Powered by Deep Web Technologies
Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


1

Ga Air Compressor, Ga Air Compressor Products, Ga Air ...  

U.S. Energy Information Administration (EIA)

Ga Air Compressor, You Can Buy Various High Quality Ga Air Compressor Products from Global Ga Air Compressor Suppliers and Ga Air Compressor ...

2

China Ga Air Compressor, China Ga Air Compressor Products ...  

U.S. Energy Information Administration (EIA)

China Ga Air Compressor, China Ga Air Compressor Suppliers and Manufacturers Directory - Source a Large Selection of Ga Air Compressor Products at ...

3

Ba-Ga (Barium - Gallium)  

Science Conference Proceedings (OSTI)

Ba-Ga crystallographic data...Ba-Ga crystallographic data Phase Composition, wt% Ga Pearson symbol Space group (Ba) 0 cI 2 Im m Ba 10 Ga 4.8 cF 176 Fd m Ba 8 Ga 7 30.8 cP 60 P 2 1 3 BaGa 2 50.4 hP 3 P 6/ mmm BaGa 4 67 tI 10 I 4/ mmm (Ga) 100 hP 2 P 6 3 / mmc...

4

Cooperative Effects in the Incorporation of Nitrogen into GaAsN ...  

Science Conference Proceedings (OSTI)

This study looks to the cooperative reactions between ammonia and alternative nitrogen sources, such as UDMH, TBHy and TBAm. In particular, the cooperative  ...

5

Ga-Zr (Gallium - Zirconium)  

Science Conference Proceedings (OSTI)

Ga-Zr crystallographic data...Ga 5 Zr 3 44.0 oC 32 Cmcm Ga 3 Zr 2 47 oF 40 Fdd 2 βGaZr 56.7 � � αGaZr 56.7 tI 16 I 4 1 / amd Ga 4 Zr 5 62.1 hP 18 P 6 3 / mcm Ga 2 Zr 3 66 tP 10 P 4/ mbm Ga 3 Zr 5 68.6 hP 16 P 6 3 / mcm GaZr 2 72.4 tI 12 I 4/ mcm (βZr) ~94 to 100 cI 2 Im m (αZr) 99.4 to 100 hP 2 P 6 3 / mmc...

6

AlGaN/GaN-based power semiconductor switches  

E-Print Network (OSTI)

AlGaN/GaN-based high-electron-mobility transistors (HEMTs) have great potential for their use as high efficiency and high speed power semiconductor switches, thanks to their high breakdown electric field, mobility and ...

Lu, Bin, Ph. D. Massachusetts Institute of Technology

2013-01-01T23:59:59.000Z

7

Polarization-engineered GaN/InGaN/GaN tunnel diodes  

E-Print Network (OSTI)

We report on the design and demonstration of polarization-engineered GaN/InGaN/GaN tunnel junction diodes with high current density and low tunneling turn-on voltage. Wentzel-Kramers-Brillouin (WKB) calculations were used to model and design tunnel junctions with narrow bandgap InGaN-based barrier layers. N-polar p-GaN/In0.33Ga0.67N/n-GaN heterostructure tunnel diodes were grown using molecular beam epitaxy. Efficient zero bias tunneling turn-on with a high current density of 118 A/cm2 at a reverse bias of 1V, reaching a maximum current density up to 9.2 kA/cm2 were obtained. These results represent the highest current density reported in III-nitride tunnel junctions, and demonstrate the potential of III-nitride tunnel devices for a broad range of optoelectronic and electronic applications.

Sriram Krishnamoorthy; Digbijoy N. Nath; Fatih Akyol; Pil Sung Park; Michele Esposto; Siddharth Rajan

2010-08-24T23:59:59.000Z

8

GaN High Power Devices  

SciTech Connect

A brief review is given of recent progress in fabrication of high voltage GaN and AlGaN rectifiers, GaN/AlGaN heterojunction bipolar transistors, GaN heterostructure and metal-oxide semiconductor field effect transistors. Improvements in epitaxial layer quality and in fabrication techniques have led to significant advances in device performance.

PEARTON,S.J.; REN,F.; ZHANG,A.P.; DANG,G.; CAO,X.A.; LEE,K.P.; CHO,H.; GILA,B.P.; JOHNSON,J.W.; MONIER,C.; ABERNATHY,C.R.; HAN,JUNG; BACA,ALBERT G.; CHYI,J.-I.; LEE,C.-M.; NEE,T.-E.; CHUO,C.-C.; CHI,G.C.; CHU,S.N.G.

2000-07-17T23:59:59.000Z

9

Category:Savannah, GA | Open Energy Information  

Open Energy Info (EERE)

Savannah, GA Savannah, GA Jump to: navigation, search Go Back to PV Economics By Location Media in category "Savannah, GA" The following 16 files are in this category, out of 16 total. SVFullServiceRestaurant Savannah GA Georgia Power Co.png SVFullServiceRestauran... 80 KB SVHospital Savannah GA Georgia Power Co.png SVHospital Savannah GA... 80 KB SVLargeHotel Savannah GA Georgia Power Co.png SVLargeHotel Savannah ... 75 KB SVLargeOffice Savannah GA Georgia Power Co.png SVLargeOffice Savannah... 82 KB SVMediumOffice Savannah GA Georgia Power Co.png SVMediumOffice Savanna... 85 KB SVMidriseApartment Savannah GA Georgia Power Co.png SVMidriseApartment Sav... 80 KB SVOutPatient Savannah GA Georgia Power Co.png SVOutPatient Savannah ... 84 KB SVPrimarySchool Savannah GA Georgia Power Co.png

10

Category:Atlanta, GA | Open Energy Information  

Open Energy Info (EERE)

GA GA Jump to: navigation, search Go Back to PV Economics By Location Media in category "Atlanta, GA" The following 16 files are in this category, out of 16 total. SVFullServiceRestaurant Atlanta GA Georgia Power Co.png SVFullServiceRestauran... 81 KB SVHospital Atlanta GA Georgia Power Co.png SVHospital Atlanta GA ... 81 KB SVLargeHotel Atlanta GA Georgia Power Co.png SVLargeHotel Atlanta G... 74 KB SVLargeOffice Atlanta GA Georgia Power Co.png SVLargeOffice Atlanta ... 82 KB SVMediumOffice Atlanta GA Georgia Power Co.png SVMediumOffice Atlanta... 84 KB SVMidriseApartment Atlanta GA Georgia Power Co.png SVMidriseApartment Atl... 82 KB SVOutPatient Atlanta GA Georgia Power Co.png SVOutPatient Atlanta G... 83 KB SVPrimarySchool Atlanta GA Georgia Power Co.png SVPrimarySchool Atlant...

11

GA SNC Solar | Open Energy Information  

Open Energy Info (EERE)

GA SNC Solar Jump to: navigation, search Name GA-SNC Solar Place Nevada Sector Solar Product Nevada-based PV project developer and joint venture of GA-Solar North America and...

12

GA-AL-SC | Department of Energy  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

GA-AL-SC GA-AL-SC GA-AL-SC October 1, 2012 ALA-1-N Wholesale Power Rate Schedule Area: PowerSouth Energy Cooperative System: Georgia-Alabama-South Carolina October 1, 2012 Duke-1-E Wholesale Power Rate Schedule Area: Duke On-System System: Georgia-Alabama-South Carolina October 1, 2012 Duke-2-E Wholesale Power Rate Schedule Area: Central System: Georgia-Alabama-South Carolina October 1, 2012 Duke-3-E Wholesale Power Rate Schedule Area: None System: Georgia-Alabama-South Carolina October 1, 2012 Duke-4-E Wholesale Power Rate Schedule Area: Duke Self-Schedulers System: Georgia-Alabama-South Carolina October 1, 2012 MISS-1-N Wholesale Power Rate Schedule Area: South Mississippi Electric Power Association System: Georgia-Alabama-South Carolina October 1, 2012 Pump-1-A Wholesale Power Rate Schedule

13

Atomic structure and energy spectrum of Ga(As,P)/GaP heterostructures  

Science Conference Proceedings (OSTI)

The atomic structure and energy spectrum of Ga(As,P)/GaP heterostructures were studied. It was shown that the deposition of GaAs of the same nominal thickness leads to the formation of pseudomorphic GaAs/GaP quantum wells (QW), fully relaxed GaAs/GaP self-assembled quantum dots (SAQDs), or pseudomorphic GaAsP/GaP SAQDs depending on the growth temperature. We demonstrate that the atomic structure of Ga(As,P)/GaP heterostructures is ruled by the temperature dependence of adatom diffusion rate and GaAs-GaP intermixing. The band alignment of pseudomorphic GaAs/GaP QW and GaAsP/GaP SAQDs is shown to be of type II, in contrast to that of fully relaxed GaAs/GaP SAQDs, which have the band alignment of type I with the lowest electronic states at the indirect L valley of the GaAs conduction band.

Abramkin, D. S.; Putyato, M. A.; Budennyy, S. A.; Gutakovskii, A. K.; Semyagin, B. R.; Preobrazhenskii, V. V.; Shamirzaev, T. S. [A. V. Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Pr. Lavrentyeva 13, 630090 Novosibirsk (Russian Federation); Kolomys, O. F.; Strelchuk, V. V. [V. E. Lashkarev Institute of Semiconductor Physics NAS of Ukraine, Pr. Nauki 41, 03028 Kiev (Ukraine)

2012-10-15T23:59:59.000Z

14

General Atomics (GA) Fusion News: A New Spin on Understanding...  

NLE Websites -- All DOE Office Websites (Extended Search)

General Atomics (GA) Fusion News: A New Spin on Understanding Plasma Confinement American Fusion News Category: General Atomics (GA) Link: General Atomics (GA) Fusion News: A New...

15

Rodefeld Landfill Ga Biomass Facility | Open Energy Information  

Open Energy Info (EERE)

Rodefeld Landfill Ga Biomass Facility Jump to: navigation, search Name Rodefeld Landfill Ga Biomass Facility Facility Rodefeld Landfill Ga Sector Biomass Facility Type Landfill Gas...

16

RECIPIENT:Gwinnett Co, GA  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Gwinnett Co, GA Gwinnett Co, GA u.s DEPARUIENT OFENllRGY EERE PROJECT MANAGEMENT CENTER NllPA DETERl\JINATION PROJECr TITLE: Gwinnett Co, GA EEC8G Page I or2 STATE: GA Funding Opportunity Announcement Number Procu~ment Instrument Number N[PA Control Number CID Number DE-EEOOOOS05.005 0 Based on my review ortbe information concerning tbe proposed action, as NEPA Compliance Officer (authorized under DOE Order 4SI.IA), I bave made the following determination: ex, EA, EIS APPENDIX AND NUMBER: Description: 8 5.1 Actions to conserve energy, demonstrate potential energy conservation, and promote energy-efficiency that do not increase the indoor concentrations of potentially harmful substances. These actions may involve financial and technical assistance to individuals (such as builders, owners, consultants, designers), organizations (such as utilities), and state

17

Intense terahertz emission from molecular beam epitaxy-grown GaAs/GaSb(001)  

SciTech Connect

Intense terahertz (THz) electromagnetic wave emission was observed in undoped GaAs thin films deposited on (100) n-GaSb substrates via molecular beam epitaxy. GaAs/n-GaSb heterostructures were found to be viable THz sources having signal amplitude 75% that of bulk p-InAs. The GaAs films were grown by interruption method during the growth initiation and using various metamorphic buffer layers. Reciprocal space maps revealed that the GaAs epilayers are tensile relaxed. Defects at the i-GaAs/n-GaSb interface were confirmed by scanning electron microscope images. Band calculations were performed to infer the depletion region and electric field at the i-GaAs/n-GaSb and the air-GaAs interfaces. However, the resulting band calculations were found to be insufficient to explain the THz emission. The enhanced THz emission is currently attributed to a piezoelectric field induced by incoherent strain and defects.

Sadia, Cyril P.; Laganapan, Aleena Maria; Agatha Tumanguil, Mae; Estacio, Elmer; Somintac, Armando; Salvador, Arnel [National Institute of Physics, University of the Philippines Diliman, Quezon City 1101 (Philippines); Que, Christopher T. [Physics Department, De La Salle University, 2401 Taft Avenue, Manila 1004 (Philippines); Yamamoto, Kohji; Tani, Masahiko [Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507 (Japan)

2012-12-15T23:59:59.000Z

18

Molecular beam epitaxy growth of GaAsBi/GaAs/AlGaAs separate confinement heterostructures  

Science Conference Proceedings (OSTI)

GaAsBi/GaAs/AlGaAs separate confinement heterostructures are grown using an asymmetric temperature profile due to the low optimal growth temperature of GaAsBi; the bottom AlGaAs barrier is grown at 610 Degree-Sign C, while the GaAsBi quantum well and the top AlGaAs barrier are grown at 320 Degree-Sign C. Cross-sectional transmission electron microscopy and room temperature photoluminescence measurements indicate that this approach results in samples with excellent structural and optical properties. The high quality of the low temperature AlGaAs barrier is attributed to the presence of Bi on the surface as indicated by a (1 Multiplication-Sign 3) surface reconstruction persisting throughout the low temperature growth.

Fan Dongsheng; Yu Shuiqing [Department of Electrical Engineering, University of Arkansas, Fayetteville, Arkansas 72701 (United States); Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701 (United States); Zeng Zhaoquan; Hu Xian; Dorogan, Vitaliy G.; Li Chen; Benamara, Mourad; Hawkridge, Michael E.; Mazur, Yuriy I.; Salamo, Gregory J. [Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701 (United States); Johnson, Shane R. [School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287-6206 (United States); Wang, Zhiming M. [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China)

2012-10-29T23:59:59.000Z

19

New GaInP/GaAs/GaInAs, Triple-Bandgap, Tandem Solar Cell for High-Efficiency Terrestrial Concentrator Systems  

DOE Green Energy (OSTI)

GaInP/GaAs/GaInAs three-junction cells are grown in an inverted configuration on GaAs, allowing high quality growth of the lattice matched GaInP and GaAs layers before a grade is used for the 1-eV GaInAs layer. Using this approach an efficiency of 37.9% was demonstrated.

Kurtz, S.; Wanlass, M.; Kramer, C.; Young, M.; Geisz, J.; Ward, S.; Duda, A.; Moriarty, T.; Carapella, J.; Ahrenkiel, P.; Emery. K.; Jones, K.; Romero, M.; Kibbler, A.; Olson, J.; Friedman, D.; McMahon, W.; Ptak, A.

2005-11-01T23:59:59.000Z

20

Ultraviolet electroabsorption modulator based on AlGaN/GaN multiple quantum wells  

E-Print Network (OSTI)

Ultraviolet electroabsorption modulator based on AlGaN/GaN multiple quantum wells I. Friel, C online 20 June 2005 An ultraviolet electroabsorption modulator based on AlGaN/GaN quantum wells is demonstrated. Enhanced excitonic absorption in the quantum wells at around 3.48 eV was achieved using

Moustakas, Theodore

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Self-aligned AlGaN/GaN transistors for sub-mm wave applications  

E-Print Network (OSTI)

This thesis describes work done towards realizing self-aligned AlGaN/GaN high electron mobility transistors (HEMTs). Self-aligned transistors are important for improving the frequency of AlGaN/GaN HEMTs by reducing source ...

