherical, and have a ratio of mean diameters or lengths between about 10:1 and 2:1. The diodes may be LEDs or photovoltaic diodes, and in some embodiments, have a junction formed at least partially as a hemispherical shell or cap.

Light Emitting, Photovoltaic or Other Electronic Apparatus and System

NASA Technical Reports Server (NTRS)

Ray, William Johnstone (Inventor); Shotton, Neil O. (Inventor); Lewandowski, Mark Allan (Inventor); Lowenthal, Mark D. (Inventor); Blanchard, Richard A. (Inventor); Fuller, Kirk A. (Inventor); Frazier, Donald Odell (Inventor)

2016-01-01

The present invention provides an electronic apparatus, such as a lighting device comprised of light emitting diodes (LEDs) or a power generating apparatus comprising photovoltaic diodes, which may be created through a printing process, using a semiconductor or other substrate particle ink or suspension and using a lens particle ink or suspension. An exemplary apparatus comprises a base; at least one first conductor; a plurality of substantially spherical or optically resonant diodes coupled to the at least one first conductor; at least one second conductor coupled to the plurality of diodes; and a plurality of substantially spherical lenses suspended in a polymer attached or deposited over the diodes. The lenses and the suspending polymer have different indices of refraction. In some embodiments, the lenses and diodes have a ratio of mean diameters or lengths between about 10:1 and 2:1. The diodes may be LEDs or photovoltaic diodes, and in some embodiments, have a junction formed at least partially as a hemispherical shell or cap.

Light emitting, photovoltaic or other electronic apparatus and system

NASA Technical Reports Server (NTRS)

Ray, William Johnstone (Inventor); Lowenthal, Mark D. (Inventor); Shotton, Neil O. (Inventor); Blanchard, Richard A. (Inventor); Lewandowski, Mark Allan (Inventor); Fuller, Kirk A. (Inventor); Frazier, Donald Odell (Inventor)

2013-01-01

The present invention provides an electronic apparatus, such as a lighting device comprised of light emitting diodes (LEDs) or a power generating apparatus comprising photovoltaic diodes, which may be created through a printing process, using a semiconductor or other substrate particle ink or suspension and using a lens particle ink or suspension. An exemplary apparatus comprises a base; at least one first conductor; a plurality of diodes coupled to the at least one first conductor; at least one second conductor coupled to the plurality of diodes; and a plurality of lenses suspended in a polymer deposited or attached over the diodes. The lenses and the suspending polymer have different indices of refraction. In some embodiments, the lenses and diodes are substantially spherical, and have a ratio of mean diameters or lengths between about 10:1 and 2:1. The diodes may be LEDs or photovoltaic diodes, and in some embodiments, have a junction formed at least partially as a hemispherical shell or cap.

Light emitting, photovoltaic or other electronic apparatus and system

NASA Technical Reports Server (NTRS)

Lowenthal, Mark D. (Inventor); Blanchard, Richard A. (Inventor); Lewandowski, Mark Allan (Inventor); Frazier, Donald Odell (Inventor); Shotton, Neil O. (Inventor); Ray, William Johnstone (Inventor); Fuller, Kirk A. (Inventor)

2013-01-01

The present invention provides an electronic apparatus, such as a lighting device comprised of light emitting diodes (LEDs) or a power generating apparatus comprising photovoltaic diodes, which may be created through a printing process, using a semiconductor or other substrate particle ink or suspension and using a lens particle ink or suspension. An exemplary apparatus comprises a base; at least one first conductor; a plurality of substantially spherical or optically resonant diodes coupled to the at least one first conductor; at least one second conductor coupled to the plurality of diodes; and a plurality of substantially spherical lenses suspended in a polymer attached or deposited over the diodes. The lenses and the suspending polymer have different indices of refraction. In some embodiments, the lenses and diodes have a ratio of mean diameters or lengths between about 10:1 and 2:1. The diodes may be LEDs or photovoltaic diodes, and in some embodiments, have a junction formed at least partially as a hemispherical shell or cap.

Relationships between junction temperature, electroluminescence spectrum and ageing of light-emitting diodes

NASA Astrophysics Data System (ADS)

Vaskuri, Anna; Kärhä, Petri; Baumgartner, Hans; Kantamaa, Olli; Pulli, Tomi; Poikonen, Tuomas; Ikonen, Erkki

2018-04-01

We have developed spectral models describing the electroluminescence spectra of AlGaInP and InGaN light-emitting diodes (LEDs) consisting of the Maxwell-Boltzmann distribution and the effective joint density of states. One spectrum at a known temperature for one LED specimen is needed for calibrating the model parameters of each LED type. Then, the model can be used for determining the junction temperature optically from the spectral measurement, because the junction temperature is one of the free parameters. We validated the models using, in total, 53 spectra of three red AlGaInP LED specimens and 72 spectra of three blue InGaN LED specimens measured at various current levels and temperatures between 303 K and 398 K. For all the spectra of red LEDs, the standard deviation between the modelled and measured junction temperatures was only 2.4 K. InGaN LEDs have a more complex effective joint density of states. For the blue LEDs, the corresponding standard deviation was 11.2 K, but it decreased to 3.5 K when each LED specimen was calibrated separately. The method of determining junction temperature was further tested on white InGaN LEDs with luminophore coating and LED lamps. The average standard deviation was 8 K for white InGaN LED types. We have six years of ageing data available for a set of LED lamps and we estimated the junction temperatures of these lamps with respect to their ageing times. It was found that the LEDs operating at higher junction temperatures were frequently more damaged.

Development and fabrication of improved Schottky power diodes

NASA Technical Reports Server (NTRS)

Cordes, L. F.; Garfinkel, M.; Taft, E. A.

1975-01-01

Reproducible methods for the fabrication of silicon Schottky diodes have been developed for tungsten, aluminum, conventional platinum silicide, and low temperature platinum silicide. Barrier heights and barrier lowering under reverse bias have been measured, permitting the accurate prediction of forward and reverse diode characteristics. Processing procedures have been developed that permit the fabrication of large area (about 1 sq cm) mesageometry power Schottky diodes with forward and reverse characteristics that approach theoretical values. A theoretical analysis of the operation of bridge rectifier circuits has been performed, which indicates the ranges of frequency and voltage for which Schottky rectifiers are preferred to p-n junctions. Power Schottky rectifiers have been fabricated and tested for voltage ratings up to 140 volts.

Dynamics of electronic transitions and frequency dependence of negative capacitance in semiconductor diodes under high forward bias

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

Bansal, Kanika; Datta, Shouvik; Henini, Mohamed

2014-09-22

We observed qualitatively dissimilar frequency dependence of negative capacitance under high charge injection in two sets of functionally different junction diodes: III-V based light emitting and Si-based non-light emitting diodes. Using an advanced approach based on bias activated differential capacitance, we developed a generalized understanding of negative capacitance phenomenon which can be extended to any diode based device structure. We explained the observations as the mutual competition of fast and slow electronic transition rates which are different in different devices. This study can be useful in understanding the interfacial effects in semiconductor heterostructures and may lead to superior device functionality.

GdN nanoisland-based GaN tunnel junctions.

PubMed

Krishnamoorthy, Sriram; Kent, Thomas F; Yang, Jing; Park, Pil Sung; Myers, Roberto C; Rajan, Siddharth

2013-06-12

Tunnel junctions could have a great impact on gallium nitride and aluminum nitride-based devices such as light-emitting diodes and lasers by overcoming critical challenges related to hole injection and p-contacts. This paper demonstrates the use of GdN nanoislands to enhance interband tunneling and hole injection into GaN p-n junctions by several orders of magnitude, resulting in low tunnel junction specific resistivity (1.3 × 10(-3) Ω-cm(2)) compared to the previous results in wide band gap semiconductors. Tunnel injection of holes was confirmed by low-temperature operation of GaN p-n junction with a tunneling contact layer, and strong electroluminescence down to 20 K. The low tunnel junction resistance combined with low optical absorption loss in GdN is very promising for incorporation in GaN-based light emitters.

Interferometric ring lasers and optical devices

DOEpatents

Hohimer, J.P.; Craft, D.C.

1995-03-14

Two ring diode lasers are optically coupled together to produce tunable, stable output through a Y-junction output coupler which may also be a laser diode or can be an active waveguide. These devices demonstrate a sharp peak in light output with an excellent side-mode-rejection ratio. The rings can also be made of passive or active waveguide material. With additional rings the device is a tunable optical multiplexer/demultiplexer. 11 figs.

Interferometric ring lasers and optical devices

DOEpatents

Hohimer, John P.; Craft, David C.

1995-01-01

Two ring diode lasers are optically coupled together to produce tunable, stable output through a Y-junction output coupler which may also be a laser diode or can be an active waveguide. These devices demonstrate a sharp peak in light output with an excellent side-mode-rejection ratio. The rings can also be made of passive or active waveguide material. With additional rings the device is a tunable optical multiplexer/demultiplexer.

Solid State Research, 1975:4

DTIC Science & Technology

1975-11-15

2.8kA/cm for broad- area devices, has been achieved for Ga. In As, _ P /inP double-heterostructure 1 -x x 1 -y y diode lasers emitting ... LIGHT (b) reverse-biasing the p -n~ junction). This should facilitate the fabrication of modulators and switches using electroabsorption and...temperature operation of Ga In As, P /inP double-heterostructure (DH) diode lasers has been achieved. Broad-area devices emitting at 1.1

Molecular diodes and ultra-thin organic rectifying junctions: Au-S-CnH2n-Q3CNQ and TCNQ derivatives.

PubMed

Ashwell, Geoffrey J; Moczko, Katarzyna; Sujka, Marta; Chwialkowska, Anna; Hermann High, L R; Sandman, Daniel J

2007-02-28

Attempts to obtain derivatives of the molecular diode, 2-{4-[1-cyano-2-(1-(omega-acetylsulfanylalkyl)-1H-quinolin-4-ylidene)-ethylidene]-cyclohexa-2,5-dienylidene}-malonitrile [1, CH(3)CO-S-C(n)H(2n)-Q3CNQ], from either 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-p-quinodimethane (TCNQF(4)) or 2,3,5,6-tetramethyl-7,7,8,8-tetracyano-p-quinodimethane (TMTCNQ) result in ring closure via the cyano group of the pi-bridge and yield di-substituted analogues: 2-{2,3,5,6-tetrafluoro-4-[6-(10-acetylsulfanyldecyl)-3-(1-(10-acetylsulfanyldecyl)-1H-quinolin-4-ylidenemethyl)-6H-benzo[f][1,7]naphthyridin-2-ylidene]-cyclohexa-2,5-dienylidene}-malonitrile (2a) and the 2,3,5,6-tetramethyl derivative (2b). Self-assembled monolayers (SAMs) of these donor-(pi-bridge)-acceptor molecular diodes exhibit asymmetric current-voltage characteristics with electron flow at forward bias from the top contact to surface C(CN)(2) groups. Comparison is made with I-V curves from ultra-thin films of an organic rectifying junction in which TCNQ(-) is electron-donating and a donor-(sigma-bridge)-acceptor diode in which TCNQ degrees is electron-accepting.

Film Reviews

ERIC Educational Resources Information Center

Dowling, John, Ed.

1976-01-01

Reviews five instructional films on: P-N junctions; crystal diodes; nuclear fusion research; Schlieren photography; and the energy crisis; including discussions of solar, nuclear, and fossil fuel energy. Also lists numerous other available films. (MLH)

Giant spin-torque diode sensitivity in the absence of bias magnetic field.

PubMed

Fang, Bin; Carpentieri, Mario; Hao, Xiaojie; Jiang, Hongwen; Katine, Jordan A; Krivorotov, Ilya N; Ocker, Berthold; Langer, Juergen; Wang, Kang L; Zhang, Baoshun; Azzerboni, Bruno; Amiri, Pedram Khalili; Finocchio, Giovanni; Zeng, Zhongming

2016-04-07

Microwave detectors based on the spin-torque diode effect are among the key emerging spintronic devices. By utilizing the spin of electrons in addition to charge, they have the potential to overcome the theoretical performance limits of their semiconductor (Schottky) counterparts. However, so far, practical implementations of spin-diode microwave detectors have been limited by the necessity to apply a magnetic field. Here, we demonstrate nanoscale magnetic tunnel junction microwave detectors, exhibiting high-detection sensitivity of 75,400 mV mW(-1) at room temperature without any external bias fields, and for low-input power (micro-Watts or lower). This sensitivity is significantly larger than both state-of-the-art Schottky diode detectors and existing spintronic diodes. Micromagnetic simulations and measurements reveal the essential role of injection locking to achieve this sensitivity performance. This mechanism may provide a pathway to enable further performance improvement of spin-torque diode microwave detectors.

Giant spin-torque diode sensitivity in the absence of bias magnetic field

PubMed Central

Fang, Bin; Carpentieri, Mario; Hao, Xiaojie; Jiang, Hongwen; Katine, Jordan A.; Krivorotov, Ilya N.; Ocker, Berthold; Langer, Juergen; Wang, Kang L.; Zhang, Baoshun; Azzerboni, Bruno; Amiri, Pedram Khalili; Finocchio, Giovanni; Zeng, Zhongming

2016-01-01

Microwave detectors based on the spin-torque diode effect are among the key emerging spintronic devices. By utilizing the spin of electrons in addition to charge, they have the potential to overcome the theoretical performance limits of their semiconductor (Schottky) counterparts. However, so far, practical implementations of spin-diode microwave detectors have been limited by the necessity to apply a magnetic field. Here, we demonstrate nanoscale magnetic tunnel junction microwave detectors, exhibiting high-detection sensitivity of 75,400 mV mW−1 at room temperature without any external bias fields, and for low-input power (micro-Watts or lower). This sensitivity is significantly larger than both state-of-the-art Schottky diode detectors and existing spintronic diodes. Micromagnetic simulations and measurements reveal the essential role of injection locking to achieve this sensitivity performance. This mechanism may provide a pathway to enable further performance improvement of spin-torque diode microwave detectors. PMID:27052973

Spin-torque diode frequency tuning via soft exchange pinning of both magnetic layers

NASA Astrophysics Data System (ADS)

Khudorozhkov, A. A.; Skirdkov, P. N.; Zvezdin, K. A.; Vetoshko, P. M.; Popkov, A. F.

2017-12-01

A spin-torque diode, which is a magnetic tunnel junction with magnetic layers softly pinned at some tilt to each other, is proposed. The resonance operating frequency of such a dual exchange-pinned spin-torque diode can be significantly higher (up to 9.5 GHz) than that of a traditional free layer spin-torque diode, and, at the same time, the sensitivity remains rather high. Using micromagnetic modeling we show that the maximum microwave sensitivity of the considered diode is reached at the bias current densities slightly below the self-sustained oscillations initiating. The dependence of the resonance frequency and the sensitivity on the angle between pinning exchange fields is presented. Thus, a way of designing spin-torque diode with a given resonance response frequency in the microwave region in the absence of an external magnetic field is proposed.

Rectifying properties of p-GaN nanowires and an n-silicon heterojunction vertical diode.

PubMed

Manna, Sujit; Ashok, Vishal D; De, S K

2010-12-01

The heterojunction of a Pd-doped p-GaN nanowire and n-Si (100) is fabricated vertically by the vapor-liquid-solid method. The average diameter of the nanowire is 40 nm. The vertical junction reveals a significantly high rectification ratio of 10(3) at 5 V, a moderate ideality factor of ∼2, and a high breakdown voltage of ∼40 V. The charge transport across the p-n junction is dominated by the electron-hole recombination process. The voltage dependence of capacitance indicates a graded-type junction. The resistance of the junction decreases with an increase in the bias voltage confirmed by impedance measurements.

Sidewall GaAs tunnel junctions fabricated using molecular layer epitaxy

PubMed Central

Ohno, Takeo; Oyama, Yutaka

2012-01-01

In this article we review the fundamental properties and applications of sidewall GaAs tunnel junctions. Heavily impurity-doped GaAs epitaxial layers were prepared using molecular layer epitaxy (MLE), in which intermittent injections of precursors in ultrahigh vacuum were applied, and sidewall tunnel junctions were fabricated using a combination of device mesa wet etching of the GaAs MLE layer and low-temperature area-selective regrowth. The fabricated tunnel junctions on the GaAs sidewall with normal mesa orientation showed a record peak current density of 35 000 A cm-2. They can potentially be used as terahertz devices such as a tunnel injection transit time effect diode or an ideal static induction transistor. PMID:27877466

GaAs/InAs Multi Quantum Well Solar Cell

DTIC Science & Technology

2012-12-01

excited states, which explains the temperature dependence of these materials and the thermoelectric or Seebeck effect. 5 Figure 4. Temperature...dependence of conductivity [from Ref. 1] The thermoelectric field E is given by the equation: dTE Q dx  (1) where Q= thermoelectric ...G. JUNCTIONS A photovoltaic cell is a basic a pn-junction diode where p-type and n-type semiconductors are combined, as shown in Figure 17

Photovoltaic and thermophotovoltaic devices with quantum barriers

DOEpatents

Wernsman, Bernard R [Jefferson Hills, PA

2007-04-10

A photovoltaic or thermophotovoltaic device includes a diode formed by p-type material and n-type material joined at a p-n junction and including a depletion region adjacent to said p-n junction, and a quantum barrier disposed near or in the depletion region of the p-n junction so as to decrease device reverse saturation current density while maintaining device short circuit current density. In one embodiment, the quantum barrier is disposed on the n-type material side of the p-n junction and decreases the reverse saturation current density due to electrons while in another, the barrier is disposed on the p-type material side of the p-n junction and decreases the reverse saturation current density due to holes. In another embodiment, both types of quantum barriers are used.

Study of phase-locked diode laser array and DFB/DBR surface emitting laser diode

NASA Astrophysics Data System (ADS)

Hsin, Wei

New types of phased-array and surface-emitting lasers are designed. The importance and approaches (or structures) of different phased array and surface emitting laser diodes are reviewed. The following are described: (1) a large optical cavity channel substrate planar laser array with layer thickness chirping; (2) a vertical cavity surface emitter with distributed feedback (DFB) optical cavity and a transverse junction buried heterostructure; (3) a microcavity distributed Bragg reflector (DBR) surface emitter; and (4) two surface emitting laser structures which utilized lateral current injection schemes to overcome the problems occurring in the vertical injection scheme.

Study and modeling of the transport mechanism in a Schottky diode on the basis of a GaAs semiinsulator

NASA Astrophysics Data System (ADS)

Resfa, A.; Smahi, Bourzig Y.; Menezla, Brahimi R.

2011-12-01

The current through a metal—semiconductor junction is mainly due to the majority carriers. Three distinctly different mechanisms exist in a Schottky diode: diffusion of the semiconductor carriers in metal, thermionic emission-diffusion (TED) of carriers through a Schottky gate, and a mechanical quantum that pierces a tunnel through the gate. The system was solved by using a coupled Poisson—Boltzmann algorithm. Schottky BH is defined as the difference in energy between the Fermi level and the metal band carrier majority of the metal—semiconductor junction to the semiconductor contacts. The insulating layer converts the MS device in an MIS device and has a strong influence on its current—voltage (I—V) and the parameters of a Schottky barrier from 3.7 to 15 eV. There are several possible reasons for the error that causes a deviation of the ideal behaviour of Schottky diodes with and without an interfacial insulator layer. These include the particular distribution of interface states, the series resistance, bias voltage and temperature. The GaAs and its large concentration values of trap centers will participate in an increase in the process of thermionic electrons and holes, which will in turn act on the I—V characteristic of the diode, and an overflow maximum value [NT = 3 × 1020] is obtained. The I—V characteristics of Schottky diodes are in the hypothesis of a parabolic summit.

All metalorganic chemical vapor phase epitaxy of p/n-GaN tunnel junction for blue light emitting diode applications

NASA Astrophysics Data System (ADS)

Neugebauer, S.; Hoffmann, M. P.; Witte, H.; Bläsing, J.; Dadgar, A.; Strittmatter, A.; Niermann, T.; Narodovitch, M.; Lehmann, M.

2017-03-01

We report on III-Nitride blue light emitting diodes (LEDs) comprising a GaN-based tunnel junction (TJ) all realized by metalorganic vapor phase epitaxy in a single growth process. The TJ grown atop the LED structures consists of a Mg-doped GaN layer and subsequently grown highly Ge-doped GaN. Long thermal annealing of 60 min at 800 °C is important to reduce the series resistance of the LEDs due to blockage of acceptor-passivating hydrogen diffusion through the n-type doped top layer. Secondary ion mass spectroscopy measurements reveal Mg-incorporation into the topmost GaN:Ge layer, implying a non-abrupt p-n tunnel junction and increased depletion width. Still, significantly improved lateral current spreading as compared to conventional semi-transparent Ni/Au p-contact metallization and consequently a more homogeneous electroluminescence distribution across 1 × 1 mm2 LED structures is achieved. Direct estimation of the depletion width is obtained from electron holography experiments, which allows for a discussion of the possible tunneling mechanism.

Determination of lifetimes and recombination currents in p-n junction solar cells, diodes, and transistors

NASA Technical Reports Server (NTRS)

Neugroschel, A.

1981-01-01

New methods are presented and illustrated that enable the accurate determination of the diffusion length of minority carriers in the narrow regions of a solar cell or a diode. Other methods now available are inaccurate for the desired case in which the width of the region is less than the diffusion length. Once the diffusion length is determined by the new methods, this result can be combined with measured dark I-V characteristics and with small-signal admittance characteristics to enable determination of the recombination currents in each quasi-neutral region of the cell - for example, in the emitter, low-doped base, and high-doped base regions of the BSF (back-surface-field) cell. This approach leads to values for the effective surface recombination velocity of the high-low junction forming the back-surface field of BSF cells or the high-low emitter junction of HLE cells. These methods are also applicable for measuring the minority-carrier lifetime in thin epitaxial layers grown on substrates with opposite conductivity type.

Junction-Free Electrospun Ag Fiber Electrodes for Flexible Organic Light-Emitting Diodes.

PubMed

Choi, Junhee; Shim, Yong Sub; Park, Cheol Hwee; Hwang, Ha; Kwack, Jin Ho; Lee, Dong Jun; Park, Young Wook; Ju, Byeong-Kwon

2018-02-01

Fabrication of junction-free Ag fiber electrodes for flexible organic light-emitting diodes (OLEDs) is demonstrated. The junction-free Ag fiber electrodes are fabricated by electrospun polymer fibers used as an etch mask and wet etching of Ag thin film. This process facilitates surface roughness control, which is important in transparent electrodes based on metal wires to prevent electrical instability of the OLEDs. The transmittance and resistance of Ag fiber electrodes can be independently adjusted by controlling spinning time and Ag deposition thickness. The Ag fiber electrode shows a transmittance of 91.8% (at 550 nm) at a sheet resistance of 22.3 Ω □ -1 , leading to the highest OLED efficiency. In addition, Ag fiber electrodes exhibit excellent mechanical durability, as shown by measuring the change in resistance under repeatable mechanical bending and various bending radii. The OLEDs with Ag fiber electrodes on a flexible substrate are successfully fabricated, and the OLEDs show an enhancement of EQE (≈19%) compared to commercial indium tin oxide electrodes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Atomistic nature in band-to-band tunneling in two-dimensional silicon pn tunnel diodes

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

Tabe, Michiharu, E-mail: tabe.michiharu@shizuoka.ac.jp; Tan, Hoang Nhat; Mizuno, Takeshi

We study low-temperature transport properties of two-dimensional (2D) Si tunnel diodes, or Si Esaki diodes, with a lateral layout. In ordinary Si Esaki diodes, interband tunneling current is severely limited because of the law of momentum conservation, while nanoscale Esaki diodes may behave differently due to the dopants in the narrow depletion region, by atomistic effects which release such current limitation. In thin-Si lateral highly doped pn diodes, we find clear signatures of interband tunneling between 2D-subbands involving phonon assistance. More importantly, the tunneling current is sharply enhanced in a narrow voltage range by resonance via a pair of amore » donor- and an acceptor-atom in the pn junction region. Such atomistic behavior is recognized as a general feature showing up only in nanoscale tunnel diodes. In particular, a donor-acceptor pair with deeper ground-state energies is likely to be responsible for such a sharply enhanced current peak, tunable by external biases.« less

Anomalous tensoelectric effects in gallium arsenide tunnel diodes

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

Alekseeva, Z.M.; Vyatkin, A.P.; Krivorotov, N.P.

Anomalous tensoelectric phenomena induced in a tunnel p-n junction by a concentrated load and by hydrostatic compression were studied. The anomalous tensoelectric effects are caused by the action of concentrators of mechanical stresses in the vicinity of the p-n junction, giving rise to local microplastic strain. Under the conditions of hydrostatic compression prolate inclusions approx.100-200 A long play the role of concentrators. Analysis of irreversible changes in the current-voltage characteristics of tunnel p-n junctions made it possible to separate the energy levels of the defects produced with plastic strain of gallium arsenide.

Minority carrier device comprising a passivating layer including a Group 13 element and a chalcogenide component

NASA Technical Reports Server (NTRS)

Barron, Andrew R. (Inventor); Hepp, Aloysius F. (Inventor); Jenkins, Phillip P. (Inventor); MacInnes, Andrew N. (Inventor)

1999-01-01

A minority carrier device includes at least one junction of at least two dissimilar materials, at least one of which is a semiconductor, and a passivating layer on at least one surface of the device. The passivating layer includes a Group 13 element and a chalcogenide component. Embodiments of the minority carrier device include, for example, laser diodes, light emitting diodes, heterojunction bipolar transistors, and solar cells.

Dark current reduction of Ge photodetector by GeO₂ surface passivation and gas-phase doping.

PubMed

Takenaka, Mitsuru; Morii, Kiyohito; Sugiyama, Masakazu; Nakano, Yoshiaki; Takagi, Shinichi

2012-04-09

We have investigated the dark current of a germanium (Ge) photodetector (PD) with a GeO₂ surface passivation layer and a gas-phase-doped n+/p junction. The gas-phase-doped PN diodes exhibited a dark current of approximately two orders of magnitude lower than that of the diodes formed by a conventional ion implantation process, indicating that gas-phase doping is suitable for low-damage PN junction formation. The bulk leakage (Jbulk) and surface leakage (Jsurf) components of the dark current were also investigated. We have found that GeO₂ surface passivation can effectively suppress the dark current of a Ge PD in conjunction with gas-phase doping, and we have obtained extremely low values of Jbulk of 0.032 mA/cm² and Jsurf of 0.27 μA/cm.

Calculation of the Electronic Parameters of an Al/DNA/p-Si Schottky Barrier Diode Influenced by Alpha Radiation

PubMed Central

Al-Ta’ii, Hassan Maktuff Jaber; Amin, Yusoff Mohd; Periasamy, Vengadesh

2015-01-01

Many types of materials such as inorganic semiconductors have been employed as detectors for nuclear radiation, the importance of which has increased significantly due to recent nuclear catastrophes. Despite the many advantages of this type of materials, the ability to measure direct cellular or biological responses to radiation might improve detector sensitivity. In this context, semiconducting organic materials such as deoxyribonucleic acid or DNA have been studied in recent years. This was established by studying the varying electronic properties of DNA-metal or semiconductor junctions when exposed to radiation. In this work, we investigated the electronics of aluminium (Al)/DNA/silicon (Si) rectifying junctions using their current-voltage (I-V) characteristics when exposed to alpha radiation. Diode parameters such as ideality factor, barrier height and series resistance were determined for different irradiation times. The observed results show significant changes with exposure time or total dosage received. An increased deviation from ideal diode conditions (7.2 to 18.0) was observed when they were bombarded with alpha particles for up to 40 min. Using the conventional technique, barrier height values were observed to generally increase after 2, 6, 10, 20 and 30 min of radiation. The same trend was seen in the values of the series resistance (0.5889–1.423 Ω for 2–8 min). These changes in the electronic properties of the DNA/Si junctions could therefore be utilized in the construction of sensitive alpha particle detectors. PMID:25730484

Structure–property relationships in atomic-scale junctions: Histograms and beyond

DOE PAGES

Mark S. Hybertsen; Venkataraman, Latha

2016-03-03

Over the past 10 years, there has been tremendous progress in the measurement, modeling and understanding of structure–function relationships in single molecule junctions. Numerous research groups have addressed significant scientific questions, directed both to conductance phenomena at the single molecule level and to the fundamental chemistry that controls junction functionality. Many different functionalities have been demonstrated, including single-molecule diodes, optically and mechanically activated switches, and, significantly, physical phenomena with no classical analogues, such as those based on quantum interference effects. Experimental techniques for reliable and reproducible single molecule junction formation and characterization have led to this progress. In particular, themore » scanning tunneling microscope based break-junction (STM-BJ) technique has enabled rapid, sequential measurement of large numbers of nanoscale junctions allowing a statistical analysis to readily distinguish reproducible characteristics. Furthermore, harnessing fundamental link chemistry has provided the necessary chemical control over junction formation, enabling measurements that revealed clear relationships between molecular structure and conductance characteristics.« less

Structure–property relationships in atomic-scale junctions: Histograms and beyond

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

Mark S. Hybertsen; Venkataraman, Latha

Over the past 10 years, there has been tremendous progress in the measurement, modeling and understanding of structure–function relationships in single molecule junctions. Numerous research groups have addressed significant scientific questions, directed both to conductance phenomena at the single molecule level and to the fundamental chemistry that controls junction functionality. Many different functionalities have been demonstrated, including single-molecule diodes, optically and mechanically activated switches, and, significantly, physical phenomena with no classical analogues, such as those based on quantum interference effects. Experimental techniques for reliable and reproducible single molecule junction formation and characterization have led to this progress. In particular, themore » scanning tunneling microscope based break-junction (STM-BJ) technique has enabled rapid, sequential measurement of large numbers of nanoscale junctions allowing a statistical analysis to readily distinguish reproducible characteristics. Furthermore, harnessing fundamental link chemistry has provided the necessary chemical control over junction formation, enabling measurements that revealed clear relationships between molecular structure and conductance characteristics.« less

Design Considerations for Heavily-Doped Cryogenic Schottky Diode Varactor Multipliers

NASA Technical Reports Server (NTRS)

Schlecht, E.; Maiwald, F.; Chattopadhyay, G.; Martin, S.; Mehdi, I.

2001-01-01

Diode modeling for Schottky varactor frequency multipliers above 500 GHz is presented with special emphasis placed on simple models and fitted equations for rapid circuit design. Temperature- and doping-dependent mobility, resistivity, and avalanche current multiplication and breakdown are presented. Next is a discussion of static junction current, including the effects of tunneling as well as thermionic emission. These results have been compared to detailed measurements made down to 80 K on diodes fabricated at JPL, followed by a discussion of the effect on multiplier efficiency. Finally, a simple model of current saturation in the undepleted active layer suitable for inclusion in harmonic balance simulators is derived.

The 20 GHz solid state transmitter design, impatt diode development and reliability assessment

NASA Technical Reports Server (NTRS)

Picone, S.; Cho, Y.; Asmus, J. R.

1984-01-01

A single drift gallium arsenide (GaAs) Schottky barrier IMPATT diode and related components were developed. The IMPATT diode reliability was assessed. A proof of concept solid state transmitter design and a technology assessment study were performed. The transmitter design utilizes technology which, upon implementation, will demonstrate readiness for development of a POC model within the 1982 time frame and will provide an information base for flight hardware capable of deployment in a 1985 to 1990 demonstrational 30/20 GHz satellite communication system. Life test data for Schottky barrier GaAs diodes and grown junction GaAs diodes are described. The results demonstrate the viability of GaAs IMPATTs as high performance, reliable RF power sources which, based on the recommendation made herein, will surpass device reliability requirements consistent with a ten year spaceborne solid state power amplifier mission.

Photo-Spectrometer Realized In A Standard Cmos Ic Process

DOEpatents

Simpson, Michael L.; Ericson, M. Nance; Dress, William B.; Jellison, Gerald E.; Sitter, Jr., David N.; Wintenberg, Alan L.

1999-10-12

A spectrometer, comprises: a semiconductor having a silicon substrate, the substrate having integrally formed thereon a plurality of layers forming photo diodes, each of the photo diodes having an independent spectral response to an input spectra within a spectral range of the semiconductor and each of the photo diodes formed only from at least one of the plurality of layers of the semiconductor above the substrate; and, a signal processing circuit for modifying signals from the photo diodes with respective weights, the weighted signals being representative of a specific spectral response. The photo diodes have different junction depths and different polycrystalline silicon and oxide coverings. The signal processing circuit applies the respective weights and sums the weighted signals. In a corresponding method, a spectrometer is manufactured by manipulating only the standard masks, materials and fabrication steps of standard semiconductor processing, and integrating the spectrometer with a signal processing circuit.

Fabrication and characterization of 8.87 THz schottky barrier mixer diodes for mixer

NASA Astrophysics Data System (ADS)

Wang, Wenjie; Li, Qian; An, Ning; Tong, Xiaodong; Zeng, Jianping

2018-04-01

In this paper we report on the fabrication and characterization of GaAs-based THz schottky barrier mixer diodes. Considering the analyzed results as well as fabrication cost and complexity, a group of trade-off parameters was determined. Electron-beam lithography and air-bridge technique have been used to obtain schottky diodes with a cut off frequency of 8.87 THz. Equivalent values of series resistance, ideal factor and junction capacitance of 10.2 (1) Ω, 1.14 (0.03) and 1.76(0.03) respectively have been measured for 0.7um diameter anode devices by DC and RF measurements. The schottky barrier diodes fabrication process is fully planar and very suitable for integration in THz frequency multiplier and mixer circuits. THz Schottky barrier diodes based on such technology with 2 μm diameter anodes have been tested at 1.6 THz in a sub-harmonic mixer.

Metal-oxide-metal point contact junction detectors. [detection mechanism and mechanical stability

NASA Technical Reports Server (NTRS)

Baird, J.; Havemann, R. H.; Fults, R. D.

1973-01-01

The detection mechanism(s) and design of a mechanically stable metal-oxide-metal point contact junction detector are considered. A prototype for a mechanically stable device has been constructed and tested. A technique has been developed which accurately predicts microwave video detector and heterodyne mixer SIM (semiconductor-insulator-metal) diode performance from low dc frequency volt-ampere curves. The difference in contact potential between the two metals and geometrically induced rectification constitute the detection mechanisms.

Tribotronic Tuning Diode for Active Analog Signal Modulation.

PubMed

Zhou, Tao; Yang, Zhi Wei; Pang, Yaokun; Xu, Liang; Zhang, Chi; Wang, Zhong Lin

2017-01-24

Realizing active interaction with external environment/stimuli is a great challenge for current electronics. In this paper, a tribotronic tuning diode (TTD) is proposed by coupling a variable capacitance diode and a triboelectric nanogenerator in free-standing sliding mode. When the friction layer is sliding on the device surface for electrification, a reverse bias voltage is created and applied to the diode for tuning the junction capacitance. When the sliding distance increases from 0 to 25 mm, the capacitance of the TTD decreases from about 39 to 8 pF. The proposed TTD has been integrated into analog circuits and exhibited excellent performances in frequency modulation, phase shift, and filtering by sliding a finger. This work has demonstrated tunable diode and active analog signal modulation by tribotronics, which has great potential to replace ordinary variable capacitance diodes in various practical applications such as signal processing, electronic tuning circuits, precise tuning circuits, active sensor networks, electronic communications, remote controls, flexible electronics, etc.

A 17 GHz molecular rectifier

PubMed Central

Trasobares, J.; Vuillaume, D.; Théron, D.; Clément, N.

2016-01-01

Molecular electronics originally proposed that small molecules sandwiched between electrodes would accomplish electronic functions and enable ultimate scaling to be reached. However, so far, functional molecular devices have only been demonstrated at low frequency. Here, we demonstrate molecular diodes operating up to 17.8 GHz. Direct current and radio frequency (RF) properties were simultaneously measured on a large array of molecular junctions composed of gold nanocrystal electrodes, ferrocenyl undecanethiol molecules and the tip of an interferometric scanning microwave microscope. The present nanometre-scale molecular diodes offer a current density increase by several orders of magnitude compared with that of micrometre-scale molecular diodes, allowing RF operation. The measured S11 parameters show a diode rectification ratio of 12 dB which is linked to the rectification behaviour of the direct current conductance. From the RF measurements, we extrapolate a cut-off frequency of 520 GHz. A comparison with the silicon RF-Schottky diodes, architecture suggests that the RF-molecular diodes are extremely attractive for scaling and high-frequency operation. PMID:27694833

ZnS-Based ZnSTe:N/n-ZnS Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Ichino, Kunio; Kojima, Takahiro; Obata, Shunsuke; Kuroyanagi, Takuma; Nakazawa, Shoichi; Kashiyama, Shota

2013-11-01

ZnS1-xTex:N/n-ZnS diodes have been fabricated in an attempt to convert ZnS into p-type by Te incorporation and the resulting upward shift of the valence band maximum. The diodes exhibit clear rectification in the current-voltage characteristic and a peak of the electron-beam-induced current at the ZnS1-xTex:N/n-ZnS interface. Furthermore, a ZnS0.85Te0.15:N/n-ZnS diode exhibits blue-green electroluminescence due to self-activated emission in n-ZnS at 290 K under a forward current. These results suggest p-type conduction in ZnS1-xTex:N, and thus the LED operation of a ZnS-based pn-junction.

Solar cell circuit and method for manufacturing solar cells

NASA Technical Reports Server (NTRS)

Mardesich, Nick (Inventor)

2010-01-01

The invention is a novel manufacturing method for making multi-junction solar cell circuits that addresses current problems associated with such circuits by allowing the formation of integral diodes in the cells and allows for a large number of circuits to readily be placed on a single silicon wafer substrate. The standard Ge wafer used as the base for multi-junction solar cells is replaced with a thinner layer of Ge or a II-V semiconductor material on a silicon/silicon dioxide substrate. This allows high-voltage cells with multiple multi-junction circuits to be manufactured on a single wafer, resulting in less array assembly mass and simplified power management.

Stretch or contraction induced inversion of rectification in diblock molecular junctions

NASA Astrophysics Data System (ADS)

Zhang, Guang-Ping; Hu, Gui-Chao; Song, Yang; Xie, Zhen; Wang, Chuan-Kui

2013-09-01

Based on ab initio theory and nonequilibrium Green's function method, the effect of stretch or contraction on the rectification in diblock co-oligomer molecular diodes is investigated theoretically. Interestingly, an inversion of rectifying direction induced by stretching or contracting the molecular junctions, which is closely related to the number of the pyrimidinyl-phenyl units, is proposed. The analysis of the molecular projected self-consistent Hamiltonian and the evolution of the frontier molecular orbitals as well as transmission coefficients under external biases gives an inside view of the observed results. It reveals that the asymmetric molecular level shift and asymmetric evolution of orbital wave functions under biases are competitive mechanisms for rectification. The stretching or contracting induced inversion of the rectification is due to the conversion of the dominant mechanism. This work suggests a feasible technique to manipulate the rectification performance in molecular diodes by use of the mechanically controllable method.

Saturation of the junction voltage in GaN-based laser diodes

NASA Astrophysics Data System (ADS)

Feng, M. X.; Liu, J. P.; Zhang, S. M.; Liu, Z. S.; Jiang, D. S.; Li, Z. C.; Wang, F.; Li, D. Y.; Zhang, L. Q.; Wang, H.; Yang, H.

2013-05-01

Saturation of the junction voltage in GaN-based laser diodes (LDs) is studied. It is found that there is a bump above the lasing transition in the I(dV/dI)-I curve, instead of a dip as that for GaAs-based LDs. The bump in I(dV/dI)-I curve moves to higher currents along with the lasing threshold. A model considering ambipolar conduction and electron overflow into p-AlGaN cladding layer due to poor carrier confinement in active region is used to explain the anomaly. The characteristic temperature of GaN-based LD is obtained by fitting threshold currents determined from I(dV/dI)-I curves. Moreover, it is found that GaN-based LDs show characteristics with a nonlinear series resistance, which may be due to the electron overflow into p-AlGaN cladding layer and the enhanced activation of Mg acceptors.

NANOELECTRONICS. Epitaxial growth of a monolayer WSe2-MoS2 lateral p-n junction with an atomically sharp interface.

PubMed

Li, Ming-Yang; Shi, Yumeng; Cheng, Chia-Chin; Lu, Li-Syuan; Lin, Yung-Chang; Tang, Hao-Lin; Tsai, Meng-Lin; Chu, Chih-Wei; Wei, Kung-Hwa; He, Jr-Hau; Chang, Wen-Hao; Suenaga, Kazu; Li, Lain-Jong

2015-07-31

Two-dimensional transition metal dichalcogenides (TMDCs) such as molybdenum sulfide MoS2 and tungsten sulfide WSe2 have potential applications in electronics because they exhibit high on-off current ratios and distinctive electro-optical properties. Spatially connected TMDC lateral heterojunctions are key components for constructing monolayer p-n rectifying diodes, light-emitting diodes, photovoltaic devices, and bipolar junction transistors. However, such structures are not readily prepared via the layer-stacking techniques, and direct growth favors the thermodynamically preferred TMDC alloys. We report the two-step epitaxial growth of lateral WSe2-MoS2 heterojunction, where the edge of WSe2 induces the epitaxial MoS2 growth despite a large lattice mismatch. The epitaxial growth process offers a controllable method to obtain lateral heterojunction with an atomically sharp interface. Copyright © 2015, American Association for the Advancement of Science.

Proposed Use of Zero Bias Diode Arrays as Thermal Electric Noise Rectifiers and Non-Thermal Energy Harvesters

NASA Astrophysics Data System (ADS)

Valone, Thomas F.

2009-03-01

The well known built-in voltage potential for some select semiconductor p-n junctions and various rectifying devices is proposed to be favorable for generating DC electricity at "zero bias" (with no DC bias voltage applied) in the presence of Johnson noise or 1/f noise which originates from the quantum vacuum (Koch et al., 1982). The 1982 Koch discovery that certain solid state devices exhibit measurable quantum noise has also recently been labeled a finding of dark energy in the lab (Beck and Mackey, 2004). Tunnel diodes are a class of rectifiers that are qualified and some have been credited with conducting only because of quantum fluctuations. Microwave diodes are also good choices since many are designed for zero bias operation. A completely passive, unamplified zero bias diode converter/detector for millimeter (GHz) waves was developed by HRL Labs in 2006 under a DARPA contract, utilizing a Sb-based "backward tunnel diode" (BTD). It is reported to be a "true zero-bias diode." It was developed for a "field radiometer" to "collect thermally radiated power" (in other words, 'night vision'). The diode array mounting allows a feed from horn antenna, which functions as a passive concentrating amplifier. An important clue is the "noise equivalent power" of 1.1 pW per root hertz and the "noise equivalent temperature difference" of 10° K, which indicate sensitivity to Johnson noise (Lynch, et al., 2006). There also have been other inventions such as "single electron transistors" that also have "the highest signal to noise ratio" near zero bias. Furthermore, "ultrasensitive" devices that convert radio frequencies have been invented that operate at outer space temperatures (3 degrees above zero point: 3° K). These devices are tiny nanotech devices which are suitable for assembly in parallel circuits (such as a 2-D array) to possibly produce zero point energy direct current electricity with significant power density (Brenning et al., 2006). Photovoltaic p-n junction cells are also considered for possible higher frequency ZPE transduction. Diode arrays of self-assembled molecular rectifiers or preferably, nano-sized cylindrical diodes are shown to reasonably provide for rectification of electron fluctuations from thermal and non-thermal ZPE sources to create an alternative energy DC electrical generator in the picowatt per diode range.

Impact of dislocation densities on n+/p and p+/n junction GaAs diodes and solar cells on SiGe virtual substrates

NASA Astrophysics Data System (ADS)

Andre, C. L.; Wilt, D. M.; Pitera, A. J.; Lee, M. L.; Fitzgerald, E. A.; Ringel, S. A.

2005-07-01

Recent experimental measurements have shown that in GaAs with elevated threading dislocation densities (TDDs) the electron lifetime is much lower than the hole lifetime [C. L. Andre, J. J. Boeckl, D. M. Wilt, A. J. Pitera, M. L. Lee, E. A. Fitzgerald, B. M. Keyes, and S. A. Ringel, Appl. Phys. Lett. 84, 3884 (2004)]. This lower electron lifetime suggests an increase in depletion region recombination and thus in the reverse saturation current (J0 for an n+/p diode compared with a p+/n diode at a given TDD. To confirm this, GaAs diodes of both polarities were grown on compositionally graded Ge /Si1-xGex/Si (SiGe) substrates with a TDD of 1×106cm-2. It is shown that the ratio of measured J0 values is consistent with the inverse ratio of the expected lifetimes. Using a TDD-dependent lifetime in solar cell current-voltage models we found that the Voc, for a given short-circuit current, also exhibits a poorer TDD tolerance for GaAs n+/p solar cells compared with GaAs p+/n solar cells. Experimentally, the open-circuit voltage (Voc) for the n+/p GaAs solar cell grown on a SiGe substrate with a TDD of ˜1×106cm-2 was ˜880mV which was significantly lower than the ˜980mV measured for a p+/n GaAs solar cell grown on SiGe at the same TDD and was consistent with the solar cell modeling results reported in this paper. We conclude that p+/n polarity GaAs junctions demonstrate superior dislocation tolerance than n+/p configured GaAs junctions, which is important for optimization of lattice-mismatched III-V devices.

Gas selectivity of SILAR grown CdS nano-bulk junction

NASA Astrophysics Data System (ADS)

Jayakrishnan, R.; Nair, Varun G.; Anand, Akhil M.; Venugopal, Meera

2018-03-01

Nano-particles of cadmium sulphide were deposited on cleaned copper substrate by an automated sequential ionic layer adsorption reaction (SILAR) system. The grown nano-bulk junction exhibits Schottky diode behavior. The response of the nano-bulk junction was investigated under oxygen and hydrogen atmospheric conditions. The gas response ratio was found to be 198% for Oxygen and 34% for Hydrogen at room temperature. An increase in the operating temperature of the nano-bulk junction resulted in a decrease in their gas response ratio. A logarithmic dependence on the oxygen partial pressure to the junction response was observed, indicating a Temkin isothermal behavior. Work function measurements using a Kelvin probe demonstrate that the exposure to an oxygen atmosphere fails to effectively separate the charges due to the built-in electric field at the interface. Based on the benefits like simple structure, ease of fabrication and response ratio the studied device is a promising candidate for gas detection applications.

Nanoscale imaging of the photoresponse in PN junctions of InGaAs infrared detector

PubMed Central

Xia, Hui; Li, Tian-Xin; Tang, Heng-Jing; Zhu, Liang; Li, Xue; Gong, Hai-Mei; Lu, Wei

2016-01-01

Electronic layout, such as distributions of charge carriers and electric field, in PN junction is determinant for the photovoltaic devices to realize their functionality. Considerable efforts have been dedicated to the carrier profiling of this specific region with Scanning Probe Microscope, yet reliable analysis was impeded by the difficulty in resolving carriers with high mobility and the unclear surface effect, particularly on compound semiconductors. Here we realize nanometer Scanning Capacitance Microscopic study on the cross-section of InGaAs/InP photodetctors with the featured dC/dV layout of PN junction unveiled for the first time. It enables us to probe the photo-excited minority carriers in junction region and diagnose the performance deficiency of the diode devices. This work provides an illuminating insight into the PN junction for assessing its basic capability of harvesting photo-carriers as well as blocking leakage current in nanoscopic scale. PMID:26892069

Humidity-controlled rectification switching in ruthenium-complex molecular junctions

NASA Astrophysics Data System (ADS)

Atesci, Huseyin; Kaliginedi, Veerabhadrarao; Celis Gil, Jose A.; Ozawa, Hiroaki; Thijssen, Joseph M.; Broekmann, Peter; Haga, Masa-aki; van der Molen, Sense Jan

2018-02-01

Although molecular rectifiers were proposed over four decades ago1,2, until recently reported rectification ratios (RR) were rather moderate2-11 (RR 101). This ceiling was convincingly broken using a eutectic GaIn top contact12 to probe molecular monolayers of coupled ferrocene groups (RR 105), as well as using scanning tunnelling microscopy-break junctions13-16 and mechanically controlled break junctions17 to probe single molecules (RR 102-103). Here, we demonstrate a device based on a molecular monolayer in which the RR can be switched by more than three orders of magnitude (between RR 100 and RR ≥ 103) in response to humidity. As the relative humidity is toggled between 5% and 60%, the current-voltage (I-V) characteristics of a monolayer of di-nuclear Ru-complex molecules reversibly change from symmetric to strongly asymmetric (diode-like). Key to this behaviour is the presence of two localized molecular orbitals in series, which are nearly degenerate in dry circumstances but become misaligned under high humidity conditions, due to the displacement of counter ions (PF6-). This asymmetric gating of the two relevant localized molecular orbital levels results in humidity-controlled diode-like behaviour.

Aging characteristics of blue InGaN micro-light emitting diodes at an extremely high current density of 3.5 kA cm-2

NASA Astrophysics Data System (ADS)

Tian, Pengfei; Althumali, Ahmad; Gu, Erdan; Watson, Ian M.; Dawson, Martin D.; Liu, Ran

2016-04-01

The aging characteristics of blue InGaN micro-light emitting diodes (micro-LEDs) with different sizes have been studied at an extremely high current density 3.5 kA cm-2 for emerging micro-LED applications including visible light communication (VLC), micro-LED pumped organic lasers and optogenetics. The light output power of micro-LEDs first increases and then decreases due to the competition of Mg activation in p-GaN layer and defect generation in the active region. The smaller micro-LEDs show less light output power degradation compared with larger micro-LEDs, which is attributed to the lower junction temperature of smaller micro-LEDs. It is found that the high current density without additional junction temperature cannot induce significant micro-LED degradation at room temperature but the combination of the high current density and high junction temperature leads to strong degradation. Furthermore, the cluster LEDs, composed of a micro-LED array, have been developed with both high light output power and less light output degradation for micro-LED applications in solid state lighting and VLC.

Towards high frequency heterojunction transistors: Electrical characterization of N-doped amorphous silicon-graphene diodes

NASA Astrophysics Data System (ADS)

Strobel, C.; Chavarin, C. A.; Kitzmann, J.; Lupina, G.; Wenger, Ch.; Albert, M.; Bartha, J. W.

2017-06-01

N-type doped amorphous hydrogenated silicon (a-Si:H) is deposited on top of graphene (Gr) by means of very high frequency (VHF) and radio frequency plasma-enhanced chemical vapor deposition (PECVD). In order to preserve the structural integrity of the monolayer graphene, a plasma excitation frequency of 140 MHz was successfully applied during the a-Si:H VHF-deposition. Raman spectroscopy results indicate the absence of a defect peak in the graphene spectrum after the VHF-PECVD of (n)-a-Si:H. The diode junction between (n)-a-Si:H and graphene was characterized using temperature dependent current-voltage (IV) and capacitance-voltage measurements, respectively. We demonstrate that the current at the (n)-a-Si:H-graphene interface is dominated by thermionic emission and recombination in the space charge region. The Schottky barrier height (qΦB), derived by temperature dependent IV-characteristics, is about 0.49 eV. The junction properties strongly depend on the applied deposition method of (n)-a-Si:H with a clear advantage of the VHF(140 MHz)-technology. We have demonstrated that (n)-a-Si:H-graphene junctions are a promising technology approach for high frequency heterojunction transistors.

Molecular diodes based on conjugated diblock co-oligomers.

PubMed

Ng, Man-Kit; Lee, Dong-Chan; Yu, Luping

2002-10-09

This report describes synthesis and characterization of a molecular diode based upon a diblock conjugated oligomer system. This system consists of two conjugated blocks with opposite electronic demand. The molecular structure exhibits a built-in electronic asymmetry, much like a semiconductor p-n junction. Electrical measurements by scanning tunneling spectroscopy (STS) clearly revealed a pronounced rectifying effect. Definitive proof for the molecular nature of the rectifying effect in this conjugated diblock molecule is provided by control experiments with a structurally similar reference compound.

Fabrication and characterization of the organic rectifying junctions by electrolysis

NASA Astrophysics Data System (ADS)

Karimov, Khasan; Ahmad, Zubair; Ali, Rashid; Noor, Adnan; Akmal, M.; Najeeb, M. A.; Shakoor, R. A.

2017-08-01

Unlike the conventional solution processable deposition techniques, in this study, we propose a novel and economical method for the fabrication of organic rectifying junctions. The solutions of the orange dye, copper phthalocyanine and NaCl were deposited on the surface-type interdigitated silver electrodes using electrolysis technique. Using the current-voltage (I-V) characteristics, the presence of rectifying behavior in the samples has been confirmed. This phenomenon, in principle, can be used for fabrication of the diodes, transistors and memory devices.

Harmonic mixing characteristics of metal-barrier-metal junctions as predicted by electron tunneling

NASA Technical Reports Server (NTRS)

Faris, S. M.; Gustafson, T. K.

1974-01-01

The bias dependence of the nonlinear mixing characteristics of metal-barrier-metal junction currents is deduced assuming an electron tunneling model. The difference-frequency beat voltage at frequency omega sub 1 - (n x omega sub 2), when n is an integer and omega sub 1 and omega sub 2 are the assumed frequencies of two induced currents, is found to have n zeros as the diode bias is varied. Recent experimental observations have demonstrated such characteristics.

Mechanisms of Current Flow in the Diode Structure with an n + - p-Junction Formed by Thermal Diffusion of Phosphorus From Porous Silicon Film

NASA Astrophysics Data System (ADS)

Tregulov, V. V.; Litvinov, V. G.; Ermachikhin, A. V.

2018-01-01

Temperature dependences of current-voltage characteristics of the photoelectric converter with an antireflective film of porous silicon and an n + -p-junction formed by thermal diffusion of phosphorus from a porous film is studied. The porous silicon film was saturated with phosphorus during its growing by electrochemical method. It is shown that the current flow processes in the structure under study are significantly influenced by traps.

Spatially Offset Raman Spectroscopy for Surgical Margin Evaluation During Breast Conserving Therapy

DTIC Science & Technology

2011-02-01

was connected to a 785 nm diode laser (I0785MB0350M, Innovative Photonics Solutions, Monmouth Junction, NJ) which delivered 80 mW of power to the...I0785MB0350M, Innovative Photonics Solutions, Monmouth Junction, New Jersey). The collection fibers deliv- ered light to a near-infrared-optimized...and Tecnology - calibrated tungsten-halogen lamp was used to correct the sys- tem response.29 After wavenumber binning (in 3.5 cm−1 steps given the

Resonant optical device with a microheater

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

Lentine, Anthony L.; DeRose, Christopher

2017-04-04

A resonant photonic device is provided. The device comprises an optical waveguiding element, such as an optical resonator, that includes a diode junction region, two signal terminals configured to apply a bias voltage across the junction region, and a heater laterally separated from the optical waveguiding element. A semiconductor electrical barrier element is juxtaposed to the heater. A metallic strip is electrically and thermally connected at one end to a signal terminal of the optical waveguiding element and thermally connected at another end to the barrier element.

Solid State Clipper Diodes for High Power Modulators.

DTIC Science & Technology

1978-11-01

modeled at low powers and later confirmed in actua l P W pulsar operation. 0~ \\ ~~~~~~~~~ . ~~~~~ .. . .— - - I. ~~~~~ 3 J~ItV~ . \\ W \\_ UNC l ASSIFIE...and CG is the di ide api-i tance to 1avg — Ip ~ j- ground . In our design the worst case diode leakage (I 2( lO ~C) was 15 milliamperes (mA) at I kV...without it. I2rms 1p 2 ~~ ( 4) the diode junction capacitance and stray l’nns — 5 x lO ~ A 2 capacitance affect the voltage division whenever the

High current density Esaki tunnel diodes based on GaSb-InAsSb heterostructure nanowires.

PubMed

Ganjipour, Bahram; Dey, Anil W; Borg, B Mattias; Ek, Martin; Pistol, Mats-Erik; Dick, Kimberly A; Wernersson, Lars-Erik; Thelander, Claes

2011-10-12

We present electrical characterization of broken gap GaSb-InAsSb nanowire heterojunctions. Esaki diode characteristics with maximum reverse current of 1750 kA/cm(2) at 0.50 V, maximum peak current of 67 kA/cm(2) at 0.11 V, and peak-to-valley ratio (PVR) of 2.1 are obtained at room temperature. The reverse current density is comparable to that of state-of-the-art tunnel diodes based on heavily doped p-n junctions. However, the GaSb-InAsSb diodes investigated in this work do not rely on heavy doping, which permits studies of transport mechanisms in simple transistor structures processed with high-κ gate dielectrics and top-gates. Such processing results in devices with improved PVR (3.5) and stability of the electrical properties.

Schottky barrier parameters and structural properties of rapidly annealed Zr Schottky electrode on p-type GaN

NASA Astrophysics Data System (ADS)

Rajagopal Reddy, V.; Asha, B.; Choi, Chel-Jong

2017-06-01

The Schottky barrier junction parameters and structural properties of Zr/p-GaN Schottky diode are explored at various annealing temperatures. Experimental analysis showed that the barrier height (BH) of the Zr/p-GaN Schottky diode increases with annealing at 400 °C (0.92 eV (I-V)/1.09 eV (C-V)) compared to the as-deposited one (0.83 eV (I-V)/0.93 eV (C-V)). However, the BH decreases after annealing at 500 °C. Also, at different annealing temperatures, the series resistance and BH are assessed by Cheung's functions and their values compared. Further, the interface state density (N SS) of the diode decreases after annealing at 400 °C and then somewhat rises upon annealing at 500 °C. Analysis reveals that the maximum BH is obtained at 400 °C, and thus the optimum annealing temperature is 400 °C for the diode. The XPS and XRD analysis revealed that the increase in BH may be attributed to the creation of Zr-N phases with increasing annealing up to 400 °C. The BH reduces for the diode annealed at 500 °C, which may be due to the formation of Ga-Zr phases at the junction. The AFM measurements reveal that the overall surface roughness of the Zr film is quite smooth during rapid annealing process. Project supported by the R&D Program for Industrial Core Technology (No. 10045216) and the Transfer Machine Specialized Lighting Core Technology Development Professional Manpower Training Project (No. N0001363) Funded by the Ministry of Trade, Industry and Energy (MOTIE), Republic of Korea.

Rectifying magnetic tunnel diode like behavior in Co2MnSi/ZnO/p-Si heterostructure

NASA Astrophysics Data System (ADS)

Maji, Nilay; Nath, T. K.

2018-04-01

The rectifying magnetic tunnel diode like behavior has been observed in Co2MnSi/ZnO/p-Si heterostructure. At first an ultra thin layer of ZnO has been deposited on p-Si (100) substrate with the help of pulsed laser deposition (PLD). After that a highly spin-polarized Heusler alloy Co2MnSi (CMS) film (250 nm) has been grown on ZnO/p-Si using electron beam physical vapor deposition technique. The phase purity of the sample has been confirmed through high resolution X-Ray diffraction technique. The electrical transport properties have been investigated at various isothermal conditions in the temperature range of 77-300 K. The current-voltage characteristics exhibit an excellent rectifying tunnel diode like behavior throughout the temperature regime. The current (I) across the junction has been found to decrease with the application of an external magnetic field parallel to the plane of the CMS film clearly indicating positive junction magnetoresistance (JMR) of the heterostructure. The magnetic field dependent JMR behavior of our heterostructure has been investigated in the same temperature range. Our heterostructure clearly demonstrates a giant positive JMR at 78 K (˜264%) and it starts decreasing with increasing temperature. If we compare our results with earlier reported results on other heterostructures, it can be seen that the JMR value for our heterojunction saturates at a much lower external magnetic field, thus creating it a better alternative for spin tunnel diodes in upcoming spintronics device applications.

Improving the beam quality of high-power laser diodes by introducing lateral periodicity into waveguides

NASA Astrophysics Data System (ADS)

Sobczak, Grzegorz; DÄ browska, ElŻbieta; Teodorczyk, Marian; Kalbarczyk, Joanna; MalÄ g, Andrzej

2013-01-01

Low quality of the optical beam emitted by high-power laser diodes is the main disadvantage of these devices. The two most important reasons are highly non-Gaussian beam profile with relatively wide divergence in the junction plane and the filamentation effect. Designing laser diode as an array of narrow, close to each other single-mode waveguides is one of the solutions to this problem. In such devices called phase locked arrays (PLA) there is no room for filaments formation. The consequence of optical coupling of many single-mode waveguides is the device emission in the form of few almost diffraction limited beams. Because of losses in regions between active stripes the PLA devices have, however, somewhat higher threshold current and lower slope efficiencies compared to wide-stripe devices of similar geometry. In this work the concept of the high-power laser diode resonator consisted of joined PLA and wide stripe segments is proposed. Resulting changes of electro-optical characteristics of PLA are discussed. The devices are based on the asymmetric heterostructure designed for improvement of the catastrophic optical damage threshold as well as thermal and electrical resistances. Due to reduced distance from the active layer to surface in this heterostructure, better stability of current (and gain) distribution with changing drive level is expected. This could lead to better stability of optical field distribution and supermodes control. The beam divergence reduction in the direction perpendicular of the junction plane has been also achieved.

An all-perovskite p-n junction based on transparent conducting p -La 1-x Sr x CrO 3 epitaxial layers

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

Du, Yingge; Li, Chen; Zhang, Kelvin H. L.

2017-08-07

Transparent, conducting p -La 1-x Sr x CrO 3 epitaxial layers were deposited on Nb-doped SrTiO 3(001) by oxygen-assisted molecular beam epitaxy to form structurally coherent p-n junctions. X-ray photoelectron spectroscopy reveals a type II or “staggered” band alignment, with valence and conduction band offsets of 2.0 eV and 0.9 eV, respectively. Diodes fabricated from these heterojunctions exhibit rectifying behavior, and the I-V characteristics are different from those for traditional semiconductor p-n junctions. A rather large ideality factor is ascribed to the complex nature of the interface.

Competitive behavior of photons contributing to junction voltage jump in narrow band-gap semiconductor multi-quantum-well laser diodes at lasing threshold

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

Feng, Liefeng, E-mail: fengliefeng@tju.edu.cn, E-mail: lihongru@nankai.edu.cn; Yang, Xiufang; Wang, Cunda

2015-04-15

The junction behavior of different narrow band-gap multi-quantum-well (MQW) laser diodes (LDs) confirmed that the jump in the junction voltage in the threshold region is a general characteristic of narrow band-gap LDs. The relative change in the 1310 nm LD is the most obvious. To analyze this sudden voltage change, the threshold region is divided into three stages by I{sub th}{sup l} and I{sub th}{sup u}, as shown in Fig. 2; I{sub th}{sup l} is the conventional threshold, and as long as the current is higher than this threshold, lasing exists and the IdV/dI-I plot drops suddenly; I{sub th}{sup u}more » is the steady lasing point, at which the separation of the quasi-Fermi levels of electron and holes across the active region (V{sub j}) is suddenly pinned. Based on the evolutionary model of dissipative structure theory, the rate equations of the photons in a single-mode LD were deduced in detail at I{sub th}{sup l} and I{sub th}{sup u}. The results proved that the observed behavior of stimulated emission suddenly substituting for spontaneous emission, in a manner similar to biological evolution, must lead to a sudden increase in the injection carriers in the threshold region, which then causes the sudden increase in the junction voltage in this region.« less

Electrical Characterization of Graphite/InP Schottky Diodes by I-V-T and C-V Methods

NASA Astrophysics Data System (ADS)

Tiagulskyi, Stanislav; Yatskiv, Roman; Grym, Jan

2018-02-01

A rectifying junction was prepared by casting a drop of colloidal graphite on the surface of an InP substrate. The electrophysical properties of graphite/InP junctions were investigated in a wide temperature range. Temperature-dependent I-V characteristics of the graphite/InP junctions are explained by the thermionic emission mechanism. The Schottky barrier height (SBH) and the ideality factor were found to be 0.9 eV and 1.47, respectively. The large value of the SBH and its weak temperature dependence are explained by lateral homogeneity of the junction, which is related to the structure of the graphite layer. The moderate disagreement between the current-voltage and capacitance-voltage measurements is attributed to the formation of interfacial native oxide film on the InP surface.

Studies of silicon PN junction solar cells

NASA Technical Reports Server (NTRS)

Lindholm, F. A.

1975-01-01

Silicon pn junction solar cells made with low-resistivity substrates show poorer performance than traditional theory predicts. The purpose of this research was to identify and characterize the physical mechanisms responsible for the discrepancy. Attention was concentrated on the open circuit voltage in shallow junction cells of 0.1 ohm-cm substrate resistivity. A number of possible mechanisms that can occur in silicon devices were considered. Two mechanisms which are likely to be of main importance in explaining the observed low values of open-circuit voltage were found: (1) recombination losses associated with defects introduced during junction formation, and (2) inhomogeneity of defects and impurities across the area of the cell. To explore these theoretical anticipations, various diode test structures were designed and fabricated and measurement configurations for characterizing the defect properties and the areal inhomogeneity were constructed.

Comparison of high speed DI-LIGBT structures

NASA Astrophysics Data System (ADS)

Sunkavalli, Ravishankar; Baliga, B. Jayant

1997-12-01

The performance of the DI segmented collector (SC)-LIGBT is compared to the collector shorted (CS)-LIGBT. The SC-LIGBT allows for adjusting the tradeoff between switching speed and on-state voltage drop by simply changing the P+ collector segment width during device layout. In contrast to previously reported junction isolated (JI) devices, the DI SC-LIGBT was observed to have a turnoff speed similar to the CS-LIGBT with a higher forward drop than the conventional LIGBT. The on-state performance of the integral diodes of the SC-LIGBTs was found to be superior to the integral diode of the CS-LIGBT. The integral diodes of both the CS and the SC-LIGBTs were found to have much superior switching characteristics compared to a lateral PiN diode at the expense of a higher on-state voltage drop. Thus, the superior switching characteristics of the integral diode in the SC-LIGBT complements its fast switching behavior making this device attractive for compact, high frequency, high efficient, power ICs.

Submicron nickel-oxide-gold tunnel diode detectors for rectennas

NASA Technical Reports Server (NTRS)

Hoofring, A. B.; Kapoor, V. J.; Krawczonek, W.

1989-01-01

The characteristics of a metal-oxide-metal (MOM) tunnel diode made of nickel, nickel-oxide, and gold, designed and fabricated by standard integrated circuit technology for use in FIR rectennas, are presented. The MOM tunnel diode was formed by overlapping a 0.8-micron-wide layer of 1000-A of nickel, which was oxidized to form a thin layer of nickel oxide, with a 1500 A-thick layer of gold. The dc current-voltage characteristics of the MOM diode showed that the current dependence on voltage was linear about zero bias up to a bias of about 70 mV. The maximum detection of a low-level signal (10-mV ac) was determined to be at a dc voltage of 70 mV across the MOM diode. The rectified output signal due to a chopped 10.6-micron CO2 laser incident upon the rectenna device was found to increase with dc bias, with a maximum value of 1000 nV for a junction bias of 100 mV at room temperature.

Photodiode arrays having minimized cross-talk between diodes

DOEpatents

Guckel, Henry; McNamara, Shamus P.

2000-10-17

Photodiode arrays are formed with close diode-to-diode spacing and minimized cross-talk between diodes in the array by isolating the diodes from one another with trenches that are formed between the photodiodes in the array. The photodiodes are formed of spaced regions in a base layer, each spaced region having an impurity type opposite to that of the base layer to define a p-n junction between the spaced regions and the base layer. The base layer meets a substrate at a boundary, with the substrate being much more heavily doped than the base layer with the same impurity type. The trenches extend through the base layer and preferably into the substrate. Minority carriers generated by absorption of light photons in the base layer can only migrate to an adjacent photodiode through the substrate. The lifetime and the corresponding diffusion length of the minority carriers in the substrate is very short so that all minority carriers recombine in the substrate before reaching an adjacent photodiode.

Effect of Atomic Layer Depositions (ALD)-Deposited Titanium Oxide (TiO2) Thickness on the Performance of Zr40Cu35Al15Ni10 (ZCAN)/TiO2/Indium (In)-Based Resistive Random Access Memory (RRAM) Structures

DTIC Science & Technology

2015-08-01

metal structures, memristors, resistive random access memory, RRAM, titanium dioxide, Zr40Cu35Al15Ni10, ZCAN, resistive memory, tunnel junction 16...TiO2 thickness ........................6 1 1. Introduction Resistive-switching memory elements based on metal-insulator-metal (MIM) diodes ...have attracted great interest due to their potential as components for simple, inexpensive, and high-density non-volatile storage devices. MIM diodes

PRECISION TIME-DELAY CIRCUIT

DOEpatents

Creveling, R.

1959-03-17

A tine-delay circuit which produces a delay time in d. The circuit a capacitor, an te back resistance, connected serially with the anode of the diode going to ground. At the start of the time delay a negative stepfunction is applied to the series circuit and initiates a half-cycle transient oscillatory voltage terminated by a transient oscillatory voltage of substantially higher frequency. The output of the delay circuit is taken at the junction of the inductor and diode where a sudden voltage rise appears after the initiation of the higher frequency transient oscillations.

Thermal imaging of high power diode lasers subject to back-irradiance

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

Li, C.; Pipe, K. P.; Cao, C.

In this study, CCD-based thermoreflectance imaging and finite element modeling are used to study the two-dimensional (2D) temperature profile of a junction-down broad-area diode laser facet subject to back-irradiance. By determining the temperature rise in the active region (ΔΤAR) at different diode laser optical powers, back-irradiance reflectance levels, and back-irradiance spot locations, we find that ΔΤAR increases by nearly a factor of three when the back-irradiance spot is centered in the absorbing substrate approximately 5 μm away from the active region, a distance roughly equal to half of the back-irradiance spot FWHM (9 μm). This corroborates prior work studying themore » relationship between the back-irradiance spot location and catastrophic optical damage, suggesting a strong thermal basis for reduced laser lifetime in the presence of back-irradiance for diode lasers fabricated on absorbing substrates.« less

Approaches toward a blue semiconductor laser

NASA Technical Reports Server (NTRS)

Ladany, I.

1989-01-01

Possible approaches for obtaining semiconductor diode laser action in the blue region of the spectrum are surveyed. A discussion of diode lasers is included along with a review of the current status of visible emitters, presently limited to 670 nm. Methods are discussed for shifting laser emission toward shorter wavelengths, including the use of II-IV materials, the increase in the bandgap of III-V materials by addition of nitrogen, and changing the bandstructure from indirect to direct by incorporating interstitial atoms or by constructing superlattices. Non-pn-junction injection methods are surveyed, including avalanche breakdown, Langmuir-Blodgett diodes, heterostructures, carrier accumulation, and Berglund diodes. Prospects of inventing new multinary semiconducting materials are discussed, and a number of novel materials described in the literature are tabulated. New approaches available through the development of quantum wells and superlattices are described, including resonant tunneling and the synthesis of arbitrary bandgap materials through multiple quantum wells.

Thermal imaging of high power diode lasers subject to back-irradiance

DOE PAGES

Li, C.; Pipe, K. P.; Cao, C.; ...

2018-03-07

In this study, CCD-based thermoreflectance imaging and finite element modeling are used to study the two-dimensional (2D) temperature profile of a junction-down broad-area diode laser facet subject to back-irradiance. By determining the temperature rise in the active region (ΔΤAR) at different diode laser optical powers, back-irradiance reflectance levels, and back-irradiance spot locations, we find that ΔΤAR increases by nearly a factor of three when the back-irradiance spot is centered in the absorbing substrate approximately 5 μm away from the active region, a distance roughly equal to half of the back-irradiance spot FWHM (9 μm). This corroborates prior work studying themore » relationship between the back-irradiance spot location and catastrophic optical damage, suggesting a strong thermal basis for reduced laser lifetime in the presence of back-irradiance for diode lasers fabricated on absorbing substrates.« less

Thermal imaging of high power diode lasers subject to back-irradiance

NASA Astrophysics Data System (ADS)

Li, C.; Pipe, K. P.; Cao, C.; Thiagarajan, P.; Deri, R. J.; Leisher, P. O.

2018-03-01

CCD-based thermoreflectance imaging and finite element modeling are used to study the two-dimensional (2D) temperature profile of a junction-down broad-area diode laser facet subject to back-irradiance. By determining the temperature rise in the active region (ΔΤAR) at different diode laser optical powers, back-irradiance reflectance levels, and back-irradiance spot locations, we find that ΔΤAR increases by nearly a factor of three when the back-irradiance spot is centered in the absorbing substrate approximately 5 μm away from the active region, a distance roughly equal to half of the back-irradiance spot FWHM (9 μm). This corroborates prior work studying the relationship between the back-irradiance spot location and catastrophic optical damage, suggesting a strong thermal basis for reduced laser lifetime in the presence of back-irradiance for diode lasers fabricated on absorbing substrates.

Influence of external mechanical stress on electrical properties of single-crystal n-3C-SiC/p-Si heterojunction diode

NASA Astrophysics Data System (ADS)

Qamar, Afzaal; Veit Dao, Dzung; Tanner, Philip; Phan, Hoang-Phuong; Dinh, Toan; Dimitrijev, Sima

2015-06-01

This article reports for the first time the electrical properties of fabricated n-3C-SiC/p-Si heterojunction diodes under external mechanical stress in the [110] direction. An anisotype heterojunction diode of n-3C-SiC/p-Si was fabricated by depositing 3C-SiC onto the Si substrate by low-pressure chemical vapor deposition. The mechanical stress significantly affected the scaling current density of the heterojunction. The scaling current density increases with stress and is explained in terms of a band offset reduction at the SiC/Si interface under applied stress. A reduction in the barrier height across the junction owing to applied stress is also explained quantitatively.

Heterojunction photodiode on cleaved SiC

NASA Astrophysics Data System (ADS)

Solovan, Mykhailo M.; Farah, John; Kovaliuk, Taras T.; Brus, Viktor V.; Mostovyi, Andrii I.; Maistruk, Eduard V.; Maryanchuk, Pavlo D.

2018-01-01

Graphite/n-SiC Shottky diodes were prepared by means of the recently proposed technique based on the transferring of drawn graphite films onto the n-SiC single crystal substrate. Current-voltage characteristics were measured and analyzed. High quality ohmic contancts were prepared by the DC magnetron sputtering of Ni thin films onto cleaved n-type SiC single crystal substrates. The height of the potential barrier and the series resistance of the graphite/n-SiC junctions were measured and analysed. The dominant current transport mechanisms through the diodes were determined. There was shown that the dominant current transport mechanisms through the graphite/n-SiC Shottky diodes were the multi-step tunnel-recombination at forward bias and the tunnelling mechanisms at reverse bias.

InGaN based micro light emitting diodes featuring a buried GaN tunnel junction

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

Malinverni, M., E-mail: marco.malinverni@epfl.ch; Martin, D.; Grandjean, N.

GaN tunnel junctions (TJs) are grown by ammonia molecular beam epitaxy. High doping levels are achieved with a net acceptor concentration close to ∼10{sup 20 }cm{sup −3}, thanks to the low growth temperature. This allows for the realization of p-n junctions with ultrathin depletion width enabling efficient interband tunneling. n-p-n structures featuring such a TJ exhibit low leakage current densities, e.g., <5 × 10{sup −5} A cm{sup −2} at reverse bias of 10 V. Under forward bias, the voltage is 3.3 V and 4.8 V for current densities of 20 A cm{sup −2} and 2000 A cm{sup −2}, respectively. The specific series resistance of the whole device ismore » 3.7 × 10{sup −4} Ω cm{sup 2}. Then micro-light emitting diodes (μ-LEDs) featuring buried TJs are fabricated. Excellent current confinement is demonstrated together with homogeneous electrical injection, as seen on electroluminescence mapping. Finally, the I-V characteristics of μ-LEDs with various diameters point out the role of the access resistance at the current aperture edge.« less

Chemically fixed p-n heterojunctions for polymer electronics by means of covalent B-F bond formation.

PubMed

Hoven, Corey V; Wang, Huiping; Elbing, Mark; Garner, Logan; Winkelhaus, Daniel; Bazan, Guillermo C

2010-03-01

Widely used solid-state devices fabricated with inorganic semiconductors, including light-emitting diodes and solar cells, derive much of their function from the p-n junction. Such junctions lead to diode characteristics and are attained when p-doped and n-doped materials come into contact with each other. Achieving bilayer p-n junctions with semiconducting polymers has been hindered by difficulties in the deposition of thin films with independent p-doped and n-doped layers. Here we report on how to achieve permanently fixed organic p-n heterojunctions by using a cationic conjugated polyelectrolyte with fluoride counteranions and an underlayer composed of a neutral conjugated polymer bearing anion-trapping functional groups. Application of a bias leads to charge injection and fluoride migration into the neutral layer, where irreversible covalent bond formation takes place. After the initial charging and doping, one obtains devices with no delay in the turn on of light-emitting electrochemical behaviour and excellent current rectification. Such devices highlight how mobile ions in organic media can open opportunities to realize device structures in ways that do not have analogies in the world of silicon and promise new opportunities for integrating organic materials within technologies now dominated by inorganic semiconductors.

Chemically fixed p-n heterojunctions for polymer electronics by means of covalent B-F bond formation

NASA Astrophysics Data System (ADS)

Hoven, Corey V.; Wang, Huiping; Elbing, Mark; Garner, Logan; Winkelhaus, Daniel; Bazan, Guillermo C.

2010-03-01

Widely used solid-state devices fabricated with inorganic semiconductors, including light-emitting diodes and solar cells, derive much of their function from the p-n junction. Such junctions lead to diode characteristics and are attained when p-doped and n-doped materials come into contact with each other. Achieving bilayer p-n junctions with semiconducting polymers has been hindered by difficulties in the deposition of thin films with independent p-doped and n-doped layers. Here we report on how to achieve permanently fixed organic p-n heterojunctions by using a cationic conjugated polyelectrolyte with fluoride counteranions and an underlayer composed of a neutral conjugated polymer bearing anion-trapping functional groups. Application of a bias leads to charge injection and fluoride migration into the neutral layer, where irreversible covalent bond formation takes place. After the initial charging and doping, one obtains devices with no delay in the turn on of light-emitting electrochemical behaviour and excellent current rectification. Such devices highlight how mobile ions in organic media can open opportunities to realize device structures in ways that do not have analogies in the world of silicon and promise new opportunities for integrating organic materials within technologies now dominated by inorganic semiconductors.

Voltage-induced ferromagnetic resonance in magnetic tunnel junctions.

PubMed

Zhu, Jian; Katine, J A; Rowlands, Graham E; Chen, Yu-Jin; Duan, Zheng; Alzate, Juan G; Upadhyaya, Pramey; Langer, Juergen; Amiri, Pedram Khalili; Wang, Kang L; Krivorotov, Ilya N

2012-05-11

We demonstrate excitation of ferromagnetic resonance in CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) by the combined action of voltage-controlled magnetic anisotropy (VCMA) and spin transfer torque (ST). Our measurements reveal that GHz-frequency VCMA torque and ST in low-resistance MTJs have similar magnitudes, and thus that both torques are equally important for understanding high-frequency voltage-driven magnetization dynamics in MTJs. As an example, we show that VCMA can increase the sensitivity of an MTJ-based microwave signal detector to the sensitivity level of semiconductor Schottky diodes.

A Wide Area Bipolar Cascade Resonant Cavity Light Emitting Diode for a Hybrid Range-Intensity Sensor

DTIC Science & Technology

2008-06-19

forward bias voltage and a small amount of current flow- ing due to a forward biased tunnel current. (d) shows a drop in the forward bias current due...flowing due to a forward biased tunnel current. (d) shows a drop in the forward bias current due to the widening of the forbidden band, and fewer...3-14 xii Figure Page 3.10. Energy bands of a tunnel junction at various bias levels. (a) shows the junction under reverse bias with holes in

Imaging the Solar Cell P-N Junction and Depletion Region Using Secondary Electron Contrast

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

Heath, J. T.; Jiang, C. S.; Al-Jassim, M. M.

2011-01-01

We report on secondary electron (SE) images of cross-sectioned multicrystalline Si and GaAs/GaInP solar cell devices, focusing on quantifying the relationship between the apparent n{sup +}-p contrast and characteristic electronic features of the device. These samples allow us to compare the SE signal from devices which have very different physical characteristics: differing materials, diffused junction versus abrupt junction, heterojunction versus homojunction. Despite these differences, we find that the SE image contrast for both types of sample, and as a function of reverse bias across the diode, closely agrees with PC1D simulations of the bulk electrostatic potential in the device, accuratelymore » yielding the depletion edge and width. A spatial derivative of the SE data shows a local maximum at the metallurgical junction. Such data are valuable, for example, in studying the conformity of a diffused junction to the textured surface topography. These data also extend our understanding of the origin of the SE contrast.« less

Design and demonstration of ultra-wide bandgap AlGaN tunnel junctions

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

Zhang, Yuewei; Krishnamoorthy, Sriram; Akyol, Fatih

Ultra violet light emitting diodes (UV LEDs) face critical limitations in both the injection efficiency and the light extraction efficiency due to the resistive and absorbing p-type contact layers. In this work, we investigate the design and application of polarization engineered tunnel junctions for ultra-wide bandgap AlGaN (Al mole fraction >50%) materials towards highly efficient UV LEDs. We demonstrate that polarization-induced three dimensional charge is beneficial in reducing tunneling barriers especially for high composition AlGaN tunnel junctions. In addition, the design of graded tunnel junction structures could lead to low tunneling resistance below 10 –3 Ω cm 2 and lowmore » voltage consumption below 1 V (at 1 kA/cm 2) for high composition AlGaN tunnel junctions. Experimental demonstration of 292 nm emission was achieved through non-equilibrium hole injection into wide bandgap materials with bandgap energy larger than 4.7 eV, and detailed modeling of tunnel junctions shows that they can be engineered to have low resistance and can enable efficient emitters in the UV-C wavelength range.« less

Design and demonstration of ultra-wide bandgap AlGaN tunnel junctions

DOE PAGES

Zhang, Yuewei; Krishnamoorthy, Sriram; Akyol, Fatih; ...

2016-09-19

Ultra violet light emitting diodes (UV LEDs) face critical limitations in both the injection efficiency and the light extraction efficiency due to the resistive and absorbing p-type contact layers. In this work, we investigate the design and application of polarization engineered tunnel junctions for ultra-wide bandgap AlGaN (Al mole fraction >50%) materials towards highly efficient UV LEDs. We demonstrate that polarization-induced three dimensional charge is beneficial in reducing tunneling barriers especially for high composition AlGaN tunnel junctions. In addition, the design of graded tunnel junction structures could lead to low tunneling resistance below 10 –3 Ω cm 2 and lowmore » voltage consumption below 1 V (at 1 kA/cm 2) for high composition AlGaN tunnel junctions. Experimental demonstration of 292 nm emission was achieved through non-equilibrium hole injection into wide bandgap materials with bandgap energy larger than 4.7 eV, and detailed modeling of tunnel junctions shows that they can be engineered to have low resistance and can enable efficient emitters in the UV-C wavelength range.« less

Visible light electroluminescent diodes of indium-gallium phosphide

NASA Technical Reports Server (NTRS)

Clough, R.; Richman, D.; Tietjen, J.

1970-01-01

Vapor deposition and acceptor impurity diffusion techniques are used to prepare indium-gallium phosphide junctions. Certain problems in preparation are overcome by altering gas flow conditions and by increasing the concentration of phosphine in the gas. A general formula is given for the alloy's composition.

Ion-implanted epitaxially grown ZnSe

NASA Technical Reports Server (NTRS)

Chernow, F.

1975-01-01

The use of ZnSe to obtain efficient, short wavelength injection luminescence was investigated. It was proposed that shorter wavelength emission and higher efficiency be achieved by employing a p-i-n diode structure rather than the normal p-n diode structure. The intervening i layer minimizes concentration quenching effects and the donor-acceptor pair states leading to long wavelength emission. The surface p layer was formed by ion implantation; implantation of the i layer rather than the n substrate permits higher, uncompensated p-type doping. An ion implanted p-n junction in ZnSe is efficiency-limited by high electron injection terminating in nonradiative recombination at the front surface, and by low hole injection resulting from the inability to obtain high conductivity p-type surface layers. While the injection ratio in p-n junctions was determined by the radio of majority carrier concentrations, the injection ratio in p-i-n structures was determined by the mobility ratios and/or space charge neutrality requirements in the i layer.

Simple phenomenological modeling of transition-region capacitance of forward-biased p-n junction diodes and transistor diodes

NASA Technical Reports Server (NTRS)

Lindholm, F. A.

1982-01-01

The derivation of a simple expression for the capacitance C(V) associated with the transition region of a p-n junction under a forward bias is derived by phenomenological reasoning. The treatment of C(V) is based on the conventional Shockley equations, and simpler expressions for C(V) result that are in general accord with the previous analytical and numerical results. C(V) consists of two components resulting from changes in majority carrier concentration and from free hole and electron accumulation in the space-charge region. The space-charge region is conceived as the intrinsic region of an n-i-p structure for a space-charge region markedly wider than the extrinsic Debye lengths at its edges. This region is excited in the sense that the forward bias creates hole and electron densities orders of magnitude larger than those in equilibrium. The recent Shirts-Gordon (1979) modeling of the space-charge region using a dielectric response function is contrasted with the more conventional Schottky-Shockley modeling.

Modeling and fabrication of 4H-SiC Schottky junction

NASA Astrophysics Data System (ADS)

Martychowiec, A.; Pedryc, A.; Kociubiński, A.

2017-08-01

The rapidly growing demand for electronic devices requires using of alternative semiconductor materials, which could replace conventional silicon. Silicon carbide has been proposed for these harsh environment applications (high temperature, high voltage, high power conditions) because of its wide bandgap, its high temperature operation ability, its excellent thermal and chemical stability, and its high breakdown electric field strength. The Schottky barrier diode (SBD) is known as one of the best refined SiC devices. This paper presents prepared model, simulations and description of technology of 4H-SiC Schottky junction as well as characterization of fabricated structures. The future aim of the application of the structures is an optical detection of an ultraviolet radiation. The model section contains a comparison of two different solutions of SBD's construction. Simulations - as a crucial process of designing electronic devices - have been performed using the ATLAS device of Silvaco TCAD software. As a final result the paper shows I-V characteristics of fabricated diodes.

A Solid State Pyranometer

NASA Astrophysics Data System (ADS)

Dumitrescu, Anca Laura; Paulescu, Marius; Ercuta, Aurel

2015-12-01

The construction of a solid state device-based pyranometer designated to broadband irradiance measurements is presented in this paper. The device is built on the physical basis that the temperature difference between two bodies of identical shape and external surface area, identically exposed to the incident radiation, but having different absorption and heat transfer coefficients (e.g. one body is painted white and the other is painted black), is proportional to the incident irradiance. This proportionality may be put in evidence if the two bodies consisting of identical arrays of correspondingly painted semiconductor diodes, due to the thermal behaviour of their p-n junction. It is theoretically predicted and experimentally confirmed that the voltage drop across a diode passed through a constant forward current linearly decreases with the temperature of the junction. In other words, a signal proportional to the irradiance of the light source may be obtained via conventional analog electronics. The calibration of the apparatus, as performed by means of a professional device (LP PYRA 03), indicates a good linearity.

In-Operando Spatial Imaging of Edge Termination Electric Fields in GaN Vertical p-n Junction Diodes

DOE PAGES

Leonard, Francois; Dickerson, J. R.; King, M. P.; ...

2016-05-03

Control of electric fields with edge terminations is critical to maximize the performance of high-power electronic devices. We proposed a variety of edge termination designs which makes the optimization of such designs challenging due to many parameters that impact their effectiveness. And while modeling has recently allowed new insight into the detailed workings of edge terminations, the experimental verification of the design effectiveness is usually done through indirect means, such as the impact on breakdown voltages. In this letter, we use scanning photocurrent microscopy to spatially map the electric fields in vertical GaN p-n junction diodes in operando. We alsomore » reveal the complex behavior of seemingly simple edge termination designs, and show how the device breakdown voltage correlates with the electric field behavior. Modeling suggests that an incomplete compensation of the p-type layer in the edge termination creates a bilayer structure that leads to these effects, with variations that significantly impact the breakdown voltage.« less

Development and fabrication of a high current, fast recovery power diode

NASA Technical Reports Server (NTRS)

Berman, A. H.; Balodis, V.; Devance, D. C.; Gaugh, C. E.; Karlsson, E. A.

1983-01-01

A high voltage (VR = 1200 V), high current (IF = 150 A), fast recovery ( 700 ns) and low forward voltage drop ( 1.5 V) silicon rectifier was designed and the process developed for its fabrication. For maximum purity, uniformity and material characteristic stability, neutron transmutation n-type doped float zone silicon is used. The design features a hexagonal chip for maximum area utilization of space available in the DO-8 diode package, PIN diffused junction structure with deep diffused D(+) anode and a shallow high concentration n(+) cathode. With the high temperature glass passivated positive bevel mesa junction termination, the achieved blocking voltage is close to the theoretical limit of the starting material. Gold diffusion is used to control the lifetime and the resulting effect on switching speed and forward voltage tradeoff. For solder reflow assembly, trimetal (Al-Ti-Ni) contacts are used. The required major device electrical characteristics were achieved. Due to the tradeoff nature of forward voltage drop and reverse recovery time, a compromise was reached for these values.

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

PubMed

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

2016-05-11

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

Measurement of Beta Particles Induced Electron-Hole Pairs Recombination in Depletion Region of GaAs PN Junction

NASA Astrophysics Data System (ADS)

Chen, Hai-Yang; Jiang, Lan; Li, Da-Rang

2011-05-01

PN junctions and schottky diodes are widely employed as electron-hole pair collectors in electron beam induced current (EBIC) techniques and betavoltaic batteries, in which the recombination in depletion regions is ignored. We measured the beta particles induced electron-hole pairs recombination in the depletion region of a GaAs P+PN+ junction, based on comparisons between measured short currents and ideal values. The results show that only 20% electron-hole pairs in the depletion can be collected, causing the short current. This indicates an electron-hole pair diffusion length of 0.2μm in the depletion region. Hence, it is necessary to evaluate the recombination in the EBIC techniques and betavoltaic design.

Thin SOI lateral IGBT with band-to-band tunneling mechanism

NASA Astrophysics Data System (ADS)

Fu, Qiang; Tang, Zhaohuan; Tan, Kaizhou; Wang, Zhikuan; Mei, Yong

2017-06-01

In this paper, a novel 200V lateral IGBT on thin SOI layer with a band-to-band tunneling junction near the anode is proposed. The structure and the operating mechanism of the proposed IGBT are described and discussed. Its main feature is that the novel IGBT structure has a unique abrupt doped p++/n++ tunneling junction in the side of the anode. By utilizing the reverse bias characteristics of the tunneling junction, the proposed IGBT can achieve excellent reverse conducting performance. Numerical simulations suggest that a low reverse conduction voltage drop VR=-1.6V at a current density of 100A/cm2 and a soft factor S=0.63 of the build-in diode are achieved.

Polarization-induced Zener tunnel diodes in GaN/InGaN/GaN heterojunctions

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

Yan, Xiaodong; Li, Wenjun; Islam, S. M.

By the insertion of thin In{sub x}Ga{sub 1−x}N layers into Nitrogen-polar GaN p-n junctions, polarization-induced Zener tunnel junctions are studied. The reverse-bias interband Zener tunneling current is found to be weakly temperature dependent, as opposed to the strongly temperature-dependent forward bias current. This indicates tunneling as the primary reverse-bias current transport mechanism. The Indium composition in the InGaN layer is systematically varied to demonstrate the increase in the interband tunneling current. Comparing the experimentally measured tunneling currents to a model helps identify the specific challenges in potentially taking such junctions towards nitride-based polarization-induced tunneling field-effect transistors.

A charge-based model of Junction Barrier Schottky rectifiers

NASA Astrophysics Data System (ADS)

Latorre-Rey, Alvaro D.; Mudholkar, Mihir; Quddus, Mohammed T.; Salih, Ali

2018-06-01

A new charge-based model of the electric field distribution for Junction Barrier Schottky (JBS) diodes is presented, based on the description of the charge-sharing effect between the vertical Schottky junction and the lateral pn-junctions that constitute the active cell of the device. In our model, the inherently 2-D problem is transformed into a simple but accurate 1-D problem which has a closed analytical solution that captures the reshaping and reduction of the electric field profile responsible for the improved electrical performance of these devices, while preserving physically meaningful expressions that depend on relevant device parameters. The validation of the model is performed by comparing calculated electric field profiles with drift-diffusion simulations of a JBS device showing good agreement. Even though other fully 2-D models already available provide higher accuracy, they lack physical insight making the proposed model an useful tool for device design.

Temperature dependent current transport of Pd/ZnO nanowire Schottky diodes

NASA Astrophysics Data System (ADS)

Gayen, R. N.; Bhattacharyya, S. R.; Jana, P.

2014-09-01

Zinc oxide (ZnO) nanowire based Schottky barrier diodes are fabricated by depositing Pd metal contact on top of vertically well-aligned ZnO nanowire arrays. A vertical array of ZnO nanowires on indium tin oxide (ITO) coated glass substrates is synthesized by hybrid wet chemical route. Scanning electron microscopy (SEM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) measurement confirm the formation of stoichiometric well-aligned hexagonal (h-ZnO) nanowire arrays with wurtzite structure. Temperature dependent current-voltage (I-V) measurements on palladium-ZnO (Pd/ZnO) nanowire Schottky junctions in the temperature range 303-383 K exhibit excellent rectifying character. From these nonlinear I-V plots, different electrical parameters of diode-like reverse saturation current, barrier height and ideality factor are determined as a function of temperature assuming pure thermionic emission model. The ideality factor is found to decrease while the barrier height increases with the increase in temperature. The series resistance values calculated from Cheung’s functions also show temperature dependency. Such behavior can be attributed to the presence of defects that traps carriers, and barrier height inhomogeneity at the interface of the barrier junction. After barrier height inhomogeneity correction, considering a Gaussian distributed barrier height fluctuation across the Pd/ZnO interface, the estimated values of mean barrier height and modified Richardson constant are more closely matched to the theoretically predicted value for Pd/ZnO Schottky barrier diodes. The variation of density of interface states as a function of interface state energy is also calculated.

Laboratory Demonstration of Low-Cost Method for Producing Thin Film on Nonconductors.