Saadat, Omair I

2010-01-01T23:59:59.000Z

22

Effect of buffer structures on AlGaN/GaN high electron mobility transistor reliability  

Science Conference Proceedings (OSTI)

AlGaN/GaN high electron mobility transistors (HEMTs) with three different types of buffer layers, including a GaN/AlGaN composite layer, or 1 or 2 lm GaN thick layers, were fabricated and their reliability compared. The HEMTs with the thick GaN buffer layer showed the lowest critical voltage (Vcri) during off-state drain step-stress, but this was increased by around 50% and 100% for devices with the composite AlGaN/GaN buffer layers or thinner GaN buffers, respectively. The Voff - state for HEMTs with thin GaN and composite buffers were 100 V, however, this degraded to 50 60V for devices with thick GaN buffers due to the difference in peak electric field near the gate edge. A similar trend was observed in the isolation breakdown voltage measurements, with the highest Viso achieved based on thin GaN or composite buffer designs (600 700 V), while a much smaller Viso of 200V was measured on HEMTs with the thick GaN buffer layers. These results demonstrate the strong influence of buffer structure and defect density on AlGaN/GaN HEMT performance and reliability.

Liu, L. [University of Florida, Gainesville; Xi, Y. Y. [University of Florida, Gainesville; Ren, F. [University of Florida; Pearton, S. J. [University of Florida; Laboutin, O. [Kopin Corporation, Taunton, MA; Cao, Yu [Kopin Corporation, Taunton, MA; Johnson, Wayne J. [Kopin Corporation, Taunton, MA; Kravchenko, Ivan I [ORNL

2012-01-01T23:59:59.000Z

23

Effect of dislocations on electron mobility in AlGaN/GaN and AlGaN/AlN/GaN heterostructures  

Science Conference Proceedings (OSTI)

Al{sub x}Ga{sub 1-x}N/GaN (x = 0.06, 0.12, 0.24) and AlGaN/AlN/GaN heterostructures were grown on 6 H-SiC, GaN-on-sapphire, and free-standing GaN, resulting in heterostructures with threading dislocation densities of {approx}2 Multiplication-Sign 10{sup 10}, {approx}5 Multiplication-Sign 10{sup 8}, and {approx}5 Multiplication-Sign 10{sup 7} cm{sup -2}, respectively. All growths were performed under Ga-rich conditions by plasma-assisted molecular beam epitaxy. Dominant scattering mechanisms with variations in threading dislocation density and sheet concentration were indicated through temperature-dependent Hall measurements. The inclusion of an AlN interlayer was also considered. Dislocation scattering contributed to reduced mobility in these heterostructures, especially when sheet concentration was low or when an AlN interlayer was present.

Kaun, Stephen W.; Burke, Peter G.; Kyle, Erin C. H.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Wong, Man Hoi; Mishra, Umesh K. [Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

2012-12-24T23:59:59.000Z

24

InGaAsN/GaAs heterojunction for multi-junction solar cells  

DOE Patents (OSTI)

An InGaAsN/GaAs semiconductor p-n heterojunction is disclosed for use in forming a 0.95-1.2 eV bandgap photodetector with application for use in high-efficiency multi-junction solar cells. The InGaAsN/GaAs p-n heterojunction is formed by epitaxially growing on a gallium arsenide (GaAs) or germanium (Ge) substrate an n-type indium gallium arsenide nitride (InGaAsN) layer having a semiconductor alloy composition In.sub.x Ga.sub.1-x As.sub.1-y N.sub.y with 0GaAs layer, with the InGaAsN and GaAs layers being lattice-matched to the substrate. The InGaAsN/GaAs p-n heterojunction can be epitaxially grown by either molecular beam epitaxy (MBE) or metalorganic chemical vapor deposition (MOCVD). The InGaAsN/GaAs p-n heterojunction provides a high open-circuit voltage of up to 0.62 volts and an internal quantum efficiency of >70%.

Kurtz, Steven R. (Albuquerque, NM); Allerman, Andrew A. (Albuquerque, NM); Klem, John F. (Albuquerque, NM); Jones, Eric D. (Edgewood, NM)

2001-01-01T23:59:59.000Z

25

Magnetism and transport properties of epitaxial Fe-Ga thin films on GaAs(001)  

SciTech Connect

Epitaxial Fe-Ga thin films in disordered bcc {alpha}-Fe crystal structure (A2) have been grown on GaAs(001) by molecular beam epitaxy. The saturated magnetization (M{sub S}) decreased from 1371 to 1105 kA/m with increasing Ga concentration from 10.5 to 24.3 % at room temperature. The lattice parameter increased with the increase in Ga content because of the larger atomic radius of Ga atom than that of Fe. The increase in carrier density with Ga content caused in lower resistivity.

Duong Anh Tuan; Shin, Yooleemi; Cho, Sunglae [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Dang Duc Dung [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Department of General Physics, School of Engineering Physics, Ha Noi University of Science and Technology, 1 Dai Co Viet road, Ha Noi (Viet Nam); Vo Thanh Son [Centers for Nanobioenineering and Spintronics, Chungnam National University, Daejon 350-746 (Korea, Republic of)

2012-04-01T23:59:59.000Z

26

passivation of InGaN/GaN nanopillar light emitting diodes.  

E-Print Network (OSTI)

??Recently, InGaN/GaN based blue light emitting diodes (LEDs) have become widely available commercially, but their efficiency is reduced due to the quantum confined Stark effect… (more)

Choi, Won

2013-01-01T23:59:59.000Z

27

Detailed Analysis of Temperature Characteristics of InGaP/InGaAs ...  

Science Conference Proceedings (OSTI)

The current-voltage (I-V) characteristics of single-junction solar cells (InGaP, InGaAs, Ge solar cells) were measured at various temperatures. The structures of  ...

28

AlGaAsSb/GaSb Distributed Bragg Reflectors Grown by Organometallic Vapor Phase Epitaxy  

SciTech Connect

The first AlGaAsSb/GaSb quarter-wave distributed Bragg reflectors grown by metallic vapor phase epitaxy are reported. The peak reflectance is 96% for a 10-period structure.

C.A. Wang; C.J. Vineis; D.R. Calawa

2002-02-13T23:59:59.000Z

29

GA 30+-90 / GA 37-90 VSD: Oil-injected rotary screw ...  

U.S. Energy Information Administration (EIA)

GA 30+-90 / GA 37-90 VSD: Oil-injected rotary screw compressors, 30-90 kW / 40-125 hp,Kunshan CompAirs Machinery Plant Co.,Ltd is the leading air ...

30

GA 11+-30/GA 15-30 VSD: Oil-injected rotary screw compressors ...  

U.S. Energy Information Administration (EIA)

GA 11+-30/GA 15-30 VSD: Oil-injected rotary screw compressors, 11-30 kW / 15-40 hp,Kunshan CompAirs Machinery Plant Co.,Ltd is the leading air ...

31

GA 90+-160+ / GA 110-160 VSD: Oil-injected rotary screw ...  

U.S. Energy Information Administration (EIA)

GA 90+-160+ / GA 110-160 VSD: Oil-injected rotary screw compressors, 90-160 kW / 125-200 hp.,Kunshan CompAirs Machinery Plant Co.,Ltd is the leading ...

32

Room temperature green light emission from nonpolar cubic InGaN/GaN multi-quantum-wells  

E-Print Network (OSTI)

Room temperature green light emission from nonpolar cubic InGaN/GaN multi-quantum-wells Shunfeng Li Cubic InGaN/GaN multi-quantum-wells MQWs with high structural and optical quality are achieved by utilizing freestanding 3C-SiC 001 substrates and optimizing InGaN quantum well growth. Superlattice peaks up

As, Donat Josef

33

Characteristics study of 2DEG transport properties of AlGaN/GaN and AlGaAs/GaAs-based HEMT  

Science Conference Proceedings (OSTI)

Growth of wide bandgap material over narrow bandgap material, results into a two dimensional electron gas (2DEG) at the heterointerface due to the conduction band discontinuity. In this paper the 2DEG transport properties of AlGaN/GaN-based high electron mobility transistor (HEMT) is discussed and its effect on various characteristics such as 2DEG density, C-V characteristics and Sheet resistances for different mole fractions are presented. The obtained results are also compared with AlGaAs/GaAs-based HEMT for the same structural parameter as like AlGaN/GaN-based HEMT. The calculated results of electron sheet concentration as a function of the Al mole fraction are in excellent agreement with some experimental data available in the literature.

Lenka, T. R., E-mail: trlenka@gmail.com; Panda, A. K., E-mail: akpanda62@hotmail.com [National Institute of Science and Technology, Palur Hills (India)

2011-05-15T23:59:59.000Z

34

Quantized states in homogenous polarized GaInN GaN quantum wells  

E-Print Network (OSTI)

Quantized states in homogenous polarized GaInN GaN quantum wells C. Wetzel1, S. Kamiyama1, H. Amano wells is calculated in a single particle model. The act- ing electric eld in the wells and the band gap-dimensional well layers our approach is based on induction from results obtained at the binary GaN barri- ers

Wetzel, Christian M.

35

PIEZOELECTRIC LEVEL SPLITTING IN GaInN/GaN QUANTUM WELLS  

E-Print Network (OSTI)

PIEZOELECTRIC LEVEL SPLITTING IN GaInN/GaN QUANTUM WELLS C. Wetzel, T. Takeuchi, H. Amano, and IInN/GaN multiple quantum well samples in a large set of variable composition a clear correspondence of transitions in photo- and electroreflection, as well as photoluminescence is found. The effective band offset across

Wetzel, Christian M.

36

Pulsed optically detected NMR of single GaAs/AlGaAs quantum wells  

E-Print Network (OSTI)

Pulsed optically detected NMR of single GaAs/AlGaAs quantum wells Marcus Eickhoff* and Dieter Suter, nanometer-sized quantum wells possible with excellent sensitivity and selectivity while avoiding.60.-k; 78.55.Cr; 78.67.De Keywords: ODNMR; Pulsed excitation; Quantum well; GaAs 1. Introduction Nuclear

Suter, Dieter

37

Spontaneous emission in GaN/InGaN photonic crystal nanopillars  

E-Print Network (OSTI)

. Sigalas, "InGaN/GaN quantum-well heterostructure light-emitting diodes employing photonic crystal, "III-nitride blue and ultraviolet photonic crystal light emitting diodes," Appl. Phys. Lett. 84, 466, and H. Benisty, "Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution

Recanati, Catherine

38

Princeton Plasma Physics Lab - General Atomics (GA)  

NLE Websites -- All DOE Office Websites (Extended Search)

general-atomics-ga General general-atomics-ga General Atomics en The Scorpion's Strategy: "Catch and Subdue" http://www.pppl.gov/node/1132

American Fusion News Category: 
ga">General Atomics (GA)
39

TMS P&GA Wired to Washington  

Science Conference Proceedings (OSTI)

P & GA COMMITTEE HOME ... the connection between MSE and such key U.S. initiatives as national security, energy independence, and economic growth.

40

Y2, Threading Defect Elimination in GaN Nanostructures  

Science Conference Proceedings (OSTI)

DD3, A New Approach to Make ZnO-Cu2O Heterojunctions for Solar Cells ... E2, AlGaAs/GaAs/GaN Wafer Fused HBTs with Ar Implanted Extrinsic Collectors.

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

GaInP/GaAs/GaInAs Monolithic Tandem Cells for High-Performance Solar Concentrators  

DOE Green Energy (OSTI)

We present a new approach for ultra-high-performance tandem solar cells that involves inverted epitaxial growth and ultra-thin device processing. The additional degree of freedom afforded by the inverted design allows the monolithic integration of high-, and medium-bandgap, lattice-matched (LM) subcell materials with lower-bandgap, lattice-mismatched (LMM) materials in a tandem structure through the use of transparent compositionally graded layers. The current work concerns an inverted, series-connected, triple-bandgap, GaInP (LM, 1.87 eV)/GaAs (LM, 1.42 eV)/GaInAs (LMM, {approx}1 eV) device structure grown on a GaAs substrate. Ultra-thin tandem devices are fabricated by mounting the epiwafers to pre-metallized Si wafer handles and selectively removing the parent GaAs substrate. The resulting handle-mounted, ultra-thin tandem cells have a number of important advantages, including improved performance and potential reclamation/reuse of the parent substrate for epitaxial growth. Additionally, realistic performance modeling calculations suggest that terrestrial concentrator efficiencies in the range of 40-45% are possible with this new tandem cell approach. A laboratory-scale (0.24 cm2), prototype GaInP/GaAs/GaInAs tandem cell with a terrestrial concentrator efficiency of 37.9% at a low concentration ratio (10.1 suns) is described, which surpasses the previous world efficiency record of 37.3%.

Wanlass, M. W.; Ahrenkiel, S. P.; Albin, D. S.; Carapella, J. J.; Duda, A.; Emery, K.; Geisz, J. F.; Jones, K.; Kurtz, S.; Moriarty, T.; Romero, M. J.

2005-08-01T23:59:59.000Z

42

Price of Elba Island, GA Liquefied Natural Gas Total Imports...  

Annual Energy Outlook 2012 (EIA)

Elba Island, GA Liquefied Natural Gas Total Imports (Dollars per Thousand Cubic Feet) Price of Elba Island, GA Liquefied Natural Gas Total Imports (Dollars per Thousand Cubic Feet)...

43

US SoAtl GA Site Consumption  

U.S. Energy Information Administration (EIA) Indexed Site

GA GA Site Consumption million Btu $0 $500 $1,000 $1,500 $2,000 $2,500 US SoAtl GA Expenditures dollars ALL ENERGY average per household (excl. transportation) 0 4,000 8,000 12,000 16,000 US SoAtl GA Site Consumption kilowatthours $0 $300 $600 $900 $1,200 $1,500 $1,800 US SoAtl GA Expenditures dollars ELECTRICITY ONLY average per household * Site energy consumption (89.5 million Btu) and energy expenditures per household ($2,067) in Georgia are similar to the U.S. household averages. * Per household electricity consumption in Georgia is among the highest in the country, but similar to other states in the South. * Forty-five percent of homes in Georgia were built since 1990, a characteristic typically associated with lower per household consumption. Georgia homes,

44

US SoAtl GA Site Consumption  

Gasoline and Diesel Fuel Update (EIA)

GA GA Site Consumption million Btu $0 $500 $1,000 $1,500 $2,000 $2,500 US SoAtl GA Expenditures dollars ALL ENERGY average per household (excl. transportation) 0 4,000 8,000 12,000 16,000 US SoAtl GA Site Consumption kilowatthours $0 $300 $600 $900 $1,200 $1,500 $1,800 US SoAtl GA Expenditures dollars ELECTRICITY ONLY average per household * Site energy consumption (89.5 million Btu) and energy expenditures per household ($2,067) in Georgia are similar to the U.S. household averages. * Per household electricity consumption in Georgia is among the highest in the country, but similar to other states in the South. * Forty-five percent of homes in Georgia were built since 1990, a characteristic typically associated with lower per household consumption. Georgia homes,

45

AlGaAs/GaAs nano-hetero-epitaxy on a patterned GaAs substrate by MBE  

SciTech Connect

An AlGaAs/GaAs resonant tunneling diode (RTD) with submicron size was fabricated on {l_brace}111{r_brace} oblique facets of GaAs with selective MBE. The method is based on the fact that a certain facet structure is formed on a patterned substrate in selective MBE because the growth rate depends strongly on the facet structure. The fabrication of a double-barrier structure was attempted on a {l_brace}111{r_brace}B facet. The current-voltage characteristics of the sample showed negative differential resistance at 77K demonstrating that we have achieved an RTD on a submicron facet.

Nishiwaki, T.; Yamaguchi, M.; Sawaki, N. [Department of Electronics, Nagoya University, Chikusa-ku, Nagoya, 464-8603 (Japan)

2007-04-10T23:59:59.000Z

46

Accelerated aging of GaAs concentrator solar cells  

DOE Green Energy (OSTI)

An accelerated aging study of AlGaAs/GaAs solar cells has been completed. The purpose of the study was to identify the possible degradation mechanisms of AlGaAs/GaAs solar cells in terrestrial applications. Thermal storage tests and accelerated AlGaAs corrosion studies were performed to provide an experimental basis for a statistical analysis of the estimated lifetime. Results of this study suggest that a properly designed and fabricated AlGaAs/GaAs solar cell can be mechanically rugged and environmentally stable with projected lifetimes exceeding 100 years.

Gregory, P.E.

1982-04-01T23:59:59.000Z

47

Characterization of high-quality InGaN/GaN multiquantum wells with time-resolved photoluminescence  

E-Print Network (OSTI)

Characterization of high-quality InGaN/GaN multiquantum wells with time-resolved photoluminescence October 1997; accepted for publication 5 January 1998 Recombination in single quantum well and multiquantum well InGaN/GaN structures is studied using time-resolved photoluminescence and pulsed

Bowers, John

48

Optical injection and coherent control of a ballistic charge current in GaAsAlGaAs quantum wells  

E-Print Network (OSTI)

Optical injection and coherent control of a ballistic charge current in GaAs�AlGaAs quantum wells of Hache´ et al.,2,3 but in this article we report injection into the plane of GaAs/AlGaAs quantum wells specific to quantum wells. Although we expect the underlying physics of injection and control of currents

Sipe,J. E.

49

Journal of Crystal Growth 298 (2007) 272275 Dislocation analysis in homoepitaxial GaInN/GaN light emitting  

E-Print Network (OSTI)

of GaInN/GaN-based light emitting diodes (LED) on quasi-bulk GaN with an atomically flat polished were much improved. The optical output power of the light emitting diode increased by more than one. Cathodoluminescence; A1. Threading dislocation density; A2. Homoepitaxial growth; B1. GaInN; B3. Light emitting diode

Wetzel, Christian M.

50

Discrete Steps in the Capacitance-Voltage Characteristics of GaInN/GaN Light Emitting Diode Structures  

E-Print Network (OSTI)

Discrete Steps in the Capacitance-Voltage Characteristics of GaInN/GaN Light Emitting Diode and GaInN/GaN heterostructures typically used for high efficiency light emitting diodes is of high materials for green, blue, and UV light emitting diodes (LED) [1-2]. It is known that huge piezoelectric

Wetzel, Christian M.

51

Analysis of Schottky gate electron tunneling in polarization induced AlGaN/GaN high electron mobility transistors  

Science Conference Proceedings (OSTI)

( gate=nickel)/(barrier=GaN/Al (y) Ga (1?y) N)/(buffer=GaN)/(substrate=SiC ) polarizationinduced high electron mobility transistors (PI-HEMTs) show promise for ultrahigh power microwave amplification. The polarization fields in these Ga-face

Lester F. Eastman

1999-01-01T23:59:59.000Z

52

GA Solar | Open Energy Information  

Open Energy Info (EERE)

Solar Solar Jump to: navigation, search Name GA-Solar Place Madrid, Spain Zip 28045 Sector Solar Product Madrid based solar project developer, owned by Spanish industrial group Corporacion Gestamp. Coordinates 40.4203°, -3.705774° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":40.4203,"lon":-3.705774,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

53

J1, MBE Growth of Metamorphic InGaP on GaAs and GaP for Wide ...  

Science Conference Proceedings (OSTI)

I4, Electrical Spin Injection in a Hybrid Organic/Inorganic Spin-Polarized Light Emitting Diode (Spin-LED) · I5, Properties of MnAs/GaMnAs/MnAs Magnetic ...

54

AlGaN/GaN high electron mobility transistors based on InGaN/GaN multi-quantum-well structures with photo-chemical vapor deposition of SiO2 dielectrics  

Science Conference Proceedings (OSTI)

AlGaN/GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) based on InGaN/GaN multi-quantum-well (MQW) structure has been fabricated with SiO"2 dielectric deposited via photo-chemical vapor deposition (PHCVD) using a deuterium lamp ... Keywords: GaN, HEMT, MQW, Photo-chemical vapor deposition, SiO 2

Kai-Hsuan Lee; Ping-Chuan Chang; Shoou-Jinn Chang

2013-04-01T23:59:59.000Z

55

Free carrier accumulation at cubic AlGaN/GaN heterojunctions  

Science Conference Proceedings (OSTI)

Cubic Al{sub 0.3}Ga{sub 0.7}N/GaN heterostructures were grown by plasma-assisted molecular beam epitaxy on 3C-SiC (001) substrates. A profile of the electrostatic potential across the cubic-AlGaN/GaN heterojunction was obtained using electron holography in the transmission electron microscope. The experimental potential profile indicates that the unintentionally doped layers show n-type behavior and accumulation of free electrons at the interface with a density of 5.1 x 10{sup 11}/cm{sup 2}, about one order of magnitude less than in wurtzite AlGaN/GaN junctions. A combination of electron holography and cathodoluminescence measurements yields a conduction-to-valence band offset ratio of 5:1 for the cubic AlGaN/GaN interface, which also promotes the electron accumulation. Band diagram simulations show that the donor states in the AlGaN layer provide the positive charges that to a great extent balance the two-dimensional electron gas.

Wei, Q. Y.; Li, T.; Huang, J. Y.; Ponce, F. A. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Tschumak, E.; Zado, A.; As, D. J. [Department of Physics, Universitaet Paderborn, D-33098 Paderborn (Germany)

2012-04-02T23:59:59.000Z

56

L1, Formation of Structural Defects in AlGaN/GaN High Electron ...  

Science Conference Proceedings (OSTI)

Transmission electron microscope (TEM) cross sectional image has shown that electrical degradation is closely related to structural damage in the GaN cap and  ...

57

Plasma Damage in p-GaN  

SciTech Connect

The effect of Inductively Coupled Plasma H{sub 2} or Ar discharges on the breakdown voltage of p-GaN diodes was measured over a range of ion energies and fluxes. The main effect of plasma exposure is a decrease in net acceptor concentration to depths of 400-550{angstrom}. At high ion fluxes or energies there can be type conversion of the initially p-GaN surface. Post etch annealing at 900 C restores the initial conductivity.

Cao, X.A.; Dang, G.T.; Hickman, R.A.; Pearton, S.J.; Ren, F.; Shul, R.J.; Van Hove, J.M.; Zhang, A.P.; Zhang, L.

1999-06-30T23:59:59.000Z

58

GaTe semiconductor for radiation detection  

SciTech Connect

GaTe semiconductor is used as a room-temperature radiation detector. GaTe has useful properties for radiation detectors: ideal bandgap, favorable mobilities, low melting point (no evaporation), non-hygroscopic nature, and availability of high-purity starting materials. The detector can be used, e.g., for detection of illicit nuclear weapons and radiological dispersed devices at ports of entry, in cities, and off shore and for determination of medical isotopes present in a patient.

Payne, Stephen A. (Castro Valley, CA); Burger, Arnold (Nashville, TN); Mandal, Krishna C. (Ashland, MA)

2009-06-23T23:59:59.000Z

59

Schottky-Drain Technology for AlGaN/GaN High-Electron Mobility Transistors  

E-Print Network (OSTI)

In this letter, we demonstrate 27% improvement in the buffer breakdown voltage of AlGaN/GaN high-electron mobility transistors (HEMTs) grown on Si substrate by using a new Schottky-drain contact technology. Schottky-drain ...

Lu, Bin

60

Simulation and Design Analysis of (A1Ga)As/GaAs MODFET Integrated Circuits  

Science Conference Proceedings (OSTI)

A new (AlGa)As/GaAs MODFET integrated circuit simulator is described. Our simulator is a customized version of SPICE incorporating the extended charge control model for MODFET's and the velocity saturation model for ungated FET's used as the load devices. ...

Choong H. Hyun; M. S. Shur; N. C. Cirillo

2006-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Nanocrystals cylindrical microcavities exploiting thin-walled InGaAs/GaAs microtubes  

Science Conference Proceedings (OSTI)

This paper relies on the design and fabrication of CdSe/ZnS core/shell colloidal nanocrystals (NCs) cylindrical microcavities for microphotonics applications. The fabrication technology relies on the release of the strain in strained heterostructures, ... Keywords: Colloidal nanocrystals, InGaAs/GaAs microtubes, Strained multilayer

C. Giordano; M. T. Todaro; A. Salhi; L. Martiradonna; I. Viola; A. Passabí; L. Carbone; G. Gigli; A. Passaseo; M. De Vittorio

2007-05-01T23:59:59.000Z

62

Two-dimensional electron gas in AlGaN/GaN heterostructures  

Science Conference Proceedings (OSTI)

The formation of a two-dimensional electron gas (2DEG) system by an AlGaN/GaN heterostructure has been further confirmed by measuring its electrical properties. The effect of persistent photoconductivity (PPC) has been observed and its unique features have been utilized to study the properties of 2DEG formed by the AlGaN/GaN heterointerface. Sharp electronic transitions from the first to the second subbands in the 2DEG channel have been observed by monitoring the 2DEG carrier mobility as a function of carrier concentration through the use of PPC. These results are expected to have significant implications on field-effect transistor and high electron mobility transistor applications based on the GaN system. {copyright} {ital 1997 American Vacuum Society.}

Li, J.Z.; Lin, J.Y.; Jiang, H.X. [Department of Physics, Kansas State University, Manhattan, Kansas 66506-2601 (United States)] [Department of Physics, Kansas State University, Manhattan, Kansas 66506-2601 (United States); Khan, M.A.; Chen, Q. [APA Optics, Inc., Blaine, Minnesota 55449 (United States)] [APA Optics, Inc., Blaine, Minnesota 55449 (United States)

1997-07-01T23:59:59.000Z

63

Lattice-matched epitaxial GaInAsSb/GaSb thermophotovoltaic devices  

DOE Green Energy (OSTI)

The materials development of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} alloys for lattice-matched thermophotovoltaic (TPV) devices is reported. Epilayers with cutoff wavelength 2--2.4 {micro}m at room temperature and lattice-matched to GaSb substrates were grown by both low-pressure organometallic vapor phase epitaxy and molecular beam epitaxy. These layers exhibit high optical and structural quality. For demonstrating lattice-matched thermophotovoltaic devices, p- and n-type doping studies were performed. Several TPV device structures were investigated, with variations in the base/emitter thicknesses and the incorporation of a high bandgap GaSb or AlGaAsSb window layer. Significant improvement in the external quantum efficiency is observed for devices with an AlGaAsSb window layer compared to those without one.

Wang, C.A.; Choi, H.K.; Turner, G.W.; Spears, D.L.; Manfra, M.J. [Massachusetts Inst. of Tech., Lexington, MA (United States). Lincoln Lab.; Charache, G.W. [Lockheed Martin, Inc., Schenectady, NY (United States)

1997-05-01T23:59:59.000Z

64

MBE growth of high electron mobility 2DEGs in AlGaN/GaN heterostructures controlled by RHEED  

Science Conference Proceedings (OSTI)

We have grown 2DEG AlGaN/GaN heterostructures by molecular beam epitaxy (MBE) with electron mobilities up to 21500 cm{sup 2}V{sup -1}s{sup -1} at 2 K. In-situ RHEED was applied to optimize different aspects of Ga-rich growth. This paper gives a compact overview of the experimental key aspects that significantly affect the low temperature electron mobility in AlGaN/GaN heterostructures. Growth at the transition towards Ga droplet formation produced the best results. A quantitative analysis of the magnetoresistance confirmes scattering at dislocations as the dominant scattering process at low temperature.

Broxtermann, D.; Sivis, M.; Malindretos, J.; Rizzi, A. [IV. physikalisches Institut, Georg-August-Universitaet Goettingen (Germany)

2012-03-15T23:59:59.000Z

65

Double pulse doped InGaAs/AlGaAs/GaAs pseudomorphic high-electron-mobility transistor heterostructures  

Science Conference Proceedings (OSTI)

Double pulse doped ({delta}-doped) InGaAs/AlGaAs/GaAs pseudomorphic high-electron-mobility transistor (HEMT) heterostructures were grown by molecular-beam epitaxy using a multiwafer technological system. The room-temperature electron mobility was determined by the Hall method as 6550 and 6000 cm{sup 2}/(V s) at sheet electron densities of 3.00 x 10{sup 12} and 3.36 x 10{sup 12} cm{sup -2}, respectively. HEMT heterostructures fabricated in a single process feature high uniformity of structural and electrical characteristics over the entire area of wafers 76.2 mm in diameter and high reproducibility of characteristics from process to process.

Egorov, A. Yu., E-mail: anton@beam.ioffe.ru; Gladyshev, A. G.; Nikitina, E. V.; Denisov, D. V.; Polyakov, N. K.; Pirogov, E. V.; Gorbazevich, A. A. [Russian Academy of Sciences, St. Petersburg Physics and Technology Center for Research and Education (Russian Federation)

2010-07-15T23:59:59.000Z

66

GaN Nanopore Arrays: Fabrication and Characterization  

E-Print Network (OSTI)

GaN nanopore arrays with pore diameters of approximately 75 nm were fabricated by inductively coupled plasma etching (ICP) using anodic aluminum oxide (AAO) films as etch masks. Nanoporous AAO films were formed on the GaN ...

Wang, Yadong

67

Magnetoelastic Coupling in NiMnGa Ferromagnetic Shape ...  

Science Conference Proceedings (OSTI)

... Magnetoelastic Coupling in NiMnGa Ferromagnetic Shape Memory Alloys. Peng Zhao (Dept. of Materials Science and ...

68

Advanced technologies for improving high frequency performance of AlGaN/GaN high electron mobility transistors  

E-Print Network (OSTI)

In this thesis, we have used a combination of physical analysis, numerical simulation and experimental work to identify and overcome some of the main challenges in AlGaN/GaN high electron mobility transistors (HEMTs) for ...

Chung, Jinwook W. (Jinwook Will)

2008-01-01T23:59:59.000Z

69

Evolution of structural defects associated with electrical degradation in AlGaN/GaN high electron mobility transistors  

E-Print Network (OSTI)

We have investigated the surface morphology of electrically stressed AlGaN/GaN high electron mobility transistors using atomic force microscopy and scanning electron microscopy after removing the gate metallization by ...