ERIC Educational Resources Information Center

Ebong, A. U.; And Others

1991-01-01

A low-cost procedure for metallizing a silicon p-n junction diode by electroless nickel plating is reported. The procedure demonstrates that expensive salts can be excluded without affecting the results. The experimental procedure, measurement, results, and discussion are included. (Author/KR)

Effect of interface layer on the performance of high power diode laser arrays

NASA Astrophysics Data System (ADS)

Zhang, Pu; Wang, Jingwei; Xiong, Lingling; Li, Xiaoning; Hou, Dong; Liu, Xingsheng

2015-02-01

Packaging is an important part of high power diode laser (HPLD) development and has become one of the key factors affecting the performance of high power diode lasers. In the package structure of HPLD, the interface layer of die bonding has significant effects on the thermal behavior of high power diode laser packages and most degradations and failures in high power diode laser packages are directly related to the interface layer. In this work, the effects of interface layer on the performance of high power diode laser array were studied numerically by modeling and experimentally. Firstly, numerical simulations using finite element method (FEM) were conducted to analyze the effects of voids in the interface layer on the temperature rise in active region of diode laser array. The correlation between junction temperature rise and voids was analyzed. According to the numerical simulation results, it was found that the local temperature rise of active region originated from the voids in the solder layer will lead to wavelength shift of some emitters. Secondly, the effects of solder interface layer on the spectrum properties of high power diode laser array were studied. It showed that the spectrum shape of diode laser array appeared "right shoulder" or "multi-peaks", which were related to the voids in the solder interface layer. Finally, "void-free" techniques were developed to minimize the voids in the solder interface layer and achieve high power diode lasers with better optical-electrical performances.

Design of thin InGaAsN(Sb) n-i-p junctions for use in four-junction concentrating photovoltaic devices

NASA Astrophysics Data System (ADS)

Wilkins, Matthew M.; Gupta, James; Jaouad, Abdelatif; Bouzazi, Boussairi; Fafard, Simon; Boucherif, Abderraouf; Valdivia, Christopher E.; Arès, Richard; Aimez, Vincent; Schriemer, Henry P.; Hinzer, Karin

2017-04-01

Four-junction solar cells for space and terrestrial applications require a junction with a band gap of ˜1 eV for optimal performance. InGaAsN or InGaAsN(Sb) dilute nitride junctions have been demonstrated for this purpose, but in achieving the 14 mA/cm2 short-circuit current needed to match typical GaInP and GaAs junctions, the open-circuit voltage (VOC) and fill factor of these junctions are compromised. In multijunction devices incorporating materials with short diffusion lengths, we study the use of thin junctions to minimize sensitivity to varying material quality and ensure adequate transmission into lower junctions. An n-i-p device with 0.65-μm absorber thickness has sufficient short-circuit current, however, it relies less heavily on field-aided collection than a device with a 1-μm absorber. Our standard cell fabrication process, which includes a rapid thermal anneal of the contacts, yields a significant improvement in diffusion length and device performance. By optimizing a four-junction cell around a smaller 1-sun short-circuit current of 12.5 mA/cm2, we produced an InGaAsN(Sb) junction with open-circuit voltage of 0.44 V at 1000 suns (1 sun=100 mW/cm2), diode ideality factor of 1.4, and sufficient light transmission to allow >12.5 mA/cm2 in all four subcells.

Demonstration of GaAsSb/InAs nanowire backward diodes grown using position-controlled vapor-liquid-solid method

NASA Astrophysics Data System (ADS)

Kawaguchi, Kenichi; Takahashi, Tsuyoshi; Okamoto, Naoya; Sato, Masaru

2018-02-01

p-GaAsSb/n-InAs type-II nanowire (NW) diodes were fabricated using the position-controlled vapor-liquid-solid growth method. InAs and GaAsSb NW segments were grown vertically on GaAs(111)B substrates with the assistance of Au catalysts. Transmission electron microscopy-energy-dispersive X-ray spectroscopy analysis revealed that the GaAsSb segments have an Sb content of 40%, which is sufficient to form a tunnel heterostructure. Scanning capacitance microscope images clearly indicated the formation of a p-n junction in the NWs. Backward diode characteristics, that is, current flow toward negative bias originating from a tunnel current and current suppression toward positive bias by a heterobarrier, were demonstrated.

Spatial nonuniformity of current flow and its consideration in determination of characteristics of surface illuminated InAsSbP/InAs-based photodiodes

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

Zotova, N. V.; Karandashev, S. A.; Matveev, B. A., E-mail: Bmat@iropt3.ioffe.ru

Current-voltage characteristics of surface-irradiated photodiodes based on the InAsSbP/InAs structures are analyzed using experimental data on the distribution of electroluminescence intensity over the diode surface and taking into account thickening the current streamlines near the contacts. The influence of the potential barrier associated with the N-InAsSbP/n-InAs junction in double heterostructures on the differential resistance of diodes under zero bias, the value of the reverse current, and spreading of the forward current is discussed.

Fabrication and characterization of a germanium nanowire light emitting diode

NASA Astrophysics Data System (ADS)

Greil, Johannes; Bertagnolli, Emmerich; Salem, Bassem; Baron, Thierry; Gentile, Pascal; Lugstein, Alois

2017-12-01

In this letter, we demonstrate the feasibility of a germanium nanowire light emitting diode as a reasonable approach for downscaling of CMOS compatible light sources. We show room-temperature direct bandgap electroluminescence from axial p-n junction nanowire devices. The electron population in the Γ valley, necessary for direct bandgap emission, is achieved by high injection current densities. Carrier temperature is consistently found to be higher than the lattice temperature, indicating inhibited carrier cooling in small diameter wires. Strong polarization of the emission parallel to the nanowire axis is observed and attributed to dielectric contrast phenomena.

The determination of modified barrier heights in Ti/GaN nano-Schottky diodes at high temperature.

PubMed

Lee, Seung-Yong; Kim, Tae-Hong; Chol, Nam-Kyu; Seong, Han-Kyu; Choi, Heon-Jin; Ahn, Byung-Guk; Lee, Sang-Kwon

2008-10-01

We have investigated the size-effect of the nano-Schottky diodes on the electrical transport properties and the temperature-dependent current transport mechanism in a metal-semiconductor nanowire junction (a Ti/GaN nano-Schottky diode) using current-voltage characterization in the range of 300-423 K. We found that the modified mean Schottky barrier height (SBH) was approximately 0.7 eV with a standard deviation of approximately 0.14 V using a Gaussian distribution model of the barrier heights. The slightly high value of the modified mean SBH (approximately 0.11 eV) compared to the results from the thin-film based Ti/GaN Schottky diodes could be due to an additional oxide layer at the interface between the Ti and GaN nanowires. Moreover, we found that the abnormal behavior of the barrier heights and the ideality factors in a Ti/GaN nano-Schottky diode at a temperature below 423 K could be explained by a combination of the enhancement of the tunneling current and a model with a Gaussian distribution of the barrier heights.

New approach to the design of Schottky barrier diodes for THz mixers

NASA Technical Reports Server (NTRS)

Jelenski, A.; Grueb, A.; Krozer, V.; Hartnagel, H. L.

1992-01-01

Near-ideal GaAs Schottky barrier diodes especially designed for mixing applications in the THz frequency range are presented. A diode fabrication process for submicron diodes with near-ideal electrical and noise characteristics is described. This process is based on the electrolytic pulse etching of GaAs in combination with an in-situ platinum plating for the formation of the Schottky contacts. Schottky barrier diodes with a diameter of 1 micron fabricated by the process have already shown excellent results in a 650 GHz waveguide mixer at room temperature. A conversion loss of 7.5 dB and a mixer noise temperature of less than 2000 K have been obtained at an intermediate frequency of 4 GHz. The optimization of the diode structure and the technology was possible due to the development of a generalized Schottky barrier diode model which is valid also at high current densities. The common diode design and optimization is discussed on the basis of the classical theory. However, the conventional fomulas are valid only in a limited forward bias range corresponding to currents much smaller than the operating currents under submillimeter mixing conditions. The generalized new model takes into account not only the phenomena occurring at the junction such as current dependent recombination and drift/diffusion velocities, but also mobility and electron temperature variations in the undepleted epi-layer. Calculated diode I/V and noise characteristics are in excellent agreement with the measured values. Thus, the model offers the possibility of optimizing the diode structure and predicting the diode performance under mixing conditions at THz frequencies.

Microscale solid-state thermal diodes enabling ambient temperature thermal circuits for energy applications.

PubMed

Wang, Song; Cottrill, Anton L; Kunai, Yuichiro; Toland, Aubrey R; Liu, Pingwei; Wang, Wen-Jun; Strano, Michael S

2017-05-24

Thermal diodes, or devices that transport thermal energy asymmetrically, analogous to electrical diodes, hold promise for thermal energy harvesting and conservation, as well as for phononics or information processing. The junction of a phase change material and phase invariant material can form a thermal diode; however, there are limited constituent materials available for a given target temperature, particularly near ambient. In this work, we demonstrate that a micro and nanoporous polystyrene foam can house a paraffin-based phase change material, fused to PMMA, to produce mechanically robust, solid-state thermal diodes capable of ambient operation with Young's moduli larger than 11.5 MPa and 55.2 MPa above and below the melting transition point, respectively. Moreover, the composites show significant changes in thermal conductivity above and below the melting point of the constituent paraffin and rectification that is well-described by our previous theory and the Maxwell-Eucken model. Maximum thermal rectifications range from 1.18 to 1.34. We show that such devices perform reliably enough to operate in thermal diode bridges, dynamic thermal circuits capable of transforming oscillating temperature inputs into single polarity temperature differences - analogous to an electrical diode bridge with widespread implications for transient thermal energy harvesting and conservation. Overall, our approach yields mechanically robust, solid-state thermal diodes capable of engineering design from a mathematical model of phase change and thermal transport, with implications for energy harvesting.

Enhancement of the Si p-n diode NIR photoresponse by embedding β-FeSi2 nanocrystallites.

PubMed

Shevlyagin, A V; Goroshko, D L; Chusovitin, E A; Galkin, K N; Galkin, N G; Gutakovskii, A K

2015-10-05

By using solid phase epitaxy of thin Fe films and molecular beam epitaxy of Si, a p(+)-Si/p-Si/β-FeSi2 nanocrystallites/n-Si(111) diode structure was fabricated. Transmission electron microscopy data confirmed a well-defined multilayered structure with embedded nanocrystallites of two typical sizes: 3-4 and 15-20 nm, and almost coherent epitaxy of the nanocrystallites with the Si matrix. The diode at zero bias conditions exhibited a current responsivity of 1.7 mA/W, an external quantum efficiency of about 0.2%, and a specific detectivity of 1.2 × 10(9) cm × Hz(1/2)/W at a wavelength of 1300 nm at room temperature. In the avalanche mode, the responsivity reached up to 20 mA/W (2% in terms of efficiency) with a value of avalanche gain equal to 5. The data obtained indicate that embedding of β-FeSi2 nanocrystallites into the depletion region of the Si p-n junction results in expansion of the spectral sensitivity up to 1600 nm and an increase of the photoresponse by more than two orders of magnitude in comparison with a conventional Si p-n junction. Thereby, fabricated structure combines advantage of the silicon photodiode functionality and simplicity with near infrared light detection capability of β-FeSi2.

Stable Molecular Diodes Based on π-π Interactions of the Molecular Frontier Orbitals with Graphene Electrodes.

PubMed

Song, Peng; Guerin, Sarah; Tan, Sherman Jun Rong; Annadata, Harshini Venkata; Yu, Xiaojiang; Scully, Micheál; Han, Ying Mei; Roemer, Max; Loh, Kian Ping; Thompson, Damien; Nijhuis, Christian A

2018-03-01

In molecular electronics, it is important to control the strength of the molecule-electrode interaction to balance the trade-off between electronic coupling strength and broadening of the molecular frontier orbitals: too strong coupling results in severe broadening of the molecular orbitals while the molecular orbitals cannot follow the changes in the Fermi levels under applied bias when the coupling is too weak. Here, a platform based on graphene bottom electrodes to which molecules can bind via π-π interactions is reported. These interactions are strong enough to induce electronic function (rectification) while minimizing broadening of the molecular frontier orbitals. Molecular tunnel junctions are fabricated based on self-assembled monolayers (SAMs) of Fc(CH 2 ) 11 X (Fc = ferrocenyl, X = NH 2 , Br, or H) on graphene bottom electrodes contacted to eutectic alloy of gallium and indium top electrodes. The Fc units interact more strongly with graphene than the X units resulting in SAMs with the Fc at the bottom of the SAM. The molecular diodes perform well with rectification ratios of 30-40, and they are stable against bias stressing under ambient conditions. Thus, tunnel junctions based on graphene with π-π molecule-electrode coupling are promising platforms to fabricate stable and well-performing molecular diodes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of a portable thermal neutron detector based on a boron rich heterodiode

NASA Astrophysics Data System (ADS)

Tomov, R.; Venn, R.; Owens, A.; Peacock, A.

2008-10-01

Results are presented on the development of a portable detector suitable for detection of individual thermal neutrons. The device is based on direct absorption of neutrons in an absorber film containing 10B. The resultant charge arising from the capture products is detected by a p-n junction partly formed from this absorber and internal to the device. When a small bias voltage is applied (typically a few volts) a current pulse is observed due to the movement of this charge in the electric field of the p-n junction. For each detected neutron the charge pulse height, rise time and time of detection are recorded. Device performance, in terms of efficiency and spectral response, is explored as a function of neutron absorber thickness, geometry and overall diode electrical characteristics and validated against neutron source measurements at the UK National Physical Laboratory (NPL). The diodes have a natural background suppression capability through traditional pulse height and pulse rise time discrimination. The manufacturing process permits fabrication of arrays of diodes, with typical areas of ~15 mm2, thus increasing the collecting area and the signal to noise ratio, albeit with increased readout complexity. The associated multi-channel readout electronics is standard, however, and commonly used in existing X-ray sensors. Simple portable sensors based on these heterodiodes are expected to have applications in the detection of nuclear materials in a variety of security related situations.

Chemical Visualization of a GaN p-n junction by XPS

PubMed Central

Caliskan, Deniz; Sezen, Hikmet; Ozbay, Ekmel; Suzer, Sefik

2015-01-01

We report on an operando XPS investigation of a GaN diode, by recording the Ga2p3/2 peak position under both forward and reverse bias. Areal maps of the peak positions under reverse bias are completely decoupled with respect to doped regions and allow a novel chemical visualization of the p-n junction in a 2-D fashion. Other electrical properties of the device, such as leakage current, resistivity of the domains are also tapped via recording line-scan spectra. Application of a triangular voltage excitation enables probing photoresponse of the device. PMID:26359762

Ideal solar cell equation in the presence of photon recycling

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

Lan, Dongchen, E-mail: d.lan@unsw.edu.au; Green, Martin A., E-mail: m.green@unsw.edu.au

Previous derivations of the ideal solar cell equation based on Shockley's p-n junction diode theory implicitly assume negligible effects of photon recycling. This paper derives the equation in the presence of photon recycling that modifies the values of dark saturation and light-generated currents, using an approach applicable to arbitrary three-dimensional geometries with arbitrary doping profile and variable band gap. The work also corrects an error in previous work and proves the validity of the reciprocity theorem for charge collection in such a more general case with the previously neglected junction depletion region included.

Photocurrent spectroscopy of exciton and free particle optical transitions in suspended carbon nanotube pn-junctions

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

Chang, Shun-Wen; Theiss, Jesse; Hazra, Jubin

2015-08-03

We study photocurrent generation in individual, suspended carbon nanotube pn-junction diodes formed by electrostatic doping using two gate electrodes. Photocurrent spectra collected under various electrostatic doping concentrations reveal distinctive behaviors for free particle optical transitions and excitonic transitions. In particular, the photocurrent generated by excitonic transitions exhibits a strong gate doping dependence, while that of the free particle transitions is gate independent. Here, the built-in potential of the pn-junction is required to separate the strongly bound electron-hole pairs of the excitons, while free particle excitations do not require this field-assisted charge separation. We observe a sharp, well defined E{sub 11}more » free particle interband transition in contrast with previous photocurrent studies. Several steps are taken to ensure that the active charge separating region of these pn-junctions is suspended off the substrate in a suspended region that is substantially longer than the exciton diffusion length and, therefore, the photocurrent does not originate from a Schottky junction. We present a detailed model of the built-in fields in these pn-junctions, which, together with phonon-assistant exciton dissociation, predicts photocurrents on the same order of those observed experimentally.« less

Quantum junction solar cells.

PubMed

Tang, Jiang; Liu, Huan; Zhitomirsky, David; Hoogland, Sjoerd; Wang, Xihua; Furukawa, Melissa; Levina, Larissa; Sargent, Edward H

2012-09-12

Colloidal quantum dot solids combine convenient solution-processing with quantum size effect tuning, offering avenues to high-efficiency multijunction cells based on a single materials synthesis and processing platform. The highest-performing colloidal quantum dot rectifying devices reported to date have relied on a junction between a quantum-tuned absorber and a bulk material (e.g., TiO(2)); however, quantum tuning of the absorber then requires complete redesign of the bulk acceptor, compromising the benefits of facile quantum tuning. Here we report rectifying junctions constructed entirely using inherently band-aligned quantum-tuned materials. Realizing these quantum junction diodes relied upon the creation of an n-type quantum dot solid having a clean bandgap. We combine stable, chemically compatible, high-performance n-type and p-type materials to create the first quantum junction solar cells. We present a family of photovoltaic devices having widely tuned bandgaps of 0.6-1.6 eV that excel where conventional quantum-to-bulk devices fail to perform. Devices having optimal single-junction bandgaps exhibit certified AM1.5 solar power conversion efficiencies of 5.4%. Control over doping in quantum solids, and the successful integration of these materials to form stable quantum junctions, offers a powerful new degree of freedom to colloidal quantum dot optoelectronics.

Lateral MoS2 p-n junction formed by chemical doping for use in high-performance optoelectronics.

PubMed

Choi, Min Sup; Qu, Deshun; Lee, Daeyeong; Liu, Xiaochi; Watanabe, Kenji; Taniguchi, Takashi; Yoo, Won Jong

2014-09-23

This paper demonstrates a technique to form a lateral homogeneous 2D MoS2 p-n junction by partially stacking 2D h-BN as a mask to p-dope MoS2. The fabricated lateral MoS2 p-n junction with asymmetric electrodes of Pd and Cr/Au displayed a highly efficient photoresponse (maximum external quantum efficiency of ∼7000%, specific detectivity of ∼5 × 10(10) Jones, and light switching ratio of ∼10(3)) and ideal rectifying behavior. The enhanced photoresponse and generation of open-circuit voltage (VOC) and short-circuit current (ISC) were understood to originate from the formation of a p-n junction after chemical doping. Due to the high photoresponse at low VD and VG attributed to its built-in potential, our MoS2 p-n diode made progress toward the realization of low-power operating photodevices. Thus, this study suggests an effective way to form a lateral p-n junction by the h-BN hard masking technique and to improve the photoresponse of MoS2 by the chemical doping process.

Zn doping induced conductivity transformation in NiO films for realization of p-n homo junction diode

NASA Astrophysics Data System (ADS)

Dewan, Sheetal; Tomar, Monika; Tandon, R. P.; Gupta, Vinay

2017-06-01

Mixed transition metal oxide, zinc doped NiO, Z n x N i 1 - x O (x = 0, 0.01, 0.02, 0.05, and 0.10), thin films have been fabricated by the RF magnetron sputtering technique in an oxygen deficit ambience at a growth temperature of 400 °C. The present report highlights the effect of Zn doping in NiO thin films on its structural, optical, and electrical properties. Optical transmission enhancement and band gap engineering in a-axis oriented NiO films have been demonstrated via Zn substitution. Hall effect measurements of the prepared samples revealed a transition from p-type to n-type conductivity in NiO at 2% Zn doping. A NiO based transparent p-n homojunction diode has been fabricated successfully, and the conduction mechanism dominating the diode properties is reported in detail. Current-voltage (I-V) characteristics of the homojunction diode are found to obey the Space Charge Limited Conduction mechanism with non-ideal square law behaviour.

The Study of 0.34 THz Monolithically Integrated Fourth Subharmonic Mixer Using Planar Schottky Barrier Diode

NASA Astrophysics Data System (ADS)

Tong, Xiaodong; Li, Qian; An, Ning; Wang, Wenjie; Deng, Xiaodong; Zhang, Liang; Liu, Haitao; Zeng, Jianping; Li, Zhiqiang; Tang, Hailing; Xiong, Yong-Zhong

2015-11-01

A planar Schottky barrier diode with the designed Schottky contact area of approximately 3 μm2 is developed on gallium arsenide (GaAs) material. The measurements of the developed planar Schottky barrier diode indicate that the zero-biased junction capacitance Cj0 is 11.0 fF, the parasitic series resistance RS is 3.0 Ω, and the cut off frequency fT is 4.8 THz. A monolithically integrated fourth subharmonic mixer with this diode operating at the radio frequency (RF) signal frequency of 0.34 THz with the chip area of 0.6 mm2 is implemented. The intermediate frequency (IF) bandwidth is from DC to 40 GHz. The local oscillator (LO) bandwidth is 37 GHz from 60 to 97 GHz. The RF bandwidth is determined by the bandwidth of the on chip antenna, which is 28 GHz from 322 to 350 GHz. The measurements of the mixer demonstrated a conversion loss of approximately 51 dB.

A single-molecule diode.

PubMed

Elbing, Mark; Ochs, Rolf; Koentopp, Max; Fischer, Matthias; von Hänisch, Carsten; Weigend, Florian; Evers, Ferdinand; Weber, Heiko B; Mayor, Marcel

2005-06-21

We have designed and synthesized a molecular rod that consists of two weakly coupled electronic pi -systems with mutually shifted energy levels. The asymmetry thus implied manifests itself in a current-voltage characteristic with pronounced dependence on the sign of the bias voltage, which makes the molecule a prototype for a molecular diode. The individual molecules were immobilized by sulfur-gold bonds between both electrodes of a mechanically controlled break junction, and their electronic transport properties have been investigated. The results indeed show diode-like current-voltage characteristics. In contrast to that, control experiments with symmetric molecular rods consisting of two identical pi-systems did not show significant asymmetries in the transport properties. To investigate the underlying transport mechanism, phenomenological arguments are combined with calculations based on density functional theory. The theoretical analysis suggests that the bias dependence of the polarizability of the molecule feeds back into the current leading to an asymmetric shape of the current-voltage characteristics, similar to the phenomena in a semiconductor diode.

A single-molecule diode

PubMed Central

Elbing, Mark; Ochs, Rolf; Koentopp, Max; Fischer, Matthias; von Hänisch, Carsten; Weigend, Florian; Evers, Ferdinand; Weber, Heiko B.; Mayor, Marcel

2005-01-01

We have designed and synthesized a molecular rod that consists of two weakly coupled electronic π -systems with mutually shifted energy levels. The asymmetry thus implied manifests itself in a current–voltage characteristic with pronounced dependence on the sign of the bias voltage, which makes the molecule a prototype for a molecular diode. The individual molecules were immobilized by sulfur–gold bonds between both electrodes of a mechanically controlled break junction, and their electronic transport properties have been investigated. The results indeed show diode-like current–voltage characteristics. In contrast to that, control experiments with symmetric molecular rods consisting of two identical π -systems did not show significant asymmetries in the transport properties. To investigate the underlying transport mechanism, phenomenological arguments are combined with calculations based on density functional theory. The theoretical analysis suggests that the bias dependence of the polarizability of the molecule feeds back into the current leading to an asymmetric shape of the current–voltage characteristics, similar to the phenomena in a semiconductor diode. PMID:15956208

One-pot growth of two-dimensional lateral heterostructures via sequential edge-epitaxy

NASA Astrophysics Data System (ADS)

Sahoo, Prasana K.; Memaran, Shahriar; Xin, Yan; Balicas, Luis; Gutiérrez, Humberto R.

2018-01-01

Two-dimensional heterojunctions of transition-metal dichalcogenides have great potential for application in low-power, high-performance and flexible electro-optical devices, such as tunnelling transistors, light-emitting diodes, photodetectors and photovoltaic cells. Although complex heterostructures have been fabricated via the van der Waals stacking of different two-dimensional materials, the in situ fabrication of high-quality lateral heterostructures with multiple junctions remains a challenge. Transition-metal-dichalcogenide lateral heterostructures have been synthesized via single-step, two-step or multi-step growth processes. However, these methods lack the flexibility to control, in situ, the growth of individual domains. In situ synthesis of multi-junction lateral heterostructures does not require multiple exchanges of sources or reactors, a limitation in previous approaches as it exposes the edges to ambient contamination, compromises the homogeneity of domain size in periodic structures, and results in long processing times. Here we report a one-pot synthetic approach, using a single heterogeneous solid source, for the continuous fabrication of lateral multi-junction heterostructures consisting of monolayers of transition-metal dichalcogenides. The sequential formation of heterojunctions is achieved solely by changing the composition of the reactive gas environment in the presence of water vapour. This enables selective control of the water-induced oxidation and volatilization of each transition-metal precursor, as well as its nucleation on the substrate, leading to sequential edge-epitaxy of distinct transition-metal dichalcogenides. Photoluminescence maps confirm the sequential spatial modulation of the bandgap, and atomic-resolution images reveal defect-free lateral connectivity between the different transition-metal-dichalcogenide domains within a single crystal structure. Electrical transport measurements revealed diode-like responses across the junctions. Our new approach offers greater flexibility and control than previous methods for continuous growth of transition-metal-dichalcogenide-based multi-junction lateral heterostructures. These findings could be extended to other families of two-dimensional materials, and establish a foundation for the development of complex and atomically thin in-plane superlattices, devices and integrated circuits.

A single-molecule diode

NASA Astrophysics Data System (ADS)

Elbing, Mark; Ochs, Rolf; Koentopp, Max; Fischer, Matthias; von Hänisch, Carsten; Weigend, Florian; Evers, Ferdinand; Weber, Heiko B.; Mayor, Marcel

2005-06-01

We have designed and synthesized a molecular rod that consists of two weakly coupled electronic π -systems with mutually shifted energy levels. The asymmetry thus implied manifests itself in a current-voltage characteristic with pronounced dependence on the sign of the bias voltage, which makes the molecule a prototype for a molecular diode. The individual molecules were immobilized by sulfur-gold bonds between both electrodes of a mechanically controlled break junction, and their electronic transport properties have been investigated. The results indeed show diode-like current-voltage characteristics. In contrast to that, control experiments with symmetric molecular rods consisting of two identical π -systems did not show significant asymmetries in the transport properties. To investigate the underlying transport mechanism, phenomenological arguments are combined with calculations based on density functional theory. The theoretical analysis suggests that the bias dependence of the polarizability of the molecule feeds back into the current leading to an asymmetric shape of the current-voltage characteristics, similar to the phenomena in a semiconductor diode. Author contributions: F.E., H.B.W., and M.M. designed research; M.E., R.O., M.K., M.F., F.E., H.B.W., and M.M. performed research; M.E., R.O., M.K., M.F., C.v.H., F.W., F.E., H.B.W., and M.M. contributed new reagents/analytic tools; M.E., R.O., M.K., C.v.H., F.E., H.B.W., and M.M. analyzed data; and F.E., H.B.W., and M.M. wrote the paper.This paper was submitted directly (Track II) to the PNAS office.Abbreviations: A, acceptor; D, donor; MCB, mechanically controlled break junction.Data deposition: The atomic coordinates have been deposited in the Cambridge Structural Database, Cambridge Crystallographic Data Centre, Cambridge CB2 1EZ, United Kingdom (CSD reference no. 241632).

ZnO PN Junctions for Highly-Efficient, Low-Cost Light Emitting Diodes

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

David P. Norton; Stephen Pearton; Fan Ren

2007-09-30

By 2015, the US Department of Energy has set as a goal the development of advanced solid state lighting technologies that are more energy efficient, longer lasting, and more cost-effective than current technology. One approach that is most attractive is to utilize light-emitting diode technologies. Although III-V compound semiconductors have been the primary focus in pursuing this objective, ZnO-based materials present some distinct advantages that could yield success in meeting this objective. As with the nitrides, ZnO is a direct bandgap semiconductor whose gap energy (3.2 eV) can be tuned from 3.0 to 4 eV with substitution of Mg formore » higher bandgap, Cd for lower bandgap. ZnO has an exciton binding energy of 60 meV, which is larger than that for the nitrides, indicating that it should be a superior light emitting semiconductor. Furthermore, ZnO thin films can be deposited at temperatures on the order of 400-600 C, which is significantly lower than that for the nitrides and should lead to lower manufacturing costs. It has also been demonstrated that functional ZnO electronic devices can be fabricated on inexpensive substrates, such as glass. Therefore, for the large-area photonic application of solid state lighting, ZnO holds unique potential. A significant impediment to exploiting ZnO in light-emitting applications has been the absence of effective p-type carrier doping. However, the recent realization of acceptor-doped ZnO material overcomes this impediment, opening the door to ZnO light emitting diode development In this project, the synthesis and properties of ZnO-based pn junctions for light emitting diodes was investigated. The focus was on three issues most pertinent to realizing a ZnO-based solid state lighting technology, namely (1) achieving high p-type carrier concentrations in epitaxial and polycrystalline films, (2) realizing band edge emission from pn homojunctions, and (3) investigating pn heterojunction constructs that should yield efficient light emission. The project engaged established expertise at the University of Florida in ZnO film growth (D. Norton), device fabrication (F. Ren) and wide bandgap photonics (S. Pearton). It addressed p-type doping and junction formation in (Zn,Mg)O alloy thin films. The project employed pulsed laser deposition for film growth. The p-type dopant of interest was primarily phosphorus, given the recent results in our laboratory and elsewhere that this anions can yield p-type ZnO-based materials. The role of Zn interstitials, oxygen vacancies, and/or hydrogen complexes in forming compensating shallow donor levels imposes the need to simultaneously consider the role of in situ and post-growth processing conditions. Temperature-dependent Hall, Seebeck, C-V, and resistivity measurements was used to determine conduction mechanisms, carrier type, and doping. Temperature-dependent photoluminescence was used to determine the location of the acceptor level, injection efficiency, and optical properties of the structures. X-ray diffraction will used to characterize film crystallinity. Using these materials, the fabrication and characterization of (Zn,Mg)O pn homojunction and heterojunction devices was pursued. Electrical characterization of the junction capacitance and I-V behavior was used to extract junction profile and minority carrier lifetime. Electroluminescence from biased junctions was the primary property of interest.« less

Various vibration modes in a silicon ring resonator driven by p–n diode actuators formed in the lateral direction

NASA Astrophysics Data System (ADS)

Tsushima, Takafumi; Asahi, Yoichi; Tanigawa, Hiroshi; Furutsuka, Takashi; Suzuki, Kenichiro

2018-06-01

In this paper, we describe p–n diode actuators that are formed in the lateral direction on resonators. Because previously reported p–n diode actuators, which were driven by a force parallel to the electrostatic force induced in a p–n diode, were fabricated in the perpendicular direction to the surface, the fabrication process to satisfy the requirement of realizing a p–n junction set in the middle of the plate thickness has been difficult. The resonators in this work are driven by p–n diodes formed in the lateral direction, making the process easy. We have fabricated a silicon ring resonator that has in-plane vibration using p–n–p and n–p–n diode actuators formed in the lateral direction. First, we consider a space charge model that can sufficiently accurately describe the force induced in p–n diode actuators and compare it with the capacitance model used in most computer simulations. Then, we show that multiplying the vibration amplitude calculated by computer simulation by the modification coefficient of 4/3 provides the vibration amplitude in the p–n diode actuators. Good agreement of the theory with experimental results of the in-plane vibration measured for silicon ring resonators is obtained. The computer simulation is very useful for evaluating various vibration modes in resonators driven by the p–n diode actuators. The small amplitude of the p–n diode actuator measured in this work is expected to increase greatly with increased doping of the actuator.

Atomically thin p-n junctions with van der Waals heterointerfaces.

PubMed

Lee, Chul-Ho; Lee, Gwan-Hyoung; van der Zande, Arend M; Chen, Wenchao; Li, Yilei; Han, Minyong; Cui, Xu; Arefe, Ghidewon; Nuckolls, Colin; Heinz, Tony F; Guo, Jing; Hone, James; Kim, Philip

2014-09-01

Semiconductor p-n junctions are essential building blocks for electronic and optoelectronic devices. In conventional p-n junctions, regions depleted of free charge carriers form on either side of the junction, generating built-in potentials associated with uncompensated dopant atoms. Carrier transport across the junction occurs by diffusion and drift processes influenced by the spatial extent of this depletion region. With the advent of atomically thin van der Waals materials and their heterostructures, it is now possible to realize a p-n junction at the ultimate thickness limit. Van der Waals junctions composed of p- and n-type semiconductors--each just one unit cell thick--are predicted to exhibit completely different charge transport characteristics than bulk heterojunctions. Here, we report the characterization of the electronic and optoelectronic properties of atomically thin p-n heterojunctions fabricated using van der Waals assembly of transition-metal dichalcogenides. We observe gate-tunable diode-like current rectification and a photovoltaic response across the p-n interface. We find that the tunnelling-assisted interlayer recombination of the majority carriers is responsible for the tunability of the electronic and optoelectronic processes. Sandwiching an atomic p-n junction between graphene layers enhances the collection of the photoexcited carriers. The atomically scaled van der Waals p-n heterostructures presented here constitute the ultimate functional unit for nanoscale electronic and optoelectronic devices.

The role of ITO resistivity on current spreading and leakage in InGaN/GaN light emitting diodes

NASA Astrophysics Data System (ADS)

Sheremet, V.; Genç, M.; Elçi, M.; Sheremet, N.; Aydınlı, A.; Altuntaş, I.; Ding, K.; Avrutin, V.; Özgür, Ü.; Morkoç, H.

2017-11-01

The effect of a transparent ITO current spreading layer on electrical and light output properties of blue InGaN/GaN light emitting diodes (LEDs) is discussed. When finite conductivity of ITO is taken into account, unlike in previous models, the topology of LED die and contacts are shown to significantly affect current spreading and light output characteristics in top emitting devices. We propose an approach for calculating the current transfer length describing current spreading. We show that an inter-digitated electrode configuration with distance between the contact pad and the edge of p-n junction equal to transfer length in the current spreading ITO layer allows one to increase the optical area of LED chip, as compared to the physical area of the die, light output power, and therefore, the LED efficiency for a given current density. A detailed study of unpassivated LEDs also shows that current transfer lengths longer than the distance between the contact pad and the edge of p-n junction leads to increasing surface leakage that can only be remedied with proper passivation.

Silver free III-nitride flip chip light-emitting-diode with wall plug efficiency over 70% utilizing a GaN tunnel junction

NASA Astrophysics Data System (ADS)

Yonkee, B. P.; Young, E. C.; DenBaars, S. P.; Nakamura, S.; Speck, J. S.

2016-11-01

A molecular beam epitaxy regrowth technique was demonstrated on standard industrial patterned sapphire substrate light-emitting diode (LED) epitaxial wafers emitting at 455 nm to form a GaN tunnel junction. By using an HF pretreatment on the wafers before regrowth, a voltage of 3.08 V at 20 A/cm2 was achieved on small area devices. A high extraction package was developed for comparison with flip chip devices which utilize an LED floating in silicone over a BaSO4 coated header and produced a peak external quantum efficiency (EQE) of 78%. A high reflectivity mirror was designed using a seven-layer dielectric coating backed by aluminum which has a calculated angular averaged reflectivity over 98% between 400 and 500 nm. This was utilized to fabricate a flip chip LED which had a peak EQE and wall plug efficiency of 76% and 73%, respectively. This flip chip could increase light extraction over a traditional flip chip LED due to the increased reflectivity of the dielectric based mirror.

Simultaneously Enhancing Light Emission and Suppressing Efficiency Droop in GaN Microwire-Based Ultraviolet Light-Emitting Diode by the Piezo-Phototronic Effect.

PubMed

Wang, Xingfu; Peng, Wenbo; Yu, Ruomeng; Zou, Haiyang; Dai, Yejing; Zi, Yunlong; Wu, Changsheng; Li, Shuti; Wang, Zhong Lin

2017-06-14

Achievement of p-n homojuncted GaN enables the birth of III-nitride light emitters. Owing to the wurtzite-structure of GaN, piezoelectric polarization charges present at the interface can effectively control/tune the optoelectric behaviors of local charge-carriers (i.e., the piezo-phototronic effect). Here, we demonstrate the significantly enhanced light-output efficiency and suppressed efficiency droop in GaN microwire (MW)-based p-n junction ultraviolet light-emitting diode (UV LED) by the piezo-phototronic effect. By applying a -0.12% static compressive strain perpendicular to the p-n junction interface, the relative external quantum efficiency of the LED is enhanced by over 600%. Furthermore, efficiency droop is markedly reduced from 46.6% to 7.5% and corresponding droop onset current density shifts from 10 to 26.7 A cm -2 . Enhanced electrons confinement and improved holes injection efficiency by the piezo-phototronic effect are revealed and theoretically confirmed as the physical mechanisms. This study offers an unconventional path to develop high efficiency, strong brightness and high power III-nitride light sources.

Current transport across the pentacene/CVD-grown graphene interface for diode applications.

PubMed

Berke, K; Tongay, S; McCarthy, M A; Rinzler, A G; Appleton, B R; Hebard, A F

2012-06-27

We investigate the electronic transport properties across the pentacene/graphene interface. Current transport across the pentacene/graphene interface is found to be strikingly different from transport across pentacene/HOPG and pentacene/Cu interfaces. At low voltages, diodes using graphene as a bottom electrode display Poole–Frenkel emission, while diodes with HOPG and Cu electrodes are dominated by thermionic emission. At high voltages conduction is dominated by Poole–Frenkel emission for all three junctions. We propose that current across these interfaces can be accurately modeled by a combination of thermionic and Poole–Frenkel emission. Results presented not only suggest that graphene provides low resistive contacts to pentacene where a flat-laying orientation of pentacene and transparent metal electrodes are desired but also provides further understanding of the physics at the organic semiconductor/graphene interface.

Rectification of Lamb wave propagation in thin plates with piezo-dielectric periodic structures

NASA Astrophysics Data System (ADS)

Iwasaki, Yuhei; Tsuruta, Kenji; Ishikawa, Atsushi

2016-07-01

Based on a heterostructured plate consisting of piezoelectric-ceramic/epoxy-resin composites with different periodicities, we design a novel acoustic diode for the symmetrical/asymmetrical (S/A) mode of Lamb wave at audible ranges. The acoustic diode is constructed with two parts, i.e., the mode conversion part and the mode selection part, and the mode conversion mechanism at the interface is applied to the mode hybridization from S to S+A and for the mode conversion from A to S. The phonon band structures for each part are calculated and optimized so that the mode selection is realized for a specific mode at the junction. Finite-element simulations prove that the proposed acoustic diode achieves efficient rectification at audio frequency ranges for both S and A mode incidences of the Lamb wave.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Frequency modulation upon nonstationary heating of the p - n junction in high-sensitive diode laser spectroscopy

NASA Astrophysics Data System (ADS)

Andreev, Sergei N.; Nikolaev, I. V.; Ochkin, Vladimir N.; Savinov, Sergei Yu; Spiridonov, Maksim V.; Tskhai, Sergei N.

2007-04-01

A special type of modulation of the injection current of a diode laser is proposed at which the frequency modulation of radiation is not accompanied by the residual amplitude modulation. This method considerably reduces the influence of the diode laser radiation instability on the recorded absorption spectra. This allows a prolonged monitoring of small amounts of impurities in gas analysis by retaining a high sensitivity. Prolonged measurements of absorption spectra are performed at a relative absorption of 8×10-7. By using a 50-cm multipass cell with the optical length of 90 m, the absorption coefficient of 1.2×10-10 cm-1 was detected. As an example, the day evolution of the background concentrations of NO2 molecules was measured in the atmosphere.

A spectral measurement method for determining white OLED average junction temperatures

NASA Astrophysics Data System (ADS)

Zhu, Yiting; Narendran, Nadarajah

2016-09-01

The objective of this study was to investigate an indirect method of measuring the average junction temperature of a white organic light-emitting diode (OLED) based on temperature sensitivity differences in the radiant power emitted by individual emitter materials (i.e., "blue," "green," and "red"). The measured spectral power distributions (SPDs) of the white OLED as a function of temperature showed amplitude decrease as a function of temperature in the different spectral bands, red, green, and blue. Analyzed data showed a good linear correlation between the integrated radiance for each spectral band and the OLED panel temperature, measured at a reference point on the back surface of the panel. The integrated radiance ratio of the spectral band green compared to red, (G/R), correlates linearly with panel temperature. Assuming that the panel reference point temperature is proportional to the average junction temperature of the OLED panel, the G/R ratio can be used for estimating the average junction temperature of an OLED panel.

Phase-Defined van der Waals Schottky Junctions with Significantly Enhanced Thermoelectric Properties.

PubMed

Wang, Qiaoming; Yang, Liangliang; Zhou, Shengwen; Ye, Xianjun; Wang, Zhe; Zhu, Wenguang; McCluskey, Matthew D; Gu, Yi

2017-07-06

We demonstrate a van der Waals Schottky junction defined by crystalline phases of multilayer In 2 Se 3 . Besides ideal diode behaviors and the gate-tunable current rectification, the thermoelectric power is significantly enhanced in these junctions by more than three orders of magnitude compared with single-phase multilayer In 2 Se 3 , with the thermoelectric figure-of-merit approaching ∼1 at room temperature. Our results suggest that these significantly improved thermoelectric properties are not due to the 2D quantum confinement effects but instead are a consequence of the Schottky barrier at the junction interface, which leads to hot carrier transport and shifts the balance between thermally and field-driven currents. This "bulk" effect extends the advantages of van der Waals materials beyond the few-layer limit. Adopting such an approach of using energy barriers between van der Waals materials, where the interface states are minimal, is expected to enhance the thermoelectric performance in other 2D materials as well.

Binding configurations and intramolecular strain in single-molecule devices.

PubMed

Rascón-Ramos, Habid; Artés, Juan Manuel; Li, Yuanhui; Hihath, Joshua

2015-05-01

The development of molecular-scale electronic devices has made considerable progress over the past decade, and single-molecule transistors, diodes and wires have all been demonstrated. Despite this remarkable progress, the agreement between theoretically predicted conductance values and those measured experimentally remains limited. One of the primary reasons for these discrepancies lies in the difficulty to experimentally determine the contact geometry and binding configuration of a single-molecule junction. In this Article, we apply a small-amplitude, high-frequency, sinusoidal mechanical signal to a series of single-molecule devices during junction formation and breakdown. By measuring the current response at this frequency, it is possible to determine the most probable binding and contact configurations for the molecular junction at room temperature in solution, and to obtain information about how an applied strain is distributed within the molecular junction. These results provide insight into the complex configuration of single-molecule devices, and are in excellent agreement with previous predictions from theoretical models.

Fabrication of n-ZnO/ p-Si (100) and n-ZnO:Al/ p-Si (100) Heterostructures and Study of Current-Voltage, Capacitance-Voltage and Room-Temperature Photoluminescence

NASA Astrophysics Data System (ADS)

Shah, M. A. H.; Khan, M. K. R.; Tanveer Karim, A. M. M.; Rahman, M. M.; Kamruzzaman, M.

2018-01-01

Heterojunction diodes of n-ZnO/ p-Si (100) and n-ZnO:Al/ p-Si (100) were fabricated by spray pyrolysis technique. X-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), and field emission scanning electron microscopy (FESEM) were used to characterize the as-prepared samples. The XRD pattern indicates the hexagonal wurzite structure of zinc oxide (ZnO) and Al-doped ZnO (AZO) thin films grown on Si (100) substrate. The compositional analysis by EDX indicates the presence of Al in the AZO structure. The FESEM image indicates the smooth and compact surface of the heterostructures. The current-voltage characteristics of the heterojunction confirm the rectifying diode behavior at different temperatures and illumination intensities. For low forward bias voltage, the ideality factors were determined to be 1.24 and 1.38 for un-doped and Al-doped heterostructures at room temperature (RT), respectively, which indicates the good diode characteristics. The capacitance-voltage response of the heterojunctions was studied for different oscillation frequencies. From the 1/ C 2- V plot, the junction built-in potentials were found 0.30 V and 0.40 V for un-doped and Al-doped junctions at RT, respectively. The differences in built-in potential for different heterojunctions indicate the different interface state densities of the junctions. From the RT photoluminescence (PL) spectrum of the n-ZnO/ p-Si (100) heterostructure, an intense main peak at near band edge (NBE) 378 nm (3.28 eV) and weak deep-level emissions (DLE) centered at 436 nm (2.84 eV) and 412 nm (3.00 eV) were observed. The NBE emission is attributed to the radiative recombination of the free and bound excitons and the DLE results from the radiative recombination through deep level defects.

Evaluation of a silicon 5 MHz p–n diode actuator with a laterally vibrating extensional mode

NASA Astrophysics Data System (ADS)

Miyazaki, Fumito; Baba, Kazuki; Tanigawa, Hiroshi; Furutsuka, Takashi; Suzuki, Kenichiro

2018-05-01

In this paper, we describe p–n diode actuators that are laterally driven by the force induced in a depletion layer. The previously reported p–n diode actuators have been vertically driven. Because the resonant frequency depends on the thickness of the vibrating plate, the integration of resonators with different frequencies on a chip has been difficult. The resonators in this work are driven laterally by using length-extensional vibration. We have developed a compact model based on an analytical expression, in which p–n diode actuators are driven by the forces induced by the spread of the depletion layer. The deflection generated by the p–n diode actuators was proportional to the ratio of the depletion layer width to the resonator thickness as well as the position of the p–n junction. Good agreement of experimental results with the theory was confirmed by comparing the measured values for silicon p–n diode rectangular-plate actuators fabricated using a silicon-on-insulator (SOI) substrate. The displacement amplitude of the actuators was proportional to the DC bias, while the resonant frequency was independent of the DC bias. The latter characteristic is very different from that of widely used electrostatic actuators. Although the amplitude of the actuator measured in this work was very small, it is expected that the amplitude will increase greatly by increasing the doping of the p–n diode actuators.

Zener behaviour of p-SnS/ZnO and p-SnS/ZnS heterojunctions

NASA Astrophysics Data System (ADS)

Gupta, Yashika; Arun, P.

2018-03-01

p-SnS absorbing layers were grown by thermal evaporation on layers of various Zinc compounds, like ZnO and ZnS. This present work reports the J-V characteristics of thus obtained p-SnS/ZnO and p-SnS/ZnS heterojunctions. The pn junctions of these structures did not show any photovoltaic activity, however a zener like behaviour was observed in the 3rd quadrant of the J-V characteristics. Our analysis of the diodes suggest that the reverse breakdown or zener voltage obtained from the dark J-V characteristics can be used to estimate the energy band diagram of the junction and in turn the band-alignment at the junction. This makes it an easy alternative to x-ray Photoelectron Spectroscopy method usually used.

Low-frequency switching in a transistor amplifier.

PubMed

Carroll, T L

2003-04-01

It is known from extensive work with the diode resonator that the nonlinear properties of a P-N junction can lead to period doubling, chaos, and other complicated behaviors in a driven circuit. There has been very little work on what happens when more than one P-N junction is present. In this work, the first step towards multiple P-N junction circuits is taken by doing both experiments and simulations with a single-transistor amplifier using a bipolar transistor. Period doubling and chaos are seen when the amplifier is driven with signals between 100 kHz and 1 MHz, and they coincide with a very low frequency switching between different period doubled (or chaotic) wave forms. The switching frequencies are between 5 and 10 Hz. The switching behavior was confirmed in a simplified model of the transistor amplifier.

Influence of the Interaction Between Graphite and Polar Surfaces of ZnO on the Formation of Schottky Contact

NASA Astrophysics Data System (ADS)

Yatskiv, R.; Grym, J.