Makaram, Prashanth

70

Enhancement-mode AlGaN/GaN HEMTs with high linearity fabricated by hydrogen plasma treatment  

E-Print Network (OSTI)

Enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistors (HEMTs) are highly desirable for power and digital electronic circuits. Several technologies have been demonstrated in the last few years to fabricate ...

Palacios, Tomas

71

GaN: Defect and Device Issues  

SciTech Connect

The role of extended and point defects, and key impurities such as C, O and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

Pearton, S.J.; Ren, F.; Shul, R.J.; Zolper, J.C.

1998-11-09T23:59:59.000Z

72

GaAs photoconductive semiconductor switch  

DOE Patents (OSTI)

A high gain, optically triggered, photoconductive semiconductor switch (PCSS) implemented in GaAs as a reverse-biased pin structure with a passivation layer above the intrinsic GaAs substrate in the gap between the two electrodes of the device. The reverse-biased configuration in combination with the addition of the passivation layer greatly reduces surface current leakage that has been a problem for prior PCSS devices and enables employment of the much less expensive and more reliable DC charging systems instead of the pulsed charging systems that needed to be used with prior PCSS devices.

Loubriel, Guillermo M. (Sandia Park, NM); Baca, Albert G. (Albuquerque, NM); Zutavern, Fred J. (Albuquerque, NM)

1998-01-01T23:59:59.000Z

73

A New Combustion Synthesis Method for GaN:Eu3+ and Ga2O3 :Eu3+  

E-Print Network (OSTI)

A New Combustion Synthesis Method for GaN:Eu3+ and Ga2O3 :Eu3+ Luminescent Powders G. A. Hirata1 between the precursors. The preparation of Eu-doped Ga2O3 powders was achieved using a new combustion)3 and Ga(NO3)3 as the precursors and hydrazine as (non-carbonaceous) fuel. A spontaneous combustion

McKittrick, Joanna

74

GaAs/AlGaAs nanostructured composites for free-space and integrated optical devices  

E-Print Network (OSTI)

Fainman, "Influence of chlorine on etched sidewalls inFainman, “Influence of chlorine on etched sidewalls inthe RIBE of GaAs with chlorine (Cl 2 ), ion beam sputtering

Tsai, Chia-Ho

2006-01-01T23:59:59.000Z

75

JJ2, Optical Polarization of Non-Polar GaInN/GaN LEDs  

Science Conference Proceedings (OSTI)

I4, Electrical Spin Injection in a Hybrid Organic/Inorganic Spin-Polarized Light Emitting Diode (Spin-LED) · I5, Properties of MnAs/GaMnAs/MnAs Magnetic ...

76

K1, Molecular Beam Epitaxy of Catalyst-Free InGaN/GaN Nanowires ...  

Science Conference Proceedings (OSTI)

I4, Electrical Spin Injection in a Hybrid Organic/Inorganic Spin-Polarized Light Emitting Diode (Spin-LED) · I5, Properties of MnAs/GaMnAs/MnAs Magnetic ...

77

Guided Neuronal Growth on Arrays of Biofunctionalized GaAs/InGaAs Semiconductor Microtubes  

E-Print Network (OSTI)

We demonstrate embedded growth of cortical mouse neurons in dense arrays of semiconductor microtubes. The microtubes, fabricated from a strained GaAs/InGaAs heterostructure, guide axon growth through them and enable electrical and optical probing of propagating action potentials. The coaxial nature of the microtubes -- similar to myelin -- is expected to enhance the signal transduction along the axon. We present a technique of suppressing arsenic toxicity and prove the success of this technique by overgrowing neuronal mouse cells.

Cornelius S. Bausch; Aune Koitmäe; Eric Stava; Amanda Price; Pedro J. Resto; Yu Huang; David Sonnenberg; Yuliya Stark; Christian Heyn; Justin C. Williams; Erik W. Dent; Robert H. Blick

2013-05-06T23:59:59.000Z

78

Recent progress in InGaAsSb/GaSb TPV devices  

DOE Green Energy (OSTI)

AstroPower is developing InGaAsSb thermophotovoltaic (TPV) devices. This photovoltaic cell is a two-layer epitaxial InGaAsSb structure formed by liquid-phase epitaxy on a GaSb substrate. The (direct) bandgap of the In{sub 1{minus}x}Ga{sub x}As{sub 1{minus}y}Sb{sub y} alloy is 0.50 to 0.55 eV, depending on its exact alloy composition (x,y); and is closely lattice-matched to the GaSb substrate. The use of the quaternary alloy, as opposed to a ternary alloy--such as, for example InGaAs/InP--permits low bandgap devices optimized for 1,000 to 1,500 C thermal sources with, at the same time, near-exact lattice matching to the GaSb substrate. Lattice matching is important since even a small degree of lattice mismatch degrades device performance and reliability and increases processing complexity. Internal quantum efficiencies as high as 95% have been measured at a wavelength of 2 microns. At 1 micron wavelengths, internal quantum efficiencies of 55% have been observed. The open-circuit voltage at currents of 0.3 A/cm{sup 2} is 0.220 volts and 0.280 V for current densities of 2 A/cm{sup 2}. Fill factors of 56% have been measured at 60 mA/cm{sup 2}. However, as current density increases there is some decrease in fill factor. The results to date show that the GaSb-based quaternary compounds provide a viable and high performance energy conversion solution for thermophotovoltaic systems operating with 1,000 to 1,500 C source temperatures.

Shellenbarger, Z.A.; Mauk, M.G.; DiNetta, L.C. [AstroPower, Inc., Newark, DE (United States); Charache, G.W. [Lockheed Martin Corp., Schenectady, NY (United States)

1996-05-01T23:59:59.000Z

79

GaNPAs Solar Cells Lattice-Matched To GaP: Preprint  

DOE Green Energy (OSTI)

This conference paper describes the III-V semiconductors grown on silicon substrates are very attractive for lower-cost, high-efficiency multijunction solar cells, but lattice-mismatched alloys that result in high dislocation densities have been unable to achieve satisfactory performance. GaNxP1-x-yAsy is a direct-gap III-V alloy that can be grown lattice-matched to Si when y= 4.7x - 0.1. We propose the use of lattice-matched GaNPAs on silicon for high-efficiency multijunction solar cells. We have grown GaNxP1-x-yAsy on GaP (with a similar lattice constant to silicon) by metal-organic chemical vapor phase epitaxy with direct band-gaps in the range of 1.5 to 2.0 eV. We demonstrate the performance of single-junction GaNxP1-x-yAsy solar cells grown on GaP substrates and discuss the prospects for the development of monolithic high-efficiency multijunction solar cells based on silicon substrates.

Geisz, J. F.; Friedman, D. J.; Kurtz, S.

2002-05-01T23:59:59.000Z

80

GaSb/GaP compliant interface for high electron mobility AlSb/InAs heterostructures on (001) GaP  

Science Conference Proceedings (OSTI)

We report on the epitaxial growth of an AlSb/InAs heterostructure on a (001) GaP substrate. We investigate the conditions for the most efficient relaxation of GaSb islands on GaP. In particular, we show that the GaP surface treatment and the growth temperature are crucial for the formation of a two-dimensional periodic array of 90 deg. misfit dislocations at the episubstrate interface. With this relaxation process, an AlSb/InAs heterostructure exhibiting a room temperature mobility of 25 500 cm{sup 2} V{sup -1} s{sup -1} on GaP is demonstrated. This result paves the way to the integration of Sb-based devices on Si substrates through the use of GaP/Si templates.

El Kazzi, S.; Desplanque, L.; Coinon, C.; Wallart, X. [Institut d'Electronique, de Microelectronique, et de Nanotechnologie, UMR-CNRS 8520, BP 60069, 59652 Villeneuve d'Ascq Cedex (France); Wang, Y.; Ruterana, P. [CIMAP UMR 6252 CNRS-ENSICAEN-CEA-UCBN, 6, Boulevard du Marechal Juin, 14050 Caen Cedex (France)

2010-11-08T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Reactive codoping of GaAlInP compound semiconductors  

DOE Patents (OSTI)

A GaAlInP compound semiconductor and a method of producing a GaAlInP compound semiconductor are provided. The apparatus and method comprises a GaAs crystal substrate in a metal organic vapor deposition reactor. Al, Ga, In vapors are prepared by thermally decomposing organometallic compounds. P vapors are prepared by thermally decomposing phospine gas, group II vapors are prepared by thermally decomposing an organometallic group IIA or IIB compound. Group VIB vapors are prepared by thermally decomposing a gaseous compound of group VIB. The Al, Ga, In, P, group II, and group VIB vapors grow a GaAlInP crystal doped with group IIA or IIB and group VIB elements on the substrate wherein the group IIA or IIB and a group VIB vapors produced a codoped GaAlInP compound semiconductor with a group IIA or IIB element serving as a p-type dopant having low group II atomic diffusion.

Hanna, Mark Cooper (Boulder, CO); Reedy, Robert (Golden, CO)

2008-02-12T23:59:59.000Z

82

Growth and photoluminescence of self-catalyzed GaP/GaNP core/shell nanowires on Si(111) by gas source molecular beam epitaxy  

Science Conference Proceedings (OSTI)

We report a study on self-catalyzed GaP/GaNP core/shell nanowires (NWs) grown on Si(111) by gas-source molecular beam epitaxy. Scanning electron microscopy images show that vertical and uniform GaP NWs and GaP/GaNP core/shell NWs are grown on Si(111). The density ranges from {approx}1 x 10{sup 7} to {approx}5 x 10{sup 8} cm{sup -2} across the substrate. Typical diameters are {approx}110 nm for GaP NWs and {approx}220 nm for GaP/GaNP NWs. Room temperature photoluminescence (PL) signal from the GaP/GaNP core/shell NWs confirms that N is incorporated in the shell and the average N content is {approx}0.9%. The PL low-energy tail is significantly reduced, compared to bulk GaNP.

Kuang, Y. J. [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States); Sukrittanon, S. [Graduate Program of Material Science and Engineering, University of California, San Diego, La Jolla, California 92093 (United States); Li, H. [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States); Tu, C. W. [Graduate Program of Material Science and Engineering, University of California, San Diego, La Jolla, California 92093 (United States); Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States)

2012-01-30T23:59:59.000Z

83

Mn-doped Ga(As,P) and (Al,Ga)As ferromagnetic semiconductors: Electronic structure calculations  

E-Print Network (OSTI)

A remarkable progress towards functional ferromagnetic semiconductor materials for spintronics has been achieved in p-type (Ga,Mn)As. Robust hole-mediated ferromagnetism has, however, been observed also in other III-V hosts such as antimonides, GaP, or (Al,Ga)As, which opens a wide area of possibilities for optimizing the host composition towards higher ferromagnetic Curie temperatures. Here we explore theoretically hole-mediated ferromagnetism and Mn incorporation in Ga(As,P) and (Al,Ga)As ternary hosts. While alloying (Ga,Mn)As with Al has only a small effect on the Curie temperature we predict a sizable enhancement of Curie temperatures in the smaller lattice constant Ga(As,P) hosts. Mn-doped Ga(As,P) is also favorable, as compared to (Al,Ga)As, with respect to the formation of carrier and moment compensating interstitial Mn impurities. In (Ga,Mn) (As,P) we find a marked decrease of the partial concentration of these detrimental impurities with increasing P content.

Masek, J.; Kudrnovsky, J.; Maca, F.; Sinova, Jairo; MacDonald, A. H.; Campion, R. P.; Gallagher, B. L.; Jungwirth, T.

2007-01-01T23:59:59.000Z

84

Temperature-Dependence of Exciton Radiative Recombination in (Al,Ga)N/GaN Quantum Wells Grown on a-Plane GaN Substrates  

E-Print Network (OSTI)

5221, 34095 Montpellier, France E-mail: pmc53@cam.ac.uk Received October 12, 2012; accepted November 22, 2012; published online May 20, 2013 This article presents the dynamics of excitons in a-plane (Al,Ga)N/GaN single quantum wells of various...

Corfdir, Pierre; Dussaigne, Amélie; Teisseyre, Henryk; Suski, Tadeusz; Grzegory, Izabella; Lefebvre, Pierre; Giraud, Etienne; Shahmohammadi, Mehran; Phillips, Richard; Ganičre, Jean-Daniel; Grandjean, Nicolas; Deveaud, Benoît

85

Growth orientation dependent photoluminescence of GaAsN alloys  

SciTech Connect

We report photoluminescence (PL) studies of both as-grown and electron-irradiated GaAsN epilayers on (311)A/B and (100) GaAs substrates. A long room-temperature (RT) PL lifetime, as well as an enhanced N incorporation, is observed in (311)B GaAsN epilayers as compared with (311)A and (100) samples. There is no direct correlation between the RT PL lifetime and the emission intensity from Ga vacancy complex detected at low temperature. The lifetime damage coefficient is relatively low for (311)B GaAsN. The irradiation-induced nonradiative recombination defects are suggested to be N- and/or As-related according to a geometrical analysis based on the tetrahedral coordination of GaAsN crystal.

Han, Xiuxun; Tanaka, Tomohiro; Kojima, Nobuaki; Ohshita, Yoshio; Yamaguchi, Masafumi [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468-8511 (Japan); Sato, Shinichiro [Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan)

2012-01-16T23:59:59.000Z

86

Effect of Temperature on GaGdO/GaN Metal Oxide Semiconductor Field Effect Transistors  

SciTech Connect

GaGdO was deposited on GaN for use as a gate dielectric in order to fabricate a depletion metal oxide semiconductor field effect transistor (MOSFET). This is the fmt demonstration of such a device in the III-Nitride system. Analysis of the effect of temperature on the device shows that gate leakage is significantly reduced at elevated temperature relative to a conventional metal semiconductor field effeet transistor (MESFET) fabricated on the same GaN layer. MOSFET device operation in fact improved upon heating to 400 C. Modeling of the effeet of temperature on contact resistance suggests that the improvement is due to a reduction in the parasitic resistances present in the device.

Abernathy, C.R.; Baca, A.; Chu, S.N.G.; Hong, M.; Lothian, J.R.; Marcus, M.A.; Pearton, S.J.; Ren, F.; Schurman, M.J.

1998-10-14T23:59:59.000Z

87

Growth and Fabrication of GaN/AlGaN Heterojunction Bipolar Transistor  

SciTech Connect

A GaN/AlGaN heterojunction bipolar transistor structure with Mg doping in the base and Si Doping in the emitter and collector regions was grown by Metal Organic Chemical Vapor Deposition in c-axis Al(2)O(3). Secondary Ion Mass Spectrometry measurements showed no increase in the O concentration (2-3x10(18) cm(-3)) in the AlGaN emitter and fairly low levels of C (~4-5x10(17) cm (-3)) throughout the structure. Due to the non-ohmic behavior of the base contact at room temperature, the current gain of large area (~90 um diameter) devices was <3. Increasing the device operating temperature led to higher ionization fractions of the mg acceptors in the base, and current gains of ~10 were obtained at 300 degree C.