2018-03-01

We show that the interaction between graphite and polar surfaces of ZnO affects electrical properties of graphite/ZnO Schottky junctions. A strong interaction of the Zn-face with the graphite contact causes interface imperfections and results in the formation of laterally inhomogeneous Schottky contacts. On the contrary, high quality Schottky junctions form on the O-face, where the interaction is significantly weaker. Charge transport through the O-face ZnO/graphite junctions is well described by the thermionic emission model in both forward and reverse directions. We further demonstrate that the parameters of the graphite/ZnO Schottky diodes can be significantly improved when a thin layer of ZnO2 forms at the interface between graphite and ZnO after hydrogen peroxide surface treatment.

Using copper substrate to enhance the thermal conductivity of top-emission organic light-emitting diodes for improving the luminance efficiency and lifetime

NASA Astrophysics Data System (ADS)

Tsai, Yu-Sheng; Wang, Shun-Hsi; Chen, Chuan-Hung; Cheng, Chien-Lung; Liao, Teh-Chao

2009-12-01

The influence of heat dissipation on the performances of organic light-emitting diode (OLED) is investigated by measuring junction temperature and by calculating the rate of heat flow. The calculated rate of heat flow reveals that the key factors include the thermal conductivity, the substrate thickness, and the UV glue. Moreover, the use of copper substrate can effectively dissipate the joule heat, which then reduces the temperature gradient. Finally, it is shown that the use of a high thermal conductivity thinner substrate can enhance the thermal conductivity of OLED and the luminance efficiency as well.

Contribution of the graded region of a HgCdTe diode to its saturation current

NASA Technical Reports Server (NTRS)

Schacham, S. E.; Finkman, E.

1990-01-01

Experimental results show that the contribution of the graded region to the current of Hg(1-x)Cd(x)Te diodes is not negligible, as compared to that of the p type bulk. The theoretical analysis reveals the influence of the electric field present outside the depletion region on the current generated by the graded region. The analysis shows the importance of the lifetime profile in the graded region, which is a function of the specific recombination mechanism and its dependence on the local dopant concentration. The effect of parameters such as substrate concentration, surface concentration, and junction depth on this current is discussed.

GaAs/AlGaAs core multishell nanowire-based light-emitting diodes on Si.

PubMed

Tomioka, Katsuhiro; Motohisa, Junichi; Hara, Shinjiroh; Hiruma, Kenji; Fukui, Takashi

2010-05-12

We report on integration of GaAs nanowire-based light-emitting-diodes (NW-LEDs) on Si substrate by selective-area metalorganic vapor phase epitaxy. The vertically aligned GaAs/AlGaAs core-multishell nanowires with radial p-n junction and NW-LED array were directly fabricated on Si. The threshold current for electroluminescence (EL) was 0.5 mA (current density was approximately 0.4 A/cm(2)), and the EL intensity superlinearly increased with increasing current injections indicating superluminescence behavior. The technology described in this letter could help open new possibilities for monolithic- and on-chip integration of III-V NWs on Si.

Lithography-Free Fabrication of Core-Shell GaAs Nanowire Tunnel Diodes.

PubMed

Darbandi, A; Kavanagh, K L; Watkins, S P

2015-08-12

GaAs core-shell p-n junction tunnel diodes were demonstrated by combining vapor-liquid-solid growth with gallium oxide deposition by atomic layer deposition for electrical isolation. The characterization of an ensemble of core-shell structures was enabled by the use of a tungsten probe in a scanning electron microscope without the need for lithographic processing. Radial tunneling transport was observed, exhibiting negative differential resistance behavior with peak-to-valley current ratios of up to 3.1. Peak current densities of up to 2.1 kA/cm(2) point the way to applications in core-shell photovoltaics and tunnel field effect transistors.

Development of a (Hg, Cd)Te photodiode detector, Phase 2. [for 10.6 micron spectral region

NASA Technical Reports Server (NTRS)

1972-01-01

High speed sensitive (Hg,Cd)Te photodiode detectors operating in the 77 to 90 K temperature range have been developed for the 10.6 micron spectral region. P-N junctions formed by impurity (gold) diffusion in p-type (Hg, Cd) Te have been investigated. It is shown that the bandwidth and quantum efficiency of a diode are a constant for a fixed ratio of mobility/lifetime ratio of minority carriers. The minority carrier mobility and lifetime uniquely determine the bandwidth and quantum efficiency and indicate the shallow n on p (Hg,Cd) Te diodes are preferable as high performance, high frequency devices.

Mechanically and optically reliable folding structure with a hyperelastic material for seamless foldable displays

NASA Astrophysics Data System (ADS)

Kwon, Hyuk-Jun; Shim, HongShik; Kim, Sunkook; Choi, Woong; Chun, Youngtea; Kee, InSeo; Lee, SangYoon

2011-04-01

We report a mechanically and optically robust folding structure to realize a foldable active matrix organic-light-emitting-diode (AMOLED) display without a visible crease at the junction. A nonlinear stress analysis, based on a finite element method, provided an optimized design. The folding-unfolding test on the structure exhibited negligible deterioration of the relative brightness at the junction of the individual panels up to 105 cycles at a folding radius of 1 mm, indicating highly reliable mechanical and optical tolerances. These results demonstrate the feasibility of seamless foldable AMOLED displays, with potentially important technical implications on fabricating large size flexible displays.

Study and modeling of the transport mechanism in a semi insulating GaAs Schottky diode

NASA Astrophysics Data System (ADS)

Resfa, A.; Smahi, Bourzig Y.; Menezla, Brahimi. R.

2012-09-01

The current through a metal-semiconductor junction is mainly due to the majority carriers. Three distinctly different mechanisms exist in a Schottky diode: diffusion of carriers from the semiconductor into the metal, thermionic emission-diffusion (TED) of carriers across the Schottky barrier and quantum-mechanical tunneling through the barrier. The insulating layer converts the MS device in an MIS device and has a strong influence on its current-voltage (I-V) and the parameters of a Schottky barrier from 3.7 to 15 eV. There are several possible reasons for the error that causes a deviation of the ideal behavior of Schottky diodes with and without an interfacial insulator layer. These include the particular distribution of interface states, the series resistance, bias voltage and temperature. The GaAs and its large concentration values of trap centers will participate in an increase of the process of thermionic electrons and holes, which will in turn the IV characteristic of the diode, and an overflow maximum value [NT = 3 × 1020] is obtained. The I-V characteristics of Schottky diodes are in the hypothesis of a parabolic summit.

Enhancement of the Si p-n diode NIR photoresponse by embedding β-FeSi2 nanocrystallites

PubMed Central

Shevlyagin, A. V.; Goroshko, D. L.; Chusovitin, E. A.; Galkin, K. N.; Galkin, N. G.; Gutakovskii, A. K.

2015-01-01

By using solid phase epitaxy of thin Fe films and molecular beam epitaxy of Si, a p+-Si/p-Si/β-FeSi2 nanocrystallites/n-Si(111) diode structure was fabricated. Transmission electron microscopy data confirmed a well-defined multilayered structure with embedded nanocrystallites of two typical sizes: 3–4 and 15–20 nm, and almost coherent epitaxy of the nanocrystallites with the Si matrix. The diode at zero bias conditions exhibited a current responsivity of 1.7 mA/W, an external quantum efficiency of about 0.2%, and a specific detectivity of 1.2 × 109 cm × Hz1/2/W at a wavelength of 1300 nm at room temperature. In the avalanche mode, the responsivity reached up to 20 mA/W (2% in terms of efficiency) with a value of avalanche gain equal to 5. The data obtained indicate that embedding of β-FeSi2 nanocrystallites into the depletion region of the Si p-n junction results in expansion of the spectral sensitivity up to 1600 nm and an increase of the photoresponse by more than two orders of magnitude in comparison with a conventional Si p-n junction. Thereby, fabricated structure combines advantage of the silicon photodiode functionality and simplicity with near infrared light detection capability of β-FeSi2. PMID:26434582

Perimeter Governed Minority Carrier Lifetimes in 4H-SiC p(+)-n Diodes Measured by Reverse Recovery Switching Transient Analysis

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.

1998-01-01

Minority carrier lifetimes in epitaxial 4H-SiC p(+)-n junction diodes were measured via an analysis of reverse recovery switching characteristics. Behavior of reverse recovery storage time (t(s)) as a function of initial ON-state forward current (I(F)) and OFF-state reverse current (I(R)) followed well-documented trends which have been observed for decades in silicon p-n rectifiers. Average minority carrier (hole) lifetimes (tau(p)) calculated from plots of t(s) vs I(R)/I(F) strongly decreased with decreasing device area. Bulk and perimeter components of average hole lifetimes were separated by plotting 1/tau(p) as a function of device perimeter-to- area ratio (P/A). This plot reveals that perimeter recombination is dominant in these devices, whose areas are all less than 1 sq mm. The bulk minority carrier (hole) lifetime extracted from the 1/tau(p) vs P/A plot is approximately 0.7 micro-s, well above the 60 ns to 300 ns average iit'eptimes obtained when perimeter recombination effects are ignored in the analysis. Given the fact that there has been little previous investigation of bipolar diode and transistor performance as a function of perimeter-to-area ratio, this work raises the possibility that perimeter recombination may be partly responsible for poor effective minority carrier lifetimes and limited performance obtained in many previous SiC bipolar junction devices.

Perimeter Governed Minority Carrier Lifetimes in 4H-SiC p+n Diodes Measured by Reverse Recovery Switching Transient Analysis

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.

1998-01-01

Minority carrier lifetimes in epitaxial 4H-SiC p-n junction diodes were measured via an analysis of reverse recovery switching characteristics. Behavior of reverse recovery storage time (t(sub s)) as a function of initial ON-state forward current (I(sub f)) and OFF-state reverse current (I(sub R)) followed well-documented trends which have been observed for decades in silicon p-n rectifiers. Average minority carrier (hole) lifetimes (tau(sub p)) calculated from plots of t(sub s) vs I(sub R)/I(sub F) strongly decreased with decreasing device area. Bulk and perimeter components of average hole lifetimes were separated by plotting tau(sub p) as a function of device perimeter-to-area ratio (P/A). This plot reveals that perimeter recombination is dominant in these devices, whose areas are all less than 1 square mm. The bulk minority carrier (hole) lifetime extracted from the 1/Tau(sub p) vs P/A plot is approximately 0.7 microns, well above the 60 ns to 300 ns average lifetimes obtained when perimeter recombination effects are ignored in the analysis. Given the fact that there has been little previous investigation of bipolar diode and transistor performance as a function of perimeter-to-area ratio, this work raises the possibility that perimeter recombination may be partly responsible for poor effective minority carrier lifetimes and limited performance obtained in many previous SiC bipolar junction devices.

Ultrafast Direct Modulation of a Single-Mode Photonic Crystal Nanocavity Light-Emitting Diode

DTIC Science & Technology

2011-11-15

nanocavity laser with world record low threshold of 208 nW based on a lateral p-i-n junction defined by ion implantation in gallium arsenide6. This...recombination effects are mini- mized. In contrast, at room temperature, thermal excitation of car- riers depopulates the quantum dots much quicker than does Pur

Rectenna that converts infrared radiation to electrical energy

DOEpatents

Davids, Paul; Peters, David W.

2016-09-06

Technologies pertaining to converting infrared (IR) radiation to DC energy are described herein. In a general embodiment, a rectenna comprises a conductive layer. A thin insulator layer is formed on the conductive layer, and a nanoantenna is formed on the thin insulator layer. The thin insulator layer acts as a tunnel junction of a tunnel diode.

Electrical characterization of the temperature dependence in CdTe/CdS heterojunctions deposited in-situ by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Avila-Avendano, Jesus; Quevedo-Lopez, Manuel; Young, Chadwin

2018-02-01

The I-V and C-V characteristics of CdTe/CdS heterojunctions deposited in-situ by Pulsed Laser Deposition (PLD) were evaluated. In-situ deposition enables the study of the CdTe/CdS interface by avoiding potential impurities at the surface and interface as a consequence of exposure to air. The I-V and C-V characteristics of the resulting junctions were obtained at different temperatures, ranging from room temperature to 150 °C, where the saturation current (from 10-8 to 10-4 A/cm2), ideality factor (between 1 and 2), series resistance (from 102 to 105 Ω), built-in potential (0.66-0.7 V), rectification factor (˜106), and carrier concentration (˜1016 cm-3) were obtained. The current-voltage temperature dependence study indicates that thermionic emission is the main transport mechanism at the CdTe/CdS interface. This study also demonstrated that the built-in potential (Vbi) calculated using a thermionic emission model is more accurate than that calculated using C-V extrapolation since C-V plots showed a Vbi shift as a function of frequency. Although CdTe/CdS is widely used for photovoltaic applications, the parameters evaluated in this work indicate that CdTe/CdS heterojunctions could be used as rectifying diodes and junction field effect transistors (JFETs). JFETs require a low PN diode saturation current, as demonstrated for the CdTe/CdS junction studied here.

Gate-Controlled BP-WSe2 Heterojunction Diode for Logic Rectifiers and Logic Optoelectronics.

PubMed

Li, Dong; Wang, Biao; Chen, Mingyuan; Zhou, Jun; Zhang, Zengxing

2017-06-01

p-n junctions play an important role in modern semiconductor electronics and optoelectronics, and field-effect transistors are often used for logic circuits. Here, gate-controlled logic rectifiers and logic optoelectronic devices based on stacked black phosphorus (BP) and tungsten diselenide (WSe 2 ) heterojunctions are reported. The gate-tunable ambipolar charge carriers in BP and WSe 2 enable a flexible, dynamic, and wide modulation on the heterojunctions as isotype (p-p and n-n) and anisotype (p-n) diodes, which exhibit disparate rectifying and photovoltaic properties. Based on such characteristics, it is demonstrated that BP-WSe 2 heterojunction diodes can be developed for high-performance logic rectifiers and logic optoelectronic devices. Logic optoelectronic devices can convert a light signal to an electric one by applied gate voltages. This work should be helpful to expand the applications of 2D crystals. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Research and development for improved lead-salt diode lasers

NASA Technical Reports Server (NTRS)

Butler, J. F.

1976-01-01

A substantial increase in output power levels for lead-salt diode lasers, through the development of improved fabrication methods, as demonstrated. The goal of 1 mW of CW, single-mode, single-ended power output, was achieved, with exceptional devices exhibiting values greater than 8 mW. It was found that the current tuning rate could be controlled by adjusting the p-n junction depth, allowing the tuning rate to be optimized for particular applications. An unexpected phenomenon was encountered when crystal composition was observed to be significantly altered by annealing at temperatures as low as 600 C; the composition was changed by transport of material through the vapor phase. This effect caused problems in obtaining diode lasers with the desired operating characteristics. It was discovered that the present packaging method introduces gross damaging effects in the laser crystal through pressure applied by the C-bend.

Optical analysis of AlGaInP laser diodes with real refractive index guided self-aligned structure

NASA Astrophysics Data System (ADS)

Xu, Yun; Zhu, Xiaopeng; Ye, Xiaojun; Kang, Xiangning; Cao, Qing; Guo, Liang; Chen, Lianghui

2004-05-01

Optical modes of AlGaInP laser diodes with real refractive index guided self-aligned (RISA) structure were analyzed theoretically on the basis of two-dimension semivectorial finite-difference methods (SV-FDMs) and the computed simulation results were presented. The eigenvalue and eigenfunction of this two-dimension waveguide were obtained and the dependence of the confinement factor and beam divergence angles in the direction of parallel and perpendicular to the pn junction on the structure parameters such as the number of quantum wells, the Al composition of the cladding layers, the ridge width, the waveguide thickness and the residual thickness of the upper P-cladding layer were investigated. The results can provide optimized structure parameters and help us design and fabricate high performance AlGaInP laser diodes with a low beam aspect ratio required for optical storage applications.

Stochastic resonance-enhanced laser-based particle detector.

PubMed

Dutta, A; Werner, C

2009-01-01

This paper presents a Laser-based particle detector whose response was enhanced by modulating the Laser diode with a white-noise generator. A Laser sheet was generated to cast a shadow of the object on a 200 dots per inch, 512 x 1 pixels linear sensor array. The Laser diode was modulated with a white-noise generator to achieve stochastic resonance. The white-noise generator essentially amplified the wide-bandwidth (several hundred MHz) noise produced by a reverse-biased zener diode operating in junction-breakdown mode. The gain in the amplifier in the white-noise generator was set such that the Receiver Operating Characteristics plot provided the best discriminability. A monofiber 40 AWG (approximately 80 microm) wire was detected with approximately 88% True Positive rate and approximately 19% False Positive rate in presence of white-noise modulation and with approximately 71% True Positive rate and approximately 15% False Positive rate in absence of white-noise modulation.

Detection and modeling of leakage current in AlGaN-based deep ultraviolet light-emitting diodes

DOE PAGES

Moseley, Michael William; Allerman, Andrew A.; Crawford, Mary H.; ...

2015-03-01

Current-voltage (IV) characteristics of two AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) with differing densities of open-core threading dislocations (nanopipes) are analyzed. A three-diode circuit is simulated to emulate the IV characteristics of the DUV-LEDs, but is only able to accurately model the lower leakage current, lower nanopipe density DUV-LED. It was found that current leakage through the nanopipes in these structures is rectifying, despite nanopipes being previously established as inherently n-type. Using defect-sensitive etching, the nanopipes are revealed to terminate within the p-type GaN capping layer of the DUV-LEDs. The circuit model is modified to account for another p-nmore » junction between the n-type nanopipes and the p-type GaN, and an excellent fit to the IV characteristics of the leaky DUV-LED is achieved.« less

In-Situ Grown P-N Junctions in MERCURY(1-X) Cadmium(x) Telluride for IR Detectors.

NASA Astrophysics Data System (ADS)

Rao, Vithal Rajaram

In-situ grown p-n junctions in mercury cadmium telluride (Hg_{1-x}Cd _{x}Te with x between 0.2-0.3) were fabricated and characterized in this study. Fabrication of these junctions involved the growth of p-n structures at 370^circC on CdTe substrates by Organometallic Vapor Phase Epitaxy. P-type doping with arsenic was achieved by using tertiarybutylarsine as the precursor. N-type doping was obtained either with indium, using trimethylindium as the precursor or by leaving the layer undoped. These p-n structures were processed to fabricate photodiodes. Their electrical performance was evaluated and conclusions regarding current mechanisms which determine their behavior were drawn. By varying the Hg pressure between 0.07-0.13 atm, p-type doping level in the 10^{16 }/cm^3-rm2times10 ^{17}/cm^3 range was achieved. At higher values of Hg pressure, the arsenic doping level in the layer increased significantly. This is possibly due to an increase in Te vacancies, allowing arsenic to occupy more group VI sites where they behave as acceptors. The activation efficiency of arsenic in the layers was measured to be equal to 50%. A high temperature anneal at 415 ^circC for 15 minutes did not result in any increase in the activation efficiency, possibly indicating the presence of stable As-complexes in the layer. Growth of p^+n structures was carried out in a single run. The acceptor concentration in the p-type cap layer was 5-rm10times10 ^{16}/cm^3. Indium doped n-type base layers had a carrier concentration of 1- rm2times10^{16}/cm^3 , while undoped layers had a n-type background carrier concentration of 4-rm6times10^ {14}/cm^3. The cap layer was 3 μm thick with x = 0.30, while the base layer was 8mum thick with x = 0.26. Under the growth conditions, arsenic showed a diffusion coefficient of rm2times10 ^{13}cm^2/s, which was higher than the interdiffusion coefficient of the alloy junction. This resulted in placement of the p-n junction in the lower bandgap base layer, which is necessary for high quantum efficiency devices. Photodiodes showed a cutoff wavelength of 7.5 mum, which correlates with the alloy composition of the base layer. Measured R_0 A of these diodes varied between 1-100 ohm-cm ^2. In the lower R_0A diodes, reverse bias was dominated by surface currents, possibly due to degradation of the passivating layer. Diodes with higher R_0A showed under reverse bias that trap assisted tunneling current dominated their performance. The origin of these traps is process related and could correspond to the presence of inactivated arsenic close to the p-n junction. Forward bias was dominated by diffusion and recombination currents, while the presence of additional leakage currents was evident.

Optoelectronic response of a WS2 tubular p-n junction

NASA Astrophysics Data System (ADS)

Zhang, Y. J.; Onga, M.; Qin, F.; Shi, W.; Zak, A.; Tenne, R.; Smet, J.; Iwasa, Y.

2018-07-01

Due to their favourable and rich electronic and optical properties, group-VI-B transition-metal dichalcogenides (TMDs) have attracted considerable interest. They have earned their position in the materials portfolio of the spintronics and valleytronics communities. The electrical performance of TMDs is enhanced by rolling up the two-dimensional (2D) sheets to form quasi-one-dimensional (1D) tubular structures. The fabrication of p-n junctions out of these tubular TMDs would boost their potential for optoelectronic devices as such junctions represent a fundamental building block. Here, we report the realization of a p-n junction out of a single, isolated WS2-nanotube (WS2-NT). Light-emitting diode operation and photovoltaic behaviour were observed based on such p-n junctions. The emitted light as well as the photovoltaic effect exhibit strong linear polarization characteristics due to the quasi-1D nature. The external quantum efficiency for the photovoltaic effect reaches a value as high as 4.8%, exceeding by far that of 2D TMDs and even approaching the internal quantum efficiency of the 2D TMDs. This efficiency improvement indicates that TMD nanotubes are superior candidates over 2D TMDs for optoelectronic applications.

Vertical versus Lateral Two-Dimensional Heterostructures: On the Topic of Atomically Abrupt p/n-Junctions.

PubMed

Zhou, Ruiping; Ostwal, Vaibhav; Appenzeller, Joerg

2017-08-09

The key appeal of two-dimensional (2D) materials such as graphene, transition metal dichalcogenides (TMDs), or phosphorene for electronic applications certainly lies in their atomically thin nature that offers opportunities for devices beyond conventional transistors. It is also this property that makes them naturally suited for a type of integration that is not possible with any three-dimensional (3D) material, that is, forming heterostructures by stacking dissimilar 2D materials together. Recently, a number of research groups have reported on the formation of atomically sharp p/n-junctions in various 2D heterostructures that show strong diode-type rectification. In this article, we will show that truly vertical heterostructures do exhibit much smaller rectification ratios and that the reported results on atomically sharp p/n-junctions can be readily understood within the framework of the gate and drain voltage response of Schottky barriers that are involved in the lateral transport.

Discovery of a photoresponse amplification mechanism in compensated PN junctions

NASA Astrophysics Data System (ADS)

Zhou, Yuchun; Liu, Yu-Hsin; Rahman, Samia N.; Hall, David; Sham, L. J.; Lo, Yu-Hwa

2015-01-01

We report the experimental evidence of uncovering a photoresponse amplification mechanism in heavily doped, partially compensated silicon p-n junctions under very low bias voltage. We show that the observed photocurrent gain occurs at a bias that is more than an order of magnitude below the threshold voltage for conventional impact ionization. Moreover, contrary to the case of avalanche detectors and p-i-n diodes, the amplified photoresponse is enhanced rather than suppressed with increasing temperature. These distinctive characteristics lead us to hypothesize that the inelastic scattering between energetic electrons (holes) and the ionized impurities in the depletion and charge neutral regions of the p-n junction in a cyclic manner plays a significant role in the amplification process. Such an internal signal amplification mechanism, which occurs at much lower bias than impact ionization and favors room temperature over cryogenic temperature, makes it promising for practical device applications.

The controlled growth of graphene nanowalls on Si for Schottky photodetector

NASA Astrophysics Data System (ADS)

Zhou, Quan; Liu, Xiangzhi; Zhang, Enliang; Luo, Shi; Shen, Jun; Wang, Yuefeng; Wei, Dapeng

2017-12-01

Schottky diode with directly-grown graphene on silicon substrate has advantage of clean junction interface, promising for photodetectors with high-speed and low noise. In this report, we carefully studied the influence of growth parameters on the junction quality and photoresponse of graphene nanowalls (GNWs)-based Schottky photodetectors. We found that shorter growth time is critical for lower dark current, but at the same time higher photocurrent. The influence of growth parameters was attributed to the defect density of various growth time, which results in different degrees of surface absorption for H2O/O2 molecules and P-type doping level. Raman characterization and vacuum annealing treatment were carried out to confirm the regulation mechanism. Meanwhile, the release of thermal stress also makes the ideality factor η of thinner sample better than the thicker. Our results are important for the response improvement of photodetectors with graphene-Si schottky junction.

Discovery of a photoresponse amplification mechanism in compensated PN junctions

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

Zhou, Yuchun; Rahman, Samia N.; Hall, David

2015-01-19

We report the experimental evidence of uncovering a photoresponse amplification mechanism in heavily doped, partially compensated silicon p-n junctions under very low bias voltage. We show that the observed photocurrent gain occurs at a bias that is more than an order of magnitude below the threshold voltage for conventional impact ionization. Moreover, contrary to the case of avalanche detectors and p-i-n diodes, the amplified photoresponse is enhanced rather than suppressed with increasing temperature. These distinctive characteristics lead us to hypothesize that the inelastic scattering between energetic electrons (holes) and the ionized impurities in the depletion and charge neutral regions ofmore » the p-n junction in a cyclic manner plays a significant role in the amplification process. Such an internal signal amplification mechanism, which occurs at much lower bias than impact ionization and favors room temperature over cryogenic temperature, makes it promising for practical device applications.« less

Epitaxial solar cells fabrication

NASA Technical Reports Server (NTRS)

Daiello, R. V.; Robinson, P. H.; Kressel, H.

1975-01-01

Silicon epitaxy has been studied for the fabrication of solar cell structures, with the intent of optimizing efficiency while maintaining suitability for space applications. SiH2CL2 yielded good quality layers and junctions with reproducible impurity profiles. Diode characteristics and lifetimes in the epitaxial layers were investigated as a function of epitaxial growth conditions and doping profile, as was the effect of substrates and epitaxial post-gettering on lifetime. The pyrolytic decomposition of SiH4 was also used in the epitaxial formation of highly doped junction layers on bulk Si wafers. The effects of junction layer thickness and bulk background doping level on cell performance, in particular, open-circuit voltage, were investigated. The most successful solar cells were fabricated with SiH2 CL2 to grow p/n layers on n(+) substrates. The best performance was obtained from a p(+)/p/n/n(+) structure grown with an exponential grade in the n-base layer.

A ceramic radial insulation structure for a relativistic electron beam vacuum diode.

PubMed

Xun, Tao; Yang, Hanwu; Zhang, Jiande; Liu, Zhenxiang; Wang, Yong; Zhao, Yansong

2008-06-01

For one kind of a high current diode composed of a small disk-type alumina ceramic insulator water/vacuum interface, the insulation structure was designed and experimentally investigated. According to the theories of vacuum flashover and the rules for radial insulators, a "cone-column" anode outline and the cathode shielding rings were adopted. The electrostatic field along the insulator surface was obtained by finite element analysis simulating. By adjusting the outline of the anode and reshaping the shielding rings, the electric fields were well distributed and the field around the cathode triple junction was effectively controlled. Area weighted statistical method was applied to estimate the surface breakdown field. In addition, the operating process of an accelerator based on a spiral pulse forming line (PFL) was simulated through the PSPICE software to get the waveform of charging and diode voltage. The high voltage test was carried out on a water dielectric spiral PFL accelerator with long pulse duration, and results show that the diode can work stably in 420 kV, 200 ns conditions. The experimental results agree with the theoretical and simulated results.

Characterization of a n+3C/n−4H SiC heterojunction diode

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

Minamisawa, R. A.; Mihaila, A.; Farkas, I.

We report on the fabrication of n + 3C/n-4H SiC heterojunction diodes (HJDs) potentially promising the ultimate thermal stability of the junction. The diodes were systematically analyzed by TEM, X-ray diffraction, AFM, and secondary ion mass spectroscopy, indicating the formation of epitaxial 3C-SiC crystal on top of 4H-SiC substrate with continuous interface, low surface roughness, and up to ∼7 × 10{sup 17 }cm{sup −3} dopant impurity concentration. The conduction band off-set is about 1 V as extracted from CV measurements, while the valence bands of both SiC polytypes are aligned. The HJDs feature opening voltage of 1.65 V, consistent with the barrier height of about 1.5 eV extractedmore » from CV measurement. We finally compare the electrical results of the n + 3C/n-4H SiC heterojunction diodes with those featuring Si and Ge doped anodes in order to evaluate current challenges involved in the fabrication of such devices.« less

Experimental and computational investigation of graphene/SAMs/n-Si Schottky diodes

NASA Astrophysics Data System (ADS)

Aydin, H.; Bacaksiz, C.; Yagmurcukardes, N.; Karakaya, C.; Mermer, O.; Can, M.; Senger, R. T.; Sahin, H.; Selamet, Y.

2018-01-01

We have investigated the effect of two different self-assembled monolayers (SAMs) on electrical characteristics of bilayer graphene (BLG)/n-Si Schottky diodes. Novel 4″bis(diphenylamino)-1, 1‧:3″-terphenyl-5‧ carboxylic acids (TPA) and 4,4-di-9H-carbazol-9-yl-1,1‧:3‧1‧-terphenyl-5‧ carboxylic acid (CAR) aromatic SAMs have been used to modify n-Si surfaces. Cyclic voltammetry (CV) and Kelvin probe force microscopy (KPFM) results have been evaluated to verify the modification of n-Si surface. The current-voltage (I-V) characteristics of bare and SAMs modified devices show rectification behaviour verifying a Schottky junction at the interface. The ideality factors (n) from ln(I)-V dependences were determined as 2.13, 1.96 and 2.07 for BLG/n-Si, BLG/TPA/n-Si and BLG/CAR/n-Si Schottky diodes, respectively. In addition, Schottky barrier height (SBH) and series resistance (Rs) of SAMs modified diodes were decreased compared to bare diode due to the formation of a compatible interface between graphene and Si as well as π-π interaction between aromatic SAMs and graphene. The CAR-based device exhibits better diode characteristic compared to the TPA-based device. Computational simulations show that the BLG/CAR system exhibits smaller energy-level-differences than the BLG/TPA, which supports the experimental findings of a lower Schottky barrier and series resistance in BLG/CAR diode.

Silicon carbide, a semiconductor for space power electronics

NASA Technical Reports Server (NTRS)

Powell, J. Anthony; Matus, Lawrence G.

1991-01-01

After many years of promise as a high temperature semiconductor, silicon carbide (SiC) is finally emerging as a useful electronic material. Recent significant progress that has led to this emergence has been in the areas of crystal growth and device fabrication technology. High quality single-crystal SiC wafers, up to 25 mm in diameter, can now be produced routinely from boules grown by a high temperature (2700 K) sublimation process. Device fabrication processes, including chemical vapor deposition (CVD), in situ doping during CVD, reactive ion etching, oxidation, metallization, etc. have been used to fabricate p-n junction diodes and MOSFETs. The diode was operated to 870 K and the MOSFET to 770 K.

980-nm diode laser and fiber optic resectoscope in endourological surgery

NASA Astrophysics Data System (ADS)

Cecchetti, Walter; Guazzieri, Stefano; Tasca, Andrea; Dal Bianco, M.; Zattoni, Filiberto; Pagano, Francesco

1996-12-01

The 980 nm Ceralas D50 diode laser, produces homogeneous lesions on tissues of different nature. In our endourological tests we used the Ceralas D50 coupled with Comeg 24 ch laser resectoscope, and we treated 22 patients: n.5 bladder cancers, n.3 uretero pelvic junction obstructions, with hydronephrosis, n.3 urethra stenosis, n1 ureter stenosis, n.4 multiple upper tract transitional cell carcinomas, n.6 BPH treatments with VLAP modalities. Using the 1000 micrometers delivery fibers with different shaped tips, we obtained a bloodless sharp cut and easily vaporizations with minimum carbonizations, with power output in the range of 8-12 W, and 18-24W for VLAP.

Millimeter-wave and optoelectronic applications of heterostructure integrated circuits

NASA Technical Reports Server (NTRS)

Pavlidis, Dimitris

1991-01-01

The properties are reviewed of heterostructure devices for microwave-monolithic-integrated circuits (MMICs) and optoelectronic integrated circuits (OICs). Specific devices examined include lattice-matched and pseudomorphic InAlAs/InGaAs high-electron mobility transistors (HEMTs), mixer/multiplier diodes, and heterojunction bipolar transistors (HBTs) developed with a number of materials. MMICs are reviewed that can be employed for amplification, mixing, and signal generation, and receiver/transmitter applications are set forth for OICs based on GaAs and InP heterostructure designs. HEMTs, HBTs, and junction-FETs can be utilized in combination with PIN, MSM, and laser diodes to develop novel communication systems based on technologies that combine microwave and photonic capabilities.

Millimeter-wave and optoelectronic applications of heterostructure integrated circuits

NASA Astrophysics Data System (ADS)

Pavlidis, Dimitris

1991-02-01

The properties are reviewed of heterostructure devices for microwave-monolithic-integrated circuits (MMICs) and optoelectronic integrated circuits (OICs). Specific devices examined include lattice-matched and pseudomorphic InAlAs/InGaAs high-electron mobility transistors (HEMTs), mixer/multiplier diodes, and heterojunction bipolar transistors (HBTs) developed with a number of materials. MMICs are reviewed that can be employed for amplification, mixing, and signal generation, and receiver/transmitter applications are set forth for OICs based on GaAs and InP heterostructure designs. HEMTs, HBTs, and junction-FETs can be utilized in combination with PIN, MSM, and laser diodes to develop novel communication systems based on technologies that combine microwave and photonic capabilities.

On the Determination of the Emission Wavelength of an Infrared LED with Common Laboratory Instruments

ERIC Educational Resources Information Center

RayChaudhuri, Barun

2011-01-01

This work demonstrates an experiment on the optoelectronic properties of a p-n junction suitable for students of undergraduate physics. It investigates, from an educational point of view, the origin of the wavelength of radiation emitted by a light emitting diode (LED) and determines the emission wavelength of an infrared LED without using…

Silicon carbide semiconductor technology for high temperature and radiation environments

NASA Technical Reports Server (NTRS)

Matus, Lawrence G.

1993-01-01

Viewgraphs on silicon carbide semiconductor technology and its potential for enabling electronic devices to function in high temperature and high radiation environments are presented. Topics covered include silicon carbide; sublimation growth of 6H-SiC boules; SiC chemical vapor deposition reaction system; 6H silicon carbide p-n junction diode; silicon carbide MOSFET; and silicon carbide JFET radiation response.

Electrical spin injection into GaAs based light emitting diodes using perpendicular magnetic tunnel junction-type spin injector

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

Tao, B. S.; Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190; Barate, P.

Remanent electrical spin injection into an InGaAs/GaAs based quantum well light emitting diode is realized by using a perpendicularly magnetized MgO/CoFeB/Ta/CoFeB/MgO spin injector. We demonstrate that the Ta interlayer plays an important role to establish the perpendicular magnetic anisotropy and the thickness of Ta interlayer determines the type of exchange coupling between the two adjacent CoFeB layers. They are ferromagnetically or antiferromagnetically coupled for a Ta thickness of 0.5 nm or 0.75 nm, respectively. A circular polarized electroluminescence (P{sub c}) of about 10% is obtained at low temperature and at zero magnetic field. The direction of the electrically injected spins is determinedmore » only by the orientation of the magnetization of the bottom CoFeB layer which is adjacent to the MgO/GaAs interface. This work proves the critical role of the bottom CoFeB/MgO interface on the spin-injection and paves the way for the electrical control of spin injection via magnetic tunnel junction-type spin injector.« less

Hybrid Tunnel Junction-Graphene Transparent Conductive Electrodes for Nitride Lateral Light Emitting Diodes.

PubMed

Wang, Liancheng; Cheng, Yan; Liu, Zhiqiang; Yi, Xiaoyan; Zhu, Hongwei; Wang, Guohong

2016-01-20

Graphene transparent conductive electrode (TCE) applications in nitride light emitting diodes (LEDs) are still limited by the large contact resistance and interface barrier between graphene and p-GaN. We propose a hybrid tunnel junction (TJ)-graphene TCE approach for nitride lateral LEDs theoretically and experimentally. Through simulation using commercial advanced physical models of semiconductor devices (APSYS), we found that low tunnel resistance can be achieved in the n(+)-GaN/u-InGaN/p(+)-GaN TJ, which has a lower tunneling barrier and an enhanced electric field due to the polarization effect. Graphene TCEs and hybrid graphene-TJ TCEs are then modeled. The designed hybrid TJ-graphene TCEs show sufficient current diffusion length (Ls), low introduced series resistance, and high transmittance. The assembled TJ LED with the triple-layer graphene (TLG) TCEs show comparable optoelectrical performance (3.99 V@20 mA, LOP = 10.8 mW) with the reference LED with ITO TCEs (3.36 V@20 mA, LOP = 12.6 mW). The experimental results further prove that the TJ-graphene structure can be successfully incorporated as TCEs for lateral nitride LEDs.

Direct determination of minority carrier diffusion lengths at axial GaAs nanowire p-n junctions.

PubMed

Gutsche, Christoph; Niepelt, Raphael; Gnauck, Martin; Lysov, Andrey; Prost, Werner; Ronning, Carsten; Tegude, Franz-Josef

2012-03-14

Axial GaAs nanowire p-n diodes, possibly one of the core elements of future nanowire solar cells and light emitters, were grown via the Au-assisted vapor-liquid-solid mode, contacted by electron beam lithography, and investigated using electron beam induced current measurements. The minority carrier diffusion lengths and dynamics of both, electrons and holes, were determined directly at the vicinity of the p-n junction. The generated photocurrent shows an exponential decay on both sides of the junction and the extracted diffusion lengths are about 1 order of magnitude lower compared to bulk material due to surface recombination. Moreover, the observed strong diameter-dependence is well in line with the surface-to-volume ratio of semiconductor nanowires. Estimating the surface recombination velocities clearly indicates a nonabrupt p-n junction, which is in essential agreement with the model of delayed dopant incorporation in the Au-assisted vapor-liquid-solid mechanism. Surface passivation using ammonium sulfide effectively reduces the surface recombination and thus leads to higher minority carrier diffusion lengths. © 2012 American Chemical Society

Controlling the rectification properties of molecular junctions through molecule–electrode coupling

DOE PAGES

Koepf, Matthieu; Koenigsmann, Christopher; Ding, Wendu; ...

2016-08-17

The development of molecular components functioning as switches, rectifiers or amplifiers is a great challenge in molecular electronics. A desirable property of such components is functional robustness, meaning that the intrinsic functionality of components must be preserved regardless of the strategy used to integrate them into the final assemblies. Here, this issue is investigated for molecular diodes based on N-phenylbenzamide (NPBA) backbones. The transport properties of molecular junctions derived from NPBA are characterized while varying the nature of the functional groups interfacing the backbone and the gold electrodes required for break-junction measurements. Furthermore, combining experimental and theoretical methods, it ismore » shown that at low bias (<0.85 V) transport is determined by the same frontier molecular orbital originating from the NPBA core, regardless of the anchoring group employed. The magnitude of rectification, however, is strongly dependent on the strength of the electronic coupling at the gold–NPBA interface and on the spatial distribution of the local density of states of the dominant transport channel of the molecular junction.« less

Controlling the rectification properties of molecular junctions through molecule–electrode coupling

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

Koepf, Matthieu; Koenigsmann, Christopher; Ding, Wendu

The development of molecular components functioning as switches, rectifiers or amplifiers is a great challenge in molecular electronics. A desirable property of such components is functional robustness, meaning that the intrinsic functionality of components must be preserved regardless of the strategy used to integrate them into the final assemblies. Here, this issue is investigated for molecular diodes based on N-phenylbenzamide (NPBA) backbones. The transport properties of molecular junctions derived from NPBA are characterized while varying the nature of the functional groups interfacing the backbone and the gold electrodes required for break-junction measurements. Furthermore, combining experimental and theoretical methods, it ismore » shown that at low bias (<0.85 V) transport is determined by the same frontier molecular orbital originating from the NPBA core, regardless of the anchoring group employed. The magnitude of rectification, however, is strongly dependent on the strength of the electronic coupling at the gold–NPBA interface and on the spatial distribution of the local density of states of the dominant transport channel of the molecular junction.« less

Thermal investigation on high power dfb broad area lasers at 975 nm, with 60% efficiency

NASA Astrophysics Data System (ADS)

Mostallino, R.; Garcia, M.; Deshayes, Y.; Larrue, A.; Robert, Y.; Vinet, E.; Bechou, L.; Lecomte, M.; Parillaud, O.; Krakowski, M.

2016-03-01

The demand of high power diode lasers in the range of 910-980nm is regularly growing. This kind of device for many applications, such as fiber laser pumping [1], material processing [1], solid-state laser pumping [1], defense and medical/dental. The key role of this device lies in the efficiency (𝜂𝐸) of converting input electrical power into output optical power. The high value of 𝜂𝐸 allows high power level and reduces the need in heat dissipation. The requirement of wavelength stabilization with temperature is more obvious in the case of multimode 975nm diode lasers used for pumping Yb, Er and Yb/Er co-doped solid-state lasers, due to the narrow absorption line close to this wavelength. Such spectral width property (<1 nm), combined with wavelength thermal stabilization (0.07 𝑛𝑚 • °𝐶-1), provided by a uniform distributed feedback grating (DFB) introduced by etching and re-growth process techniques, is achievable in high power diode lasers using optical feedback. This paper reports on the development of the diode laser structure and the process techniques required to write the gratings taking into account of the thermal dissipation and optical performances. Performances are particularly determined in terms of experimental electro-optical characterizations. One of the main objectives is to determine the thermal resistance of the complete assembly to ensure the mastering of the diode laser temperature for operating condition. The classical approach to determine junction temperature is based on the infrared thermal camera, the spectral measurement and the pulse electrical method. In our case, we base our measurement on the spectral measurement but this approach is not well adapted to the high power diodes laser studied. We develop a new measurement based on the pulse electrical method and using the T3STERequipment. This method is well known for electronic devices and LEDs but is weakly developed for the high power diodes laser. This crucial measurement compared to spectral one is critical for understand the thermal management of diode laser device and improve the structure based on design for reliability. To have a perfect relation between structure, and their modification, and temperature, FEM simulations are performed using COMSOL software. In this case, we can understand the impact of structure on the isothermal distribution and then reveal the sensitive zones in the diode laser. To validate the simulation, we compare the simulation results to the experimental one and develop an analytical model to determine the different contributions of the thermal heating. This paper reports on the development laser structure and the process techniques required to write the gratings. Performances are particularly characterized in terms of experimental electro-optical characterization and spectral response. The extraction of thermal resistance (Rth) is particularly difficult, because of the implicit low value (Rth ≈ 2𝐾/𝑊) and the multimodal nature of the diode laser. In such a context, thermal resistance has been measured using a dedicated equipment namely T3STER©. The results have been compared with those given by the well-known technique achieved from the spectrum of the diode laser (central wavelength variations vs temperature) that is more difficult to apply for multimodal diodes laser. The last section deals with thermal simulations based on finite elements method (FEM) modeling in order to estimate junction temperature . This study represent a significant part of the general Design for Reliability (DfR) effort carried out on such devices to produce efficient and reliable high power devices at the industrial level.

Electronic Properties of DNA-Based Schottky Barrier Diodes in Response to Alpha Particles.

PubMed

Al-Ta'ii, Hassan Maktuff Jaber; Periasamy, Vengadesh; Amin, Yusoff Mohd

2015-05-21

Detection of nuclear radiation such as alpha particles has become an important field of research in recent history due to nuclear threats and accidents. In this context; deoxyribonucleic acid (DNA) acting as an organic semiconducting material could be utilized in a metal/semiconductor Schottky junction for detecting alpha particles. In this work we demonstrate for the first time the effect of alpha irradiation on an Al/DNA/p-Si/Al Schottky diode by investigating its current-voltage characteristics. The diodes were exposed for different periods (0-20 min) of irradiation. Various diode parameters such as ideality factor, barrier height, series resistance, Richardson constant and saturation current were then determined using conventional, Cheung and Cheung's and Norde methods. Generally, ideality factor or n values were observed to be greater than unity, which indicates the influence of some other current transport mechanism besides thermionic processes. Results indicated ideality factor variation between 9.97 and 9.57 for irradiation times between the ranges 0 to 20 min. Increase in the series resistance with increase in irradiation time was also observed when calculated using conventional and Cheung and Cheung's methods. These responses demonstrate that changes in the electrical characteristics of the metal-semiconductor-metal diode could be further utilized as sensing elements to detect alpha particles.

Study on electrical properties of metal/GaSb junctions using metal-GaSb alloys

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

Nishi, Koichi, E-mail: nishi@mosfet.t.u-tokyo.ac.jp; Yokoyama, Masafumi; Kim, Sanghyeon

2014-01-21

We study the metal-GaSb alloy formation, the structural properties and the electrical characteristics of the metal-alloy/GaSb diodes by employing metal materials such as Ni, Pd, Co, Ti, Al, and Ta, in order to clarify metals suitable for GaSb p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) as metal-GaSb alloy source/drain (S/D). It is found that Ni, Pd, Co, and Ti can form alloy with GaSb by rapid thermal annealing at 250, 250, 350, and 450 °C, respectively. The Ni-GaSb and Pd-GaSb alloy formation temperature of 250 °C is lower than the conventional dopant activation annealing for ion implantation, which enable us to lower the processmore » temperature. The alloy layers show lower sheet resistance (R{sub Sheet}) than that of p{sup +}-GaSb layer formed by ion implantation and activation annealing. We also study the electrical characteristics of the metal-alloy/GaSb junctions. The alloy/n-GaSb contact has large Schottky barrier height (ϕ{sub B}) for electrons, ∼0.6 eV, and low ϕ{sub B} for holes, ∼0.2 eV, which enable us to realize high on/off ratio in pMOSFETs. We have found that the Ni-GaSb/GaSb Schottky junction shows the best electrical characteristics with ideal factor (n) of 1.1 and on-current/off-current ratio (I{sub on}/I{sub off}) of ∼10{sup 4} among the metal-GaSb alloy/GaSb junctions evaluated in the present study. These electrical properties are also superior to those of a p{sup +}-n diode fabricated by Be ion implantation with activation annealing at 350 °C. As a result, the Ni-GaSb alloy can be regarded as one of the best materials to realize metal S/D in GaSb pMOSFETs.« less

Transistor Laser Optical NOR Gate for High Speed Optical Logic Processors

DTIC Science & Technology

2017-03-20

proposes an optical bistable latch can be built with two universal photonic NOR gate circuits, which are implemented by the three-port tunneling ... Tunneling Junction Transistor Laser (TJ-TL); Optical NOR Gate. Introduction To fulfill the future national security and intelligence needs in this...two-terminal diode lasers. Three-Port Transistor Laser – an Integration of Quantum-Wells into Heterojunction Bipolar Transistor Different than

Van der Waals heterojunction diode composed of WS2 flake placed on p-type Si substrate

NASA Astrophysics Data System (ADS)

Aftab, Sikandar; Farooq Khan, M.; Min, Kyung-Ah; Nazir, Ghazanfar; Afzal, Amir Muhammad; Dastgeer, Ghulam; Akhtar, Imtisal; Seo, Yongho; Hong, Suklyun; Eom, Jonghwa

2018-01-01

P-N junctions represent the fundamental building blocks of most semiconductors for optoelectronic functions. This work demonstrates a technique for forming a WS2/Si van der Waals junction based on mechanical exfoliation. Multilayered WS2 nanoflakes were exfoliated on the surface of bulk p-type Si substrates using a polydimethylsiloxane stamp. We found that the fabricated WS2/Si p-n junctions exhibited rectifying characteristics. We studied the effect of annealing processes on the performance of the WS2/Si van der Waals p-n junction and demonstrated that annealing improved its electrical characteristics. However, devices with vacuum annealing have an enhanced forward-bias current compared to those annealed in a gaseous environment. We also studied the top-gate-tunable rectification characteristics across the p-n junction interface in experiments as well as density functional theory calculations. Under various temperatures, Zener breakdown occurred at low reverse-bias voltages, and its breakdown voltage exhibited a negative coefficient of temperature. Another breakdown voltage was observed, which increased with temperature, suggesting a positive coefficient of temperature. Therefore, such a breakdown can be assigned to avalanche breakdown. This work demonstrates a promising application of two-dimensional materials placed directly on conventional bulk Si substrates.

Internal optical losses in very thin CW heterojunction laser diodes

NASA Technical Reports Server (NTRS)

Butler, J. K.; Kressel, H.; Ladany, I.

1975-01-01

Theoretical calculations are presented showing the relationship between the internal laser absorption and structural parameters appropriate for CW room-temperature lasers. These diodes have submicron-thick recombination regions, and very small spacings between the heat sink and the recombination region to minimize the thermal resistance. The optical loss is shown to be strongly dependent on the degree of radiation confinement to the active region. In particular, absorption in the surface GaAs layer providing the ohmic contact becomes very significant when the intermediate (AlGa)As layer is reduced below about 1 micron. It is further shown that excessive penetration into the GaAs regions gives rise to anomalies in the far-field radiation profiles in the direction perpendicular to the junction plane.

276 nm Substrate-Free Flip-Chip AlGaN Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Hwang, Seongmo; Morgan, Daniel; Kesler, Amanda; Lachab, Mohamed; Zhang, Bin; Heidari, Ahmad; Nazir, Haseeb; Ahmad, Iftikhar; Dion, Joe; Fareed, Qhalid; Adivarahan, Vinod; Islam, Monirul; Khan, Asif

2011-03-01

Lateral-conduction, substrate-free flip-chip (SFFC) light-emitting diodes (LEDs) with peak emission at 276 nm are demonstrated for the first time. The AlGaN multiple quantum well LED structures were grown by metal-organic chemical vapor deposition (MOCVD) on thick-AlN laterally overgrown on sapphire substrates. To fabricate the SFFC LEDs, a newly-developed laser-assisted ablation process was employed to separate the substrate from the LED chips. The chips had physical dimensions of 1100×900 µm2, and were comprised of four devices each with a 100×100 µm2 junction area. Electrical and optical characterization of the devices revealed no noticeable degradation to their performance due to the laser-lift-off process.

Linewidth measurements of tunable diode lasers using heterodyne and etalon techniques

NASA Technical Reports Server (NTRS)

Reid, J.; Cassidy, D. T.; Menzies, R. T.

1982-01-01

Measurements of the linewidths of Pb-salt diode lasers operating in the 8- and 9-micron region are reported. The linewidths of the 9-micron lasers were determined by conventional heterodyne techniques, while for the 8-micron lasers a new technique based on a Fabry-Perot etalon was used. The new technique avoids the complexity and limited wavelength range of the heterodyne measurements and can be used for any tunable laser. The linewidths observed varied from 0.6 to more than 500-MHz FWHM. The linewidth was found to vary dramatically from device to device, to depend strongly on junction temperature and injection current, and to be correlated with vibrations caused by operation of a closed-cycle refrigerator.

Resistive switching mechanism in the one diode-one resistor memory based on p+-Si/n-ZnO heterostructure revealed by in-situ TEM

NASA Astrophysics Data System (ADS)

Zhang, Lei; Zhu, Liang; Li, Xiaomei; Xu, Zhi; Wang, Wenlong; Bai, Xuedong

2017-03-01

One diode-one resistor (1D1R) memory is an effective architecture to suppress the crosstalk interference, realizing the crossbar network integration of resistive random access memory (RRAM). Herein, we designed a p+-Si/n-ZnO heterostructure with 1D1R function. Compared with the conventional multilayer 1D1R devices, the structure and fabrication technique can be largely simplified. The real-time imaging of formation/rupture process of conductive filament (CF) process demonstrated the RS mechanism by in-situ transmission electron microscopy (TEM). Meanwhile, we observed that the formed CF is only confined to the outside of depletion region of Si/ZnO pn junction, and the formation of CF does not degrade the diode performance, which allows the coexistence of RS and rectifying behaviors, revealing the 1D1R switching model. Furthermore, it has been confirmed that the CF is consisting of the oxygen vacancy by in-situ TEM characterization.

Improved heat dissipation in gallium nitride light-emitting diodes with embedded graphene oxide pattern.

PubMed

Han, Nam; Cuong, Tran Viet; Han, Min; Ryu, Beo Deul; Chandramohan, S; Park, Jong Bae; Kang, Ji Hye; Park, Young-Jae; Ko, Kang Bok; Kim, Hee Yun; Kim, Hyun Kyu; Ryu, Jae Hyoung; Katharria, Y S; Choi, Chel-Jong; Hong, Chang-Hee

2013-01-01

The future of solid-state lighting relies on how the performance parameters will be improved further for developing high-brightness light-emitting diodes. Eventually, heat removal is becoming a crucial issue because the requirement of high brightness necessitates high-operating current densities that would trigger more joule heating. Here we demonstrate that the embedded graphene oxide in a gallium nitride light-emitting diode alleviates the self-heating issues by virtue of its heat-spreading ability and reducing the thermal boundary resistance. The fabrication process involves the generation of scalable graphene oxide microscale patterns on a sapphire substrate, followed by its thermal reduction and epitaxial lateral overgrowth of gallium nitride in a metal-organic chemical vapour deposition system under one-step process. The device with embedded graphene oxide outperforms its conventional counterpart by emitting bright light with relatively low-junction temperature and thermal resistance. This facile strategy may enable integration of large-scale graphene into practical devices for effective heat removal.

Planar doped barrier subharmonic mixers

NASA Technical Reports Server (NTRS)

Lee, T. H.; East, J. R.; Haddad, G. I.

1992-01-01

The Planar Doped Barrier (PDB) diode is a device consisting of a p(+) doping spike between two intrinsic layers and n(+) ohmic contacts. This device has the advantages of controllable barrier height, diode capacitance and forward to reverse current ratio. A symmetrically designed PDB has an anti-symmetric current vs. voltage characteristic and is ideal for use as millimeter wave subharmonic mixers. We have fabricated such devices with barrier heights of 0.3, 0.5 and 0.7 volts from GaAs and InGaAs using a multijunction honeycomb structure with junction diameters between one and ten microns. Initial RF measurements are encouraging. The 0.7 volt barrier height 4 micron GaAs devices were tested as subharmonic mixers at 202 GHz with an IF frequency of 1 GHz and had 18 dB of conversion loss. The estimated mismatch loss was 7 dB and was due to higher diode capacitance. The LO frequency was 100.5 GHz and the pump power was 8 mW.

Electrical characterization of Au/quercetin/n-Si heterojunction diode and optical analysis of quercetin thin film

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

Tombak, Ahmet, E-mail: tahmet@yahoo.com; Özaydin, C.; Boğa, M.

2016-03-25

Quercetin (3,5,7,3’,4’-pentahydroxyflavone, QE), one of the most widely distributed flavonoids in fruits and vegetables, has been reported to possess a wide variety of biological effects, including anti-oxidative, anti-inflammatory, anti-apoptosis, hepatoprotective, renoprotective and neuroprotective effects. In this study organic-inorganic junctions were fabricated by forming quercetin complex thin film using spin coating technique on n-Si and evaporating Au metal on the film. Optical properties of quercetin thin film were studied with the help of spectrophotometer. The current-voltage (I-V) characteristic of Au/quercetin/n-Si heterojunction diode was investigated at room temperature in dark. Some basic parameters of the diode such as ideality factor, rectification ratio,more » barrier height, series resistance and shunt resistance were calculated using dark current-voltage measurement. It was also seen that the device had good sensitivity to the light under 40-100 mW/cm{sup 2} illumination conditions.« less

Broadband mid-infrared superlattice light-emitting diodes

NASA Astrophysics Data System (ADS)

Ricker, R. J.; Provence, S. R.; Norton, D. T.; Boggess, T. F.; Prineas, J. P.

2017-05-01

InAs/GaSb type-II superlattice light-emitting diodes were fabricated to form a device that provides emission over the entire 3-5 μm mid-infrared transmission window. Variable bandgap emission regions were coupled together using tunnel junctions to emit at peak wavelengths of 3.3 μm, 3.5 μm, 3.7 μm, 3.9 μm, 4.1 μm, 4.4 μm, 4.7 μm, and 5.0 μm. Cascading the structure recycles the electrons in each emission region to emit several wavelengths simultaneously. At high current densities, the light-emitting diode spectra broadened into a continuous, broadband spectrum that covered the entire mid-infrared band. When cooled to 77 K, radiances of over 1 W/cm2 sr were achieved, demonstrating apparent temperatures above 1000 K over the 3-5 μm band. InAs/GaSb type-II superlattices are capable of emitting from 3 μm to 30 μm, and the device design can be expanded to include longer emission wavelengths.

Single In x Ga1-x As nanowire/p-Si heterojunction based nano-rectifier diode.

PubMed

Sarkar, K; Palit, M; Guhathakurata, S; Chattopadhyay, S; Banerji, P

2017-09-20

Nanoscale power supply units will be indispensable for fabricating next generation smart nanoelectronic integrated circuits. Fabrication of nanoscale rectifier circuits on a Si platform is required for integrating nanoelectronic devices with on-chip power supply units. In the present study, a nanorectifier diode based on a single standalone In x Ga 1-x As nanowire/p-Si (111) heterojunction fabricated by metal organic chemical vapor deposition technique has been studied. The nanoheterojunction diodes have shown good rectification and fast switching characteristics. The rectification characteristics of the nanoheterojunction have been demonstrated by different standard waveforms of sinusoidal, square, sawtooth and triangular for two different frequencies of 1 and 0.1 Hz. Reverse recovery time of around 150 ms has been observed in all wave response. A half wave rectifier circuit with a simple capacitor filter has been assembled with this nanoheterojunction diode which provides 12% output efficiency. The transport of carriers through the heterojunction is investigated. The interface states density of the nanoheterojunction has also been determined. Occurrence of output waveforms incommensurate with the input is attributed to higher series resistance of the diode which is further explained considering the dimension of p-side and n-side of the junction. The sudden change of ideality factor after 1.7 V bias is attributed to recombination through interface states in space charge region. Low interface states density as well as high rectification ratio makes this heterojunction diode a promising candidate for future nanoscale electronics.

Electrical Investigation of Nanostructured Fe2O3/p-Si Heterojunction Diode Fabricated Using the Sol-Gel Technique

NASA Astrophysics Data System (ADS)

Mansour, Shehab A.; Ibrahim, Mervat M.

2017-11-01

Iron oxide (α-Fe2O3) nanocrystals have been synthesized via the sol-gel technique. The structural and morphological features of these nanocrystals were studied using x-ray diffraction, Fourier transform-infrared spectroscopy and transmission electron microscopy. Colloidal solution of synthesized α-Fe2O3 (hematite) was spin-coated onto a single-crystal p-type silicon (p-Si) wafer to fabricate a heterojunction diode with Mansourconfiguration Ag/Fe2O3/p-Si/Al. This diode was electrically characterized at room temperature using current-voltage (I-V) characteristics in the voltage range from -9 V to +9 V. The fabricated diode showed a good rectification behavior with a rectification factor 1.115 × 102 at 6 V. The junction parameters such as ideality factor, barrier height, series resistance and shunt resistance are determined using conventional I-V characteristics. For low forward voltage, the conduction mechanism is dominated by the defect-assisted tunneling process with conventional electron-hole recombination. However, at higher voltage, I-V ohmic and space charge-limited current conduction was became less effective with the contribution of the trapped-charge-limited current at the highest voltage range.

Black phosphorus-monolayer MoS2 van der Waals heterojunction p-n diode.

PubMed

Deng, Yexin; Luo, Zhe; Conrad, Nathan J; Liu, Han; Gong, Yongji; Najmaei, Sina; Ajayan, Pulickel M; Lou, Jun; Xu, Xianfan; Ye, Peide D

2014-08-26

Phosphorene, a elemental 2D material, which is the monolayer of black phosphorus, has been mechanically exfoliated recently. In its bulk form, black phosphorus shows high carrier mobility (∼10,000 cm(2)/V·s) and a ∼0.3 eV direct band gap. Well-behaved p-type field-effect transistors with mobilities of up to 1000 cm(2)/V·s, as well as phototransistors, have been demonstrated on few-layer black phosphorus, showing its promise for electronics and optoelectronics applications due to its high hole mobility and thickness-dependent direct band gap. However, p–n junctions, the basic building blocks of modern electronic and optoelectronic devices, have not yet been realized based on black phosphorus. In this paper, we demonstrate a gate-tunable p–n diode based on a p-type black phosphorus/n-type monolayer MoS2 van der Waals p–n heterojunction. Upon illumination, these ultrathin p–n diodes show a maximum photodetection responsivity of 418 mA/W at the wavelength of 633 nm and photovoltaic energy conversion with an external quantum efficiency of 0.3%. These p–n diodes show promise for broad-band photodetection and solar energy harvesting.

Pronounced Photovoltaic Response from Multilayered Transition-Metal Dichalcogenides PN-Junctions.

PubMed

Memaran, Shahriar; Pradhan, Nihar R; Lu, Zhengguang; Rhodes, Daniel; Ludwig, Jonathan; Zhou, Qiong; Ogunsolu, Omotola; Ajayan, Pulickel M; Smirnov, Dmitry; Fernández-Domínguez, Antonio I; García-Vidal, Francisco J; Balicas, Luis

2015-11-11

Transition metal dichalcogenides (TMDs) are layered semiconductors with indirect band gaps comparable to Si. These compounds can be grown in large area, while their gap(s) can be tuned by changing their chemical composition or by applying a gate voltage. The experimental evidence collected so far points toward a strong interaction with light, which contrasts with the small photovoltaic efficiencies η ≤ 1% extracted from bulk crystals or exfoliated monolayers. Here, we evaluate the potential of these compounds by studying the photovoltaic response of electrostatically generated PN-junctions composed of approximately 10 atomic layers of MoSe2 stacked onto the dielectric h-BN. In addition to ideal diode-like response, we find that these junctions can yield, under AM-1.5 illumination, photovoltaic efficiencies η exceeding 14%, with fill factors of ~70%. Given the available strategies for increasing η such as gap tuning, improving the quality of the electrical contacts, or the fabrication of tandem cells, our study suggests a remarkable potential for photovoltaic applications based on TMDs.

Method for forming p-n junctions and solar-cells by laser-beam processing

DOEpatents

Narayan, Jagdish; Young, Rosa T.

1979-01-01

This invention is an improved method for preparing p-n junction devices, such as diodes and solar cells. High-quality junctions are prepared by effecting laser-diffusion of a selected dopant into silicon by means of laser pulses having a wavelength of from about 0.3 to 1.1 .mu.m, an energy area density of from about 1.0 to 2.0 J/cm.sup.2, and a duration of from about 20 to 60 nanoseconds. Initially, the dopant is deposited on the silicon as a superficial layer, preferably one having a thickness in the range of from about 50 to 100 A. Depending on the application, the values for the above-mentioned pulse parameters are selected to produce melting of the silicon to depths in the range from about 1000 A to 1 .mu.m. The invention has been used to produce solar cells having a one-sun conversion efficiency of 10.6%, these cells having no antireflective coating or back-surface fields.

Antenna-coupled photon emission from hexagonal boron nitride tunnel junctions.

PubMed

Parzefall, M; Bharadwaj, P; Jain, A; Taniguchi, T; Watanabe, K; Novotny, L

2015-12-01

The ultrafast conversion of electrical signals to optical signals at the nanoscale is of fundamental interest for data processing, telecommunication and optical interconnects. However, the modulation bandwidths of semiconductor light-emitting diodes are limited by the spontaneous recombination rate of electron-hole pairs, and the footprint of electrically driven ultrafast lasers is too large for practical on-chip integration. A metal-insulator-metal tunnel junction approaches the ultimate size limit of electronic devices and its operating speed is fundamentally limited only by the tunnelling time. Here, we study the conversion of electrons (localized in vertical gold-hexagonal boron nitride-gold tunnel junctions) to free-space photons, mediated by resonant slot antennas. Optical antennas efficiently bridge the size mismatch between nanoscale volumes and far-field radiation and strongly enhance the electron-photon conversion efficiency. We achieve polarized, directional and resonantly enhanced light emission from inelastic electron tunnelling and establish a novel platform for studying the interaction of electrons with strongly localized electromagnetic fields.

Electro-Thermal Simulation Studies of SiC Junction Diodes Containing Screw Dislocations Under High Reverse-Bias Operation

NASA Technical Reports Server (NTRS)

Joshi, R. P.

2001-01-01

The objective of this work was to conduct a modeling study of SiC P-N junction diodes operating under high reverse biased conditions. Analytical models and numerical simulation capabilities were to be developed for self-consistent electro-thermal analysis of the diode current-voltage (I-V) characteristics. Data from GRC indicate that screw dislocations are unavoidable in large area SiC devices, and lead to changes in the SiC diode electrical response characteristics under high field conditions. For example, device instability and failures linked to internal current filamentation have been observed. The physical origin of these processes is not well understood, and quantitative projections of the electrical behavior under high field and temperature conditions are lacking. Thermal calculations for SiC devices have not been reported in the literature either. So estimates or projections of peak device temperatures and power limitations do not exist. This numerical study and simulation analysis was aimed at resolving some of the above issues. The following tasks were successfully accomplished: (1) Development of physically based models using one- and two-dimensional drift-diffusion theory for the transport behavior and I-V characteristics; (2) One- and two-dimensional heat flow to account for internal device heating. This led to calculations of the internal temperature profiles, which in turn, were used to update the electrical transport parameters for a self-consistent analysis. The temperature profiles and the peak values were thus obtainable for a given device operating condition; (3) Inclusion of traps assumed to model the presence of internal screw dislocations running along the longitudinal direction; (4) Predictions of the operating characteristics with and without heating as a function of applied bias with and without traps. Both one and two-dimensional cases were implemented; (5) Assessment of device stability based on the operating characteristics. The presence of internal non-uniformities, particularly filamentary structures, was probed and demonstrated; (6) Cause and physical origins of filamentary behavior and unstable I-V characteristics were made transparent; (7) It was demonstrated that diodes containing defects would be more prone to thermal breakdown associated with the temperature dependent decrease in the thermal conductivity; and (8) Finally, negative differential resistance (S-shaped NDR) which can potential lead to device instability and filamentary behavior was shown to occur for diodes containing a line of defects such as could be associated with a screw dislocation line.

Current-voltage characteristics in macroporous silicon/SiOx/SnO2:F heterojunctions.

PubMed

Garcés, Felipe A; Urteaga, Raul; Acquaroli, Leandro N; Koropecki, Roberto R; Arce, Roberto D

2012-07-25

We study the electrical characteristics of macroporous silicon/transparent conductor oxide junctions obtained by the deposition of fluorine doped-SnO2 onto macroporous silicon thin films using the spray pyrolysis technique. Macroporous silicon was prepared by the electrochemical anodization of a silicon wafer to produce pore sizes ranging between 0.9 to 1.2 μm in diameter. Scanning electronic microscopy was performed to confirm the pore filling and surface coverage. The transport of charge carriers through the interface was studied by measuring the current-voltage curves in the dark and under illumination. In the best configuration, we obtain a modest open-circuit voltage of about 70 mV and a short-circuit current of 3.5 mA/cm2 at an illumination of 110 mW/cm2. In order to analyze the effects of the illumination on the electrical properties of the junction, we proposed a model of two opposing diodes, each one associated with an independent current source. We obtain a good accordance between the experimental data and the model. The current-voltage curves in illuminated conditions are well fitted with the same parameters obtained in the dark where only the photocurrent intensities in the diodes are free parameters.

Fabrication and Characterization of N-Type Zinc Oxide/P-Type Boron Doped Diamond Heterojunction

NASA Astrophysics Data System (ADS)

Marton, Marián; Mikolášek, Miroslav; Bruncko, Jaroslav; Novotný, Ivan; Ižák, Tibor; Vojs, Marian; Kozak, Halyna; Varga, Marián; Artemenko, Anna; Kromka, Alexander

2015-09-01

Diamond and ZnO are very promising wide-bandgap materials for electronic, photovoltaic and sensor applications because of their excellent electrical, optical, physical and electrochemical properties and biocompatibility. In this contribution we show that the combination of these two materials opens up the potential for fabrication of bipolar heterojunctions. Semiconducting boron doped diamond (BDD) thin films were grown on Si and UV grade silica glass substrates by HFCVD method with various boron concentration in the gas mixture. Doped zinc oxide (ZnO:Al, ZnO:Ge) thin layers were deposited by diode sputtering and pulsed lased deposition as the second semiconducting layer on the diamond films. The amount of dopants within the films was varied to obtain optimal semiconducting properties to form a bipolar p-n junction. Finally, different ZnO/BDD heterostructures were prepared and analyzed. Raman spectroscopy, SEM, Hall constant and I-V measurements were used to investigate the quality, structural and electrical properties of deposited heterostructures, respectively. I-V measurements of ZnO/BDD diodes show a rectifying ratio of 55 at ±4 V. We found that only very low dopant concentrations for both semiconducting materials enabled us to fabricate a functional p-n junction. Obtained results are promising for fabrication of optically transparent ZnO/BDD bipolar heterojunction.

Tunnel-injected sub 290 nm ultra-violet light emitting diodes with 2.8% external quantum efficiency

NASA Astrophysics Data System (ADS)

Zhang, Yuewei; Jamal-Eddine, Zane; Akyol, Fatih; Bajaj, Sanyam; Johnson, Jared M.; Calderon, Gabriel; Allerman, Andrew A.; Moseley, Michael W.; Armstrong, Andrew M.; Hwang, Jinwoo; Rajan, Siddharth

2018-02-01

We report on the high efficiency tunnel-injected ultraviolet light emitting diodes (UV LEDs) emitting at 287 nm. Deep UV LED performance has been limited by the severe internal light absorption in the p-type contact layers and low electrical injection efficiency due to poor p-type conduction. In this work, a polarization engineered Al0.65Ga0.35N/In0.2Ga0.8N tunnel junction layer is adopted for non-equilibrium hole injection to replace the conventionally used direct p-type contact. A reverse-graded AlGaN contact layer is further introduced to realize a low resistance contact to the top n-AlGaN layer. This led to the demonstration of a low tunnel junction resistance of 1.9 × 10-3 Ω cm2 obtained at 1 kA/cm2. Light emission at 287 nm with an on-wafer peak external quantum efficiency of 2.8% and a wall-plug efficiency of 1.1% was achieved. The measured power density at 1 kA/cm2 was 54.4 W/cm2, confirming the efficient hole injection through interband tunneling. With the benefits of the minimized internal absorption and efficient hole injection, a tunnel-injected UV LED structure could enable future high efficiency UV emitters.

Low Temperature Electrical Spin Injection from Highly Spin Polarized Co₂CrAl Heusler Alloy into p-Si.

PubMed

Kar, Uddipta; Panda, J; Nath, T K

2018-06-01

The low temperature spin accumulation in p-Si using Co2CrAl/SiO2 tunnel junction has been investigated in detail. The heterojunction has been fabricated using electron beam evaporation (EBE) technique. The 3-terminal contacts in Hanle geometry has been made for spin transport measurements. The electrical transport properties have been investigated at different isothermal conditions in the temperature range of 10-300 K. The current-voltage characteristics of the junction shows excellent rectifying magnetic diode like behaviour in lower temperature range (below 200 K). At higher temperature, the junction shows nonlinear behaviour without rectifying characteristics. We have observed spin accumulation signal in p-Si semiconductor using SiO2/Co2CrAl tunnel junction in the low temperature regime (30-100 K). Hence the highly spin polarized Full Heusler alloys compounds, like Co2CrAl etc., are very attractive and can act as efficient tunnel device for spin injection in the area of spintronics devices in near future. The estimated spin life time is τ = 54 pS and spin diffusion length inside p-Si is LSD = 289 nm at 30 K for this heterostructure.

Bias Selective Operation of Sb-Based Two-Color Photodetectors

NASA Technical Reports Server (NTRS)

Abedin, M. N.; Refaat, Tamer F.; Bhat, Ishwara B.; Xiao, Yegao; Johnson, David G.

2006-01-01

Multicolor detectors have a strong potential to replace conventional single-color detectors in application dealing with the simultaneous detection of more than one wavelength. This will lead to the reduction of heavy and complex optical components now required for spectral discrimination for multi-wavelengths applications. This multicolor technology is simpler, lighter, compact and cheaper with respect to the single-color ones. In this paper, Sb-based two-color detectors fabrication and characterization are presented. The color separation is achieved by fabricating dual band pn junction on a GaSb substrate. The first band consists of an InGaAsSb pn junction for long wavelength detection, while the second band consists of a GaSb pn junction for shorter wavelength detection. Three metal contacts were deposited to access the individual junctions. Surface morphology of multi-layer thin films and also device characteristics of quasi-dual band photodetector were characterized using standard optical microscope and electro-optic techniques respectively. Dark current measurements illustrated the diode behavior of both lattice-matched detector bands. Spectral response measurements indicated either independent operation of both detectors simultaneously, or selective operation of one detector, by the polarity of the bias voltage, while serially accessing both devices.

Radiation detection measurements with a new ``Buried Junction'' silicon avalanche photodiode

NASA Astrophysics Data System (ADS)

Lecomte, R.; Pepin, C.; Rouleau, D.; Dautet, H.; McIntyre, R. J.; McSween, D.; Webb, P.

1999-02-01

An improved version of a recently developed "Buried Junction" avalanche photodiode (APD), designed for use with scintillators, is described and characterized. This device, also called the "Reverse APD", is designed to have a wide depletion layer and thus low capacitance, but to have high gain only for e-h pairs generated within the first few microns of the depletion layer. Thus it has high gain for light from scintillators emitting in the 400-600 nm range, with relatively low dark current noise and it is relatively insensitive to minimum ionizing particles (MIPs). An additional feature is that the metallurgical junction is at the back of the wafer, leaving the front surface free to be coupled to a scintillator without fear of junction contamination. The modifications made in this device, as compared with the earlier diode, have resulted in a lower excess noise factor, lower dark current, and much-reduced trapping. The electrical and optical characteristics of this device are described and measurements of energy and timing resolution of this device with several scintillators (BGO, LSO and GSO) of potential interest in high-energy physics and PET imaging systems are presented.

Current-voltage characteristics of manganite-titanite perovskite junctions.

PubMed

Ifland, Benedikt; Peretzki, Patrick; Kressdorf, Birte; Saring, Philipp; Kelling, Andreas; Seibt, Michael; Jooss, Christian

2015-01-01

After a general introduction into the Shockley theory of current voltage (J-V) characteristics of inorganic and organic semiconductor junctions of different bandwidth, we apply the Shockley theory-based, one diode model to a new type of perovskite junctions with polaronic charge carriers. In particular, we studied manganite-titanate p-n heterojunctions made of n-doped SrTi1- y Nb y O3, y = 0.002 and p-doped Pr1- x Ca x MnO3, x = 0.34 having a strongly correlated electron system. The diffusion length of the polaron carriers was analyzed by electron beam-induced current (EBIC) in a thin cross plane lamella of the junction. In the J-V characteristics, the polaronic nature of the charge carriers is exhibited mainly by the temperature dependence of the microscopic parameters, such as the hopping mobility of the series resistance and a colossal electro-resistance (CER) effect in the parallel resistance. We conclude that a modification of the Shockley equation incorporating voltage-dependent microscopic polaron parameters is required. Specifically, the voltage dependence of the reverse saturation current density is analyzed and interpreted as a voltage-dependent electron-polaron hole-polaron pair generation and separation at the interface.

Wavelength-dependent visible light response in vertically aligned nanohelical TiO2-based Schottky diodes

NASA Astrophysics Data System (ADS)

Kwon, Hyunah; Sung, Ji Ho; Lee, Yuna; Jo, Moon-Ho; Kim, Jong Kyu

2018-01-01

Enhancements in photocatalytic performance under visible light have been reported by noble metal functionalization on nanostructured TiO2; however, the non-uniform and discrete distribution of metal nanoparticles on the TiO2 surface makes it difficult to directly clarify the optical and electrical mechanisms. Here, we investigate the light absorption and the charge separation at the metal/TiO2 Schottky junctions by using a unique device architecture with an array of TiO2 nanohelixes (NHs) forming Schottky junctions both with Au-top and Pt-bottom electrodes. Wavelength-dependent photocurrent measurements through the Pt/TiO2 NHs/Au structures revealed that the origin of the visible light absorption and the separation of photogenerated carriers is the internal photoemission at the metal/nanostructured TiO2 Schottky junctions. In addition, a huge persistent photoconductivity was observed by the time-dependent photocurrent measurement, implying a long lifetime of the photogenerated carriers before recombination. We believe that the results help one to understand the role of metal functionalization on TiO2 and hence to enhance the photocatalytic efficiency by utilizing appropriately designed Schottky junctions.

Current–voltage characteristics of manganite–titanite perovskite junctions

PubMed Central

Ifland, Benedikt; Peretzki, Patrick; Kressdorf, Birte; Saring, Philipp; Kelling, Andreas; Seibt, Michael

2015-01-01

Summary After a general introduction into the Shockley theory of current voltage (J–V) characteristics of inorganic and organic semiconductor junctions of different bandwidth, we apply the Shockley theory-based, one diode model to a new type of perovskite junctions with polaronic charge carriers. In particular, we studied manganite–titanate p–n heterojunctions made of n-doped SrTi1− yNbyO3, y = 0.002 and p-doped Pr1− xCaxMnO3, x = 0.34 having a strongly correlated electron system. The diffusion length of the polaron carriers was analyzed by electron beam-induced current (EBIC) in a thin cross plane lamella of the junction. In the J–V characteristics, the polaronic nature of the charge carriers is exhibited mainly by the temperature dependence of the microscopic parameters, such as the hopping mobility of the series resistance and a colossal electro-resistance (CER) effect in the parallel resistance. We conclude that a modification of the Shockley equation incorporating voltage-dependent microscopic polaron parameters is required. Specifically, the voltage dependence of the reverse saturation current density is analyzed and interpreted as a voltage-dependent electron–polaron hole–polaron pair generation and separation at the interface. PMID:26199851

The role of the substrate in Graphene/Silicon photodiodes

NASA Astrophysics Data System (ADS)

Luongo, G.; Giubileo, F.; Iemmo, L.; Di Bartolomeo, A.

2018-01-01

The Graphene/Silicon (Gr/Si) junction can function as a Schottky diode with performances strictly related to the quality of the interface. Here, we focus on the substrate geometry and on its effects on Gr/Si junction physics. We fabricate and study the electrical and optical behaviour of two types of devices: one made of a Gr/Si planar junction, the second realized with graphene on an array of Si nanotips. We show that the Gr/Si flat device exhibits a reverse photocurrent higher than the forward current and achieves a photoresponsivity of 2.5 A/W. The high photoresponse is due to the charges photogenerated in Si below a parasitic graphene/SiO2/Si structure, which are injected into the Gr/Si junction region. The other device with graphene on Si-tips displays a reverse current that grows exponentially with the bias. We explain this behaviour by taking into account the tip geometry of the substrate, which magnifies the electric field and shifts the Fermi level of graphene, thus enabling fine-tuning of the Schottky barrier height. The Gr/Si-tip device achieves a higher photoresponsivity, up to 3 A/W, likely due to photocharge internal multiplication.

Gate-tunable carbon nanotube-MoS2 heterojunction p-n diode.

PubMed

Jariwala, Deep; Sangwan, Vinod K; Wu, Chung-Chiang; Prabhumirashi, Pradyumna L; Geier, Michael L; Marks, Tobin J; Lauhon, Lincoln J; Hersam, Mark C

2013-11-05

The p-n junction diode and field-effect transistor are the two most ubiquitous building blocks of modern electronics and optoelectronics. In recent years, the emergence of reduced dimensionality materials has suggested that these components can be scaled down to atomic thicknesses. Although high-performance field-effect devices have been achieved from monolayered materials and their heterostructures, a p-n heterojunction diode derived from ultrathin materials is notably absent and constrains the fabrication of complex electronic and optoelectronic circuits. Here we demonstrate a gate-tunable p-n heterojunction diode using semiconducting single-walled carbon nanotubes (SWCNTs) and single-layer molybdenum disulfide as p-type and n-type semiconductors, respectively. The vertical stacking of these two direct band gap semiconductors forms a heterojunction with electrical characteristics that can be tuned with an applied gate bias to achieve a wide range of charge transport behavior ranging from insulating to rectifying with forward-to-reverse bias current ratios exceeding 10(4). This heterojunction diode also responds strongly to optical irradiation with an external quantum efficiency of 25% and fast photoresponse <15 μs. Because SWCNTs have a diverse range of electrical properties as a function of chirality and an increasing number of atomically thin 2D nanomaterials are being isolated, the gate-tunable p-n heterojunction concept presented here should be widely generalizable to realize diverse ultrathin, high-performance electronics and optoelectronics.

An in-vitro evaluation of the effect of 980 nm diode laser irradiation on intra-canal dentin surface and dentinal tubule openings after biomechanical preparation: Scanning electron microscopic study

PubMed Central

Jhingan, Pulkit; Sandhu, Meera; Jindal, Garima; Goel, Deepti; Sachdev, Vinod

2015-01-01

Context: Very recently, diode laser has been used for disinfecting the root canals in endodontic treatment and increasing its success rate and longevity utilizing the thermal effect of laser on surrounding tissues. Aims: The aim of this study is to evaluate the effect of 980 nm laser irradiation on intra-canal dentin surface – scanning electron microscopic (SEM) - in-vitro study. Methods: A total of 40 single-rooted freshly extracted permanent teeth were collected. Teeth were sectioned at the cemento-enamel junction using diamond disc. Root canals of all samples were prepared using hand ProTaper, which were randomly assigned into two groups (n = 20 each). Group 1: Receiving no treatment after biomechanical preparation; Group 2: 980 nm diode laser-treated root canals. Teeth were prepared for SEM analysis to check the size of intra-canal dentinal tubule openings. Statistical Analysis Used: Data were analyzed using SPSS V.16 software and compared using Levene's and independent t-test. Results: On statistical analysis, width of intracanal dentinal tubule openings in Group 1 (control) was significantly higher than those observed in Group 2 (diode laser-treated) (P < 0.001). Conclusion: This study showed that the application of 980 nm diode laser on intra-radicular dentin resulted in ultrastructural alterations resulting in melting of dentin. PMID:26097338

808nm high-power high-efficiency GaAsP/GaInP laser bars

NASA Astrophysics Data System (ADS)

Wang, Ye; Yang, Ye; Qin, Li; Wang, Chao; Yao, Di; Liu, Yun; Wang, Lijun

2008-11-01

808nm high power diode lasers, which is rapidly maturing technology technically and commercially since the introduction in 1999 of complete kilowatt-scale diode laser systems, have important applications in the fields of industry and pumping solid-state lasers (DPSSL). High power and high power conversion efficiency are extremely important in diode lasers, and they could lead to new applications where space, weight and electrical power are critical. High efficiency devices generate less waste heat, which means less strain on the cooling system and more tolerance to thermal conductivity variation, a lower junction temperature and longer lifetimes. Diode lasers with Al-free materials have superior power conversion efficiency compared with conventional AlGaAs/GaAs devices because of their lower differential series resistance and higher thermal conductivity. 808nm GaAsP/GaInP broad-waveguide emitting diode laser bars with 1mm cavity length have been fabricated. The peak power can reach to 100.9W at 106.5A at quasicontinuous wave operation (200μs, 1000Hz). The maximum power conversion efficiency is 57.38%. Based on these high power laser bars, we fabricate a 1x3 arrays, the maximum power is 64.3W in continuous wave mode when the current is 25.0A. And the threshold current is 5.9A, the slope efficiency is 3.37 W/A.

Experimental investigation of factors limiting slow axis beam quality in 9xx nm high power broad area diode lasers

NASA Astrophysics Data System (ADS)

Winterfeldt, M.; Crump, P.; Wenzel, H.; Erbert, G.; Tränkle, G.

2014-08-01

GaAs-based broad-area diode lasers are needed with improved lateral beam parameter product (BPPlat) at high power. An experimental study of the factors limiting BPPlat is therefore presented, using extreme double-asymmetric (EDAS) vertical structures emitting at 910 nm. Continuous wave, pulsed and polarization-resolved measurements are presented and compared to thermal simulation. The importance of thermal and packaging-induced effects is determined by comparing junction -up and -down devices. Process factors are clarified by comparing diodes with and without index-guiding trenches. We show that in all cases studied, BPPlat is limited by a non-thermal BPP ground-level and a thermal BPP, which depends linearly on self-heating. Measurements as a function of pulse width confirm that self-heating rather than bias-level dominates. Diodes without trenches show low BPP ground-level, and a thermal BPP which depends strongly on mounting, due to changes in the temperature profile. The additional lateral guiding in diodes with trenches strongly increases the BPP ground-level, but optically isolates the stripe from the device edges, suppressing the influence of the thermal profile, leading to a BPP-slope that is low and independent of mounting. Trenches are also shown to initiate strain fields that cause parasitic TM-polarized emission with large BPPlat, whose influence on total BPPlat remains small, provided the overall polarization purity is >95%.

Gate-tunable carbon nanotube–MoS2 heterojunction p-n diode

PubMed Central

Jariwala, Deep; Sangwan, Vinod K.; Wu, Chung-Chiang; Prabhumirashi, Pradyumna L.; Geier, Michael L.; Marks, Tobin J.; Lauhon, Lincoln J.; Hersam, Mark C.

2013-01-01

The p-n junction diode and field-effect transistor are the two most ubiquitous building blocks of modern electronics and optoelectronics. In recent years, the emergence of reduced dimensionality materials has suggested that these components can be scaled down to atomic thicknesses. Although high-performance field-effect devices have been achieved from monolayered materials and their heterostructures, a p-n heterojunction diode derived from ultrathin materials is notably absent and constrains the fabrication of complex electronic and optoelectronic circuits. Here we demonstrate a gate-tunable p-n heterojunction diode using semiconducting single-walled carbon nanotubes (SWCNTs) and single-layer molybdenum disulfide as p-type and n-type semiconductors, respectively. The vertical stacking of these two direct band gap semiconductors forms a heterojunction with electrical characteristics that can be tuned with an applied gate bias to achieve a wide range of charge transport behavior ranging from insulating to rectifying with forward-to-reverse bias current ratios exceeding 104. This heterojunction diode also responds strongly to optical irradiation with an external quantum efficiency of 25% and fast photoresponse <15 μs. Because SWCNTs have a diverse range of electrical properties as a function of chirality and an increasing number of atomically thin 2D nanomaterials are being isolated, the gate-tunable p-n heterojunction concept presented here should be widely generalizable to realize diverse ultrathin, high-performance electronics and optoelectronics. PMID:24145425

Electron transport through rectifying self-assembled monolayer diodes on silicon: Fermi-level pinning at the molecule-metal interface.

PubMed

Lenfant, S; Guerin, D; Tran Van, F; Chevrot, C; Palacin, S; Bourgoin, J P; Bouloussa, O; Rondelez, F; Vuillaume, D

2006-07-20

We report the synthesis and characterization of molecular rectifying diodes on silicon using sequential grafting of self-assembled monolayers of alkyl chains bearing a pi group at their outer end (Si/sigma-pi/metal junctions). We investigate the structure-performance relationships of these molecular devices, and we examine the extent to which the nature of the pi end group (change in the energy position of their molecular orbitals) drives the properties of these molecular diodes. Self-assembled monolayers of alkyl chains (different chain lengths from 6 to 15 methylene groups) functionalized by phenyl, anthracene, pyrene, ethylene dioxythiophene, ethylene dioxyphenyl, thiophene, terthiophene, and quaterthiophene were synthesized and characterized by contact angle measurements, ellipsometry, Fourier transform infrared spectroscopy, and atomic force microscopy. We demonstrate that reasonably well-packed monolayers are obtained in all cases. Their electrical properties were assessed by dc current-voltage characteristics and high-frequency (1-MHz) capacitance measurements. For all of the pi groups investigated here, we observed rectification behavior. These results extend our preliminary work using phenyl and thiophene groups (Lenfant et al., Nano Lett. 2003, 3, 741). The experimental current-voltage curves were analyzed with a simple analytical model, from which we extracted the energy position of the molecular orbital of the pi group in resonance with the Fermi energy of the electrodes. We report experimental studies of the band lineup in these silicon/alkyl pi-conjugated molecule/metal junctions. We conclude that Fermi-level pinning at the pi group/metal interface is mainly responsible for the observed absence of a dependence of the rectification effect on the nature of the pi groups, even though the groups examined were selected to have significant variations in their electronic molecular orbitals.

Strong Depletion in Hybrid Perovskite p-n Junctions Induced by Local Electronic Doping.

PubMed

Ou, Qingdong; Zhang, Yupeng; Wang, Ziyu; Yuwono, Jodie A; Wang, Rongbin; Dai, Zhigao; Li, Wei; Zheng, Changxi; Xu, Zai-Quan; Qi, Xiang; Duhm, Steffen; Medhekar, Nikhil V; Zhang, Han; Bao, Qiaoliang

2018-04-01

A semiconductor p-n junction typically has a doping-induced carrier depletion region, where the doping level positively correlates with the built-in potential and negatively correlates with the depletion layer width. In conventional bulk and atomically thin junctions, this correlation challenges the synergy of the internal field and its spatial extent in carrier generation/transport. Organic-inorganic hybrid perovskites, a class of crystalline ionic semiconductors, are promising alternatives because of their direct badgap, long diffusion length, and large dielectric constant. Here, strong depletion in a lateral p-n junction induced by local electronic doping at the surface of individual CH 3 NH 3 PbI 3 perovskite nanosheets is reported. Unlike conventional surface doping with a weak van der Waals adsorption, covalent bonding and hydrogen bonding between a MoO 3 dopant and the perovskite are theoretically predicted and experimentally verified. The strong hybridization-induced electronic coupling leads to an enhanced built-in electric field. The large electric permittivity arising from the ionic polarizability further contributes to the formation of an unusually broad depletion region up to 10 µm in the junction. Under visible optical excitation without electrical bias, the lateral diode demonstrates unprecedented photovoltaic conversion with an external quantum efficiency of 3.93% and a photodetection responsivity of 1.42 A W -1 . © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of ion implanted gallium arsenide transistors

NASA Technical Reports Server (NTRS)

Hunsperger, R.; Baron, R.

1972-01-01

Techniques were developed for creating bipolar microwave transistors in GaAs by ion implantation doping. The electrical properties of doped layers produced by the implantation of the light ions Be, Mg, and S were studied. Be, Mg, and S are suitable for forming the relatively deep base-collector junction at low ion energies. The electrical characteristics of ion-implanted diodes of both the mesa and planar types were determined. Some n-p-n planar transistor structures were fabricated by implantation of Mg to form the base regions and Si to form the emitters. These devices were found to have reasonably good base-collector and emitter-base junctions, but the current gain beta was small. The low was attributable to radiative recombination in the base region, which was extremely wide.

Silicon-based visible and near-infrared optoelectric devices

DOEpatents

Mazur, Eric; Carey, James Edward

2017-10-17

In one aspect, the present invention provides a silicon photodetector having a surface layer that is doped with sulfur inclusions with an average concentration in a range of about 0.5 atom percent to about 1.5 atom percent. The surface layer forms a diode junction with an underlying portion of the substrate. A plurality of electrical contacts allow application of a reverse bias voltage to the junction in order to facilitate generation of an electrical signal, e.g., a photocurrent, in response to irradiation of the surface layer. The photodetector exhibits a responsivity greater than about 1 A/W for incident wavelengths in a range of about 250 nm to about 1050 nm, and a responsivity greater than about 0.1 A/W for longer wavelengths, e.g., up to about 3.5 microns.

Silicon-based visible and near-infrared optoelectric devices

DOEpatents

Mazur, Eric [Concord, MA; Carey, III, James E.

2011-02-08

In one aspect, the present invention provides a silicon photodetector having a surface layer that is doped with sulfur inclusions with an average concentration in a range of about 0.5 atom percent to about 1.5 atom percent. The surface layer forms a diode junction with an underlying portion of the substrate. A plurality of electrical contacts allow application of a reverse bias voltage to the junction in order to facilitate generation of an electrical signal, e.g., a photocurrent, in response to irradiation of the surface layer. The photodetector exhibits a responsivity greater than about 1 A/W for incident wavelengths in a range of about 250 nm to about 1050 nm, and a responsivity greater than about 0.1 A/W for longer wavelengths, e.g., up to about 3.5 microns.

Silicon-based visible and near-infrared optoelectric devices

DOEpatents

Mazur, Eric; Carey, III, James E.

2010-08-24

In one aspect, the present invention provides a silicon photodetector having a surface layer that is doped with sulfur inclusions with an average concentration in a range of about 0.5 atom percent to about 1.5 atom percent. The surface layer forms a diode junction with an underlying portion of the substrate. A plurality of electrical contacts allow application of a reverse bias voltage to the junction in order to facilitate generation of an electrical signal, e.g., a photocurrent, in response to irradiation of the surface layer. The photodetector exhibits a responsivity greater than about 1 A/W for incident wavelengths in a range of about 250 nm to about 1050 nm, and a responsivity greater than about 0.1 A/W for longer wavelengths, e.g., up to about 3.5 microns.

Silicon-based visible and near-infrared optoelectric devices

DOEpatents

Mazur, Eric [Concord, MA; Carey, III, James Edward

2009-03-17

In one aspect, the present invention provides a silicon photodetector having a surface layer that is doped with sulfur inclusions with an average concentration in a range of about 0.5 atom percent to about 1.5 atom percent. The surface layer forms a diode junction with an underlying portion of the substrate. A plurality of electrical contacts allow application of a reverse bias voltage to the junction in order to facilitate generation of an electrical signal, e.g., a photocurrent, in response to irradiation of the surface layer. The photodetector exhibits a responsivity greater than about 1 A/W for incident wavelengths in a range of about 250 nm to about 1050 nm, and a responsivity greater than about 0.1 A/W for longer wavelengths, e.g., up to about 3.5 microns.

Silicon-based visible and near-infrared optoelectric devices

DOEpatents

Carey, III, James Edward; Mazur, Eric [Concord, MA

2011-12-20

In one aspect, the present invention provides a silicon photodetector having a surface layer that is doped with sulfur inclusions with an average concentration in a range of about 0.5 atom percent to about 1.5 atom percent. The surface layer forms a diode junction with an underlying portion of the substrate. A plurality of electrical contacts allow application of a reverse bias voltage to the junction in order to facilitate generation of an electrical signal, e.g., a photocurrent, in response to irradiation of the surface layer. The photodetector exhibits a responsivity greater than about 1 A/W for incident wavelengths in a range of about 250 nm to about 1050 nm, and a responsivity greater than about 0.1 A/W for longer wavelengths, e.g., up to about 3.5 microns.