Abernathy, C.R.; Baca, A.G.; Cao, X.A.; Cho, H.; Dang, G.T.; Donovan, S.M.; Han, J.; Jung, K.B.; Pearton, S.J.; Ren, F.; Shul, R.J.; Willison, C.G.; Wilson, R.G.; Zhang, A.P.; Zhang, L

1999-03-16T23:59:59.000Z

88

A InGaN/GaN quantum dot green ({lambda}=524 nm) laser  

SciTech Connect

The characteristics of self-organized InGaN/GaN quantum dot lasers are reported. The laser heterostructures were grown on c-plane GaN substrates by plasma-assisted molecular beam epitaxy and the laser facets were formed by focused ion beam etching with gallium. Emission above threshold is characterized by a peak at 524 nm (green) and linewidth of 0.7 nm. The lowest measured threshold current density is 1.2 kA/cm{sup 2} at 278 K. The slope and wall plug efficiencies are 0.74 W/A and {approx}1.1%, respectively, at 1.3 kA/cm{sup 2}. The value of T{sub 0}=233 K in the temperature range of 260-300 K.

Zhang Meng; Banerjee, Animesh; Lee, Chi-Sen; Hinckley, John M.; Bhattacharya, Pallab [Department of Electrical Engineering and Computer Science, Center for Nanoscale Photonics and Spintronics, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States)

2011-05-30T23:59:59.000Z

89

Evaluation of defects and degradation in GaAs-GaAlAs wafers using transmission cathodoluminescence  

Science Conference Proceedings (OSTI)

A large number of GaAs substrates GaAlAs double-heterostructure (DH) wafers, and high-radiance GaAlAs DH light-emitting diodes (LEDS) were evaluated using transmission cathodoluminescence (TCL). We show that only epitaxial wafers with a high defect density as revealed by TCL readily develop dark line defects (DLDs) with current injection, optical excitation, or electron beam excitation. Furthermore, in agreement with the previous work, the electron-beam-induced DLDs originate at dislocations and their growth requires minority-carrier injection. Based on these results, it is inferred that TCL can serve as a nondestructive screening technique for the selection of materials that produces a high yield of reliable LEDs.

Chin, A.K.; Keramidas, V.G.; Johnston, W.D. Jr.; Mahajan, S.; Roccasecca, D.D.

1980-02-01T23:59:59.000Z

90

GaInSb and GaInAsSb thermophotovoltaic device fabrication and characterization  

DOE Green Energy (OSTI)

Thermophotovoltaic (TPV) devices have been fabricated using epitaxial ternary and quaternary layers grown on GaSb substrates. The GaInSb layers were grown by organometallic vapor phase epitaxy (OMVPE) and the InGaAsSb lattice-matched layers were grown by liquid phase epitaxy (LPE). Device fabrication steps include unannealed p-type ohmic contacts, annealed Sn/Au n-type ohmic contacts, and a thick Ag top-surface contact using a lift-off process. Devices are characterized primarily by dark I-V, photo I-V, and quantum efficiency measurements, which are correlated to microscopic and macroscopic material properties. Particular emphasis has been on material enhancements to increase quantum efficiency and decrease dark saturation current density. TPV device performance is presently limited by the base diffusion length, typically 1 to 2 microns.

Hitchcock, C.; Gutmann, R.; Borrego, J.; Ehsani, H.; Bhat, I. [Rensselaer Polytechnic Inst., Troy, NY (United States); Freeman, M.; Charache, G. [Lockheed Martin, Inc., Schenectady, NY (United States)

1997-05-01T23:59:59.000Z

91

Transport properties of InGaAs/GaAs Heterostructures with {delta}-doped quantum wells  

Science Conference Proceedings (OSTI)

The lateral transport of electrons in single- and double-well pseudomorphic GaAs/n-InGaAs/GaAs heterostructures with quantum wells 50-100 meV deep and impurity {delta}-layers in the wells, with concentrations in the range 10{sup 11} electron mobility with an increase in the impurity concentration. The results obtained indicate that the impurity-band electron states play an important role in the conductivity of these structures. Involvement of the impurity band also allows to explain adequately the characteristics of the conductivity of double-well structures; in contrast to single-well structures, band bending caused by asymmetric doping is of great importance. The numerical calculations of conductivity within the model under consideration confirm these suggestions.

Baidus, N. V. [Nizhni Novgorod State University, Physical-Technical Research Institute (Russian Federation); Vainberg, V. V. [National Academy of Sciences of Ukraine, Institute of Physics (Ukraine); Zvonkov, B. N. [Nizhni Novgorod State University, Physical-Technical Research Institute (Russian Federation); Pylypchuk, A. S., E-mail: pylypchuk@iop.kiev.ua; Poroshin, V. N.; Sarbey, O. G. [National Academy of Sciences of Ukraine, Institute of Physics (Ukraine)

2012-05-15T23:59:59.000Z

92

Radiation Hard AlGaN Detectors and Imager  

Science Conference Proceedings (OSTI)

Radiation hardness of AlGaN photodiodes was tested using a 65 MeV proton beam with a total proton fluence of 3x10{sup 12} protons/cm{sup 2}. AlGaN Deep UV Photodiode have extremely high radiation hardness. These new devices have mission critical applications in high energy density physics (HEDP) and space explorations. These new devices satisfy radiation hardness requirements by NIF. NSTec is developing next generation AlGaN optoelectronics and imagers.

None

2012-05-01T23:59:59.000Z

93

InGaAs and Ge MOSFETs with high ? dielectrics  

Science Conference Proceedings (OSTI)

InGaAs and Ge MOSFETs with high @k's are now the leading candidates for technology beyond the 15nm node CMOS. The UHV-Al"2O"3/Ga"2O"3(Gd"2O"3) [GGO]/InGaAs has low electrical leakage current densities, C-V characteristics with low interfacial densities ... Keywords: Atomic layer deposition, Germanium, High ? dielectrics, III-V Compound semiconductor, MOSFETs, Molecular beam epitaxy

W. C. Lee; P. Chang; T. D. Lin; L. K. Chu; H. C. Chiu; J. Kwo; M. Hong

2011-04-01T23:59:59.000Z

94

Atomistic Modeling of Thermodynamic Properties of Pu-Ga Alloys ...  

Science Conference Proceedings (OSTI)

Atomistic Modeling of Thermodynamic Properties of Pu-Ga Alloys Based on the ... Resources for the Selection and Use of Interatomic Potentials in Atomistic ...

95

GA Hot Cell D&D Closeout Report  

Office of Legacy Management (LM)

contractors supported the dismantlement including asbestos removal and concrete cutting, electrical, and HVAC. Project support functions were provided by GA organizations...

96

Light emission from InGaAs:Bi/GaAs quantum wells at 1.3 {mu}m  

Science Conference Proceedings (OSTI)

Highly strained InGaAs:Bi quantum wells (QWs) were grown on (001)-oriented GaAs substrates by molecular beam epitaxy (MBE). Photoluminescence (PL) reveals strong improvements in the optical properties evidenced by 10 times enhancement in PL intensity and extended emission wavelength up to 1.29 {mu}m when Bi is introduced to InGaAs/GaAs QWs. The improved optical quality results from the Bi surfactant effect as well as the Bi incorporation. Post growth thermal annealing shows that Bi atoms in InGaAs/GaAs QWs do not show good thermal stability at 650 Degree-Sign C and tend to diffuse out of the QWs resulting in large wavelength blue-shifts.

Ye Hong; Song Yuxin; Wang Shumin [Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg SE-41296 (Sweden); Gu Yi [Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

2012-12-15T23:59:59.000Z

97

Impact of the Ga/In ratio on the N incorporation into (In,Ga)(As,N) quantum dots  

Science Conference Proceedings (OSTI)

In this work, we demonstrate the dependence of the nitrogen incorporation on the Ga/In content into (In,Ga)(As,N) quantum dots (QDs) grown on GaAs (100) by radio-frequency plasma assisted molecular beam epitaxy (MBE). Morphological analysis by atomic force microscopy and cross-sectional transmission electron microscopy, together with an estimation of the transition thickness, monitored in situ during the growth, predict a maximum in the N incorporation for 30% Ga content. This result is confirmed by photoluminescence measurements of the as-grown and post-growth annealed samples. We attribute this behavior to a trade off between two mechanisms depending on the Ga/In content: one related to the stability of the Ga-N bond, and the other related to the surface strain and/or In segregation.

Gargallo-Caballero, R.; Guzman, A.; Ulloa, J. M.; Hierro, A. [Instituto de Sistemas Optoelectronicos y Microtecnologia (ISOM)-Departamento de Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Hopkinson, M. [Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom); Luna, E.; Trampert, A. [Paul Drude Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

2012-04-15T23:59:59.000Z

98

Bulk growth of GaSb and Ga{sub 1{minus}x}In{sub x}Sb  

DOE Green Energy (OSTI)

GaSb and InGaSb have been demonstrated to be suitable choices for high efficiency thermophotovoltaic (TPV) cells. Synthesis and growth of bulk GaSb single crystals and GaInSb polycrystals have been carried out by the vertical Bridgman technique, with a baffle immersed in the melt and by complete encapsulation of the melt by low melting temperature alkali halides or oxides. The critical roles of the baffle and the encapsulation are discussed. Efforts in obtaining device grade GaSb with superior structural and electrical properties and compositionally homogeneous GaInSb are described, emphasizing the key steps in the growth cycle developed to obtain good crystalline quality.

Dutta, P.S.; Ostrogorsky, A.G.; Gutmann, R.J.

1997-05-01T23:59:59.000Z

99

P8, Fabrication of Subwavelength Pillar Arrays on GaAs by Confined ...  

Science Conference Proceedings (OSTI)

DD3, A New Approach to Make ZnO-Cu2O Heterojunctions for Solar Cells ... E2, AlGaAs/GaAs/GaN Wafer Fused HBTs with Ar Implanted Extrinsic Collectors.

100

II4, Compositionally-Graded Layers Composed of Tandem InGaAs ...  

Science Conference Proceedings (OSTI)

The specification of the 6° miscut is important because it provides step ..... of Metamorphic InGaP on GaAs and GaP for Wide-Bandgap Photovoltaic Junctions.

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Highly Polarized Green Light Emitting Diode in m-Axis GaInN/GaN Shi You, Theeradetch Detchprohm, Mingwei Zhu  

E-Print Network (OSTI)

Highly Polarized Green Light Emitting Diode in m-Axis GaInN/GaN Shi You, Theeradetch Detchprohm in nonpolar light-emitting diodes (LEDs) covering the blue to green spectral range. In photo- luminescence, m's overall power efficiency. Linearly polarized light can be efficiently generated in GaInN/GaN-based light-emitting

Wetzel, Christian M.

102

An inverted AlGaAs/GaAs patterned-Ge tunnel junction cascade concentrator solar cell  

DOE Green Energy (OSTI)

This report describes work to develop inverted-grown Al[sub 0.34]Ga[sub 0.66]As/GaAs cascades. Several significant developments are reported on as follows: (1) The AM1.5 1-sun total-area efficiency of the top Al[sub 0.34]Ga[sub 0.66]As cell for the cascade was improved from 11.3% to 13.2% (NREL measurement [total-area]). (2) The cycled'' organometallic vapor phase epitaxy growth (OMVPE) was studied in detail utilizing a combination of characterization techniques including Hall-data, photoluminescence, and secondary ion mass spectroscopy. (3) A technique called eutectic-metal-bonding (EMB) was developed by strain-free mounting of thin GaAs-AlGaAs films (based on lattice-matched growth on Ge substrates and selective plasma etching of Ge substrates) onto Si carrier substrates. Minority-carrier lifetime in an EMB GaAs double-heterostructure was measured as high as 103 nsec, the highest lifetime report for a freestanding GaAs thin film. (4) A thin-film, inverted-grown GaAs cell with a 1-sun AM1.5 active-area efficiency of 20.3% was obtained. This cell was eutectic-metal-bonded onto Si. (5) A thin-film inverted-grown, Al[sub 0.34]Ga[sub 0.66]As/GaAs cascade with AM1.5 efficiency of 19.9% and 21% at 1-sun and 7-suns, respectively, was obtained. This represents an important milestone in the development of an AlGaAs/GaAs cascade by OMVPE utilizing a tunnel interconnect and demonstrates a proof-of-concept for the inverted-growth approach.

Venkatasubramanian, R. (Research Triangle Inst., Research Triangle Park, NC (United States))

1993-01-01T23:59:59.000Z

103

Effect of gas feeding methods on optical properties of GaN grown by rapid thermal chemical vapor deposition reactor  

Science Conference Proceedings (OSTI)

Keywords: Ga vacancies, GaN growth, gas feeding method, optical property, rapid thermal chemical vapor deposition (RTCVD), yellow luminescence

Sun Jung Kim; Young Hun Seo; Kee Suk Nahm; Yun Bong Hahn; Hyun Wook Shim; Eun-Kyung Suh; Kee Young Lim; Hyung Jae Lee

1999-08-01T23:59:59.000Z

104

Functional Imprinting Structures on GaN-Based Light-Emitting ...  

Science Conference Proceedings (OSTI)

Keywords: GaN, light-emitting diode (LED), imprinting technology, far-field pattern modulation, light extraction. 1. Introduction. GaN-based light-emitting diodes ...

105

Bonding and gap states at GaAs-oxide interfaces  

Science Conference Proceedings (OSTI)

The nature of bonding and possible causes of Fermi level pinning at high mobility-high dielectric constant oxide GaAs:HfO"2 interfaces are discussed. It is argued that these are atoms with defective bonding, rather than states due to the bulk semiconductor ... Keywords: GaAs, bonding, interface

John Robertson; Liang Lin

2011-04-01T23:59:59.000Z

106

Elastic properties of Pu metal and Pu-Ga alloys  

Science Conference Proceedings (OSTI)

We present elastic properties, theoretical and experimental, of Pu metal and Pu-Ga ({delta}) alloys together with ab initio equilibrium equation-of-state for these systems. For the theoretical treatment we employ density-functional theory in conjunction with spin-orbit coupling and orbital polarization for the metal and coherent-potential approximation for the alloys. Pu and Pu-Ga alloys are also investigated experimentally using resonant ultrasound spectroscopy. We show that orbital correlations become more important proceeding from {alpha} {yields} {beta} {yields} {gamma} plutonium, thus suggesting increasing f-electron correlation (localization). For the {delta}-Pu-Ga alloys we find a softening with larger Ga content, i.e., atomic volume, bulk modulus, and elastic constants, suggest a weakened chemical bonding with addition of Ga. Our measurements confirm qualitatively the theory but uncertainties remain when comparing the model with experiments.

Soderlind, P; Landa, A; Klepeis, J E; Suzuki, Y; Migliori, A

2010-01-05T23:59:59.000Z

107

Lasing characteristics of GaSb/GaAs self-assembled quantum dots embedded in an InGaAs quantum well  

E-Print Network (OSTI)

be applicable to light sources in fiber-optic communication systems.13 However, there have been no reports intriguing optoelectronic device possibilities on GaAs substrates including lasers, detectors, or solar cells

Jalali. Bahram

108

Near ultraviolet emission from nonpolar cubic AlxGa1-xN/GaN quantum wells  

E-Print Network (OSTI)

Near ultraviolet emission from nonpolar cubic AlxGa1-xN/GaN quantum wells J. Schörmann,a S and multiple quantum wells. The well widths ranged from 2.5 to 7.5 nm. Samples were grown by rf-plasma assisted wells clear reflection high energy electron diffraction oscillations were observed indicating a two

As, Donat Josef

109

High Breakdown ( > \\hbox {1500 V} ) AlGaN/GaN HEMTs by Substrate-Transfer Technology  

E-Print Network (OSTI)

In this letter, we present a new technology to increase the breakdown voltage of AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on Si substrates. This new technology is based on the removal of the original Si ...