Silicon-based visible and near-infrared optoelectric devices

DOEpatents

Carey, III, James Edward; Mazur, Eric

2006-06-06

In one aspect, the present invention provides a silicon photodetector having a surface layer that is doped with sulfur inclusions with an average concentration in a range of about 0.5 atom percent to about 1.5 atom percent. The surface layer forms a diode junction with an underlying portion of the substrate. A plurality of electrical contacts allow application of a reverse bias voltage to the junction in order to facilitate generation of an electrical signal, e.g., a photocurrent, in response to irradiation of the surface layer. The photodetector exhibits a responsivity greater than about 1 A/W for incident wavelengths in a range of about 250 nm to about 1050 nm, and a responsivity greater than about 0.1 A/W for longer wavelengths, e.g., up to about 3.5 microns.

Silicon-based visible and near-infrared optoelectric devices

DOEpatents

Mazur, Eric; Carey, James Edward

2016-03-01

In one aspect, the present invention provides a silicon photodetector having a surface layer that is doped with sulfur inclusions with an average concentration in a range of about 0.5 atom percent to about 1.5 atom percent. The surface layer forms a diode junction with an underlying portion of the substrate. A plurality of electrical contacts allow application of a reverse bias voltage to the junction in order to facilitate generation of an electrical signal, e.g., a photocurrent, in response to irradiation of the surface layer. The photodetector exhibits a responsivity greater than about 1 A/W for incident wavelengths in a range of about 250 nm to about 1050 nm, and a responsivity greater than about 0.1 A/W for longer wavelengths, e.g., up to about 3.5 microns.

Silicon-based visible and near-infrared optoelectric devices

DOEpatents

Mazur, Eric; Carey, James Edward

2013-12-10

In one aspect, the present invention provides a silicon photodetector having a surface layer that is doped with sulfur inclusions with an average concentration in a range of about 0.5 atom percent to about 1.5 atom percent. The surface layer forms a diode junction with an underlying portion of the substrate. A plurality of electrical contacts allow application of a reverse bias voltage to the junction in order to facilitate generation of an electrical signal, e.g., a photocurrent, in response to irradiation of the surface layer. The photodetector exhibits a responsivity great than about 1 A/W for incident wavelengths in a range of about 250 nm to about 1050 nm, and a responsivity greater than about 0.1 A/W for longer wavelenths, e.g., up to about 3.5 microns.

Structure–function relationships in single molecule rectification by N-phenylbenzamide derivatives

DOE PAGES

Koenigsmann, Christopher; Ding, Wendu; Koepf, Matthieu; ...

2016-06-30

Here, we examine structure–function relationships in a series of N-phenylbenzamide (NPBA) derivatives by using computational modeling to identify molecular structures that exhibit both rectification and good conductance together with experimental studies of bias-dependent single molecule conductance and rectification behavior using the scanning tunneling microscopy break-junction technique. From a large number of computationally screened molecular diode structures, we have identified NPBA as a promising candidate, relative to the other structures that were screened. We demonstrate experimentally that conductance and rectification are both enhanced by functionalization of the NPBA 4-carboxamido-aniline moiety with electron donating methoxy groups, and are strongly correlated with themore » energy of the conducting frontier orbital relative to the Fermi level of the gold leads used in break-junction experiments.« less

Structure–function relationships in single molecule rectification by N-phenylbenzamide derivatives

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

Koenigsmann, Christopher; Ding, Wendu; Koepf, Matthieu

Here, we examine structure–function relationships in a series of N-phenylbenzamide (NPBA) derivatives by using computational modeling to identify molecular structures that exhibit both rectification and good conductance together with experimental studies of bias-dependent single molecule conductance and rectification behavior using the scanning tunneling microscopy break-junction technique. From a large number of computationally screened molecular diode structures, we have identified NPBA as a promising candidate, relative to the other structures that were screened. We demonstrate experimentally that conductance and rectification are both enhanced by functionalization of the NPBA 4-carboxamido-aniline moiety with electron donating methoxy groups, and are strongly correlated with themore » energy of the conducting frontier orbital relative to the Fermi level of the gold leads used in break-junction experiments.« less

Multifunctional hybrid diode: Study of photoresponse, high responsivity, and charge injection mechanisms

NASA Astrophysics Data System (ADS)

Singh, Jitendra; Singh, R. G.; Gautam, Subodh K.; Singh, Fouran

2018-05-01

A multifunctional hybrid heterojunction diode is developed on porous silicon and its current density-voltage characteristics reveal a good rectification ratio along with other superior parameters such as ideality factor, barrier height and series resistance. The diode also functions as an efficient photodiode to manifest high photosensitivity with high responsivity under illumination with broadband solar light, UV light, and green light. The diode is also carefully scrutinized for its sensitivity and repeatability over many cycles under UV and green light and is found to have a quick response and extremely fast recovery times. The notable responsivity is attributed to the generation of high density of excitons in the depletion region by the absorption of incident photons and their separation by an internal electric field besides an additional photocurrent due to the charging of polymer chains. The mechanisms of generation, injection and transport of charge carriers are explained by developing a schematic energy band diagram. The transport phenomenon of carriers is further investigated from room temperature down to a very low temperature of 10 K. An Arrhenius plot is made to determine the Richardson constant. Various diode parameters as mentioned above are also determined and the dominance of the transport mechanism of charge carriers in different temperature regimes such as diffusion across the junction and/or quantum tunneling through the barriers are explained. The developed multifunction heterojunction hybrid diodes have implications for highly sensitive photodiodes in the UV and visible range of electromagnetic spectrum that can be very promising for efficient optoelectronic devices.

Schottky barrier betavoltaic battery

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

Manasse, F.K.; Pinajian, J.J.; Tse, A.N.

1976-02-01

A new nuclear betavoltaic battery is described. It uses a Schottky barrier in place of the more standard p-n junction diode, along with $sup 147$Pm metal film rather than Pm$sub 2$O$sub 3$ oxide as in the commercially available Betacel. Design details of the battery including measurement of absorption, conversion efficiency, thickness etc. as functions of resistivity and other cell parameters are described. A prototype design is discussed and its performance assessed. (auth)

Test-beds for molecular electronics: metal-molecules-metal junctions based on Hg electrodes.

PubMed

Simeone, Felice Carlo; Rampi, Maria Anita

2010-01-01

Junctions based on mesoscopic Hg electrodes are used to characterize the electrical properties of the organic molecules organized in self-assembled monolayers (SAMs). The junctions M-SAM//SAM-Hg are formed by one electrode based on metals (M) such as Hg, Ag, Au, covered by a SAM, and by a second electrode always formed by a Hg drop carrying also a SAM. The electrodes, brought together by using a micromanipulator, sandwich SAMs of different nature at the contact area (approximately = 0.7 microm2). The high versatility of the system allows a series of both electrical and electrochemical junctions to be assembled and characterized: (i) The compliant nature of the Hg electrodes allows incorporation into the junction and measurement of the electrical behavior of a large number of molecular systems and correlation of their electronic structure to the electrical behavior; (ii) by functionalizing both electrodes with SAMs exposing different functional groups, X and Y, it is possible to compare the rate of electron transfer through different X...Y molecular interactions; (iii) when the junction incorporates one of the electrode formed by a semitransparent film of Au, it allows electrical measurements under irradiation of the sandwiched SAMs. In this case the junction behaves as a photoswitch; iv) incorporation of redox centres with low lying, easily reachable energy levels, provides electron stations as indicated by the hopping mechanism dominating the current flow; (v) electrochemical junctions incorporating redox centres by both covalent and electrostatic interactions permit control of the potential of the electrodes with respect to that of the redox state by means of an external reference electrode. Both these junctions show an electrical behavior similar to that of conventional diodes, even though the mechanism generating the current flow is different. These systems, demonstrating high mechanical stability and reproducibility, easy assembly, and a wide variety of produced results, are convenient test-beds for molecular electronics and represent a useful complement to physics-based experimental methods.

Effect of interleaved Si layer on the magnetotransport and semiconducting properties of n-Si/Fe Schottky junctions

NASA Astrophysics Data System (ADS)

Das, Sudhansu Sekhar; Kumar, M. Senthil

2017-12-01

Heterostructure films of the form n-Si/Si(tSi)/Fe(800 Å) were prepared by DC magnetron sputtering. In these films, the Si and Fe (800 Å) films were deposited onto n-Si(100) substrates. Substrates with different doping concentration ND were used. The thickness tSi of the interleaved Si layer is varied. For tSi = 0, the heterostructures form n-Si/Fe Schottky junctions. Structural studies on the samples as performed through XRD indicate the polycrystalline nature of the films. The magnetization data showed that the samples have in-plane easy axis of magnetization. The coercivity of the samples is of the order of 90 Oe. The I-V measurements on the samples showed nonlinear behavior. The diode ideality factor η = 2.6 is observed for the junction with ND = 1018 cm-3. The leakage current I0 increases with the increase of ND. Magnetic field has less effect on the electrical properties of the junctions. A positive magnetoresistance in the range 1 - 10 % was observed for the Si/Fe Schottky junctions in the presence of magnetic field of strength 2 T. The origin of the MR is analyzed using a model where the ratio of the currents across the junctions with and without the applied magnetic field, IH=2T/IH=0 is studied as a function of the bias voltage Vbias. The ratio IH=2T/IH=0 shows a decreasing trend with the Vbias, suggesting that the contribution to the MR in our n-Si/Fe Schottky junctions due to the spin dependent scattering is very less as compared to that due to the suppression of the impact ionization process.

A theoretical analysis of steady-state photocurrents in simple silicon diodes

NASA Technical Reports Server (NTRS)

Edmonds, L.

1995-01-01

A theoretical analysis solves for the steady-state photocurrents produced by a given photo-generation rate function with negligible recombination in simple silicon diodes, consisting of a uniformly doped quasi-neutral region (called 'substrate' below) adjacent to a p-n junction depletion region (DR). Special attention is given to conditions that produce 'funneling' (a term used by the single-eventeffects community) under steady-state conditions. Funneling occurs when carriers are generated so fast that the DR becomes flooded and partially or completely collapses. Some or nearly all of the applied voltage, plus built-in potential normally across the DR, is now across the substrate. This substrate voltage drop affects substrate currents. The steady-state problem can provide some qualitative insights into the more difficult transient problem. First, it was found that funneling can be induced from a distance, i.e., from carriers generated at locations outside of the DR. Secondly, it was found that the substrate can divide into two subregions, with one controlling substrate resistance and the other characterized by ambipolar diffusion. Finally, funneling was found to be more difficult to induce in the p(sup +)/n diode than in the n(sup +)/p diode. The carrier density exceeding the doping density in the substrate and at the DR boundary is not a sufficient condition to collapse a DR.

Concurrent ionic migration and electronic effects at the memristive TiO x /La1/3Ca2/3MnO3-x interface

NASA Astrophysics Data System (ADS)

Román Acevedo, W.; Ferreyra, C.; Sánchez, M. J.; Acha, C.; Gay, R.; Rubi, D.

2018-03-01

The development of reliable redox-based resistive random-access memory devices requires understanding and disentangling concurrent effects present at memristive interfaces. We report on the fabrication and electrical characterization of TiO x /La1/3Ca2/3MnO3-x microstructured interfaces and on the modeling of their memristive behavior. We show that a careful tuning of the applied external electrical stimuli allows controlling the redox process between both layers, obtaining multilevel non-volatile resistance states. We simulate the oxygen vacancies dynamics at the interface between both oxides, and successfully reproduce the experimental electrical behavior after the inclusion of an electronic effect, related to the presence of an n-p diode at the interface. The formation of the diode is due to the n- and p-character of TiO x and La1/3Ca2/3MnO3-x , respectively. Our analysis indicates that oxygen vacancies migration between both layers is triggered after the diode is polarized either in forward mode or in reverse mode above breakdown. Electrical measurements at different temperatures suggest that the diode can be characterized as Zener-type. The advantages of our junctions for their implementation in RRAM devices are finally discussed.

Design of high breakdown voltage vertical GaN p-n diodes with high-K/low-K compound dielectric structure for power electronics applications

NASA Astrophysics Data System (ADS)

Du, Jiangfeng; Li, Zhenchao; Liu, Dong; Bai, Zhiyuan; Liu, Yang; Yu, Qi

2017-11-01

In this work, a vertical GaN p-n diode with a high-K/low-K compound dielectric structure (GaN CD-VGD) is proposed and designed to achieve a record high breakdown voltage (BV) with a low specific on-resistance (Ron,sp). By introducing compound dielectric structure, the electric field near the p-n junction interface is suppressed due to the effects of high-K passivation layer, and a new electric field peak is induced into the n-type drift region, because of a discontinuity of electrical field at the interface of high-K and low-K layer. Therefore the distribution of electric field in GaN p-n diode becomes more uniform and an enhancement of breakdown voltage can be achieved. Numerical simulations demonstrate that GaN CD-VGD with a BV of 10650 V and a Ron,sp of 14.3 mΩ cm2, resulting in a record high figure-of-merit of 8 GW/cm2.

Optical characterization of magnesium incorporation in p-GaN layers for core–shell nanorod light-emitting diodes

NASA Astrophysics Data System (ADS)

Gîrgel, I.; Šatka, A.; Priesol, J.; Coulon, P.-M.; Le Boulbar, E. D.; Batten, T.; Allsopp, D. W. E.; Shields, P. A.

2018-04-01

III-nitride nanostructures are of interest for a new generation of light-emitting diodes (LEDs). However, the characterization of doping incorporation in nanorod (NR) structures, which is essential for creating the p-n junction diodes, is extremely challenging. This is because the established electrical measurement techniques (such as capacitance–voltage or Hall-effect methods) require a simple sample geometry and reliable ohmic contacts, both of which are difficult to achieve in nanoscale devices. The need for homogenous, conformal n-type or p-type layers in core–shell nanostructures magnifies these challenges. Consequently, we demonstrate how a combination of non-contact methods (micro-photoluminescence, micro-Raman and cathodoluminescence), as well as electron-beam-induced-current, can be used to analyze the uniformity of magnesium incorporation in core–shell NRs and make a first estimate of doping levels by the evolution of band transitions, strain and current mapping. These techniques have been used to optimize the growth of core–shell nanostructures for electrical carrier injection, a significant milestone for their use in LEDs.

High current density 2D/3D MoS2/GaN Esaki tunnel diodes

NASA Astrophysics Data System (ADS)

Krishnamoorthy, Sriram; Lee, Edwin W.; Lee, Choong Hee; Zhang, Yuewei; McCulloch, William D.; Johnson, Jared M.; Hwang, Jinwoo; Wu, Yiying; Rajan, Siddharth

2016-10-01

The integration of two-dimensional materials such as transition metal dichalcogenides with bulk semiconductors offer interesting opportunities for 2D/3D heterojunction-based device structures without any constraints of lattice matching. By exploiting the favorable band alignment at the GaN/MoS2 heterojunction, an Esaki interband tunnel diode is demonstrated by transferring large area Nb-doped, p-type MoS2 onto heavily n-doped GaN. A peak current density of 446 A/cm2 with repeatable room temperature negative differential resistance, peak to valley current ratio of 1.2, and minimal hysteresis was measured in the MoS2/GaN non-epitaxial tunnel diode. A high current density of 1 kA/cm2 was measured in the Zener mode (reverse bias) at -1 V bias. The GaN/MoS2 tunnel junction was also modeled by treating MoS2 as a bulk semiconductor, and the electrostatics at the 2D/3D interface was found to be crucial in explaining the experimentally observed device characteristics.

A Pt/TiO(2)/Ti Schottky-type selection diode for alleviating the sneak current in resistance switching memory arrays.

PubMed

Park, Woo Young; Kim, Gun Hwan; Seok, Jun Yeong; Kim, Kyung Min; Song, Seul Ji; Lee, Min Hwan; Hwang, Cheol Seong

2010-05-14

This study examined the properties of Schottky-type diodes composed of Pt/TiO(2)/Ti, where the Pt/TiO(2) and TiO(2)/Ti junctions correspond to the blocking and ohmic contacts, respectively, as the selection device for a resistive switching cross-bar array. An extremely high forward-to-reverse current ratio of approximately 10(9) was achieved at 1 V when the TiO(2) film thickness was 19 nm. TiO(2) film was grown by atomic layer deposition at a substrate temperature of 250 degrees C. Conductive atomic force microscopy revealed that the forward current flew locally, which limits the maximum forward current density to < 10 A cm(-2) for a large electrode (an area of approximately 60 000 microm(2)). However, the local current measurement showed a local forward current density as high as approximately 10(5) A cm(-2). Therefore, it is expected that this type of Schottky diode effectively suppresses the sneak current without adverse interference effects in a nano-scale resistive switching cross-bar array with high block density.

Flexible Lamination-Fabricated Ultra-High Frequency Diodes Based on Self-Supporting Semiconducting Composite Film of Silicon Micro-Particles and Nano-Fibrillated Cellulose.

PubMed

Sani, Negar; Wang, Xin; Granberg, Hjalmar; Andersson Ersman, Peter; Crispin, Xavier; Dyreklev, Peter; Engquist, Isak; Gustafsson, Göran; Berggren, Magnus

2016-06-30

Low cost and flexible devices such as wearable electronics, e-labels and distributed sensors will make the future "internet of things" viable. To power and communicate with such systems, high frequency rectifiers are crucial components. We present a simple method to manufacture flexible diodes, operating at GHz frequencies, based on self-adhesive composite films of silicon micro-particles (Si-μPs) and glycerol dispersed in nanofibrillated cellulose (NFC). NFC, Si-μPs and glycerol are mixed in a water suspension, forming a self-supporting nanocellulose-silicon composite film after drying. This film is cut and laminated between a flexible pre-patterned Al bottom electrode and a conductive Ni-coated carbon tape top contact. A Schottky junction is established between the Al electrode and the Si-μPs. The resulting flexible diodes show current levels on the order of mA for an area of 2 mm(2), a current rectification ratio up to 4 × 10(3) between 1 and 2 V bias and a cut-off frequency of 1.8 GHz. Energy harvesting experiments have been demonstrated using resistors as the load at 900 MHz and 1.8 GHz. The diode stack can be delaminated away from the Al electrode and then later on be transferred and reconfigured to another substrate. This provides us with reconfigurable GHz-operating diode circuits.

Flexible Lamination-Fabricated Ultra-High Frequency Diodes Based on Self-Supporting Semiconducting Composite Film of Silicon Micro-Particles and Nano-Fibrillated Cellulose

PubMed Central

Sani, Negar; Wang, Xin; Granberg, Hjalmar; Andersson Ersman, Peter; Crispin, Xavier; Dyreklev, Peter; Engquist, Isak; Gustafsson, Göran; Berggren, Magnus

2016-01-01

Low cost and flexible devices such as wearable electronics, e-labels and distributed sensors will make the future “internet of things” viable. To power and communicate with such systems, high frequency rectifiers are crucial components. We present a simple method to manufacture flexible diodes, operating at GHz frequencies, based on self-adhesive composite films of silicon micro-particles (Si-μPs) and glycerol dispersed in nanofibrillated cellulose (NFC). NFC, Si-μPs and glycerol are mixed in a water suspension, forming a self-supporting nanocellulose-silicon composite film after drying. This film is cut and laminated between a flexible pre-patterned Al bottom electrode and a conductive Ni-coated carbon tape top contact. A Schottky junction is established between the Al electrode and the Si-μPs. The resulting flexible diodes show current levels on the order of mA for an area of 2 mm2, a current rectification ratio up to 4 × 103 between 1 and 2 V bias and a cut-off frequency of 1.8 GHz. Energy harvesting experiments have been demonstrated using resistors as the load at 900 MHz and 1.8 GHz. The diode stack can be delaminated away from the Al electrode and then later on be transferred and reconfigured to another substrate. This provides us with reconfigurable GHz-operating diode circuits. PMID:27357006

Flexible Lamination-Fabricated Ultra-High Frequency Diodes Based on Self-Supporting Semiconducting Composite Film of Silicon Micro-Particles and Nano-Fibrillated Cellulose

NASA Astrophysics Data System (ADS)

Sani, Negar; Wang, Xin; Granberg, Hjalmar; Andersson Ersman, Peter; Crispin, Xavier; Dyreklev, Peter; Engquist, Isak; Gustafsson, Göran; Berggren, Magnus

2016-06-01

Low cost and flexible devices such as wearable electronics, e-labels and distributed sensors will make the future “internet of things” viable. To power and communicate with such systems, high frequency rectifiers are crucial components. We present a simple method to manufacture flexible diodes, operating at GHz frequencies, based on self-adhesive composite films of silicon micro-particles (Si-μPs) and glycerol dispersed in nanofibrillated cellulose (NFC). NFC, Si-μPs and glycerol are mixed in a water suspension, forming a self-supporting nanocellulose-silicon composite film after drying. This film is cut and laminated between a flexible pre-patterned Al bottom electrode and a conductive Ni-coated carbon tape top contact. A Schottky junction is established between the Al electrode and the Si-μPs. The resulting flexible diodes show current levels on the order of mA for an area of 2 mm2, a current rectification ratio up to 4 × 103 between 1 and 2 V bias and a cut-off frequency of 1.8 GHz. Energy harvesting experiments have been demonstrated using resistors as the load at 900 MHz and 1.8 GHz. The diode stack can be delaminated away from the Al electrode and then later on be transferred and reconfigured to another substrate. This provides us with reconfigurable GHz-operating diode circuits.

Electrical Properties of a p-n Heterojunction of Li-Doped NiO and Al-Doped ZnO for Thermoelectrics

NASA Astrophysics Data System (ADS)

Desissa, Temesgen D.; Schrade, Matthias; Norby, Truls

2018-06-01

The electrical properties of a p-n heterojunction of polycrystalline p-type Ni0.98Li0.02O and n-type Zn0.98Al0.02O have been investigated for potential applications in high-temperature oxide-based thermoelectric generators without metallic interconnects. Current-voltage characteristics of the junction were measured in a two-electrode setup in ambient air at 500-1000°C. The resistance and rectification of the junction decreased with increasing temperature. A non-ideal Shockley diode model was used to fit the measured current-voltage data in order to extract characteristic parameters of the junction, such as area-specific series resistance R s and parallel shunt resistance R p, non-ideality factor, and the saturation current density. R s and R p decreased exponentially with temperature, with activation energies of 0.4 ± 0.1 eV and 1.1 ± 0.2 eV, respectively. The interface resistance of the direct p-n junction studied here is as such too high for practical applications in thermoelectrics. However, it is demonstrated that it can be reduced by an order of magnitude by using a composite of the individual materials at the interface, yielding a large effective contact area.

Spontaneous and Selective Nanowelding of Silver Nanowires by Electrochemical Ostwald Ripening and High Electrostatic Potential at the Junctions for High-Performance Stretchable Transparent Electrodes.

PubMed

Lee, Hyo-Ju; Oh, Semi; Cho, Ki-Yeop; Jeong, Woo-Lim; Lee, Dong-Seon; Park, Seong-Ju

2018-04-25

Metal nanowires have been gaining increasing attention as the most promising stretchable transparent electrodes for emerging field of stretchable optoelectronic devices. Nanowelding technology is a major challenge in the fabrication of metal nanowire networks because the optoelectronic performances of metal nanowire networks are mostly limited by the high junction resistance between nanowires. We demonstrate the spontaneous and selective welding of Ag nanowires (AgNWs) by Ag solders via an electrochemical Ostwald ripening process and high electrostatic potential at the junctions of AgNWs. The AgNWs were welded by depositing Ag nanoparticles (AgNPs) on the conducting substrate and then exposing them to water at room temperature. The AgNPs were spontaneously dissolved in water to form Ag + ions, which were then reduced to single-crystal Ag solders selectively at the junctions of the AgNWs. Hence, the welded AgNWs showed higher optoelectronic and stretchable performance compared to that of as-formed AgNWs. These results indicate that electrochemical Ostwald ripening-based welding can be used as a promising method for high-performance metal nanowire electrodes in various next-generation devices such as stretchable solar cells, stretchable displays, organic light-emitting diodes, and skin sensors.

Radioisotope battery using Schottky barrier devices

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

Manasse, F.K.; Tse, A.N.

1976-05-01

Based on the well-known betavoltaic effect, a new nuclear battery, which uses a Schottky barrier, has been used in place of the more standard p-n junction diode, along with /sup 147/Pm metal film rather than Pm/sub 2/O/sub 3/ oxide, as in the commercially available Betacel. Measurement of absorption, conversion efficiency, thickness, etc., as functions of resistivity and other cell parameters, and assessment of performance are being researched to design a prototype battery.

Wide Band-Gap Semiconductors. 1991 Materials Research Society Symposium Proceedings

DTIC Science & Technology

1992-09-01

attention of many research groups bccause the instrumental simplicity and high growth rate (1,2). One of the basic problems with this technique, other than...solution with group 1a element as a dopant under controlled Zn vapor pressure. p-n junction diodes are also prepared by the Ga diffusion from Zn solution...stoichiometric composition catl be controlled by the application of the vapor pressure. Mat. Res. Soc. Symp. Proc. Vol. 242. 1992 Materials Research Society 180

Determination on the Coefficient of Thermal Expansion in High-Power InGaN-based Light-emitting Diodes by Optical Coherence Tomography.

PubMed

Lee, Ya-Ju; Chou, Chun-Yang; Huang, Chun-Ying; Yao, Yung-Chi; Haung, Yi-Kai; Tsai, Meng-Tsan

2017-10-31

The coefficient of thermal expansion (CTE) is a physical quantity that indicates the thermal expansion value of a material upon heating. For advanced thermal management, the accurate and immediate determination of the CTE of packaging materials is gaining importance because the demand for high-power lighting-emitting diodes (LEDs) is currently increasing. In this study, we used optical coherence tomography (OCT) to measure the CTE of an InGaN-based (λ = 450 nm) high-power LED encapsulated in polystyrene resin. The distances between individual interfaces of the OCT images were observed and recorded to derive the instantaneous CTE of the packaged LED under different injected currents. The LED junction temperature at different injected currents was established with the forward voltage method. Accordingly, the measured instantaneous CTE of polystyrene resin varied from 5.86 × 10 -5  °C -1 to 14.10 × 10 -5  °C -1 in the junction temperature range 25-225 °C and exhibited a uniform distribution in an OCT scanning area of 200 × 200 μm. Most importantly, this work validates the hypothesis that OCT can provide an alternative way to directly and nondestructively determine the spatially resolved CTE of the packaged LED device, which offers significant advantages over traditional CTE measurement techniques.

Light emitting diodes as a plant lighting source

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

Bula, R.J.; Tennessen, D.J.; Morrow, R.C.

1994-12-31

Electroluminescence in solid materials is defined as the generation of light by the passage of an electric current through a body of solid material under an applied electric field. A specific type of electroluminescence, first noted by Lossew in 1923, involves the generation of photons when electrons are passed through a p-n junction of certain solid materials (junction of a n-type semiconductor, an electron donor, and a p-type semiconductor, an electron acceptor). Development efforts to translate these observations into visible light emitting devices, however, was not undertaken until the 1950s. The term, light emitting diode (LEDs), was first used inmore » a report by Wolfe, et al., in 1955. The development of this light emitting semiconductor technology dates back less than 30 years. During this period of time, the LED has evolved from a rare and expensive light generating device to one of the most widely used electronic components. The most popular applications of the LED are as indicators or as optoelectronic switches. However, several recent advances in LED technology have made possible the utilization of LEDs for applications that require a high photon flux, such as for plant lighting in controlled environments. The new generation of LEDs based on a gallium aluminum arsenide (GaAlAS) semiconductor material fabricated as a double heterostructure on a transparent substrate has opened up many new applications for these LEDs.« less

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Calculation of the temperature distribution in ridged-waveguide laser diodes

NASA Astrophysics Data System (ADS)

Piprek, J.; Nürnberg, R.

1988-11-01

A numerical solution is obtained of the steady-state heat conduction equation for InGaAsP/InP ridge-waveguide lasers (λ = 1.3 μm) soldered upside down to a heat sink. Two-dimensional temperature distributions perpendicular to the ridge are obtained. It is assumed that the heat sources inside such a laser are the active region and the contact at the top of the ridge. An increase in the temperature of the junction and the corresponding thermal resistance of a laser chip and solder are calculated for several sets of laser parameters. The results indicate that the thermal properties are particularly sensitive to the width of the ridge and the thickness of the solder. The results obtained should be useful in thermal optimization of ridge-waveguide laser diodes.

Reverse-bias-driven dichromatic electroluminescence of n-ZnO wire arrays/p-GaN film heterojunction light-emitting diodes

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

Jeong, Junseok; Choi, Ji Eun; Hong, Young Joon, E-mail: yjhong@sejong.ac.kr

Position-controlled n-ZnO microwire (MW) and nanowire-bundle (NW-B) arrays were fabricated using hydrothermal growth of ZnO on a patterned p-GaN film. Both the wire/film p–n heterojunctions showed electrical rectification features at reverse-bias (rb) voltages, analogous to backward diodes. Dichromatic electroluminescence (EL) emissions with 445- and 560-nm-wavelength peaks displayed whitish-blue and greenish-yellow light from MW- and NW-B-based heterojunctions at rb voltages, respectively. The different dichromatic EL emission colors were studied based on photoluminescence spectra and the dichromatic EL peak intensity ratios as a function of the rb voltage. The different EL colors are discussed with respect to depletion thickness and electron tunnelingmore » probability determined by wire/film junction geometry and size.« less

Reverse-bias-driven dichromatic electroluminescence of n-ZnO wire arrays/p-GaN film heterojunction light-emitting diodes

NASA Astrophysics Data System (ADS)

Jeong, Junseok; Choi, Ji Eun; Kim, Yong-Jin; Hwang, Sunyong; Kim, Sung Kyu; Kim, Jong Kyu; Jeong, Hu Young; Hong, Young Joon

2016-09-01

Position-controlled n-ZnO microwire (MW) and nanowire-bundle (NW-B) arrays were fabricated using hydrothermal growth of ZnO on a patterned p-GaN film. Both the wire/film p-n heterojunctions showed electrical rectification features at reverse-bias (rb) voltages, analogous to backward diodes. Dichromatic electroluminescence (EL) emissions with 445- and 560-nm-wavelength peaks displayed whitish-blue and greenish-yellow light from MW- and NW-B-based heterojunctions at rb voltages, respectively. The different dichromatic EL emission colors were studied based on photoluminescence spectra and the dichromatic EL peak intensity ratios as a function of the rb voltage. The different EL colors are discussed with respect to depletion thickness and electron tunneling probability determined by wire/film junction geometry and size.

Planar micro- and nano-patterning of GaN light-emitting diodes: Guidelines and limitations

NASA Astrophysics Data System (ADS)

Herrnsdorf, Johannes; Xie, Enyuan; Watson, Ian M.; Laurand, Nicolas; Dawson, Martin D.

2014-02-01

The emission area of GaN light-emitting diodes can be patterned by etch-free current aperturing methods which exploit the thin and highly resistive nature of the p-doped layer in these devices. Here, the fundamental underlying electrical and optical aspects of high-resolution current aperturing are investigated theoretically. The most critical parameter for the possible resolution is the thickness d of the p-GaN layer, but the interplay of p-GaN resistivity and electrical junction characteristics is also important. A spatial resolution of 1.59d can in principle be achieved, corresponding to about 300 nm in typical epitaxial structures. Furthermore, the emission from such a small emitter will spread by about 600 nm while propagating through the p-GaN. Both values can be reduced by reducing d.

Investigation of solar cells fabricated on low-cost silicon sheet materials using 1 MeV electron irradiation

NASA Technical Reports Server (NTRS)

Kachare, A. H.; Hyland, S. L.; Garlick, G. F. J.

1981-01-01

The use of high energy electron irradiation is investigated as a controlled means to study in more detail the junction depletion layer processes of solar cells made on various low-cost silicon sheet materials. Results show that solar cells made on Czochralski grown silicon exhibit enhancement of spectral response in the shorter wavelength region when irradiated with high energy electrons. The base region damage can be reduced by subsequent annealing at 450 C which restores the degraded longer wavelength response, although the shorter wavelength enhancement persists. The second diode component of the cell dark forward bias current is also reduced by electron irradiation, while thermal annealing at 450 C without electron irradiation can also produce these same effects. Electron irradiation produces small changes in the shorter wavelength spectral responses and junction improvements in solar cells made on WEB, EFG, and HEM silicon. It is concluded that these beneficial effects on cell characteristics are due to the reduction of oxygen associated deep level recombination centers in the N(+) diffused layer and in the junction.

The interface modification for GNWs/Si Schottky junction with PEI/PEIE interlayers

NASA Astrophysics Data System (ADS)

Zhou, Quan; Liu, Xiangzhi; Luo, Wei; Shen, Jun; Wang, Yuefeng; Wei, Dapeng

2018-03-01

Polyethylenimine ethoxylated (PEIE) and polyethyl-enimine (PEI), the two kinds of interface buffer layer, are widely used in the organic light-emitting diodes and solar cells for band alignment adjustment. In this report, we carefully studied the influence of the inserting organic layer on the graphene nanowalls(GNWS)/Si junction quality and the photoresponse of the Schottky devices. We found that thinner layers of PEI could decrease the dark current and improve the photo-to-dark ratio to 105 for n-Si devices. The s-kink effect and degradation of open circuit voltage could be observed for thicker thickness and excessive doping. Relatively, PEIE with stable thin layer not only improve the rectifying characteristics of p-Si devices but also the incident photon conversion efficiency. The maximus IPCE could reach 44% and be adjusted to zero by the reverse bias. The tunneling inhibition for electrons can be alleviated by increasing the barrier height. Our results provide an attractive method to improve the efficiency of pristine GNWs/Si junction with interface doping and passivation.

Inelastic effects in molecular transport junctions: The probe technique at high bias

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

Kilgour, Michael; Segal, Dvira, E-mail: dsegal@chem.utoronto.ca

2016-03-28

We extend the Landauer-Büttiker probe formalism for conductances to the high bias regime and study the effects of environmentally induced elastic and inelastic scattering on charge current in single molecule junctions, focusing on high-bias effects. The probe technique phenomenologically incorporates incoherent elastic and inelastic effects to the fully coherent case, mimicking a rich physical environment at trivial cost. We further identify environmentally induced mechanisms which generate an asymmetry in the current, manifested as a weak diode behavior. This rectifying behavior, found in two types of molecular junction models, is absent in the coherent-elastic limit and is only active in themore » case with incoherent-inelastic scattering. Our work illustrates that in the low bias-linear response regime, the commonly used “dephasing probe” (mimicking only elastic decoherence effects) operates nearly indistinguishably from a “voltage probe” (admitting inelastic-dissipative effects). However, these probes realize fundamentally distinct I-V characteristics at high biases, reflecting the central roles of dissipation and inelastic scattering processes on molecular electronic transport far-from-equilibrium.« less

Superluminescence from an optically pumped molecular tunneling junction by injection of plasmon induced hot electrons

PubMed Central

Braun, Kai; Wang, Xiao; Kern, Andreas M; Adler, Hilmar; Peisert, Heiko; Chassé, Thomas; Zhang, Dai

2015-01-01

Summary Here, we demonstrate a bias-driven superluminescent point light-source based on an optically pumped molecular junction (gold substrate/self-assembled molecular monolayer/gold tip) of a scanning tunneling microscope, operating at ambient conditions and providing almost three orders of magnitude higher electron-to-photon conversion efficiency than electroluminescence induced by inelastic tunneling without optical pumping. A positive, steadily increasing bias voltage induces a step-like rise of the Stokes shifted optical signal emitted from the junction. This emission is strongly attenuated by reversing the applied bias voltage. At high bias voltage, the emission intensity depends non-linearly on the optical pump power. The enhanced emission can be modelled by rate equations taking into account hole injection from the tip (anode) into the highest occupied orbital of the closest substrate-bound molecule (lower level) and radiative recombination with an electron from above the Fermi level (upper level), hence feeding photons back by stimulated emission resonant with the gap mode. The system reflects many essential features of a superluminescent light emitting diode. PMID:26171286

Effect of reabsorbed recombination radiation on the saturation current of direct gap p-n junctions

NASA Technical Reports Server (NTRS)

Von Roos, O.; Mavromatis, H.

1984-01-01

The application of the radiative transfer theory for semiconductors to p-n homojunctions subject to low level injection conditions is discussed. By virtue of the interaction of the radiation field with free carriers across the depletion layer, the saturation current density in Shockley's expression for the diode current is reduced at high doping levels. The reduction, due to self-induced photon generation, is noticeable for n-type material owing to the small electron effective mass in direct band-gap III-V compounds. The effect is insignificant in p-type material. At an equilibrium electron concentration of 2 x 10 to the 18th/cu cm in GaAs, a reduction of the saturation current density by 15 percent is predicted. It is concluded that realistic GaAs p-n junctions possess a finite thickness.

Observation of quantum oscillation of work function in ultrathin-metal/semiconductor junctions

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

Takhar, Kuldeep; Meer, Mudassar; Khachariya, Dolar

2015-09-15

Quantization in energy level due to confinement is generally observed for semiconductors. This property is used for various quantum devices, and it helps to improve the characteristics of conventional devices. Here, the authors have demonstrated the quantum size effects in ultrathin metal (Ni) layers sandwiched between two large band-gap materials. The metal work function is found to oscillate as a function of its thickness. The thermionic emission current bears the signature of the oscillating work function, which has a linear relationship with barrier heights. This methodology allows direct observation of quantum oscillations in metals at room temperature using a Schottkymore » diode and electrical measurements using source-measure-units. The observed phenomena can provide additional mechanism to tune the barrier height of metal/semiconductor junctions, which are used for various electronic devices.« less

Construction and evaluation of high-quality n-ZnO nanorod/p-diamond heterojunctions.

PubMed

Wang, C D; Jha, S K; Chen, Z H; Ng, T W; Liu, Y K; Yuen, M F; Lu, Z Z; Kwok, S Y; Zapien, J A; Bello, I; Lee, C S; Zhang, W J

2012-06-01

Vertically-aligned ZnO nanorods (NRs) arrays were synthesized by a low-temperature solution method on boron-doped diamond (BDD) films. The morphology, growth direction, and crystallinity of the ZnO NRs were studied by scanning electron microscopy, X-ray diffraction and cathodoluminescence. Electrical characterization of the ZnO NR/BBD heterostructures revealed characteristic p-n junction properties with an on/off ratio of about 50 at +/- 4 V and a small reverse leakage current approximately 1 microA. Moreover, the junctions showed an ideality factor around 1.0 at a low forward voltage from 0 to 0.3 V and about 2.1 for an increased voltage ranging from 1.2 to 3.0 V, being consistent with that of an ideal diode according to the Sah-Noyce-Shockley theory.

Transient photocurrent in molecular junctions: singlet switching on and triplet blocking.

PubMed

Petrov, E G; Leonov, V O; Snitsarev, V

2013-05-14

The kinetic approach adapted to describe charge transmission in molecular junctions, is used for the analysis of the photocurrent under conditions of moderate light intensity of the photochromic molecule. In the framework of the HOMO-LUMO model for the single electron molecular states, the analytic expressions describing the temporary behavior of the transient and steady state sequential (hopping) as well as direct (tunnel) current components have been derived. The conditions at which the current components achieve their maximal values are indicated. It is shown that if the rates of charge transmission in the unbiased molecular diode are much lower than the intramolecular singlet-singlet excitation/de-excitation rate, and the threefold degenerated triplet excited state of the molecule behaves like a trap blocking the charge transmission, a possibility of a large peak-like transient switch-on photocurrent arises.

Light-induced negative differential resistance in gate-controlled graphene-silicon photodiode

NASA Astrophysics Data System (ADS)

Liu, Wei; Guo, Hongwei; Li, Wei; Wan, Xia; Bodepudi, Srikrishna Chanakya; Shehzad, Khurram; Xu, Yang

2018-05-01

In this letter, we investigated light-induced negative differential resistance (L-NDR) effects in a hybrid photodiode formed by a graphene-silicon (GS) junction and a neighboring graphene-oxide-Si (GOS) capacitor. We observed two distinct L-NDR effects originating from the gate-dependent surface recombination and the potential-well-induced confinement of photo-carriers in the GOS region. We verified this by studying the gate-controlled GS diode, which can distinguish the photocurrent from the GS region with that from the GOS region (gate). A large peak-to-valley ratio of up to 12.1 has been obtained for the L-NDR due to gate-dependent surface recombination. Such strong L-NDR effect provides an opportunity to further engineer the optoelectronic properties of GS junctions along with exploring its potential applications in photodetectors, photo-memories, and position sensitive devices.

CMOS Image Sensor Using SOI-MOS/Photodiode Composite Photodetector Device

NASA Astrophysics Data System (ADS)

Uryu, Yuko; Asano, Tanemasa

2002-04-01

A new photodetector device composed of a lateral junction photodiode and a metal-oxide-semiconductor field-effect-transistor (MOSFET), in which the output of the diode is fed through the body of the MOSFET, has been investigated. It is shown that the silicon-on-insulator (SOI)-MOSFET amplifies the junction photodiode current due to the lateral bipolar action. It is also shown that the presence of the electrically floating gate enhances the current amplification factor of the SOI-MOSFET. The output current of this composite device linearly responds by four orders of illumination intensity. As an application of the composite device, a complementary-metal-oxide-semiconductor (CMOS) line sensor incorporating the composite device is fabricated and its operation is demonstrated. The output signal of the line sensor using the composite device was two times larger than that using the lateral photodiode.

Force and Conductance Spectroscopy of Single Molecule Junctions

NASA Astrophysics Data System (ADS)

Frei, Michael

Investigation of mechanical properties of single molecule junctions is crucial to develop an understanding and enable control of single molecular junctions. This work presents an experimental and analytical approach that enables the statistical evaluation of force and simultaneous conductance data of metallic atomic point contacts and molecular junctions. A conductive atomic force microscope based break junction technique is developed to form single molecular junctions and collect conductance and force data simultaneously. Improvements of the optical components have been achieved through the use of a super-luminescent diode, enabling tremendous increases in force resolution. An experimental procedure to collect data for various molecular junctions has been developed and includes deposition, calibration, and analysis methods. For the statistical analysis of force, novel approaches based on two dimensional histograms and a direct force identification method are presented. The two dimensional method allows for an unbiased evaluation of force events that are identified using corresponding conductance signatures. This is not always possible however, and in these situations, the force based identification of junction rearrangement events is an attractive alternative method. This combined experimental and analytical approach is then applied to three studies: First, the impact of molecular backbones to the mechanical behavior of single molecule junctions is investigated and it is found that junctions formed with identical linkers but different backbone structure result in junctions with varying breaking forces. All molecules used show a clear molecular signature and force data can be evaluated using the 2D method. Second, the effects of the linker group used to attach molecules to gold electrodes are investigated. A study of four alkane molecules with different linkers finds a drastic difference in the evolution of donor-acceptor and covalently bonded molecules respectively. In fact, the covalent bond is found to significantly distort the metal electrode rearrangement such that junction rearrangement events can no longer be identified with a clean and well defined conductance signature. For this case, the force based identification process is used. Third, results for break junction measurements with different metals are presented. It is found that silver and palladium junctions rupture with forces different from those of gold contacts. In the case of silver experiments in ambient conditions, we can also identify oxygen impurities in the silver contact formation process, leading to force and conductance measurements of silver-oxygen structures. For the future, this work provides an experimental and analytical foundation that will enable insights into single molecule systems not previously accessible.

Bipolar Transistor and Diode Failure to Electrical Transients-Predictive Failure Modeling versus Experimental Damage Testing. 1 Junction Capacitance Damage Model

DTIC Science & Technology

1981-06-01

into the Wunsch-Bell equation) are P = A R , 1t-0 5 1.2 PD) = A26B2t-.5 (3) JAJ where A,*, A, B1, and B2 are experimentally determined constants and TJ...ATTN CODE 7240, S. N. LICHT’NAN PATRICK AID, FL 32J25 DIV COIMAND SAN DIEGO, CA 92152 ATTN D]PN-ATC AF WEAPONS LABORATORY, AFSC ATTN DRCFN- TDS -DSI

High efficiency thin-film crystalline Si/Ge tandem solar cell.

PubMed

Sun, G; Chang, F; Soref, R A

2010-02-15

We propose and simulate a photovoltaic solar cell comprised of Si and Ge pn junctions in tandem. With an anti-reflection film at the front surface, we have shown that optimal solar cells favor a thin Si layer and a thick Ge layer with a thin tunnel hetero-diode placed in between. We predict efficiency ranging from 19% to 28% for AM1.5G solar irradiance concentrated from 1 approximately 1000 Suns for a cell with a total thickness approximately 100 microm.

Efficiency and weight of voltage multiplier type ultra lightweight dc-dc converters

NASA Technical Reports Server (NTRS)

Harrigill, W. T., Jr.; Myers, I. T.

1975-01-01

An analytical and experimental study was made of a capacitor-diode voltage multiplier without a transformer which offers the possibility of high efficiency with light weight. The dc-dc conversion efficiencies of about 94 percent were achieved at output powers of 150 watts at 1000 volts using 8x multiplication. A detailed identification of losses was made, including forward drop losses in component, switching losses, reverse junction capacitance charging losses, and charging losses in the main ladder capacitors.

Bipolar Cascade Emitters for Radio-Frequency and Electro-Optical Applications

DTIC Science & Technology

2008-05-01

conduction band of the subsequent stage. (2) At the 50 mA bias , the p-doped OA tunneling region is ∼0.5 eV and the n-doped OA tunneling region is ∼0.1...bands are forward biased at an injection current of 50 mA except for the 3-stage p-doped OA BC LED which at a low voltage bias of 4.3 V, which...Resonant Cavity Light Emitting Diode . . . . . . . 40 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.2 Tunnel Junction

How Small is too Small True Microrobots and Nanorobots for Military Applications in 2035

DTIC Science & Technology

2010-04-01

field effect transistor or diode junction based.41 Additionally, NEMS sensors based on resonating thin films and nanowires42 and optical based...acoustic sensor is fabricated from piezoelectric thin films and measures 600 µm by 600 µm by 2.2 µm thick with a total volume of 0.0008 mm3.50 Since...microrobot systems by 2035. Reduction in thin film width dimensions (under 600 µm), in order to be able to physically incorporate this into a

Advances in Sensors and Their Integration into Aircraft Guidance and Control Systems,

DTIC Science & Technology

1983-06-01

this function taking account of the limitations of the existing air- craft systems such as:- (a) Cockpit space (b) use of existing controls particularly...electrostatically focused under the influence of high potentials to form an electron image on a thin silicon wafer target upon which a very tightly spaced ...matrix of p-n junctions have been formed. The spacing of the diodes is of the order of n m. A gain mechanism is caused because the photo electrons

High Power Laser Diode Array Qualification and Guidelines for Space Flight Environments

NASA Technical Reports Server (NTRS)

Eegholm, Niels; Ott, Melanie; Stephen, Mark; Leidecker, Henning

2005-01-01

Semiconductor laser diodes emit coherent light by simulated emission generated inside the cavity formed by the cleaved end facets of a slab of semiconductor that is typically less than a millimeter in any dimension for single emitters. The diode is pumped by current injection in the p-n junction through the metallic contacts. Laser diodes emitting in the range of 0.8 micron to 1.06 micron have a wide variety of applications from pumping erbium doped fiber amplifiers, dual-clad fiber lasers, solid-state lasers used in telecom, aerospace, military, medical purposes and all the way to CD players, laser printers and other consumer and industrial products. Laser diode bars have many single emitters side by side and spaced approximately .5 mm on a single slab of semiconductor material approximately .5 mm x 10 mm. The individual emitters are connected in parallel maintaining the voltage at -2V but increasing the current to 50-100A/bar. Stacking these laser diode bars in multiple layers, 2 to 20+ high, yields high power laser diode arrays capable of emitting several hundreds of Watts. Electrically the bars are wired in series increasing the voltage by 2V/bar but maintaining the total current at 50-100A. These arrays are one of the enabling technologies for efficient, high power solid-state lasers. Traditionally these arrays are operated in QCW (Quasi CW) mode with pulse widths 10-200 (mu)s and with repetition rates of 10-200Hz. In QCW mode the wavelength and the output power of the laser reaches steady-state but the temperature does not. The advantage is a substantially higher output power than in CW mode, where the output power would be limited by the internal heating and hence the thermal and heat sinking properties of the device. The down side is a much higher thermal induced mechanical stress caused by the constant heating and cooling cycle inherent to the QCW mode.

Accurate diode behavioral model with reverse recovery

NASA Astrophysics Data System (ADS)

Banáš, Stanislav; Divín, Jan; Dobeš, Josef; Paňko, Václav

2018-01-01

This paper deals with the comprehensive behavioral model of p-n junction diode containing reverse recovery effect, applicable to all standard SPICE simulators supporting Verilog-A language. The model has been successfully used in several production designs, which require its full complexity, robustness and set of tuning parameters comparable with standard compact SPICE diode model. The model is like standard compact model scalable with area and temperature and can be used as a stand-alone diode or as a part of more complex device macro-model, e.g. LDMOS, JFET, bipolar transistor. The paper briefly presents the state of the art followed by the chapter describing the model development and achieved solutions. During precise model verification some of them were found non-robust or poorly converging and replaced by more robust solutions, demonstrated in the paper. The measurement results of different technologies and different devices compared with a simulation using the new behavioral model are presented as the model validation. The comparison of model validation in time and frequency domains demonstrates that the implemented reverse recovery effect with correctly extracted parameters improves the model simulation results not only in switching from ON to OFF state, which is often published, but also its impedance/admittance frequency dependency in GHz range. Finally the model parameter extraction and the comparison with SPICE compact models containing reverse recovery effect is presented.

Al0 0.3Ga 0.7N PN diode with breakdown voltage >1600 V

DOE PAGES

Allerman, A. A.; Armstrong, A. M.; Fischer, A. J.; ...

2016-07-21

Demonstration of Al0 0.3Ga 0.7N PN diodes grown with breakdown voltages in excess of 1600 V is reported. The total epilayer thickness is 9.1 μm and was grown by metal-organic vapour-phase epitaxy on 1.3-mm-thick sapphire in order to achieve crack-free structures. A junction termination edge structure was employed to control the lateral electric fields. A current density of 3.5 kA/cm 2 was achieved under DC forward bias and a reverse leakage current <3 nA was measured for voltages <1200 V. The differential on-resistance of 16 mΩ cm 2 is limited by the lateral conductivity of the n-type contact layer requiredmore » by the front-surface contact geometry of the device. An effective critical electric field of 5.9 MV/cm was determined from the epilayer properties and the reverse current–voltage characteristics. To our knowledge, this is the first aluminium gallium nitride (AlGaN)-based PN diode exhibiting a breakdown voltage in excess of 1 kV. Finally, we note that a Baliga figure of merit (V br 2/R spec,on) of 150 MW/cm 2 found is the highest reported for an AlGaN PN diode and illustrates the potential of larger-bandgap AlGaN alloys for high-voltage devices.« less

Charge transfer in rectifying oxide heterostructures and oxide access elements in ReRAM

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

Stefanovich, G. B.; Pergament, A. L.; Boriskov, P. P.

2016-05-15

The main aspects of the synthesis and experimental research of oxide diode heterostructures are discussed with respect to their use as selector diodes, i.e., access elements in oxide resistive memory. It is shown that charge transfer in these materials differs significantly from the conduction mechanism in p–n junctions based on conventional semiconductors (Si, Ge, A{sup III}–B{sup V}), and the model should take into account the electronic properties of oxides, primarily the low carrier drift mobility. It is found that an increase in the forward current requires an oxide with a small band gap (<1.3 eV) in the heterostructure composition. Heterostructuresmore » with Zn, In–Zn (IZO), Ti, Ni, and Cu oxides are studied; it is found that the CuO–IZO heterojunction has the highest forward current density (10{sup 4} A/cm{sup 2}).« less

Terahertz optoelectronics with surface plasmon polariton diode.

PubMed

Vinnakota, Raj K; Genov, Dentcho A

2014-05-09

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

Low-Temperature Electrical Characteristics of Si-Based Device with New Tetrakis NiPc-SNS Active Layer

NASA Astrophysics Data System (ADS)

Yavuz, Arzu Büyükyağci; Carbas, Buket Bezgın; Sönmezoğlu, Savaş; Soylu, Murat

2016-01-01

A new tetrakis 4-(2,5-di-2-thiophen-2-yl-pyrrol-1-yl)-substituted nickel phthalocyanine (NiPc-SNS) has been synthesized. This synthesized NiPc-SNS thin film was deposited on p-type Si substrate using the spin coating method (SCM) to fabricate a NiPc-SNS/ p-Si heterojunction diode. The temperature-dependent electrical characteristics of the NiPc-SNS/ p-Si heterojunction with good rectifying behavior were investigated by current-voltage ( I- V) measurements between 50 K and 300 K. The results indicate that the ideality factor decreases while the barrier height increases with increasing temperature. The barrier inhomogeneity across the NiPc-SNS/ p-Si heterojunction reveals a Gaussian distribution at low temperatures. These results provide further evidence of the more complicated mechanisms occurring in this heterojunction. Based on these findings, NiPc-SNS/ p-Si junction diodes are feasible for use in low-temperature applications.

Surface half-metallicity of CrS thin films and perfect spin filtering and spin diode effects of CrS/ZnSe heterostructure

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

Gao, G. Y., E-mail: guoying-gao@mail.hust.edu.cn; Yao, K. L., E-mail: klyao@mail.hust.edu.cn

2014-11-03

Recently, ferromagnetic zinc-blende Mn{sub 1−x}Cr{sub x}S thin films (above x = 0.5) were fabricated experimentally on ZnSe substrate, which confirmed the previous theoretical prediction of half-metallic ferromagnetism in zinc-blende CrS. Here, we theoretically reveal that both Cr- and S-terminated (001) surfaces of the CrS thin films retain the half-metallicity. The CrS/ZnSe(001) heterogeneous junction exhibits excellent spin filtering and spin diode effects, which are explained by the calculated band structure and transmission spectra. The perfect spin transport properties indicate the potential applications of half-metallic CrS in spintronic devices. All computational results are obtained by using the density functional theory combined with nonequilibrium Green'smore » function.« less

Spin-torque resonant expulsion of the vortex core for an efficient radiofrequency detection scheme.

PubMed

Jenkins, A S; Lebrun, R; Grimaldi, E; Tsunegi, S; Bortolotti, P; Kubota, H; Yakushiji, K; Fukushima, A; de Loubens, G; Klein, O; Yuasa, S; Cros, V

2016-04-01

It has been proposed that high-frequency detectors based on the so-called spin-torque diode effect in spin transfer oscillators could eventually replace conventional Schottky diodes due to their nanoscale size, frequency tunability and large output sensitivity. Although a promising candidate for information and communications technology applications, the output voltage generated from this effect has still to be improved and, more pertinently, reduces drastically with decreasing radiofrequency (RF) current. Here we present a scheme for a new type of spintronics-based high-frequency detector based on the expulsion of the vortex core in a magnetic tunnel junction (MTJ). The resonant expulsion of the core leads to a large and sharp change in resistance associated with the difference in magnetoresistance between the vortex ground state and the final C-state configuration. Interestingly, this reversible effect is independent of the incoming RF current amplitude, offering a fast real-time RF threshold detector.

Flexible White Light Emitting Diodes Based on Nitride Nanowires and Nanophosphors

PubMed Central

2016-01-01

We report the first demonstration of flexible white phosphor-converted light emitting diodes (LEDs) based on p–n junction core/shell nitride nanowires. GaN nanowires containing seven radial In0.2Ga0.8N/GaN quantum wells were grown by metal–organic chemical vapor deposition on a sapphire substrate by a catalyst-free approach. To fabricate the flexible LED, the nanowires are embedded into a phosphor-doped polymer matrix, peeled off from the growth substrate, and contacted using a flexible and transparent silver nanowire mesh. The electroluminescence of a flexible device presents a cool-white color with a spectral distribution covering a broad spectral range from 400 to 700 nm. Mechanical bending stress down to a curvature radius of 5 mm does not yield any degradation of the LED performance. The maximal measured external quantum efficiency of the white LED is 9.3%, and the wall plug efficiency is 2.4%. PMID:27331079

Organic/Inorganic Hybrid p-n Junction with PEDOT Nanoparticles for Light-Emitting Diode

NASA Astrophysics Data System (ADS)

Kim, M. S.; Jin, S. M.; Cho, M. Y.; Choi, H. Y.; Kim, G. S.; Jeon, S. M.; Yim, K. G.; Kim, H. G.; Shim, K. B.; Kang, B. K.; Kim, Y.; Lee, D. Y.; Kim, J. S.; Kim, J. S.; Leem, J. Y.

2011-12-01

A heavily Si-doped GaN/polymer hybrid structure with p-type poly(3,4-ethylene-dioxythiophene):beta-1,3-glucan (PEDOT nanoparticle) interface layer has been fabricated. The Si-doped GaN thin film with carrier concentration of 1×1019 cm-3 was grown by metal-organic chemical vapor deposition (MOCVD). The PEDOT nanoparticle with various sizes ranging from 60 to 120 nm was synthesized via a miniemulsion polymerization process. The electrical conductivity of the PEDOT nanoparticle is less than 1.2 S/cm. The current-voltage (I-V) characteristic of the hybrid structure shows diode-like behavior. The I-V characteristic was examined in the framework of the thermionic emission model. The ideality factor and barrier height of the hybrid structure were obtained as 5.6 and 0.41 eV, respectively. The value of ideality factor is decreased by inserting the PEDOT nanoparticle interface layer.

Improved InGaN/GaN light-emitting diodes with a p-GaN/n-GaN/p-GaN/n-GaN/p-GaN current-spreading layer.

PubMed

Zhang, Zi-Hui; Tan, Swee Tiam; Liu, Wei; Ju, Zhengang; Zheng, Ke; Kyaw, Zabu; Ji, Yun; Hasanov, Namig; Sun, Xiao Wei; Demir, Hilmi Volkan

2013-02-25

This work reports both experimental and theoretical studies on the InGaN/GaN light-emitting diodes (LEDs) with optical output power and external quantum efficiency (EQE) levels substantially enhanced by incorporating p-GaN/n-GaN/p-GaN/n-GaN/p-GaN (PNPNP-GaN) current spreading layers in p-GaN. Each thin n-GaN layer sandwiched in the PNPNP-GaN structure is completely depleted due to the built-in electric field in the PNPNP-GaN junctions, and the ionized donors in these n-GaN layers serve as the hole spreaders. As a result, the electrical performance of the proposed device is improved and the optical output power and EQE are enhanced.

Titanium-dioxide nanotube p-n homojunction diode

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

The Numerical Simulation of the Nanosecond Switching of a p-SOS Diode

NASA Astrophysics Data System (ADS)

Podolska, N. I.; Lyublinskiy, A. G.; Grekhov, I. V.

2017-12-01

Abrupt high-density reverse current interruption has been numerically simulated for switching from forward to reverse bias in a silicon p + P 0 n + structure ( p-SOS diode). It has been shown that the current interruption in this structure occurs as a result of the formation of two dynamic domains of a strong electric field in regions in which the free carrier concentration substantially exceeds the concentration of the doping impurity. The first domain is formed in the n + region at the n + P 0 junction, while the second domain is formed in the P 0 region at the interface with the p + layer. The second domain expands much faster, and this domain mainly determines the current interruption rate. Good agreement is achieved between the simulation results and the experimental data when the actual electric circuit determining the electron-hole plasma pumping in and out is accurately taken into account.

InGaP Heterojunction Barrier Solar Cells

NASA Technical Reports Server (NTRS)

Welser, Roger E. (Inventor)

2014-01-01

A new solar cell structure called a heterojunction barrier solar cell is described. As with previously reported quantum-well and quantum-dot solar cell structures, a layer of narrow band-gap material, such as GaAs or indium-rich InGaP, is inserted into the depletion region of a wide band-gap PN junction. Rather than being thin, however, the layer of narrow band-gap material is about 400-430 nm wide and forms a single, ultrawide well in the depletion region. Thin (e.g., 20-50 nm), wide band-gap InGaP barrier layers in the depletion region reduce the diode dark current. Engineering the electric field and barrier profile of the absorber layer, barrier layer, and p-type layer of the PN junction maximizes photogenerated carrier escape. This new twist on nanostructured solar cell design allows the separate optimization of current and voltage to maximize conversion efficiency.

Chemical fabrication of heterometallic nanogaps for molecular transport junctions.

PubMed

Chen, Xiaodong; Yeganeh, Sina; Qin, Lidong; Li, Shuzhou; Xue, Can; Braunschweig, Adam B; Schatz, George C; Ratner, Mark A; Mirkin, Chad A

2009-12-01

We report a simple and reproducible method for fabricating heterometallic nanogaps, which are made of two different metal nanorods separated by a nanometer-sized gap. The method is based upon on-wire lithography, which is a chemically enabled technique used to synthesize a wide variety of nanowire-based structures (e.g., nanogaps and disk arrays). This method can be used to fabricate pairs of metallic electrodes, which exhibit distinct work functions and are separated by gaps as small as 2 nm. Furthermore, we demonstrate that a symmetric thiol-terminated molecule can be assembled into such heterometallic nanogaps to form molecular transport junctions (MTJs) that exhibit molecular diode behavior. Theoretical calculations demonstrate that the coupling strength between gold and sulfur (Au-S) is 2.5 times stronger than that of Pt-S. In addition, the structures form Raman hot spots in the gap, allowing the spectroscopic characterization of the molecules that make up the MTJs.

thin film capacitors

NASA Astrophysics Data System (ADS)

Bodeux, Romain; Gervais, Monique; Wolfman, Jérôme; Gervais, François

2014-09-01

CaCu3Ti4O12 (CCTO) thin films were grown by pulsed laser deposition on Pt and La0.9Sr1.1NiO4 (LSNO) bottom electrodes. The electrical characteristics of the CCTO/Pt and CCTO/LSNO Schottky junctions have been analyzed by impedance spectroscopy, capacitance-voltage (C-V) and current-voltage (I-V) measurements as a function of frequency (40 Hz-1 MHz) and temperature (300-475 K). Similar results were obtained for the two Schottky diodes. The conduction mechanism through the Schottky junctions was described using a thermionic emission model and the electrical parameters were determined. The strong deviation from the ideal I-V characteristics and the increase in capacitance at low frequency for -0.5 V bias are in agreement with the presence of traps near the interfaces. Results point toward the important effect of defects generated at the interface by deposition of CCTO.

Single Molecule Electronics and Devices

PubMed Central

Tsutsui, Makusu; Taniguchi, Masateru

2012-01-01

The manufacture of integrated circuits with single-molecule building blocks is a goal of molecular electronics. While research in the past has been limited to bulk experiments on self-assembled monolayers, advances in technology have now enabled us to fabricate single-molecule junctions. This has led to significant progress in understanding electron transport in molecular systems at the single-molecule level and the concomitant emergence of new device concepts. Here, we review recent developments in this field. We summarize the methods currently used to form metal-molecule-metal structures and some single-molecule techniques essential for characterizing molecular junctions such as inelastic electron tunnelling spectroscopy. We then highlight several important achievements, including demonstration of single-molecule diodes, transistors, and switches that make use of electrical, photo, and mechanical stimulation to control the electron transport. We also discuss intriguing issues to be addressed further in the future such as heat and thermoelectric transport in an individual molecule. PMID:22969345

Reinventing solid state electronics: Harnessing quantum confinement in bismuth thin films

NASA Astrophysics Data System (ADS)

Gity, Farzan; Ansari, Lida; Lanius, Martin; Schüffelgen, Peter; Mussler, Gregor; Grützmacher, Detlev; Greer, J. C.

2017-02-01

Solid state electronics relies on the intentional introduction of impurity atoms or dopants into a semiconductor crystal and/or the formation of junctions between different materials (heterojunctions) to create rectifiers, potential barriers, and conducting pathways. With these building blocks, switching and amplification of electrical currents and voltages are achieved. As miniaturisation continues to ultra-scaled transistors with critical dimensions on the order of ten atomic lengths, the concept of doping to form junctions fails and forming heterojunctions becomes extremely difficult. Here, it is shown that it is not needed to introduce dopant atoms nor is a heterojunction required to achieve the fundamental electronic function of current rectification. Ideal diode behavior or rectification is achieved solely by manipulation of quantum confinement using approximately 2 nm thick films consisting of a single atomic element, the semimetal bismuth. Crucially for nanoelectronics, this approach enables room temperature operation.

Characterization of electrically-active defects in ultraviolet light-emitting diodes with laser-based failure analysis techniques

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

Miller, Mary A.; Tangyunyong, Paiboon; Cole, Edward I.

2016-01-14

Laser-based failure analysis techniques demonstrate the ability to quickly and non-intrusively screen deep ultraviolet light-emitting diodes (LEDs) for electrically-active defects. In particular, two laser-based techniques, light-induced voltage alteration and thermally-induced voltage alteration, generate applied voltage maps (AVMs) that provide information on electrically-active defect behavior including turn-on bias, density, and spatial location. Here, multiple commercial LEDs were examined and found to have dark defect signals in the AVM indicating a site of reduced resistance or leakage through the diode. The existence of the dark defect signals in the AVM correlates strongly with an increased forward-bias leakage current. This increased leakage ismore » not present in devices without AVM signals. Transmission electron microscopy analysis of a dark defect signal site revealed a dislocation cluster through the pn junction. The cluster included an open core dislocation. Even though LEDs with few dark AVM defect signals did not correlate strongly with power loss, direct association between increased open core dislocation densities and reduced LED device performance has been presented elsewhere [M. W. Moseley et al., J. Appl. Phys. 117, 095301 (2015)].« less

Characterization of electrically-active defects in ultraviolet light-emitting diodes with laser-based failure analysis techniques

DOE PAGES

Miller, Mary A.; Tangyunyong, Paiboon; Edward I. Cole, Jr.

2016-01-12

In this study, laser-based failure analysis techniques demonstrate the ability to quickly and non-intrusively screen deep ultraviolet light-emitting diodes(LEDs) for electrically-active defects. In particular, two laser-based techniques, light-induced voltage alteration and thermally-induced voltage alteration, generate applied voltage maps (AVMs) that provide information on electrically-active defect behavior including turn-on bias, density, and spatial location. Here, multiple commercial LEDs were examined and found to have dark defect signals in the AVM indicating a site of reduced resistance or leakage through the diode. The existence of the dark defect signals in the AVM correlates strongly with an increased forward-bias leakage current. This increasedmore » leakage is not present in devices without AVM signals. Transmission electron microscopyanalysis of a dark defect signal site revealed a dislocation cluster through the pn junction. The cluster included an open core dislocation. Even though LEDs with few dark AVM defect signals did not correlate strongly with power loss, direct association between increased open core dislocation densities and reduced LED device performance has been presented elsewhere [M. W. Moseley et al., J. Appl. Phys. 117, 095301 (2015)].« less

Developing high-transmittance heterojunction diodes based on NiO/TZO bilayer thin films

PubMed Central

2013-01-01

In this study, radio frequency magnetron sputtering was used to deposit nickel oxide thin films (NiO, deposition power of 100 W) and titanium-doped zinc oxide thin films (TZO, varying deposition powers) on glass substrates to form p(NiO)-n(TZO) heterojunction diodes with high transmittance. The structural, optical, and electrical properties of the TZO and NiO thin films and NiO/TZO heterojunction devices were investigated with scanning electron microscopy, X-ray diffraction (XRD) patterns, UV-visible spectroscopy, Hall effect analysis, and current-voltage (I-V) analysis. XRD analysis showed that only the (111) diffraction peak of NiO and the (002) and (004) diffraction peaks of TZO were observable in the NiO/TZO heterojunction devices, indicating that the TZO thin films showed a good c-axis orientation perpendicular to the glass substrates. When the sputtering deposition power for the TZO thin films was 100, 125, and 150 W, the I-V characteristics confirmed that a p-n junction characteristic was successfully formed in the NiO/TZO heterojunction devices. We show that the NiO/TZO heterojunction diode was dominated by the space-charge limited current theory. PMID:23634999

Strong room temperature electroluminescence from lateral p-SiGe/i-Ge/n-SiGe heterojunction diodes on silicon-on-insulator substrate

NASA Astrophysics Data System (ADS)

Lin, Guangyang; Yi, Xiaohui; Li, Cheng; Chen, Ningli; Zhang, Lu; Chen, Songyan; Huang, Wei; Wang, Jianyuan; Xiong, Xihuan; Sun, Jiaming

2016-10-01

A lateral p-Si0.05Ge0.95/i-Ge/n-Si0.05Ge0.95 heterojunction light emitting diode on a silicon-on-insulator (SOI) substrate was proposed, which is profitable to achieve higher luminous extraction compared to vertical junctions. Due to the high carrier injection ratio of heterostructures and optical reflection at the SiO2/Si interface of the SOI, strong room temperature electroluminescence (EL) at around 1600 nm from the direct bandgap of i-Ge with 0.30% tensile strain was observed. The EL peak intensity of the lateral heterojunction is enhanced by ˜4 folds with a larger peak energy than that of the vertical Ge p-i-n homojunction, suggesting that the light emitting efficiency of the lateral heterojunction is effectively improved. The EL peak intensity of the lateral heterojunction, which increases quadratically with injection current density, becomes stronger for diodes with a wider i-Ge region. The CMOS compatible fabrication process of the lateral heterojunctions paves the way for the integration of the light source with the Ge metal-oxide-semiconductor field-effect-transistor.

Charge transport with single molecules--an electrochemical approach.

PubMed

Li, Chen; Mishchenko, Artem; Pobelov, Ilya; Wandlowski, Thomas

2010-01-01

After an introduction and brief review of charge transport in nanoscale molecular systems we report on experimental studies in gold / (single) molecule / gold junctions at solid / liquid interfaces employing a scanning tunneling microscopy (STM)-based 'break junction' technique. We demonstrate attempts in developing basic relationships between molecular structure, conductance properties and nanoscale electrochemical concepts based on four case studies from our own work. In experiments with alpha, omega-alkanedithiol and biphenyldithiol molecular junctions we address the role of sulfur-gold couplings and molecular conformation, such as gauche defects in the alkyl chains and the torsion angle between two phenyl rings. Combination with quantum chemistry calculations enabled a detailed molecular-level understanding of the electronic structure and transport characteristics of both systems. Employing the concept of 'electrolyte gating' with redox-active molecules, such as thiol-terminated derivatives of viologens (HS-6V6-SH or (HS-6V6)) we demonstrate the construction of symmetric and asymmetric active molecular junctions with transistor- or diode-like behavior upon polarization in an electrochemical environment. The experimental data could be represented quantitatively by the Kutznetsov/Ulstrup model assuming a two-step electron transfer with partial vibration relaxation. Finally, we show that surface-immobilized gold nanoparticles with a diameter of (2.4 +/- 0.5) nm exhibit features of locally addressable multi-state electronic switching upon electrolyte gating, which appears to be reminiscent of a sequential charging through several 'oxidation/reduction states'.

Current-voltage characteristics of single-molecule diarylethene junctions measured with adjustable gold electrodes in solution.

PubMed

Briechle, Bernd M; Kim, Youngsang; Ehrenreich, Philipp; Erbe, Artur; Sysoiev, Dmytro; Huhn, Thomas; Groth, Ulrich; Scheer, Elke

2012-01-01

We report on an experimental analysis of the charge transport through sulfur-free photochromic molecular junctions. The conductance of individual molecules contacted with gold electrodes and the current-voltage characteristics of these junctions are measured in a mechanically controlled break-junction system at room temperature and in liquid environment. We compare the transport properties of a series of molecules, labeled TSC, MN, and 4Py, with the same switching core but varying side-arms and end-groups designed for providing the mechanical and electrical contact to the gold electrodes. We perform a detailed analysis of the transport properties of TSC in its open and closed states. We find rather broad distributions of conductance values in both states. The analysis, based on the assumption that the current is carried by a single dominating molecular orbital, reveals distinct differences between both states. We discuss the appearance of diode-like behavior for the particular species 4Py that features end-groups, which preferentially couple to the metal electrode by physisorption. We show that the energetic position of the molecular orbital varies as a function of the transmission. Finally, we show for the species MN that the use of two cyano end-groups on each side considerably enhances the coupling strength compared to the typical behavior of a single cyano group.

Reduced junction temperature and enhanced performance of high power light-emitting diodes using reduced graphene oxide pattern

NASA Astrophysics Data System (ADS)

Han, Nam; Jung, Eunjin; Han, Min; Deul Ryu, Beo; Bok Ko, Kang; Park, Young Jae; Cuong, TranViet; Cho, Jaehee; Kim, Hyunsoo; Hong, Chang-Hee

2015-07-01

Thermal management has become a crucial area for further development of high-power light-emitting didoes (LEDs) due to the high operating current densities that are required and result in additional joule heating. This increased joule heating negatively affects the performance of the LEDs since it greatly decreases both the optical performance and the lifetime. To circumvent this problem, a reduced graphene oxide (rGO) layer can be inserted to act as a heat spreader. In this study, current-voltage and light-output-current measurements are systematically performed at different temperatures from 30 to 190 °C to investigate the effect that the embedded rGO pattern has on the device performance. At a high temperature and high operating current, the junction temperature (Tj) is 23% lower and the external quantum efficiency (EQE) is 24% higher for the rGO embedded LEDs relative to those of conventional LEDs. In addition, the thermal activation energy of the rGO embedded LEDs exhibits a 30% enhancement as a function of the temperature at a bias of  -5 V. This indicates that the rGO pattern plays an essential role in decreasing the junction temperature and results in a favorable performance in terms of the temperature of the high power GaN-based LED junction.

A solar photovoltaic system with ideal efficiency close to the theoretical limit.

PubMed

Zhao, Yuan; Sheng, Ming-Yu; Zhou, Wei-Xi; Shen, Yan; Hu, Er-Tao; Chen, Jian-Bo; Xu, Min; Zheng, Yu-Xiang; Lee, Young-Pak; Lynch, David W; Chen, Liang-Yao

2012-01-02

In order to overcome some physical limits, a solar system consisting of five single-junction photocells with four optical filters is studied. The four filters divide the solar spectrum into five spectral regions. Each single-junction photocell with the highest photovoltaic efficiency in a narrower spectral region is chosen to optimally fit into the bandwidth of that spectral region. Under the condition of solar radiation ranging from 2.4 SUN to 3.8 SUN (AM1.5G), the measured peak efficiency under 2.8 SUN radiation reaches about 35.6%, corresponding to an ideal efficiency of about 42.7%, achieved for the photocell system with a perfect diode structure. Based on the detailed-balance model, the calculated theoretical efficiency limit for the system consisting of 5 single-junction photocells can be about 52.9% under 2.8 SUN (AM1.5G) radiation, implying that the ratio of the highest photovoltaic conversion efficiency for the ideal photodiode structure to the theoretical efficiency limit can reach about 80.7%. The results of this work will provide a way to further enhance the photovoltaic conversion efficiency for solar cell systems in future applications.

Electronic components embedded in a single graphene nanoribbon.

PubMed

Jacobse, P H; Kimouche, A; Gebraad, T; Ervasti, M M; Thijssen, J M; Liljeroth, P; Swart, I

2017-07-25

The use of graphene in electronic devices requires a band gap, which can be achieved by creating nanostructures such as graphene nanoribbons. A wide variety of atomically precise graphene nanoribbons can be prepared through on-surface synthesis, bringing the concept of graphene nanoribbon electronics closer to reality. For future applications it is beneficial to integrate contacts and more functionality directly into single ribbons by using heterostructures. Here, we use the on-surface synthesis approach to fabricate a metal-semiconductor junction and a tunnel barrier in a single graphene nanoribbon consisting of 5- and 7-atom wide segments. We characterize the atomic scale geometry and electronic structure by combined atomic force microscopy, scanning tunneling microscopy, and conductance measurements complemented by density functional theory and transport calculations. These junctions are relevant for developing contacts in all-graphene nanoribbon devices and creating diodes and transistors, and act as a first step toward complete electronic devices built into a single graphene nanoribbon.Adding functional electronic components to graphene nanoribbons requires precise control over their atomic structure. Here, the authors use a bottom-up approach to build a metal-semiconductor junction and a tunnel barrier directly into a single graphene nanoribbon, an exciting development for graphene-based electronic devices.

Tunnel magnetoresistance for coherent spin-flip processes on an interacting quantum dot.

PubMed

Rudziński, W

2009-01-28

Spin-polarized electronic tunneling through a quantum dot coupled to ferromagnetic electrodes is investigated within a nonequilibrium Green function approach. An interplay between coherent intradot spin-flip transitions, tunneling processes and Coulomb correlations on the dot is studied for current-voltage characteristics of the tunneling junction in parallel and antiparallel magnetic configurations of the leads. It is found that due to the spin-flip processes electric current in the antiparallel configuration tends to the current characteristics in the parallel configuration, thus giving rise to suppression of the tunnel magnetoresistance (TMR) between the threshold bias voltages at which the dot energy level becomes active in tunneling. Also, the effect of a negative differential conductance in symmetrical junctions, splitting of the conductance peaks, significant modulation of TMR peaks around the threshold bias voltages as well as suppression of the diode-like behavior in asymmetrical junctions is discussed in the context of coherent intradot spin-flip transitions. It is also shown that TMR may be inverted at selected gate voltages, which qualitatively reproduces the TMR behavior predicted recently for temperatures in the Kondo regime, and observed experimentally beyond the Kondo regime for a semiconductor InAs quantum dot coupled to nickel electrodes.

InP tunnel junction for InGaAs/InP tandem solar cells

NASA Technical Reports Server (NTRS)

Vilela, M. F.; Freundlich, A.; Bensaoula, A.; Medelci, N.; Renaud, P.

1995-01-01

Chemical beam epitaxy (CBE) has been shown to allow the growth of high quality materials with reproducible complex compositional and doping profiles. The main advantage of CBE compared to metalorganic chemical vapor deposition (MOCVD), the most popular technique for InP-based photovoltaic device fabrication, is the ability to grow high purity epilayers at much lower temperatures (450-530 C). We have previously shown that CBE is perfectly suited toward the fabrication of complex photovoltaic devices such as InP/InGaAs monolithically integrated tandem solar cells, because its low process temperature preserves the electrical characteristics of the InGaAs tunnel junction commonly used as an ohmic interconnect. In this work using CBE for the fabrication of optically transparent (with respect to the bottom cell) InP tunnel diodes is demonstrated. Epitaxial growth were performed in a Riber CBE 32 system using PH3 and TMIn as III and V precursors. Solid Be (p-type) and Si (n-type) have been used as doping sources, allowing doping levels up to 2 x 10(exp -19)/cu cm and 1 x 10(exp -19)/cu cm for n and p type respectively. The InP tunnel junction characteristics and the influence of the growth's conditions (temperature, growth rate) over its performance have been carefully investigated. InP p(++)/n(++) tunnel junction with peak current densities up to 1600 A/sq cm and maximum specific resistivities (V(sub p)/I(sub p) - peak voltage to peak current ratio) in the range of 10(exp -4) Omega-sq cm were obtained. The obtained peak current densities exceed the highest results previously reported for their lattice matched counterparts, In(0.53)Ga( 0.47)As and should allow the realization of improved minimal absorption losses in the interconnect InP/InGaAs tandem devices for Space applications. Owing to the low process temperature required for the top cell, these devices exhibit almost no degradation of its characteristics after the growth of subsequent thick InP layer suggesting minimal doping cross diffusion in the narrow space-charge region (approximately 1-5 nm) of the device. The fabrication of tandem devices using InP tunnel diodes as interconnect is in progress and will be reported at the conference.

Tuning electronic transport in epitaxial graphene-based van der Waals heterostructures

NASA Astrophysics Data System (ADS)

Lin, Yu-Chuan; Li, Jun; de La Barrera, Sergio C.; Eichfeld, Sarah M.; Nie, Yifan; Addou, Rafik; Mende, Patrick C.; Wallace, Robert M.; Cho, Kyeongjae; Feenstra, Randall M.; Robinson, Joshua A.

2016-04-01

Two-dimensional tungsten diselenide (WSe2) has been used as a component in atomically thin photovoltaic devices, field effect transistors, and tunneling diodes in tandem with graphene. In some applications it is necessary to achieve efficient charge transport across the interface of layered WSe2-graphene, a semiconductor to semimetal junction with a van der Waals (vdW) gap. In such cases, band alignment engineering is required to ensure a low-resistance, ohmic contact. In this work, we investigate the impact of graphene electronic properties on the transport at the WSe2-graphene interface. Electrical transport measurements reveal a lower resistance between WSe2 and fully hydrogenated epitaxial graphene (EGFH) compared to WSe2 grown on partially hydrogenated epitaxial graphene (EGPH). Using low-energy electron microscopy and reflectivity on these samples, we extract the work function difference between the WSe2 and graphene and employ a charge transfer model to determine the WSe2 carrier density in both cases. The results indicate that WSe2-EGFH displays ohmic behavior at small biases due to a large hole density in the WSe2, whereas WSe2-EGPH forms a Schottky barrier junction.Two-dimensional tungsten diselenide (WSe2) has been used as a component in atomically thin photovoltaic devices, field effect transistors, and tunneling diodes in tandem with graphene. In some applications it is necessary to achieve efficient charge transport across the interface of layered WSe2-graphene, a semiconductor to semimetal junction with a van der Waals (vdW) gap. In such cases, band alignment engineering is required to ensure a low-resistance, ohmic contact. In this work, we investigate the impact of graphene electronic properties on the transport at the WSe2-graphene interface. Electrical transport measurements reveal a lower resistance between WSe2 and fully hydrogenated epitaxial graphene (EGFH) compared to WSe2 grown on partially hydrogenated epitaxial graphene (EGPH). Using low-energy electron microscopy and reflectivity on these samples, we extract the work function difference between the WSe2 and graphene and employ a charge transfer model to determine the WSe2 carrier density in both cases. The results indicate that WSe2-EGFH displays ohmic behavior at small biases due to a large hole density in the WSe2, whereas WSe2-EGPH forms a Schottky barrier junction. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01902a

Characterisation of diode-connected SiGe BiCMOS HBTs for space applications

NASA Astrophysics Data System (ADS)

Venter, Johan; Sinha, Saurabh; Lambrechts, Wynand

2016-02-01

Silicon-germanium (SiGe) bipolar complementary metal-oxide semiconductor (BiCMOS) transistors have vertical doping profiles reaching deeper into the substrate when compared to lateral CMOS transistors. Apart from benefiting from high-speed, high current gain and low-output resistance due to its vertical profile, BiCMOS technology is increasingly becoming a preferred technology for researchers to realise next-generation space-based optoelectronic applications. BiCMOS transistors have inherent radiation hardening, to an extent predictable cryogenic performance and monolithic integration potential. SiGe BiCMOS transistors and p-n junction diodes have been researched and used as a primary active component for over the last two decades. However, further research can be conducted with diode-connected heterojunction bipolar transistors (HBTs) operating at cryogenic temperatures. This work investigates these characteristics and models devices by adapting standard fabrication technology components. This work focuses on measurements of the current-voltage relationship (I-V curves) and capacitance-voltage relationships (C-V curves) of diode-connected HBTs. One configuration is proposed and measured, which is emitterbase shorted. The I-V curves are measured for various temperature points ranging from room temperature (300 K) to the temperature of liquid nitrogen (77 K). The measured datasets are used to extract a model of the formed diode operating at cryogenic temperatures and used as a standard library component in computer aided software designs. The advantage of having broad-range temperature models of SiGe transistors becomes apparent when considering implementation of application-specific integrated circuits and silicon-based infrared radiation photodetectors on a single wafer, thus shortening interconnects and lowering parasitic interference, decreasing the overall die size and improving on overall cost-effectiveness. Primary applications include space-based geothermal radiation sensing and cryogenic terahertz radiation sensing.

Spintronic logic: from switching devices to computing systems

NASA Astrophysics Data System (ADS)

Friedman, Joseph S.

2017-09-01

Though numerous spintronic switching devices have been proposed or demonstrated, there has been significant difficulty in translating these advances into practical computing systems. The challenge of cascading has impeded the integration of multiple devices into a logic family, and several proposed solutions potentially overcome these challenges. Here, the cascading techniques by which the output of each spintronic device can drive the input of another device are described for several logic families, including spin-diode logic (in particular, all-carbon spin logic), complementary magnetic tunnel junction logic (CMAT), and emitter-coupled spin-transistor logic (ECSTL).

Current development and patents on high-brightness white LED for illumination.

PubMed

Pang, Wen-Yuan; Lo, Ikai; Hsieh, Chia-Ho; Hsu, Yu-Chi; Chou, Ming-Chi; Shih, Cheng-Hung

2010-01-01

In this paper, we reviewed the current development and patents for the application of high-brightness and high-efficiency white light-emitting diode (LED). The high-efficiency GaN nanostructures, such as disk, pyramid, and rod were grown on LiAlO(2) substrate by plasma-assisted molecular-beam epitaxy, and a model was developed to demonstrate the growth of the GaN nanostructures. Based on the results, the GaN disk p-n junction was designed for the application of high brightness and high efficiency white LED.

Electroluminescence of a polythiophene molecular wire suspended between a metallic surface and the tip of a scanning tunneling microscope.

PubMed

Reecht, Gaël; Scheurer, Fabrice; Speisser, Virginie; Dappe, Yannick J; Mathevet, Fabrice; Schull, Guillaume

2014-01-31

The electroluminescence of a polythiophene wire suspended between a metallic surface and the tip of a scanning tunneling microscope is reported. Under positive sample voltage, the spectral and voltage dependencies of the emitted light are consistent with the fluorescence of the wire junction mediated by localized plasmons. This emission is strongly attenuated for the opposite polarity. Both emission mechanism and polarity dependence are similar to what occurs in organic light emitting diodes (OLED) but at the level of a single molecular wire.

Achieving a stable time response in polymeric radiation sensors under charge injection by X-rays.

PubMed

Intaniwet, Akarin; Mills, Christopher A; Sellin, Paul J; Shkunov, Maxim; Keddie, Joseph L

2010-06-01

Existing inorganic materials for radiation sensors suffer from several drawbacks, including their inability to cover large curved areas, lack of tissue-equivalence, toxicity, and mechanical inflexibility. As an alternative to inorganics, poly(triarylamine) (PTAA) diodes have been evaluated for their suitability for detecting radiation via the direct creation of X-ray induced photocurrents. A single layer of PTAA is deposited on indium tin oxide (ITO) substrates, with top electrodes selected from Al, Au, Ni, and Pd. The choice of metal electrode has a pronounced effect on the performance of the device; there is a direct correlation between the diode rectification factor and the metal-PTAA barrier height. A diode with an Al contact shows the highest quality of rectifying junction, and it produces a high X-ray photocurrent (several nA) that is stable during continuous exposure to 50 kV Mo Kalpha X-radiation over long time scales, combined with a high signal-to-noise ratio with fast response times of less than 0.25 s. Diodes with a low band gap, 'Ohmic' contact, such as ITO/PTAA/Au, show a slow transient response. This result can be explained by the build-up of space charge at the metal-PTAA interface, caused by a high level of charge injection due to X-ray-induced carriers. These data provide new insights into the optimum selection of metals for Schottky contacts on organic materials, with wider applications in light sensors and photovoltaic devices.

A carbon nanotube optical rectenna

NASA Astrophysics Data System (ADS)

Sharma, Asha; Singh, Virendra; Bougher, Thomas L.; Cola, Baratunde A.

2015-12-01

An optical rectenna—a device that directly converts free-propagating electromagnetic waves at optical frequencies to direct current—was first proposed over 40 years ago, yet this concept has not been demonstrated experimentally due to fabrication challenges at the nanoscale. Realizing an optical rectenna requires that an antenna be coupled to a diode that operates on the order of 1 PHz (switching speed on the order of 1 fs). Diodes operating at these frequencies are feasible if their capacitance is on the order of a few attofarads, but they remain extremely difficult to fabricate and to reliably couple to a nanoscale antenna. Here we demonstrate an optical rectenna by engineering metal-insulator-metal tunnel diodes, with a junction capacitance of ˜2 aF, at the tip of vertically aligned multiwalled carbon nanotubes (˜10 nm in diameter), which act as the antenna. Upon irradiation with visible and infrared light, we measure a d.c. open-circuit voltage and a short-circuit current that appear to be due to a rectification process (we account for a very small but quantifiable contribution from thermal effects). In contrast to recent reports of photodetection based on hot electron decay in a plasmonic nanoscale antenna, a coherent optical antenna field appears to be rectified directly in our devices, consistent with rectenna theory. Finally, power rectification is observed under simulated solar illumination, and there is no detectable change in diode performance after numerous current-voltage scans between 5 and 77 °C, indicating a potential for robust operation.

A carbon nanotube optical rectenna.

PubMed

Sharma, Asha; Singh, Virendra; Bougher, Thomas L; Cola, Baratunde A

2015-12-01

An optical rectenna--a device that directly converts free-propagating electromagnetic waves at optical frequencies to direct current--was first proposed over 40 years ago, yet this concept has not been demonstrated experimentally due to fabrication challenges at the nanoscale. Realizing an optical rectenna requires that an antenna be coupled to a diode that operates on the order of 1 PHz (switching speed on the order of 1 fs). Diodes operating at these frequencies are feasible if their capacitance is on the order of a few attofarads, but they remain extremely difficult to fabricate and to reliably couple to a nanoscale antenna. Here we demonstrate an optical rectenna by engineering metal-insulator-metal tunnel diodes, with a junction capacitance of ∼2 aF, at the tip of vertically aligned multiwalled carbon nanotubes (∼10 nm in diameter), which act as the antenna. Upon irradiation with visible and infrared light, we measure a d.c. open-circuit voltage and a short-circuit current that appear to be due to a rectification process (we account for a very small but quantifiable contribution from thermal effects). In contrast to recent reports of photodetection based on hot electron decay in a plasmonic nanoscale antenna, a coherent optical antenna field appears to be rectified directly in our devices, consistent with rectenna theory. Finally, power rectification is observed under simulated solar illumination, and there is no detectable change in diode performance after numerous current-voltage scans between 5 and 77 °C, indicating a potential for robust operation.

High Aspect Ratio Semiconductor Heterojunction Solar Cells

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

Redwing, Joan; Mallouk, Tom; Mayer, Theresa

2013-05-17

The project focused on the development of high aspect ratio silicon heterojunction (HARSH) solar cells. The solar cells developed in this study consisted of high density vertical arrays of radial junction silicon microwires/pillars formed on Si substrates. Prior studies have demonstrated that vertical Si wire/pillar arrays enable reduced reflectivity and improved light trapping characteristics compared to planar solar cells. In addition, the radial junction structure offers the possibility of increased carrier collection in solar cells fabricated using material with short carrier diffusion lengths. However, the high junction and surface area of radial junction Si wire/pillar array devices can be problematicmore » and lead to increased diode leakage and enhanced surface recombination. This study investigated the use of amorphous hydrogenated Si in the form of a heterojunction-intrinsic-thin layer (HIT) structure as a junction formation method for these devices. The HIT layer structure has widely been employed to reduce surface recombination in planar crystalline Si solar cells. Consequently, it was anticipated that it would also provide significant benefits to the performance of radial junction Si wire/pillar array devices. The overall goals of the project were to demonstrate a HARSH cell with a HIT-type structure in the radial junction Si wire/pillar array configuration and to develop potentially low cost pathways to fabricate these devices. Our studies demonstrated that the HIT structure lead to significant improvements in the open circuit voltage (V oc>0.5) of radial junction Si pillar array devices compared to devices fabricated using junctions formed by thermal diffusion or low pressure chemical vapor deposition (LPCVD). In addition, our work experimentally demonstrated that the radial junction structure lead to improvements in efficiency compared to comparable planar devices for devices fabricated using heavily doped Si that had reduced carrier diffusion lengths. Furthermore, we made significant advances in employing the bottom-up vapor-liquid-solid (VLS) growth technique for the fabrication of the Si wire arrays. Our work elucidated the effects of growth conditions and substrate pattern geometry on the growth of large area Si microwire arrays grown with SiCl4. In addition, we also developed a process to grow p-type Si nanowire arrays using aluminum as the catalyst metal instead of gold. Finally, our work demonstrated the feasibility of growing vertical arrays of Si wires on non-crystalline glass substrates using polycrystalline Si template layers. The accomplishments demonstrated in this project will pave the way for future advances in radial junction wire array solar cells.« less

Modeling Changes in Measured Conductance of Thin Boron Carbide Semiconducting Films Under Irradiation

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

Peterson, George G.; Wang, Yongqiang; Ianno, N. J.

Semiconducting, p-type, amorphous partially dehydrogenated boron carbide films (a-B 10C 2+x:H y) were deposited utilizing plasma enhanced chemical vapor deposition (PECVD) onto n-type silicon thus creating a heterojunction diode. A model was developed for the conductance of the device as a function of perturbation frequency (f) that incorporates changes of the electrical properties for both the a-B 10C 2+x:H y film and the silicon substrate when irradiated. The virgin model has 3 independent variables (R1, C1, R3), and 1 dependent variable (f). These samples were then irradiated with 200 keV He + ions, and the conductance model was matched tomore » the measured data. It was found that initial irradiation (0.1 displacements per atom (dpa) equivalent) resulted in a decrease in the parallel junction resistance parameter from 6032 Ω to 2705 Ω. Further irradiation drastically increased the parallel junction resistance parameter to 39000 Ω (0.2 dpa equivalent), 77440 Ω (0.3 dpa equivalent), and 190000 Ω (0.5 dpa equivalent). It is believed that the initial irradiation causes type inversion of the silicon substrate changing the original junction from a p-n to a p-p+ with a much lower barrier height leading to a lower junction resistance component between the a-B 10C 2+x:H y and irradiated silicon. In addition, it was found that after irradiation, a second parallel resistor and capacitor component is required for the model, introducing 2 additional independent variables (R2, C2). This is interpreted as the junction between the irradiated and virgin silicon near ion end of range.« less

Modeling Changes in Measured Conductance of Thin Boron Carbide Semiconducting Films Under Irradiation

DOE PAGES

Peterson, George G.; Wang, Yongqiang; Ianno, N. J.; ...