Lu, Bin

110

Development of high power green light emitting diode dies in piezoelectric GaInN/GaN  

E-Print Network (OSTI)

Development of high power green light emitting diode dies in piezoelectric GaInN/GaN Christian in green light emitting diodes is one of the big challenges towards all-solid- state lighting. The prime,3], and commercialization [4,5] of high brightness light emitting diodes LEDs has led to a 1.82 Billion-$/year world market

Detchprohm, Theeradetch

111

Wavelength-resolved low-frequency noise of GaInN/GaN green light emitting diodes  

E-Print Network (OSTI)

Wavelength-resolved low-frequency noise of GaInN/GaN green light emitting diodes S. L. Rumyantseva well light emitting diodes. The light intensity noise was measured as a function of wavelength within the light emitting diode spectral emission line. The spectral noise density is found to increase

Wetzel, Christian M.

112

Structural and optical studies of nitrogen incorporation into GaSb-based GaInSb quantum wells  

Science Conference Proceedings (OSTI)

We investigate the incorporation of nitrogen into (Ga,In)Sb grown on GaSb and report room temperature photoluminescence from GaInSb(N) quantum wells. X-ray diffraction and channeling nuclear reaction analysis, together with Rutherford backscattering, were employed to identify the optimal molecular beam epitaxial growth conditions that minimized the incorporation of non-substitutional nitrogen into GaNSb. Consistent with this hypothesis, GaInSb(N) quantum wells grown under the conditions that minimized non-substitutional nitrogen exhibited room temperature photoluminescence, indicative of significantly improved radiative efficiency. Further development of this material system could enable type-I laser diodes emitting throughout the (3-5 {mu}m) wavelength range.

Nair, Hari P.; Crook, Adam M.; Bank, Seth R. [Microelectronics Research Center, Electrical and Computer Engineering, University of Texas at Austin, 10100 Burnet Rd, Austin, Texas 78712 (United States); Yu, Kin M. [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2012-01-09T23:59:59.000Z

113

GaSb/GaAs quantum dot formation and demolition studied with cross-sectional scanning tunneling microscopy  

Science Conference Proceedings (OSTI)

We present a cross-sectional scanning tunneling microscopy study of GaSb/GaAs quantum dots grown by molecular beam epitaxy. Various nanostructures are observed as a function of the growth parameters. During growth, relaxation of the high local strain fields of the nanostructures plays an important role in their formation. Pyramidal dots with a high Sb content are often accompanied by threading dislocations above them. GaSb ring formation is favored by the use of a thin GaAs first cap layer and a high growth temperature of the second cap layer. At these capping conditions, strain-driven Sb diffusion combined with As/Sb exchange and Sb segregation remove the center of a nanostructure, creating a ring. Clusters of GaSb without a well defined morphology also appear regularly, often with a highly inhomogeneous structure which is sometimes divided up in fragments.

Smakman, E. P.; Garleff, J. K.; Rambabu, P.; Koenraad, P. M. [Department of Applied Physics, Eindhoven University of Technology, Eindhoven 5612 AZ (Netherlands); Young, R. J.; Hayne, M. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)

2012-04-02T23:59:59.000Z

114

Effect of Sb on the Properties of GaInP Top Cells (Presentation)  

DOE Green Energy (OSTI)

The summary of this report is that: (1) Sb can be used to increase V{sub oc} of a GaInP top cell; (2) the photovoltaic quality of GaInP is relatively unaffected by the presence of Sb; and (3) Sb-doped GaInP/GaAs tandem cells show promise for achieving efficiencies over 32%.

Olson, J. M.; McMahon, W. E.; Kurtz, S.

2006-05-01T23:59:59.000Z

115

Dielectrics for GaN based MIS-diodes  

SciTech Connect

GaN MIS diodes were demonstrated utilizing AlN and Ga{sub 2}O{sub 3}(Gd{sub 2}O{sub 3}) as insulators. A 345 {angstrom} of AlN was grown on the MOCVD grown n-GaN in a MOMBE system using trimethylamine alane as Al precursor and nitrogen generated from a wavemat ECR N2 plasma. For the Ga{sub 2}O{sub 3}(Gd{sub 2}O{sub 3}) growth, a multi MBE chamber was used and a 195 {angstrom} oxide is E-beam evaporated from a single crystal source of Ga{sub 5}Gd{sub 3}O{sub 12}. The forward breakdown voltage of AlN and Ga{sub 2}O{sub 3}(Gd{sub 2}O{sub 3}) diodes are 5V and 6V, respectively, which are significantly improved from {approximately} 1.2 V of schottky contact. From the C-V measurements, both kinds of diodes showed good charge modulation from accumulation to depletion at different frequencies. The insulator GaN interface roughness and the thickness of the insulator were measured with x-ray reflectivity.

Ren, F.; Abernathy, C.R.; MacKenzie, J.D. [Univ. of Florida, Gainesville, FL (United States)] [and others

1998-02-01T23:59:59.000Z

116

Atomic hydrogen cleaning of polarized GaAs photocathodes  

DOE Green Energy (OSTI)

Atomic hydrogen cleaning followed by heat cleaning at 450 C was used to prepare negative-electron-affinity GaAs photocathodes. When hydrogen ions were eliminated, quantum efficiencies of 15% were obtained for bulk GaAs cathodes, higher than the results obtained using conventional 600 C heat cleaning. The low-temperature cleaning technique was successfully applied to thin, strained GaAs cathodes used for producing highly polarized electrons. No depolarization was observed even when the optimum cleaning time of about 30 seconds was extended by a factor of 100.

Maruyama, Takashi

2003-04-03T23:59:59.000Z

117

Outdoor Testing of GaInP2/GaAs Tandem Cells with Top Cell Thickness Varied  

DOE Green Energy (OSTI)

In this study, we measure the performance of GaInP2/GaAs tandem cells under direct beam sunlight outdoors in order to quantify their sensitivity to both spectral variation and GaInP2 top-cell thickness. A set of cells with five different top-cell thicknesses was mounted on a two-axis tracker with the incident sunlight collimated to exclude all except the direct beam. Current-voltage (I-V) curves were taken throughout the course of several days, along with measurements of the direct solar spectrum. Our two major conclusions are: (1) GaInP2/GaAs tandem cells designed for either the ASTM G-173 direct (G-173D) spectrum or the "air mass 1.5 global" (AM1.5G) spectrum perform the best, and (2) cells can be characterized indoors and modeled using outdoor spectra with the same result. These results are equally valid for GaInP2/GaAs/Ge triple-junction cells.

McMahon, W. E.; Emergy, K. E.; Friedman, D. J.; Ottoson, L.; Young, M. S.; Ward, J. S.; Kramer, C. M.; Duda, A.; Kurtz, S.

2005-08-01T23:59:59.000Z

118

On-Sun Comparison of GaInP2/GaAs Tandem Cells with Top Cell Thickness Varied  

DOE Green Energy (OSTI)

This study compares the on-sun performance of a set of GaInP2/GaAs tandem cells with different GaInP2 top-cell thicknesses. Because high-efficiency III-V cells are best suited to concentrating photovoltaic (CPV) applications, the cells were mounted on a two-axis tracker with the incident sunlight collimated to exclude all except the direct beam. Current-voltage (I-V) curves were taken throughout the course of several days, along with measurements of the direct solar spectrum. Our two major conclusions are: (1) GaInP2/GaAs tandem cells designed for an ''air mass 1.5 global'' (AM 1.5G) or a ''low aerosol optical depth'' (Low AOD) spectrum perform the best, and (2) cells can be characterized indoors and modeled using outdoor spectra to predict the correct result. These results are equally valid for GaInP2/GaAs/Ge triple-junction cells.

McMahon, W. E.; Emery, K. E.; Friedman, D. J.; Ottoson, L.; Young, M. S.; Ward, J. S.; Kramer, C. M.; Duda, A.; Kurtz, S.

2005-02-01T23:59:59.000Z

119

lntersubbancl transitions in high indium content InGaAs/AIGaAs quantum wells  

E-Print Network (OSTI)

lntersubbancl transitions in high indium content InGaAs/AIGaAs quantum wells H. C. Chui, S. M. Lord report the first observation of intersubband transitions in In,Ga, -#s(y=O.3,0.5)/ AlGaAs quantum wells. These quantum wells were grown on a GaAs substrate with a linearly graded InGaAs buffer to achieve strain

Fejer, Martin M.

120

Realization of compressively strained GaN films grown on Si(110) substrates by inserting a thin AlN/GaN superlattice interlayer  

Science Conference Proceedings (OSTI)

We investigate the strain properties of GaN films grown by plasma-assisted molecular beam epitaxy on Si(110) substrates. It is found that the strain of the GaN film can be converted from a tensile to a compressive state simply by inserting a thin AlN/GaN superlattice structure (SLs) within the GaN film. The GaN layers seperated by the SLs can have different strain states, which indicates that the SLs plays a key role in the strain modulation during the growth and the cooling down processes. Using this simple technique, we grow a crack-free GaN film exceeding 2-{mu}m-thick. The realization of the compressively strained GaN film makes it possible to grow thick GaN films without crack generation on Si substrates for optic and electronic device applications.

Shen, X. Q.; Takahashi, T.; Kawashima, H.; Ide, T.; Shimizu, M. [Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Central 2, Tsukuba-shi, Ibaraki 305-8568 (Japan)

2012-07-16T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

Fabrication of Two-Dimensional Photonic Crystals in AlGaInP/GaInP Membranes by Inductively Coupled Plasma Etching  

E-Print Network (OSTI)

The fabrication process of two-dimensional photonic crystals in an AlGaInP/GaInP multi-quantum-well membrane structure is developed. The process includes high resolution electron-beam lithography, pattern transfer into ...

Chen, A.

122

FUPWG Meeting Agenda - Atlanta, GA | Department of Energy  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Atlanta, GA Atlanta, GA FUPWG Meeting Agenda - Atlanta, GA October 7, 2013 - 3:16pm Addthis Energy on My Mind / FUPWG / Atlanta, GA / May 3-4, 2006 Hosted by: AGL Resources Logo May 3-4, 2006 Hosted by AGL Resources Atlanta, Georgia Tuesday, May 2, 2006 5:00 - 6:30 Steering Committee meeting in the Danube Tigris Room 6:30 until... Networking dinner at the Marriott Wednesday, May 3, 2006 7:45 am Registration/Continental Breakfast 8:30 - 8:45 Welcome from Suzanne Sitherwood, SVP, Southern Operations, President, Atlanta Gas Light, Chattanooga Gas & Florida City Gas 8:45 - 9:00 FEMP Southeast Regional Office Welcome Traci Leath, FEMP 9:00 - 9:45 Washington Update David McAndrew, FEMP 9:45 - 10:15 Break - Networking 10:15 - 11:20 Navy Technical Program Update Paul Kistler, U.S. Navy

123

Elba Island, GA Liquefied Natural Gas Imports from Qatar (Million...  

U.S. Energy Information Administration (EIA) Indexed Site

Liquefied Natural Gas Imports from Qatar (Million Cubic Feet) Elba Island, GA Liquefied Natural Gas Imports from Qatar (Million Cubic Feet) Year Jan Feb Mar Apr May Jun Jul Aug Sep...

124

Lattice vibrations of pure and doped GaSe  

Science Conference Proceedings (OSTI)

The Bridgman method is used to grow especially undoped and doped single crystals of GaSe. Composition and impurity content of the grown crystals were determined using X-ray fluorescence (XRF) method. X-ray diffraction, Raman scattering, photoluminescence (PL), and IR transmission measurements were performed at room temperature. The long wavelength lattice vibrations of four modifications of GaSe were described in the framework of modified one-layer linear-chain model which also takes into consideration the interaction of the selenium (Se) atom with the second nearest neighbor gallium (Ga) atom in the same layer. The existence of an eight-layer modification of GaSe is suggested and the vibrational frequencies of this modification are explained in the framework of a lattice dynamical model considered in the present work. Frequencies and the type of vibrations (gap, local, or resonance) for the impurity atoms were calculated and compared with the experimental results.

Allakhverdiev, K. [Materials Institute, Marmara Research Center, TUBITAK, Gebze/Kocaeli 41470 (Turkey) and Institute of Physics, Azerbaijan National Academy of Sciences, Baku AZ1143 (Azerbaijan)]. E-mail: kerim.allahverdi@mam.gov.tr; Baykara, T. [Materials Institute, Marmara Research Center, TUBITAK, Gebze/Kocaeli 41470 (Turkey); Ellialtioglu, S. [Department of Physics, Middle East Technical University, Ankara 06531 (Turkey); Hashimzade, F. [Institute of Physics, Azerbaijan National Academy of Sciences, Baku AZ1143 (Azerbaijan); Huseinova, D. [Institute of Physics, Azerbaijan National Academy of Sciences, Baku AZ1143 (Azerbaijan); Kawamura, K. [Institute of Materials Science, University of Tsukuba 305-8573 (Japan); Kaya, A.A. [Materials Institute, Marmara Research Center, TUBITAK, Gebze/Kocaeli 41470 (Turkey); Kulibekov, A.M. [Department of Physics, Mugla University, Mugla 48000 (Turkey); Onari, S. [Institute of Materials Science, University of Tsukuba 305-8573 (Japan)

2006-04-13T23:59:59.000Z

125

HH5, Antiferromagnetic Interlayer Exchange Couplings in Ga  

Science Conference Proceedings (OSTI)

Author(s), Sun Jae Chung, Sanghoon Lee, Brian J. Kirby, Julie A. Borchers, ... LATE NEWS: KK3, Non-Catalytic Synthesis of GaN Nanostructures at Low ...

126

Preparation of GaAs photocathodes at low temperature  

SciTech Connect

The preparation of an atomically clean surface is a necessary step in the formation of negative electron affinity (NEA) GaAs. Traditional methods to this end include cleaving, heat cleaning and epitaxial growth. Cleaving has the advantage of yielding a fresh surface after each cleave, but is limited to small areas and is not suitable for specialized structures. Heat cleaning is both simple and highly successful, so it is used as a preparation method in virtually all laboratories employing a NEA source on a regular basis. Due to its high cost and complexity, epitaxial growth of GaAs with subsequent in vacuo transfer is not a practical solution for most end users of GaAs as a NEA electron source. While simple, the heating cleaning process has a number of disadvantages. Here, a variety of cleaning techniques related to preparation of an atomically clean GaAs surface without heating to 600 C are discussed and evaluated.

Mulhollan, G.; Clendenin, J.; Tang, H.

1996-10-01T23:59:59.000Z

127

Elba Island, GA Natural Gas Liquefied Natural Gas Imports from...  

Gasoline and Diesel Fuel Update (EIA)

Trinidad and Tobago (Million Cubic Feet) Elba Island, GA Natural Gas Liquefied Natural Gas Imports from Trinidad and Tobago (Million Cubic Feet) Year Jan Feb Mar Apr May Jun Jul...

128

Elba Island, GA Natural Gas Liquefied Natural Gas Imports from...  