2016-11-09

Semiconducting, p-type, amorphous partially dehydrogenated boron carbide films (a-B 10C 2+x:H y) were deposited utilizing plasma enhanced chemical vapor deposition (PECVD) onto n-type silicon thus creating a heterojunction diode. A model was developed for the conductance of the device as a function of perturbation frequency (f) that incorporates changes of the electrical properties for both the a-B 10C 2+x:H y film and the silicon substrate when irradiated. The virgin model has 3 independent variables (R1, C1, R3), and 1 dependent variable (f). These samples were then irradiated with 200 keV He + ions, and the conductance model was matched tomore » the measured data. It was found that initial irradiation (0.1 displacements per atom (dpa) equivalent) resulted in a decrease in the parallel junction resistance parameter from 6032 Ω to 2705 Ω. Further irradiation drastically increased the parallel junction resistance parameter to 39000 Ω (0.2 dpa equivalent), 77440 Ω (0.3 dpa equivalent), and 190000 Ω (0.5 dpa equivalent). It is believed that the initial irradiation causes type inversion of the silicon substrate changing the original junction from a p-n to a p-p+ with a much lower barrier height leading to a lower junction resistance component between the a-B 10C 2+x:H y and irradiated silicon. In addition, it was found that after irradiation, a second parallel resistor and capacitor component is required for the model, introducing 2 additional independent variables (R2, C2). This is interpreted as the junction between the irradiated and virgin silicon near ion end of range.« less

Study of Bulk and Elementary Screw Dislocation Assisted Reverse Breakdown in Low-Voltage (less than 250 V) 4H-SiC p(+)n Junction diodes. Part 1; DC Properties

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Huang, Wei; Dudley, Michael

1998-01-01

Given the high density (approx. 10(exp 4)/sq cm) of elementary screw dislocations (Burgers vector = 1c with no hollow core) in commercial SiC wafers and epilayers, all appreciable current (greater than 1 A) SiC power devices will likely contain elementary screw dislocations for the foreseeable future. It is therefore important to ascertain the electrical impact of these defects, particularly in high-field vertical power device topologies where SiC is expected to enable large performance improvements in solid-state high-power systems. This paper compares the DC-measured reverse-breakdown characteristics of low-voltage (less than 250 V) small-area (less than 5 x 10(exp -4)/sq cm) 4H-SiC p(+)n diodes with and without elementary screw dislocations. Compared to screw dislocation-free devices, diodes containing elementary screw dislocations exhibited higher pre-breakdown reverse leakage currents, softer reverse breakdown I-V knees, and highly localized microplasmic breakdown current filaments. The observed localized 4H-SiC breakdown parallels microplasmic breakdowns observed in silicon and other semiconductors, in which space-charge effects limit current conduction through the local microplasma as reverse bias is increased.

Study of Bulk and Elementary Screw Dislocation Assisted Reverse Breakdown in Low-Voltage (<250 V) 4H-SiC p+n Junction Diodes - Part 1: DC Properties

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Huang, Wei; Dudley, Michael

1999-01-01

Given the high density (approx. 10(exp 4)/sq cm) of elementary screw dislocations (Burgers vector = lc with no hollow core) in commercial SiC wafers and epilayers, all appreciable current (greater than 1 A) SiC power devices will likely contain elementary screw dislocations for the foreseeable future. It is therefore important to ascertain the electrical impact of these defects, particularly in high-field vertical power device topologies where SiC is expected to enable large performance improvements in solid-state high-power systems. This paper compares the DC-measured reverse-breakdown characteristics of low-voltage (less than 250 V) small-area (less than 5 x 10(exp -4) sq cm) 4H-SiC p(+)n diodes with and without elementary screw dislocations. Compared to screw dislocation-free devices, diodes containing elementary screw dislocations exhibited higher pre-breakdown reverse leakage currents, softer reverse breakdown I-V knees, and highly localized microplasmic breakdown current filaments. The observed localized 4H-SiC breakdown parallels microplasmic breakdowns observed in silicon and other semiconductors, in which space-charge effects limit current conduction through the local microplasma as reverse bias is increased.

Annealing of irradiated n+p InP buried homojunctions

NASA Technical Reports Server (NTRS)

Walters, Robert J.; Summers, Geoffrey P.; Timmons, M. L.; Venkatasubramanian, R.; Hancock, J. A.; Hills, J. S.

1994-01-01

At the last SPRAT conference, the Naval Research Laboratory (NRL) presented results from two experiments. One studied n+p diffused junction (DJ) InP solar cells, and the other studied n+p shallow homojunction (SHJ) InP mesa diodes grown by metalorganic chemical vapor deposition (MOCVD). The former work showed that a DJ solar cell in which the maximum power P(sub max) had been degraded by nearly 80 percent under irradiation recovered completely under short circuit illumination at 450K. The recovery was accompanied by the removal of all but one of the radiation-induced defect levels. The latter work, on the other hand, showed that the radiation-induced defects in the SHJ diodes did not anneal until the temperature reached 650K. These results suggest that an irradiated DJ solar cell, under illumination, will anneal at a temperature 200K lower than an irradiated SHJ cell. This is an unexpected result considering the similarity of the devices. The goal of the present research is to explain this different behavior. This paper investigates two points which arose from the previous studies. The first point is that the DJ cells were annealed under illumination while the SHJ diodes were annealed without bias. The second point investigated here is that the emitters of the DJ and SHJ devices were significantly different.

Characterization of Lateral Structure of the p-i-n Diode for Thin-Film Silicon Solar Cell.

PubMed

Kiaee, Zohreh; Joo, Seung Ki

2018-03-01

The lateral structure of the p-i-n diode was characterized for thin-film silicon solar cell application. The structure can benefit from a wide intrinsic layer, which can improve efficiency without increasing cell thickness. Compared with conventional thin-film p-i-n cells, the p-i-n diode lateral structure exploited direct light irradiation on the absorber layer, one-side contact, and bifacial irradiation. Considering the effect of different carrier lifetimes and recombinations, we calculated efficiency parameters by using a commercially available simulation program as a function of intrinsic layer width, as well as the distance between p/i or n/i junctions to contacts. We then obtained excellent parameter values of 706.52 mV open-circuit voltage, 24.16 mA/Cm2 short-circuit current, 82.66% fill factor, and 14.11% efficiency from a lateral cell (thickness = 3 μm; intrinsic layer width = 53 μm) in monofacial irradiation mode (i.e., only sunlight from the front side was considered). Simulation results of the cell without using rear-side reflector in bifacial irradiation mode showed 11.26% front and 9.72% rear efficiencies. Our findings confirmed that the laterally structured p-i-n cell can be a potentially powerful means for producing highly efficient, thin-film silicon solar cells.

Silicon controlled rectifier polyphase bridge inverter commutated with gate-turn-off thyristor

NASA Technical Reports Server (NTRS)

Edwards, Dean B. (Inventor); Rippel, Wally E. (Inventor)

1986-01-01

A polyphase SCR inverter (10) having N switching poles, each comprised of two SCR switches (1A, 1B; 2A, 2B . . . NA, NB) and two diodes (D1B; D1B; D2A, D2B . . . DNA, DNB) in series opposition with saturable reactors (L1A, L1B; L2A, L2B . . . LNA, LNB) connecting the junctions between the SCR switches and diodes to an output terminal (1, 2 . . . 3) is commutated with only one GTO thyristor (16) connected between the common negative terminal of a dc source and a tap of a series inductor (14) connected to the positive terminal of the dc source. A clamp winding (22) and diode (24) are provided, as is a snubber (18) which may have its capacitance (c) sized for maximum load current divided into a plurality of capacitors (C.sub.1, C.sub.2 . . . C.sub.N), each in series with an SCR switch S.sub.1, S.sub.2 . . . S.sub.N). The total capacitance may be selected by activating selected switches as a function of load current. A resistor 28 and SCR switch 26 shunt reverse current when the load acts as a generator, such as a motor while braking.

Towards substrate engineering of graphene-silicon Schottky diode photodetectors.

PubMed

Selvi, Hakan; Unsuree, Nawapong; Whittaker, Eric; Halsall, Matthew P; Hill, Ernie W; Thomas, Andrew; Parkinson, Patrick; Echtermeyer, Tim J

2018-02-15

Graphene-silicon Schottky diode photodetectors possess beneficial properties such as high responsivities and detectivities, broad spectral wavelength operation and high operating speeds. Various routes and architectures have been employed in the past to fabricate devices. Devices are commonly based on the removal of the silicon-oxide layer on the surface of silicon by wet-etching before deposition of graphene on top of silicon to form the graphene-silicon Schottky junction. In this work, we systematically investigate the influence of the interfacial oxide layer, the fabrication technique employed and the silicon substrate on the light detection capabilities of graphene-silicon Schottky diode photodetectors. The properties of devices are investigated over a broad wavelength range from near-UV to short-/mid-infrared radiation, radiation intensities covering over five orders of magnitude as well as the suitability of devices for high speed operation. Results show that the interfacial layer, depending on the required application, is in fact beneficial to enhance the photodetection properties of such devices. Further, we demonstrate the influence of the silicon substrate on the spectral response and operating speed. Fabricated devices operate over a broad spectral wavelength range from the near-UV to the short-/mid-infrared (thermal) wavelength regime, exhibit high photovoltage responses approaching 10 6 V W -1 and short rise- and fall-times of tens of nanoseconds.

Optimum Design of ARC-less InGaP/GaAs DJ Solar Cell with Hetero Tunnel Junction

NASA Astrophysics Data System (ADS)

Abbasian, Sobhan; Sabbaghi-Nadooshan, Reza

2018-07-01

The operation of hetero In0.49Ga0.51P-Al0.7Ga0.3As tunnel diodes has been evaluated, and an approach for optimizing the back surface field (BSF) layer of a InGaP/GaAs dual-junction (DJ) solar cell developed. The results show that the hetero In0.49Ga0.51P-Al0.7Ga0.3As tunnel diode transferred more electrons and holes and showed less recombination between the top and bottom cells with increased efficiency ( η) in the InGaP/GaAs DJ solar cell. To achieve higher open-circuit voltage ( V oc), GaAs semiconductor was investigated to match with Al0.52In0.48P with bandgap of 2.4 eV, and replacement of the bottom cell in the InGaP/GaAs DJ solar cell with such an Al0.52In0.48P-GaAs heterojunction increased the photogeneration in this region. In the next step, addition of a BSF layer to the top cell required two BSF layers in the bottom cell to optimize the short-circuit current ( J sc) and η. The thickness and doping of the BSF layers were increased to obtain the highest η for the cell. The proposed structure was then compared with previous works. The proposed structure yielded V oc = 2.46 V, J sc = 30 mA/cm2, fill factor (FF) = 88.61%, and η = 65.51% under AM1.5 (1 sun) illumination.

High Current ESD Test of Advanced Triple Junction Solar Array Coupon

NASA Technical Reports Server (NTRS)

Wright, Kenneth H., Jr.; Schneider, Todd A.; Vaughn, Jason A.; Hoang, Bao; Wong, Frankie

2015-01-01

A test was conducted on an Advanced Triple Junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by SSL. The ATJ coupon was a small, 4-cell, two-string configuration that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The coupon has many attributes of the flight design; e.g., substrate structure with graphite face sheets, integrated by-pass diodes, cell interconnects, RTV grout, wire routing, etc. The objective of the present test was to evaluate the performance of the coupon after being subjected to induced electrostatic discharge testing at two string voltages (100 V, 150 V) and four array current (1.65 A, 2.0 A, 2.475 A, and 3.3 A). An ESD test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc flashover circuitry. A total of 73 primary arcs were obtained that included 7 temporary sustained arcs (TSA) events. The durations of the TSAs ranged from 50 micros to 2.9 ms. All TSAs occurred at a string voltage of 150 V. Post-test Large Area Pulsed Solar Simulator (LAPSS), Dark I-V, and By-Pass Diode tests showed that no degradation occurred due to the TSA events. In addition, the post-test insulation resistance measured was > 50 G-ohms between cells and substrate. These test results indicate a robust design for application to a high-current, high-power mission application.

High Current ESD Test of Advanced Triple Junction Solar Array Coupon

NASA Technical Reports Server (NTRS)

Wright, K. H.; Schneider, T. A.; Vaughn, J. A.; Hoang, B.; Wong, F.

2014-01-01

A test was conducted on an Advanced Triple Junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by SSL. The ATJ coupon was a small, 4-cell, two-string configuration that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The coupon has many attributes of the flight design; e.g., substrate structure with graphite face sheets, integrated by-pass diodes, cell interconnects, RTV grout, wire routing, etc. The objective of the present test was to evaluate the performance of the coupon after being subjected to induced electrostatic discharge testing at two string voltages (100 V, 150 V) and four array current (1.65 A, 2.0 A, 2.475 A, and 3.3 A). An ESD test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc flashover circuitry. A total of 73 primary arcs were obtained that included 7 temporary sustained arcs (TSA) events. The durations of the TSAs ranged from 50 µs to 2.9 ms. All TSAs occurred at a string voltage of 150 V. Post-test Large Area Pulsed Solar Simulator (LAPSS), Dark I-V, and By-Pass Diode tests showed that no degradation occurred due to the TSA events. In addition, the post-test insulation resistance measured was > 50 G-ohms between cells and substrate. These test results indicate a robust design for application to a high-current, high-power mission application.

High Current ESD Test of Advanced Triple Junction Solar Array Coupon

NASA Technical Reports Server (NTRS)

Wright, Kenneth H., Jr.; Schneider, Todd A.; Vaughn, Jason A.; Hoang, Bao; Wong, Frankie

2014-01-01

Testing was conducted on an Advanced Triple Junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by Space Systems/Loral, LLC (SSL). The ATJ coupon was a small, 4-cell, two-string configuration that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The coupon has many attributes of the flight design; e.g., substrate structure with graphite face sheets, integrated by-pass diodes, cell interconnects, RTV grout, wire routing, etc. The objective of the present test was to evaluate the performance of the coupon after being subjected to induced electrostatic discharge (ESD) testing at two string voltages (100 V, 150 V) and four array currents (1.65 A, 2.0 A, 2.475 A, and 3.3 A). An ESD test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc flashover circuitry. A total of 73 primary arcs were obtained that included 7 temporary sustained arcs (TSA) events. The durations of the TSAs ranged from 50 micro-seconds to 2.75 milli-seconds. All TSAs occurred at a string voltage of 150 V. Post-test Large Area Pulsed Solar Simulator (LAPSS), Dark I-V, and By-Pass Diode tests showed that no degradation occurred due to the TSA events. In addition, the post-test insulation resistance measured was > 50 G-ohms between cells and substrate. These test results indicate a robust design for application to a high-current, high-power mission.

Safety assessment of near infrared light emitting diodes for diffuse optical measurements

PubMed Central

Bozkurt, Alper; Onaral, Banu

2004-01-01

Background Near infrared (NIR) light has been used widely to monitor important hemodynamic parameters in tissue non-invasively. Pulse oximetry, near infrared spectroscopy, and diffuse optical tomography are examples of such NIR light-based applications. These and other similar applications employ either lasers or light emitting diodes (LED) as the source of the NIR light. Although the hazards of laser sources have been addressed in regulations, the risk of LED sources in such applications is still unknown. Methods Temperature increase of the human skin caused by near infrared LED has been measured by means of in-vivo and in-vitro experiments. Effects of the conducted and radiated heat in the temperature increase have been analyzed separately. Results Elevations in skin temperature up to 10°C have been observed. The effect of radiated heat due to NIR absorption is low – less than 0.5°C – since emitted light power is comparable to the NIR part of sunlight. The conducted heat due to semiconductor junction of the LED can cause temperature increases up to 9°C. It has been shown that adjusting operational parameters by amplitude modulating or time multiplexing the LED decreases the temperature increase of the skin significantly. Conclusion In this study, we demonstrate that the major risk source of the LED in direct contact with skin is the conducted heat of the LED semiconductor junction, which may cause serious skin burns. Adjusting operational parameters by amplitude modulating or time multiplexing the LED can keep the LED within safe temperature ranges. PMID:15035670

Spin-Torque Diode Effect in Magnetic Tunnel Junctions

NASA Astrophysics Data System (ADS)

Suzuki, Yoshishige

2007-03-01

Spin-injection magnetization switching (SIMS) technique [1] made it possible to control magnetization by a direct current. A discovery of spontaneous rf oscillation from CPP-GMR nano-pillars and a real time observation of the switching process have revealed essential amplification function of a precession in the magnetic nano-pillars under a direct current [2]. Beside of those progresses, developments of giant tunneling magneto-resistive (GTMR) effect using an MgO barrier [3] made it possible to utilize a very large resistance change according to the magnetization switching. In this talk, several attempts to utilize interplay between spin-torque and giant-TMR effect will be presented referring to a ``spin-torque diode effect'' [4] and other properties such like rf noise control and possible signal amplification using magnetic tunnel junctions (MTJs). [1] J. C. Slonczewski, J. Magn. Magn. Mater. 159, L1 (1996) , L. Berger, Phys. Rev. B 54, 9353 (1996), and E. B. Myers, et al., Science 285, 867 (1999). [2] S. I. Kiselev et al., Nature 425, 380 (2003), I. N. Krivorotov et al., Science, 307, 228 (2005). [3] W. Wulfhekel, et al. Appl. Phys. Lett. 78, 509--511 (2001), M. Bowen, et al. Appl. Phys. Lett. 79, 1655--1657 (2001), J. Faure-Vincent, et al. Appl. Phys. Lett. 82, 4507--4509 (2003), S. Yuasa, et al., Jpn. J. Appl. Phys. Part 2, 43, L588 (2004), S. Yuasa, et al., Nature Mat. 3, 868 (2004), S. S. P. Parkin et al., Nature Mat. 3, 862 (2004), and D. D. Djayaprawira et al., Appl. Phys. Lett. 86, 092502 (2005). [4] A. A. Tulapurkar, et al., Nature, 438, 339 (2005).

Magnetically modulated electroluminescence from hybrid organic/inorganic light-emitting diodes based on electron donor-acceptor exciplex blends

NASA Astrophysics Data System (ADS)

Pang, Zhiyong; Baniya, Sangita; Zhang, Chuang; Sun, Dali; Vardeny, Z. Valy

2016-03-01

We report room temperature magnetically modulated electroluminescence from a hybrid organic/inorganic light-emitting diode (h-OLED), in which an inorganic magnetic tunnel junction (MTJ) with large room temperature magnetoresistance is coupled to an N,N,N ',N '-Tetrakis(4-methoxyphenyl)benzidine (MeO-TPD): tris-[3-(3-pyridyl)mesityl]borane (3TPYMB) [D-A] based OLED that shows thermally activated delayed luminescence. The exciplex-based OLED provides two spin-mixing channels: upper energy channel of polaron pairs and lower energy channel of exciplexes. In operation, the large resistance mismatch between the MTJ and OLED components is suppressed due to the non-linear I-V characteristic of the OLED. This leads to enhanced giant magneto-electroluminescence (MEL) at room temperature. We measured MEL of ~ 75% at ambient conditions. Supported by SAMSUNG Global Research Outreach (GRO) program, and also by the NSF-Material Science & Engineering Center (MRSEC) program at the University of Utah (DMR-1121252).

Synergetic electrode architecture for efficient graphene-based flexible organic light-emitting diodes

PubMed Central

Lee, Jaeho; Han, Tae-Hee; Park, Min-Ho; Jung, Dae Yool; Seo, Jeongmin; Seo, Hong-Kyu; Cho, Hyunsu; Kim, Eunhye; Chung, Jin; Choi, Sung-Yool; Kim, Taek-Soo; Lee, Tae-Woo; Yoo, Seunghyup

2016-01-01

Graphene-based organic light-emitting diodes (OLEDs) have recently emerged as a key element essential in next-generation displays and lighting, mainly due to their promise for highly flexible light sources. However, their efficiency has been, at best, similar to that of conventional, indium tin oxide-based counterparts. We here propose an ideal electrode structure based on a synergetic interplay of high-index TiO2 layers and low-index hole-injection layers sandwiching graphene electrodes, which results in an ideal situation where enhancement by cavity resonance is maximized yet loss to surface plasmon polariton is mitigated. The proposed approach leads to OLEDs exhibiting ultrahigh external quantum efficiency of 40.8 and 62.1% (64.7 and 103% with a half-ball lens) for single- and multi-junction devices, respectively. The OLEDs made on plastics with those electrodes are repeatedly bendable at a radius of 2.3 mm, partly due to the TiO2 layers withstanding flexural strain up to 4% via crack-deflection toughening. PMID:27250743

Modification of the Tunneling Barrier in Polymer Light-Emitting Diodes Through Doping

NASA Astrophysics Data System (ADS)

Romero, Danilo

1996-03-01

Improvement in the performance of polymer light-emitting diodes (LEDs) is achieved upon light doping of the organic layer. The LEDs betrayed symmetrical electrical and light-emission characteristics. Their turn-on voltage is lower and their external quantum and power conversion efficiencies are higher by nearly an order of magnitude when compared with devices that utilized a nominally undoped organic layer. We attributed these results to the modification of the tunneling barrier in metal-polymer-metal junctions due to the presence of an induced polarization electric field associated with the ionized dopant counterions and charged polymer chains. Acknowledgement: I would like to thank my collaborators in this work: B. Cesar and B. François at the Institut Charles Sadron in Strasbourg, France and M. Schaer and especially Professor Libero Zuppiroli who has been the main driving force for the direction of the polymer LED project in Lausanne. I would like to acknowledge the financial support of the Optics Priority Program in Switzerland.

Improving lumen maintenance by nanopore array dispersed quantum dots for on-chip light emitting diodes

NASA Astrophysics Data System (ADS)

Chen, Quan; Yang, Fan; Wan, Renzhuo; Fang, Dong

2017-12-01

The temperature stability of quantum dots (QDs), which is crucial for integrating into high power light-emitting diodes (LEDs) in the on-chip configuration, needs to be further improved. In this letter, we report warm white LEDs, where CdSe/ZnS nanoparticles were incorporated into a porous anodic alumina (PAA) matrix with a chain structure by the self-assembly method. Experiments demonstrate that the QD concentration range in toluene solvent from 1% mg/μl to 1.2% mg/μl in combination with the PAA matrix shows the best luminous property. To verify the reliability of the as-prepared device, a comparison experiment was conducted. It indicates excellent lumen maintenance of the light source and less chromaticity coordinate shift under accelerated life testing conditions. Experiments also prove that optical depreciation was only up to 4.6% of its initial value after the 1500 h aging test at the junction temperature of 76 °C.

Characterization of high-dose and high-energy implanted gate and source diode and analysis of lateral spreading of p gate profile in high voltage SiC static induction transistors

NASA Astrophysics Data System (ADS)

Onose, Hidekatsu; Kobayashi, Yutaka; Onuki, Jin

2017-03-01

The effect of the p gate dose on the characteristics of the gate-source diode in SiC static induction transistors (SIT) was investigated. It was found that a dose of 1.5 × 1014 cm-2 yields a pn junction breakdown voltage higher than 60 V and good forward characteristics. A normally on SiC SIT was fabricated and demonstrated. A blocking voltage higher than 2.0 kV at a gate-source voltage of -50 V and on-resistance of 70 mΩ cm2 were obtained. Device simulations were performed to investigate the effect of the lateral spreading. By comparing the measured I-V curves with simulation results, the lateral spreading factor was estimated to be about 0.5. The lateral spreading detrimentally affected the electrical properties of the SIT made using implantations at energies higher than 1 MeV.

Inelastic transport and low-bias rectification in a single-molecule diode.

PubMed

Hihath, Joshua; Bruot, Christopher; Nakamura, Hisao; Asai, Yoshihiro; Díez-Pérez, Ismael; Lee, Youngu; Yu, Luping; Tao, Nongjian

2011-10-25

Designing, controlling, and understanding rectification behavior in molecular-scale devices has been a goal of the molecular electronics community for many years. Here we study the transport behavior of a single molecule diode, and its nonrectifying, symmetric counterpart at low temperatures, and at both low and high biases to help elucidate the electron-phonon interactions and transport mechanisms in the rectifying system. We find that the onset of current rectification occurs at low biases, indicating a significant change in the elastic transport pathway. However, the peaks in the inelastic electron tunneling (IET) spectrum are antisymmetric about zero bias and show no significant changes in energy or intensity in the forward or reverse bias directions, indicating that despite the change in the elastic transmission probability there is little impact on the inelastic pathway. These results agree with first principles calculations performed to evaluate the IETS, which also allow us to identify which modes are active in the single molecule junction.

Simultaneous light emission and detection of InGaN/GaN multiple quantum well diodes for in-plane visible light communication

NASA Astrophysics Data System (ADS)

Wang, Yongjin; Xu, Yin; Yang, Yongchao; Gao, Xumin; Zhu, Bingcheng; Cai, Wei; Yuan, Jialei; Zhang, Rong; Zhu, Hongbo

2017-03-01

This paper presents the design, fabrication, and experimental characterization of monolithically integrated p-n junction InGaN/GaN multiple quantum well diodes (MQWDs) and suspended waveguides. Suspended MQWDs can be used as transmitters and receivers simultaneously, and suspended waveguides are used for light coupling to create an in-plane visible light communication system. Compared to the waveguide with separation trench, the calculated total light efficiency is increased from 18% to 22% for the continuous waveguide. The MQWDs are characterized by their typical current-voltage performance, and the pulse excitation measurements confirm that the InGaN/GaN MQWDs can achieve the light emission and photodetection at the same time. The photocurrent measurements indicate that the photocurrent is modulated by a bias voltage and that the photons are being supplied from another transmitter. An experimental demonstration is presented showing that the proposed device works well for in-plane full-duplex communication using visible light.

Design of p-type cladding layers for tunnel-injected UV-A light emitting diodes

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

Zhang, Yuewei; Krishnamoorthy, Sriram; Akyol, Fatih

Here, we discuss the engineering of p-AlGaN cladding layers for achieving efficient tunnel-injected III-Nitride ultraviolet light emitting diodes (UV LEDs) in the UV-A spectral range. We show that the capacitance-voltage measurements can be used to estimate the compensation and doping in the p-AlGaN layers located between the multi-quantum well region and the tunnel junction layer. By increasing the p-type doping concentration to overcome the background compensation, on-wafer external quantum efficiency and wall-plug efficiency of 3.37% and 1.62%, respectively, were achieved for the tunnel-injected UV LEDs emitting at 325 nm. We also show that interband tunneling hole injection can be usedmore » to realize UV LEDs without any acceptor doping. The work discussed here provides new understanding of hole doping and transport in AlGaN-based UV LEDs and demonstrates the excellent performance of tunnel-injected LEDs for the UV-A wavelength range.« less

Design of p-type cladding layers for tunnel-injected UV-A light emitting diodes

DOE PAGES

Zhang, Yuewei; Krishnamoorthy, Sriram; Akyol, Fatih; ...

2016-11-09

Here, we discuss the engineering of p-AlGaN cladding layers for achieving efficient tunnel-injected III-Nitride ultraviolet light emitting diodes (UV LEDs) in the UV-A spectral range. We show that the capacitance-voltage measurements can be used to estimate the compensation and doping in the p-AlGaN layers located between the multi-quantum well region and the tunnel junction layer. By increasing the p-type doping concentration to overcome the background compensation, on-wafer external quantum efficiency and wall-plug efficiency of 3.37% and 1.62%, respectively, were achieved for the tunnel-injected UV LEDs emitting at 325 nm. We also show that interband tunneling hole injection can be usedmore » to realize UV LEDs without any acceptor doping. The work discussed here provides new understanding of hole doping and transport in AlGaN-based UV LEDs and demonstrates the excellent performance of tunnel-injected LEDs for the UV-A wavelength range.« less

Effect of interface voids on electroluminescence colors for ZnO microdisk/p-GaN heterojunction light-emitting diodes

NASA Astrophysics Data System (ADS)

Mo, Ran; Choi, Ji Eun; Kim, Hyeong Jin; Jeong, Junseok; Kim, Jong Chan; Kim, Yong-Jin; Jeong, Hu Young; Hong, Young Joon

2017-10-01

This study investigates the influence of voids on the electroluminescence (EL) emission color of ZnO microdisk/p-GaN heterojunction light-emitting diodes (LEDs). For this study, position-controlled microdisk arrays were fabricated on patterned p-GaN via wet chemical epitaxy of ZnO, and specifically, the use of trisodium citrate dihydrate (TCD) yielded high-density voids at the bottom of the microdisk. Greenish yellow or whitish blue EL was emitted from the microdisk LEDs formed with or without TCD, respectively, at reverse-bias voltages. Such different EL colors were found to be responsible for the relative EL intensity ratio between indigo and yellow emission peaks, which were originated from radiative recombination at p-GaN and ZnO, respectively. The relative EL intensity between dichromatic emissions is discussed in terms of (i) junction edge effect provoked by interfacial voids and (ii) electron tunneling probability depending on the depletion layer geometry.

InGaN/GaN blue light emitting diodes using Al-doped ZnO grown by atomic layer deposition as a current spreading layer

NASA Astrophysics Data System (ADS)

Kong, Bo Hyun; Cho, Hyung Koun; Kim, Mi Yang; Choi, Rak Jun; Kim, Bae Kyun

2011-07-01

For the fabrication of InGaN/GaN multiple quantum well-based blue light emitting diodes (LEDs) showing large area emission, transparent Al-doped ZnO (AZO) films grown by atomic layer deposition at relatively low temperatures were introduced as current spreading layers. These AZO films with an Al content of 3 at% showed a low electrical resistivity of <10 -3-10 -4 Ω cm, a high carrier concentration of >10 20 cm -3, and an excellent optical transmittance of ˜85%, in spite of the low growth temperature. The deposition of the AZO film induced an intense blue emission from the whole surface of the p-GaN and weak ultraviolet emission from the n-AZO and p-GaN junction. At an injection current of 50 mA, the output powers of the blue LEDs were 1760 and 1440 mcd for the samples with AZO thicknesses of 100 and 300 nm, respectively.

Solution of the hydrodynamic device model using high-order non-oscillatory shock capturing algorithms. [for junction diodes simulation

NASA Technical Reports Server (NTRS)

Fatemi, Emad; Osher, Stanley; Jerome, Joseph

1991-01-01

A micron n+ - n - n+ silicon diode is simulated via the hydrodynamic model for carrier transport. The numerical algorithms employed are for the non-steady case, and a limiting process is used to reach steady state. The simulation employs shock capturing algorithms, and indeed shocks, or very rapid transition regimes, are observed in the transient case for the coupled system, consisting of the potential equation and the conservation equations describing charge, momentum, and energy transfer for the electron carriers. These algorithms, termed essentially nonoscillatory, were successfully applied in other contexts to model the flow in gas dynamics, magnetohydrodynamics, and other physical situations involving the conservation laws in fluid mechanics. The method here is first order in time, but the use of small time steps allows for good accuracy. Runge-Kutta methods allow one to achieve higher accuracy in time if desired. The spatial accuracy is of high order in regions of smoothness.

Synergetic electrode architecture for efficient graphene-based flexible organic light-emitting diodes.

PubMed

Lee, Jaeho; Han, Tae-Hee; Park, Min-Ho; Jung, Dae Yool; Seo, Jeongmin; Seo, Hong-Kyu; Cho, Hyunsu; Kim, Eunhye; Chung, Jin; Choi, Sung-Yool; Kim, Taek-Soo; Lee, Tae-Woo; Yoo, Seunghyup

2016-06-02

Graphene-based organic light-emitting diodes (OLEDs) have recently emerged as a key element essential in next-generation displays and lighting, mainly due to their promise for highly flexible light sources. However, their efficiency has been, at best, similar to that of conventional, indium tin oxide-based counterparts. We here propose an ideal electrode structure based on a synergetic interplay of high-index TiO2 layers and low-index hole-injection layers sandwiching graphene electrodes, which results in an ideal situation where enhancement by cavity resonance is maximized yet loss to surface plasmon polariton is mitigated. The proposed approach leads to OLEDs exhibiting ultrahigh external quantum efficiency of 40.8 and 62.1% (64.7 and 103% with a half-ball lens) for single- and multi-junction devices, respectively. The OLEDs made on plastics with those electrodes are repeatedly bendable at a radius of 2.3 mm, partly due to the TiO2 layers withstanding flexural strain up to 4% via crack-deflection toughening.

Graphene/h-BN/GaAs sandwich diode as solar cell and photodetector.

PubMed

Li, Xiaoqiang; Lin, Shisheng; Lin, Xing; Xu, Zhijuan; Wang, Peng; Zhang, Shengjiao; Zhong, Huikai; Xu, Wenli; Wu, Zhiqian; Fang, Wei

2016-01-11

In graphene/semiconductor heterojunction, the statistic charge transfer between graphene and semiconductor leads to decreased junction barrier height and limits the Fermi level tuning effect in graphene, which greatly affects the final performance of the device. In this work, we have designed a sandwich diode for solar cells and photodetectors through inserting 2D hexagonal boron nitride (h-BN) into graphene/GaAs heterostructure to suppress the static charge transfer. The barrier height of graphene/GaAs heterojunction can be increased from 0.88 eV to 1.02 eV by inserting h-BN. Based on the enhanced Fermi level tuning effect with interface h-BN, through adopting photo-induced doping into the device, power conversion efficiency (PCE) of 10.18% has been achieved for graphene/h-BN/GaAs compared with 8.63% of graphene/GaAs structure. The performance of graphene/h-BN/GaAs based photodetector is also improved with on/off ratio increased by one magnitude compared with graphene/GaAs structure.

Electronic properties of defects in silicon and related materials

NASA Astrophysics Data System (ADS)

Mitromara, Niki

Efforts in the current semiconductor industry are focused on the production of smaller, more efficient and inexpensive devices of higher packing density. As silicon is the dominant semiconductor implemented for the fabrication of the majority of semiconductor devices, perpetual research has focused on the improvement of its properties and the realisation of the most efficient structures. This thesis presents the electrical characterisation of two different diode structures that are important for the present and future generations of electronic devices.The first part of the thesis is focused on the electrical characterisation of Ultra-Shallow Junction (USJs) Si diodes. Both p+n and n+p USJ structures that contained different implants were examined. These were very highly doped and intended to simulate the situation where a doping well is formed after heavy doping in Si for the fabrication of transistors currently used in Complementary-Metal-Oxide-Semiconductor (CMOS) technology. The implanted USJ diodes were provided by NXP, Belgium and contact deposition was performed before their electrical characterisation as part of this project. Subsequently the p+n and n+p USJ diodes were characterised by the use of Capacitance-Voltage (CV), Current-Voltage (IV), Deep Level Transient Spectroscopy (DLTS) and high resolution Laplace DLTS (LDLTS). DLTS and LDLTS are very powerful spectroscopic techniques for the profiling of defects in the bandgap of a semiconductor as well as for the identification of the electrical signatures of these defects. Transient-Enhanced Diffusion (TED) related defects were detected in these diodes as the presence of mainly carbon-related interstitial complexes was observed. In addition, certain vacancy or vacancy-dopant related levels were also discerned.The second part of this thesis presents the electrical characterisation from Schottky p-diamond/p-Si and p-diamond/n-Si p-n diodes. These diodes were readily provided, grown by the Chemical Vapour Deposition (CVD) technique, for the electrical characterisation that was performed as part of this project. The purpose of characterising both Schottky and p-n diamond on Si diodes was to detect defects near the surface of the films and near the interface with Si and hence provide a comparison between defects present at the beginning and end of growth. More defects were found near the interface with Si and the majority of observed defects were related to extended defects while the presence of grain boundaries in polycrystalline diamond was discussed.

On-chip photonic system using suspended p-n junction InGaN/GaN multiple quantum wells device and multiple waveguides

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

Wang, Yongjin, E-mail: wangyj@njupt.edu.cn; Zhu, Guixia; Gao, Xumin

We propose, fabricate, and characterize the on-chip integration of suspended p-n junction InGaN/GaN multiple quantum wells (MQWs) device and multiple waveguides on the same GaN-on-silicon platform. The integrated devices are fabricated via a wafer-level process and exhibit selectable functionalities for diverse applications. As the suspended p-n junction InGaN/GaN MQWs device operates under a light emitting diode (LED) mode, part of the light emission is confined and guided by the suspended waveguides. The in-plane propagation along the suspended waveguides is measured by a micro-transmittance setup. The on-chip data transmission is demonstrated for the proof-of-concept photonic integration. As the suspended p-n junctionmore » InGaN/GaN MQWs device operates under photodiode mode, the light is illuminated on the suspended waveguides with the aid of the micro-transmittance setup and, thus, coupled into the suspended waveguides. The guided light is finally sensed by the photodiode, and the induced photocurrent trace shows a distinct on/off switching performance. These experimental results indicate that the on-chip photonic integration is promising for the development of sophisticated integrated photonic circuits in the visible wavelength region.« less

Third order intermodulation distortion in HTS Josephson Junction downconverter at 12GHz

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

Suzuki, Katsumi; Hayashi, Kunihiko; Fujimoto, Manabu

1994-12-31

Here the authors first report on the microwave characteristics of the third order intermodulation distortion(IMD3) in High-Tc Superconductor (HTS) Josephson Junction (JJ) Downconverter at 12GHz. They have successfully developed high quality nonlinear YBCO microbridge Josephson junctions for such an active MMIC as a mixer with RF, LO, IF and bias filters, which have been fabricated on (100) MgO substrates with 20mm x 20mm x 0.5mm dimensions. The minimum conversion loss of the JJ mixer is 11 dB at very small local microwave input power LO= {minus}20dBm which is two order less than Schottky diode mixer. Consequently, this small optimum LOmore » power gives the small RF input power at which the output IF power of the YBCO mixer saturates. Two-tone third-order intercept point(IP3) performance is a significantly important figure of merit typically used to define linearity of devices and circuits. The RF input power = {minus}15dBm at the IP3 point is obtained for the YBCO mixer at 15K and LO = 10.935GHz with {minus}22dBm. The have successfully measured the dependence of IMD3 on temperature, bias current and LO power.« less

A fast and zero-biased photodetector based on GaTe-InSe vertical 2D p-n heterojunction

NASA Astrophysics Data System (ADS)

Feng, W.; Jin, Z.; Yuan, J.; Zhang, J.; Jia, S.; Dong, L.; Yoon, J.; Zhou, L.; Vajtai, R.; Tour, J. M.; Ajayan, P. M.; Hu, P.; Lou, J.

2018-04-01

p-n junctions serve as the building blocks for fundamental semiconductor devices, such as solar cells, light-emitting diodes (LEDs) and photodetectors. With recent studies unveiling the excellent optoelectronic properties of two-dimensional (2D) semiconductors, they are considered to be superb candidates for high performance p-n junctions. Here, we fabricate a vertical GaTe-InSe van der Waals (vdWs) p-n heterojunction by a PDMS-assisted transfer technique without etching. The fabricated p-n heterojunction shows gate-tunable current-rectifying behavior with a rectification factor reaching 1000. In addition, it features fast photodetection under zero bias as well as a high power conversion efficiency (PCE). Under 405 nm laser excitation, the zero-biased photodetector shows a high responsivity of 13.8 mA W-1 as well as a high external quantum efficiency (EQE) of 4.2%. Long-term stability is also observed and a response time of 20 µs is achieved due to stable and fast carrier transit through the built-in electric field in the depletion region. Fast and efficient charge separation in the vertical 2D p-n junction paves the way for developing 2D photodetectors with zero dark current, high speed and low power consumption.

Narrowband light detection via internal quantum efficiency manipulation of organic photodiodes

NASA Astrophysics Data System (ADS)

Armin, Ardalan; Jansen-van Vuuren, Ross D.; Kopidakis, Nikos; Burn, Paul L.; Meredith, Paul

2015-02-01

Spectrally selective light detection is vital for full-colour and near-infrared (NIR) imaging and machine vision. This is not possible with traditional broadband-absorbing inorganic semiconductors without input filtering, and is yet to be achieved for narrowband absorbing organic semiconductors. We demonstrate the first sub-100 nm full-width-at-half-maximum visible-blind red and NIR photodetectors with state-of-the-art performance across critical response metrics. These devices are based on organic photodiodes with optically thick junctions. Paradoxically, we use broadband-absorbing organic semiconductors and utilize the electro-optical properties of the junction to create the narrowest NIR-band photoresponses yet demonstrated. In this context, these photodiodes outperform the encumbent technology (input filtered inorganic semiconductor diodes) and emerging technologies such as narrow absorber organic semiconductors or quantum nanocrystals. The design concept allows for response tuning and is generic for other spectral windows. Furthermore, it is material-agnostic and applicable to other disordered and polycrystalline semiconductors.

The role of geometry in nanoscale rectennas for rectification and energy conversion

NASA Astrophysics Data System (ADS)

Miskovsky, N. M.; Cutler, P. H.; Mayer, A.; Willis, B. G.; Zimmerman, D. T.; Weisel, G. J.; Chen, James M.; Sullivan, T. E.; Lerner, P. B.

2013-09-01

We have previously presented a method for optical rectification that has been demonstrated both theoretically and experimentally and can be used for the development of a practical rectification and energy conversion device for the electromagnetic spectrum including the visible portion. This technique for optical frequency rectification is based, not on conventional material or temperature asymmetry as used in MIM or Schottky diodes, but on a purely geometric property of the antenna tip or other sharp edges that may be incorporated on patch antennas. This "tip" or edge in conjunction with a collector anode providing connection to the external circuit constitutes a tunnel junction. Because such devices act as both the absorber of the incident radiation and the rectifier, they are referred to as "rectennas." Using current nanofabrication techniques and the selective Atomic Layer Deposition (ALD) process, junctions of 1 nm can be fabricated, which allow for rectification of frequencies up to the blue portion of the spectrum (see Section 2).

Effect of 100 MeV Si7+ ions' irradiation on Pd/n-GaAs Schottky diodes

NASA Astrophysics Data System (ADS)

Sinha, O. P.

2017-12-01

Pd/n-GaAs realized devices (junction made on a virgin substrate prior to irradiation) and Pd/n-GaAs fabricated devices (junction realized after the virgin substrate irradiation) have been irradiated with 100 MeV Si7+ ions for the varying fluence of 1012-1013 ions/cm2. The devices have been characterized by I-V and C-V techniques for an electrical response. The electrical characterization of these devices shows the presence of interfacial layer. Moreover, the C-V characteristics show strong frequency dependence behavior, which indicates the involvement of interfacial charge layer with deep electron states. The hydrogenation of these devices has not caused any significant change in the electrical (I-V and C-V) characteristics. The observed results have been discussed in the realm of radiation-induced defects, which cause the carrier removal and compensation phenomena to cause the observed high resistivity and filling and unfilling of these traps' level to cause strong frequency dependence behavior.

Effects of P3HT concentration on the electrical properties of the Au/PEDOT:PSS/P3HT/n-GaN hybrid junction structure

NASA Astrophysics Data System (ADS)

Noh, Ji-yeon; Lee, Ha Young; Lim, Kyung-won; Ahn, Hyung Soo; Yi, Sam Nyung; Jeon, Hunsoo; Shin, Min Jeong; Yu, Young Moon; Ha, Dong Han

2017-09-01

An inorganic-organic hybrid junction has been fabricated by spin coating the p-type poly(3- hexylthiophene-2,5-diyl)(P3HT) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS) on an n-type GaN layer. The GaN layer was formed on Al2O3 by metal organic chemical vapor deposition(MOCVD) method. To investigate the effects of P3HT concentration on the electrical properties, we changed P3HT solution concentration and speed of spin coater. The currentvoltage (I-V ) characteristic of Au/PEDOT:PSS/P3HT/n-GaN shows rectifying behavior. The I-V characteristic was examined in the frame work of the thermionic emission model. The most proper rectifying behavior was obtained for 0.6 wt% and thickness below 65 nm of P3HT used diode. We expect that such hybrid structures, suitably developed, might be enable the fabrication of highquality electronic and optoelectronic devices.

Nanowelding and patterning of silver nanowires via mask-free atmospheric cold plasma-jet scanning

NASA Astrophysics Data System (ADS)

Liu, Lang; Li, Han-Yu; Ye, Dong; Yu, Yao; Liu, Lin; Wu, Yue

2017-06-01

Silver nanowire (AgNW) thin film is a promising candidate to replace traditional indium tin oxide in optoelectronics applications. To date however, the widespread application of AgNW thin film is limited by the weak point contacts between individual AgNWs and the lack of facile patterning techniques. Here, we demonstrate a novel and facile method to not only nanoweld AgNW junctions but also pattern AgNW thin films via mask-free cold plasma-jet scanning in ambient conditions. After the plasma-jet nanowelding treatment, the morphology of AgNWs change substantially and the junctions are welded together. The nanowelded AgNWs-based thin film shows enhanced electrical and mechanical properties. On the other hand, after the plasma-jet patterning treatment, the AgNWs are etched and transformed into separated large particles. Different kinds of patterns are produced via this patterning technique. At last, a simple light emitting diode circuit is fabricated to demonstrate the suitability of the nanowelded and patterned AgNW electrodes for flexible electronic devices.

Electrical and optical characterization of n-InAsSb/n-GaSb heterojunctions

NASA Astrophysics Data System (ADS)

Lackner, D.; Martine, M.; Cherng, Y. T.; Steger, M.; Walukiewicz, W.; Thewalt, M. L. W.; Mooney, P. M.; Watkins, S. P.

2010-01-01

We report the electrical properties of n-InAsSb/n-GaSb heterojunctions as a function of the GaSb doping concentration. Because of the staggered type II band alignment, strong electron accumulation occurs on the InAsSb side. For low GaSb doping, depletion occurs on the GaSb side resulting in a Schottky-like junction as previously reported. As the GaSb doping increases, the built-in voltage as well as depletion width decreases as shown using self-consistent simulations. For GaSb doping levels above 5×1017 cm-3, the junction loses its rectifying properties due to tunneling. Under zero and reverse bias voltage, the photoresponse of these diodes is solely due to the photovoltaic effect in the GaSb depletion region. For forward bias voltages >400 mV, we also observed a photoconductive response from the InAsSb layer. The proposed physical mechanism is quite different from the one suggested in a recent paper.

A superconducting tunnel junction receiver for millimeter-wave astronomy

NASA Technical Reports Server (NTRS)

Pan, S. K.; Kerr, A. R.

1986-01-01

The development and construction of an ultralow noise heterodyne receiver for millimeter wave astronomy is described along with its use for 115.3 GHz Co line observations. The receiver uses a Superconductor-Insulator-Superconductor (SIS) quasiparticle tunnel junction mixer to convert the millimeter wave signal to a microwave intermediate frequency. Experiments aimed at quantitative verification of J. R. Tucker's quantum mixer theory are studied, to see whether it could be used as the basis for the design of a practical receiver. The experimental results were in excellent agreement with the theory, assuming the three frequency approximation. Infinite available gain and negative output resistance were observed for the first time, nonclassical effects which are not seen in conventional diode mixers. Using Tucker's theory, an SIS receiver was then designed and constructed. At 115 GHz, the single sideband receiver noise temperature is 83K, the lowest ever reported in this frequency range. A CO survey toward Cygnus-X region, using this SIS receiver on the Columbia-GISS 4 ft. telescope, is also described.

Narrowband Light Detection via Internal Quantum Efficiency Manipulation of Organic Photodiodes

DOE PAGES

Armin, A.; Jansen-van Vuuren, R. D.; Kopidakis, N.; ...

2015-02-01

Spectrally selective light detection is vital for full-colour and near-infrared (NIR) imaging and machine vision. This is not possible with traditional broadband-absorbing inorganic semiconductors without input filtering, and is yet to be achieved for narrowband absorbing organic semiconductors. We demonstrate the first sub-100 nm full-width-at-half-maximum visible-blind red and NIR photodetectors with state-of-the-art performance across critical response metrics. These devices are based on organic photodiodes with optically thick junctions. Paradoxically, we use broadband-absorbing organic semiconductors and utilize the electro-optical properties of the junction to create the narrowest NIR-band photoresponses yet demonstrated. In this context, these photodiodes outperform the encumbent technology (inputmore » filtered inorganic semiconductor diodes) and emerging technologies such as narrow absorber organic semiconductors or quantum nanocrystals. The design concept allows for response tuning and is generic for other spectral windows. Furthermore, it is materialagnostic and applicable to other disordered and polycrystalline semiconductors.« less