Gasoline and Diesel Fuel Update (EIA)

Egypt (Million Cubic Feet) Elba Island, GA Natural Gas Liquefied Natural Gas Imports from Egypt (Million Cubic Feet) Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 5,780...

129

Elba Island, GA Liquefied Natural Gas Total Imports (Million...  

U.S. Energy Information Administration (EIA) Indexed Site

Liquefied Natural Gas Total Imports (Million Cubic Feet) Elba Island, GA Liquefied Natural Gas Total Imports (Million Cubic Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5...

130

GaAs Films Prepared by RF-Magnetron Sputtering  

DOE Green Energy (OSTI)

The authors reported on the optical absorption, adhesion, and microstructure of RF-magnetron sputtered films of hydrogenated amorphous and microcrystalline GaAs films for the 1 to 25 {micro}m infrared wavelength rate. Sputtering parameters which were varied include sputtering power, temperature and pressure, and hydrogen sputtering-gas concentration. TEM results show a sharp transition from purely amorphous GaAs to a mixture of microcrystalline GaAs in an amorphous matrix at 34 {+-} 2 C. By optimizing the sputtering parameters, the optical absorption coefficient can be decreased below 100 cm{sup -1} for wavelengths greater than about 1.25 {micro}m. These results represent the lowest reported values of optical absorption for sputtered films of GaAs directly measured by spectrophotometry for the near-infrared wavelength region.

L.H. Ouyang; D.L. Rode; T. Zulkifli; B. Abraham-Shrauner; N. Lewis; M.R. Freeman

2001-08-01T23:59:59.000Z

131

Micro Raman Spectroscopy of Annealed Erbium Implanted GaN  

E-Print Network (OSTI)

Wurtzite GaN epilayers grown by metal organic chemical vapor deposition on sapphire substrates were subsequently ion implanted with Er to a dose of 5×10ą? cm?˛. The implanted samples were annealed in nitrogen atmosphere ...

Vajpeyi, Agam P.

132

Elba Island, GA Natural Gas Liquefied Natural Gas Imports from...  

U.S. Energy Information Administration (EIA) Indexed Site

Equatorial Guinea (Million Cubic Feet) Elba Island, GA Natural Gas Liquefied Natural Gas Imports from Equatorial Guinea (Million Cubic Feet) Decade Year-0 Year-1 Year-2 Year-3...

133

Elba Island, GA Natural Gas Liquefied Natural Gas Imports from...  

U.S. Energy Information Administration (EIA) Indexed Site

Nigeria (Million Cubic Feet) Elba Island, GA Natural Gas Liquefied Natural Gas Imports from Nigeria (Million Cubic Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6...

134

Cathodoluminescence Microanalysis of Suspended GaN Nano ...  

Science Conference Proceedings (OSTI)

CL from bulk GaN is dominated by the ~3.4 eV near-band-edge emission. In contrast, the suspended nano-membranes emit a broad defect associated emission ...

135

BB2, Novel Cs-Free GaN Photocathodes  

Science Conference Proceedings (OSTI)

L6, PECVD-SiN, Si or Si/Al2O3-Capped ED-Mode AlN/GaN Inverters · Hide details for [

136

Thermal carrier emission and nonradiative recombinations in nonpolar (Al,Ga)N/GaN quantum wells grown on bulk GaN  

Science Conference Proceedings (OSTI)

We investigate, via time-resolved photoluminescence, the temperature-dependence of charge carrier recombination mechanisms in nonpolar (Al,Ga)N/GaN single quantum wells (QWs) grown via molecular beam epitaxy on the a-facet of bulk GaN crystals. We study the influence of both QW width and barrier Al content on the dynamics of excitons in the 10-320 K range. We first show that the effective lifetime of QW excitons {tau} increases with temperature, which is evidence that nonradiative mechanisms do not play any significant role in the low-temperature range. The temperature range for increasing {tau} depends on the QW width and Al content in the (Al,Ga)N barriers. For higher temperatures, we observe a reduction in the QW emission lifetime combined with an increase in the decay time for excitons in the barriers, until both exciton populations get fully thermalized. Based on analysis of the ratio between barrier and QW emission intensities, we demonstrate that the main mechanism limiting the radiative efficiency in our set of samples is related to nonradiative recombination in the (Al,Ga)N barriers of charge carriers that have been thermally emitted from the QWs.

Corfdir, P.; Dussaigne, A.; Giraud, E.; Ganiere, J.-D.; Grandjean, N.; Deveaud-Pledran, B. [Institute of Condensed Matter Physics, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Teisseyre, H. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Institute of High Pressure Physics, Polish Academy of Sciences, 01-142 Warsaw (Poland); Suski, T.; Grzegory, I. [Institute of High Pressure Physics, Polish Academy of Sciences, 01-142 Warsaw (Poland); Lefebvre, P. [Laboratoire Charles Coulomb - UMR5221 - CNRS - Universite Montpellier 2, 34095 Montpellier (France)

2012-02-01T23:59:59.000Z

137

Modeling of InGaSb thermophotovoltaic cells and materials  

DOE Green Energy (OSTI)

A closed form computer program has been developed for the simulation and optimization of In{sub x}Ga{sub 1{minus}x}Sb thermophotovoltaic cells operating at room temperature. The program includes material parameter models of the energy bandgap, optical absorption constant, electron and hole mobility, intrinsic carrier concentration and index of refraction for any composition of GaInSb alloys.

Zierak, M.; Borrego, J.M.; Bhat, I.; Gutmann, R.J. [Rensselaer Polytechnic Inst., Troy, NY (United States); Charache, G. [Lockheed Martin, Inc., Schenectady, NY (United States)

1997-05-01T23:59:59.000Z

138

SEU design consideration for MESFETs on LT GaAs  

SciTech Connect

Computer simulation results are reported on transistor design and single-event charge collection modeling of metal-semiconductor field effect transistors (MESFETs) fabricated in the Vitesse H-GaAsIII{reg_sign} process on Low Temperature grown (LT) GaAs epitaxial layers. Tradeoffs in Single Event Upset (SEU) immunity and transistor design are discussed. Effects due to active loads and diffusion barriers are examined.

Weatherford, T.R.; Radice, R.; Eskins, D. [Naval Postgraduate School, Monterey, CA (United States)] [and others

1997-12-01T23:59:59.000Z

139

Influence of defect formation as a result of incorporation of a Mn {delta} layer on the photosensitiviy spectrum of InGaAs/GaAs quantum wells  

Science Conference Proceedings (OSTI)

The influence of defect formation upon the deposition of a Mn {delta} layer and a GaAs coating layer (with the use of laser evaporation) on the photosensitivity spectra of heterostructures with InGaAs/GaAs quantum wells located in the near-surface region has been studied.

Gorshkov, A. P., E-mail: gorskovap@phys.unn.ru; Karpovich, I. A.; Pavlova, E. D.; Kalenteva, I. L. [Lobachevsky State University of Nizhny Novgorod (Russian Federation)

2012-02-15T23:59:59.000Z

140

Charge Profiling of the p-AlGaN Electron Blocking Layer in AlGaInN Light Emitting Diode Structures  

E-Print Network (OSTI)

Charge Profiling of the p-AlGaN Electron Blocking Layer in AlGaInN Light Emitting Diode Structures, U.S.A. ABSTRACT Characterization of operational AlGaInN heterostructure light emitting diodes (LEDs the device lifetime in a non-destructive mode. INTRODUCTION Group ­ III nitride light emitting diodes (LEDs

Wetzel, Christian M.

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Excitons in single and double GaAs/AlGaAs/ZnSe/Zn(Cd)MnSe heterovalent quantum wells  

Science Conference Proceedings (OSTI)

Exciton photoluminescence spectra, photoluminescence excitation spectra, and magnetophotoluminescence spectra of single (GaAs/AlGaAs/ZnMnSe) and double (GaAs/AlGaAs/ZnSe/ZnCdMnSe) heterovalent quantum wells formed by molecular beam epitaxy are studied. It is shown that the exciton absorption spectrum of such quantum wells mainly reproduces the resonant exciton spectrum expected for usual quantum wells with similar parameters, while the radiative exciton recombination have substantial distinctions, in particular the additional localization mechanism determined by defects generated by heterovalent interface exists. The nature of these localization centers is not currently clarified; their presence leads to broadening of photoluminescence lines and to an increase in the Stokes shift between the peaks of luminescence and absorption, as well as determining the variation in the magnetic g factor of bound exciton complexes.

Toropov, A. A., E-mail: toropov@beam.ioffe.ru; Kaibyshev, V. Kh.; Terent'ev, Ya. V.; Ivanov, S. V.; Kop'ev, P. S. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

2011-02-15T23:59:59.000Z

142

Mechanism for radiative recombination and defect properties of GaP/GaNP core/shell nanowires  

SciTech Connect

Recombination processes in GaP/GaNP core/shell nanowires (NWs) grown on a Si substrate by molecular beam epitaxy are examined using a variety of optical characterization techniques, including cw- and time-resolved photoluminescence and optically detected magnetic resonance (ODMR). Superior optical quality of the structures is demonstrated based on the observation of intense emission from a single NW at room temperature. This emission is shown to originate from radiative transitions within N-related localized states. From ODMR, growth of GaP/GaNP NWs is also found to facilitate formation of complex defects containing a P atom at its core that act as centers of competing non-radiative recombination.

Dobrovolsky, A.; Stehr, J. E.; Chen, S. L.; Chen, W. M.; Buyanova, I. A. [Department of Physics, Chemistry and Biology, Linkoeping University, S-581 83 Linkoeping (Sweden); Kuang, Y. J. [Department of Physics, University of California, La Jolla, California 92093 (United States); Sukrittanon, S. [Graduate Program of Materials Science and Engineering, La Jolla, California 92093 (United States); Tu, C. W. [Department of Electrical and Computer Engineering, University of California, La Jolla, California 92093 (United States)

2012-10-15T23:59:59.000Z

143

Optical anisotropy of GaSb type-II nanorods on vicinal (111)B GaAs  

SciTech Connect

We form self-assembled GaSb type-II nanorods on a vicinal (111)B GaAs substrate by molecular beam epitaxy and study their optical anisotropy. The GaSb nanorods are elongated and aligned along the [-1 0 1] direction, where the average length, width, and height are about 84, 30, and 2.5 nm. In polarized photoluminescence (PL) measurements, the peak of the GaSb nanorods is observed at about 1.1 eV, where the PL intensity is largest for the [-1 0 1] polarization and smallest for the polarization perpendicular to it. The degree of polarization is more than 20% and depends on the recombination energy. By comparing with a theoretical model based on 4 x 4 Luttinger-Kohn Hamiltonian, we find that the experimental results are explained by considering the Sb/As inter-diffusion and the nanorod height distribution.

Kawazu, Takuya; Noda, Takeshi; Mano, Takaaki; Sakuma, Yoshiki [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Akiyama, Yoshihiro [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya (Japan); Sakaki, Hiroyuki [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya (Japan)

2011-12-05T23:59:59.000Z

144

EE9, MBE Grown InGaAsSbN/GaSb Single Quantum Wells for Mid ...  

Science Conference Proceedings (OSTI)

I4, Electrical Spin Injection in a Hybrid Organic/Inorganic Spin-Polarized Light Emitting Diode (Spin-LED) · I5, Properties of MnAs/GaMnAs/MnAs Magnetic ...

145

II3, 2?m Thick Device Quality GaN on Si(111) Using AlGaN Graded ...  

Science Conference Proceedings (OSTI)

I4, Electrical Spin Injection in a Hybrid Organic/Inorganic Spin-Polarized Light Emitting Diode (Spin-LED) · I5, Properties of MnAs/GaMnAs/MnAs Magnetic ...

146

JJ1, Internal Quantum Efficiency of Polar and Non-Polar GaInN/GaN ...  

Science Conference Proceedings (OSTI)

I4, Electrical Spin Injection in a Hybrid Organic/Inorganic Spin-Polarized Light Emitting Diode (Spin-LED) · I5, Properties of MnAs/GaMnAs/MnAs Magnetic ...

147

Reducing the efficiency droop by lateral carrier confinement in InGaN/GaN quantum-well nanorods  

E-Print Network (OSTI)

Efficiency droop is a major obstacle facing high-power application of InGaN/GaN quantum-well (QW) light-emitting diodes. In this letter, we report the suppression of efficiency droop induced by density-activated defect recombination in nanorod structure of a-plane InGaN/GaN QWs. In the high carrier density regime, the retained emission efficiency in a dry-etched nanorod sample is observed to be over two times higher than that in its parent QW sample. We further argue that the improvement is a combined effect of the amendment contributed by lateral carrier confinement and the deterioration made by surface trapping.

Shi, Chentian; Yang, Fan; Park, Min Joo; Kwak, Joon Seop; Jung, Sukkoo; Choi, Yoon-Ho; Wang, Xiaoyong; Xiao, Min

2013-01-01T23:59:59.000Z

148

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

Science Conference Proceedings (OSTI)

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

Hung, S.T. [Feng Chia University, Taichung, Taiwan; Chung, Chi-Jung [Feng Chia University, Taichung, Taiwan; Chen, Chin Ching [University of Florida, Gainesville; Lo, C. F. [University of Florida; Ren, F. [University of Florida; Pearton, S. J. [University of Florida; Kravchenko, Ivan I [ORNL

2012-01-01T23:59:59.000Z

149

High Voltage GaN Schottky Rectifiers  

SciTech Connect

Mesa and planar GaN Schottky diode rectifiers with reverse breakdown voltages (V{sub RB}) up to 550V and >2000V, respectively, have been fabricated. The on-state resistance, R{sub ON}, was 6m{Omega}{center_dot} cm{sup 2} and 0.8{Omega}cm{sup 2}, respectively, producing figure-of-merit values for (V{sub RB}){sup 2}/R{sub ON} in the range 5-48 MW{center_dot}cm{sup -2}. At low biases the reverse leakage current was proportional to the size of the rectifying contact perimeter, while at high biases the current was proportional to the area of this contact. These results suggest that at low reverse biases, the leakage is dominated by the surface component, while at higher biases the bulk component dominates. On-state voltages were 3.5V for the 550V diodes and {ge}15 for the 2kV diodes. Reverse recovery times were <0.2{micro}sec for devices switched from a forward current density of {approx}500A{center_dot}cm{sup -2} to a reverse bias of 100V.

CAO,X.A.; CHO,H.; CHU,S.N.G.; CHUO,C.-C.; CHYI,J.-I.; DANG,G.T.; HAN,JUNG; LEE,C.-M.; PEARTON,S.J.; REN,F.; WILSON,R.G.; ZHANG,A.P.

1999-10-25T23:59:59.000Z

150

Suppression of nuclear spin diffusion at a GaAs/AlGaAs interface measured with a single quantum dot nano-probe  

E-Print Network (OSTI)

Nuclear spin polarization dynamics are measured in optically pumped individual GaAs/AlGaAs interface quantum dots by detecting the time-dependence of the Overhauser shift in photoluminescence (PL) spectra. Long nuclear polarization decay times of ~ 1 minute have been found indicating inefficient nuclear spin diffusion from the GaAs dot into the surrounding AlGaAs matrix in externally applied magnetic field. A spin diffusion coefficient two orders lower than that previously found in bulk GaAs is deduced.

A. E. Nikolaenko; E. A. Chekhovich; M. N. Makhonin; I. W. Drouzas; A. B. Vankov; J. Skiba-Szymanska; M. S. Skolnick; P. Senellart; A. Lemaitre; A. I. Tartakovskii

2009-01-15T23:59:59.000Z

151

Elimination of charge-enhancement effects in GaAs FETs with a low-temperature grown GaAs buffer layer  

Science Conference Proceedings (OSTI)

The use of low temperature grown GaAs (LT GaAs) buffer layer in GaAs FETs is shown via computer simulation and experimental measurement to reduce ion-induced charge collection by two to three orders of magnitude. This reduction in collected charge is associated with the efficient reduction of charge-enhancement mechanisms in the FETs. Error rate calculations indicate that the soft error rate of LT GaAs integrated circuits will be reduced by several orders of magnitude when compared to conventional FET-based GaAs ICs.

McMorrow, D.; Weatherford, T.R.; Curtice, W.R.; Knudson, A.R.; Buchner, S.; Melinger, J.S.; Tran, L.H.; Campbell, A.B. [Naval Research Lab., Washington, DC (United States)

1995-12-01T23:59:59.000Z

152

Active region based on graded-gap InGaN/GaN superlattices for high-power 440- to 470-nm light-emitting diodes  

SciTech Connect

The structural and optical properties of light-emitting diode structures with an active region based on ultrathin InGaN quantum wells limited by short-period InGaN/GaN superlattices from both sides have been investigated. The dependences of the external quantum efficiency on the active region design are analyzed. It is shown that the use of InGaN/GaN structures as limiting graded-gap short-period superlattices may significantly increase the quantum efficiency.

Tsatsulnikov, A. F., E-mail: Andrew@beam.ioffe.ru; Lundin, W. V.; Sakharov, A. V.; Zavarin, E. E.; Usov, S. O.; Nikolaev, A. E.; Cherkashin, N. A.; Ber, B. Ya.; Kazantsev, D. Yu. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Mizerov, M. N. [Russian Academy of Sciences, Center for Microelectronics, Ioffe Physicotechnical Institute (Russian Federation); Park, Hee Seok [Samsung Electro-Mechanics Co. Ltd. (Korea, Republic of); Hytch, M.; Hue, F. [National Center for Scientific Research, Center for Material Elaboration and Structural Studies (France)

2010-01-15T23:59:59.000Z

153

CC2, Two-Dimensional Electron Gas in In X Al 1-X N/Aln/GaN ...  

Science Conference Proceedings (OSTI)

DD3, A New Approach to Make ZnO-Cu2O Heterojunctions for Solar Cells ... E2, AlGaAs/GaAs/GaN Wafer Fused HBTs with Ar Implanted Extrinsic Collectors.

154

Phonon Knudsen flow in GaAs/AlAs superlattices  

DOE Green Energy (OSTI)

The measured in-plane thermal conductivity, {delta}{sub SL} of GaAs/AlAs superlattices with even moderate layer thicknesses are significantly smaller than the weighted average, {delta}{sub l} = 67 W/Km, of the bulk GaAs and AlAs conductivities. One expects a suppression of the thermal conductivity to that of an actual Al{sub 0.5}Ga{sub 0.5}As alloy when the thickness of the GaAs and AlAs layers approaches that of a single monolayer. However, the observed superlattice thermal conductivity remains suppressed even at layer thickness {approx_gt} 10 nm. The low thermal conductivities, and very high mobilities, make n-doped GaAs/AlAs superlattices attractive possibilities for thermoelectric devices. With Molecular-Beam-Epitaxial grown GaAs/AlAs superlattices one can expect the individual GaAs and AlAs layers to be extremely clean. Defect and/or alloy scattering is limited to be near the heterostructure interfaces. The authors estimate the room-temperature phonon mean-free-path to be 42 (22) nm for the longitudinal (transverse) mode and thus comparable to or smaller than the layer thicknesses. Thus they expect an important phonon scattering at the interfaces. They study this phonon scattering at the superlattice interfaces assuming a Knudsen flow characterized by diffusive scattering. The solid curve in the figure shows the Knudsen-flow theory estimated for the superlattice thermal conductivity which shows a significant reduction when the layer thickness is shorter than the estimated phonon mean free paths.

Hyldgaard, P.; Mahan, G.D. [Oak Ridge National Lab., TN (United States). Solid State Div.]|[Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy

1995-09-01T23:59:59.000Z

155

Strain relaxation in GaN/Al{sub x}Ga{sub 1-x}N superlattices grown by plasma-assisted molecular-beam epitaxy  

SciTech Connect

We have investigated the misfit relaxation process in GaN/Al{sub x}Ga{sub 1-x}N (x = 0.1, 0.3, 0.44) superlattices (SL) deposited by plasma-assisted molecular beam epitaxy. The SLs under consideration were designed to achieve intersubband absorption in the mid-infrared spectral range. We have considered the case of growth on GaN (tensile stress) and on AlGaN (compressive stress) buffer layers, both deposited on GaN-on-sapphire templates. Using GaN buffer layers, the SL remains almost pseudomorphic for x = 0.1, 0.3, with edge-type threading dislocation densities below 9 x 10{sup 8} cm{sup -2} to 2 x 10{sup 9} cm{sup -2}. Increasing the Al mole fraction to 0.44, we observe an enhancement of misfit relaxation resulting in dislocation densities above 10{sup 10} cm{sup -2}. In the case of growth on AlGaN, strain relaxation is systematically stronger, with the corresponding increase in the dislocation density. In addition to the average relaxation trend of the SL, in situ measurements indicate a periodic fluctuation of the in-plane lattice parameter, which is explained by the different elastic response of the GaN and AlGaN surfaces to the Ga excess at the growth front. The results are compared with GaN/AlN SLs designed for near-infrared intersubband absorption.

Kotsar, Y.; Bellet-Amalric, E.; Das, A.; Monroy, E. [CEA-Grenoble, INAC/SP2M/NPSC, 17 Rue des Martyrs, 38054 Grenoble cedex 9 (France); Doisneau, B. [SIMaP, Grenoble INP, Domaine Universitaire, BP 75, 38402 Saint Martin d'Heres (France); Sarigiannidou, E. [LMGP, Grenoble INP, 3 Parvis Louis Neel, BP 257, 38016 Grenoble cedex 1 (France)

2011-08-01T23:59:59.000Z

156

Testing of ethylene propylene seals for the GA-4/GA-9 casks  

SciTech Connect

The primary O-ring seal of the GA-4 and GA-9 casks was tested for leakage with a full-scale mockup of the cask lid and flange. Tests were performed at temperatures of ambient, {minus}41{degrees}, 121{degrees}, and 193{degrees}C. Shim plates between the lid and flange simulated gaps caused by thermal distortion. The testing used a helium mass spectrometer leak detector (MSLD). Results showed that the primary seal was leaktight for all test conditions. Helium permeation through the seal began in 13--23 minutes for the ambient tests and in 1--2 minutes for the tests at elevated temperatures. After each test several hours of the pumping were typically required to reduce the MSLD background reading to an acceptable level for the next test, indicating that the seal had become saturated with helium. To verify that the test results showed permeation and not real leakage, several response checks were conducted in which a calibrated leak source was inserted in the detector line near the seal. When the leak source was activated the detector responded within seconds.

Boonstra, R.H.

1993-08-01T23:59:59.000Z

157

Nanostructuring of silicon substrates for the site-controlled growth of GaAs/In0.15Ga0.85As/GaAs nanostructures  

Science Conference Proceedings (OSTI)

We report the optimization of electron beam lithography and inductively coupled plasma (ICP) dry etching processes to fabricate pre-patterned Si (100) substrates with sub-100nm holes with controlled size and shape. An efficient in situ cleaning sequence ... Keywords: Electron beam lithography, ICP dry etching, InGaAs quantum dots, MBE growth, Nanostructuring of silicon

Muhammad Usman; Tariq Alzoubi; Mohamed Benyoucef; Johann Peter Reithmaier

2012-09-01T23:59:59.000Z

158

Electric field engineering in GaN high electron mobility transistors  

E-Print Network (OSTI)

In the last few years, AlGaN/GaN high electron mobility transistors (HEMTs) have become the top choice for power amplification at frequencies up to 20 GHz. Great interest currently exists in industry and academia to increase ...

Zhao, Xu, S.M. Massachusetts Institute of Technology

2008-01-01T23:59:59.000Z

159

Light extraction in individual GaN nanowires on Si for LEDs  

E-Print Network (OSTI)

GaN-based nanowires hold great promise for solid state lighting applications because of their waveguiding properties and the ability to grow nonpolar GaN nanowire-based heterostructures, which could lead to increased light ...

Zhou, Xiang

160

High electron mobility in Ga(In)NAs films grown by molecular beam epitaxy  

Science Conference Proceedings (OSTI)

We report the highest mobility values above 2000 cm{sup 2}/Vs in Si doped GaNAs film grown by molecular beam epitaxy. To understand the feature of the origin which limits the electron mobility in GaNAs, temperature dependences of mobility were measured for high mobility GaNAs and referential low mobility GaInNAs. Temperature dependent mobility for high mobility GaNAs is similar to the GaAs case, while that for low mobility GaInNAs shows large decrease in lower temperature region. The electron mobility of high quality GaNAs can be explained by intrinsic limiting factor of random alloy scattering and extrinsic factor of ionized impurity scattering.

Miyashita, Naoya; Ahsan, Nazmul; Monirul Islam, Muhammad; Okada, Yoshitaka [Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan); Inagaki, Makoto [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya 468-8511, Aichi (Japan); Yamaguchi, Masafumi [Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan); Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya 468-8511, Aichi (Japan)

2012-11-26T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Black-body radiation shift of the Ga$^{+}$ clock transition  

E-Print Network (OSTI)

The blackbody radiation shift of the Ga$^+$ $4s^2 \\ ^1S^e_0 \\to 4s4p \\ ^3P^o_0$ clock transition is computed to be $-$$0.0140 \\pm 0.0048$ Hz at 300 K. The small shift is consistent with the blackbody shifts of the clock transitions of other group III ions which are of a similar size. The polarizabilities of the Ga$^+$ $4s^2 \\ ^1S^e_0$, $4s4p \\ ^3P^o_0$, and $4s4p \\ ^1P^o_1$ states were computed using the configuration interaction method with an underlying semi-empirical core potential. A byproduct of the analysis involved large scale calculations of the low lying spectrum and oscillator strengths of the Ga$^{2+}$ ion.

Cheng, Yongjun

2013-01-01T23:59:59.000Z

162

Aug. 8-9, 2006 HAPL meeting, GA Open Discussion on Advanced Armor  

E-Print Network (OSTI)

Aug. 8-9, 2006 HAPL meeting, GA 1 Open Discussion on Advanced Armor Concepts Moderated by A. René in case the W armor does not work. #12;Aug. 8-9, 2006 HAPL meeting, GA 3 Roman Aquaduct at Pont du Gard, Provence #12;Aug. 8-9, 2006 HAPL meeting, GA 4 Possible Advanced Armor Options Include: · Engineered

Raffray, A. René

163

Current injection efficiency of InGaAsN quantum-well lasers Nelson Tansua  

E-Print Network (OSTI)

Current injection efficiency of InGaAsN quantum-well lasers Nelson Tansua Department of Electrical-threshold current injection efficiency of quantum well QW lasers is clarified. The analysis presented here is applied to the current injection efficiency of 1200 nm emitting InGaAs and 1300 nm emitting InGaAsN QW

Gilchrist, James F.

164

ANN-based GA for generating the sizing curve of stand-alone photovoltaic systems  

Science Conference Proceedings (OSTI)

Recent advances in artificial intelligence techniques have allowed the application of such technologies in real engineering problems. In this paper, an artificial neural network-based genetic algorithm (ANN-GA) model was developed for generating the ... Keywords: ANN, ANN-GA, GA, Prediction, Sizing curve, Stand-alone PV system

Adel Mellit

2010-05-01T23:59:59.000Z

165

Luminescence Enhancement in InGaN and ZnO by Water Vapor ...  

Science Conference Proceedings (OSTI)

Dependence of Ag/In Ratio of AgInS2 Crystals Grown by Hot-Press Method ... Analysis of Temperature Characteristics of InGaP/InGaAs/Ge Triple-Junction Solar Cell ... Luminescence Enhancement in InGaN and ZnO by Water Vapor Remote ...

166

Surface plasmon enhanced InGaN light emitter Koichi Okamoto*a  

E-Print Network (OSTI)

is a very promising method for developing the super bright light emitting diodes (LEDs). Moreover, we foundGaN/GaN, light emitting diode, quantum well, internal quantum efficiency, solid-state light source 1. INTRODUCTION Since 1993, InGaN quantum wells (QW)-based light emitting diodes (LEDs) have been continuously

Okamoto, Koichi

167

TESLA-FEL 2007-03 Application of low cost GaAs LED as neutron  

E-Print Network (OSTI)

neutrons in unbiased Gallium Arsenide (GaAs) Light Emitting Diodes (LED) resulted in a reduction Keywords: COTS components, Displacement damage, Electron Linear Accelerator, GaAs Light emitting diode (LED) Gallium Arsenide (GaAs) light emitting diode (LED) for the assessment of integrated neutron fluence

168

Seamless On-Wafer Integration of Si(100) MOSFETs and GaN HEMTs  

E-Print Network (OSTI)

The first on-wafer integration of Si(100) MOSFETs and AlGaN/GaN high electron mobility transistors (HEMTs) is demonstrated. To enable a fully Si-compatible process, we fabricated a novel Si(100)-GaN-Si(100) virtual substrate ...

Piner, Edwin L.

169

Vertically aligned GaN nanotubes - Fabrication and current image analysis  

Science Conference Proceedings (OSTI)

In this work, we present a one step formation method of nanotubes on GaN film, and then map out local current of nanotubes. GaN nanotubes were formed by inductively coupled plasma (ICP) etching and found that tops of these nanotubes were hexagonal with ... Keywords: C-AFM, FESEM, GaN, ICP, Nanotubes

Shang-Chao Hung; Yan-Kuin Su; Shoou-Jinn Chang; Y. H. Chen

2006-11-01T23:59:59.000Z

170

Epitaxial EuO thin films on GaAs  

SciTech Connect

We demonstrate the epitaxial growth of EuO on GaAs by reactive molecular beam epitaxy. Thin films are grown in an adsorption-controlled regime with the aid of an MgO diffusion barrier. Despite the large lattice mismatch, it is shown that EuO grows well on MgO(001) with excellent magnetic properties. Epitaxy on GaAs is cube-on-cube and longitudinal magneto-optic Kerr effect measurements demonstrate a large Kerr rotation of 0.57 deg., a significant remanent magnetization, and a Curie temperature of 69 K.

Swartz, A. G.; Ciraldo, J.; Wong, J. J. I.; Li Yan; Han Wei; Lin Tao; Shi, J.; Kawakami, R. K. [Department of Physics and Astronomy, University of California, Riverside, California 92521 (United States); Mack, S.; Awschalom, D. D. [Center for Spintronics and Quantum Computation, University of California, Santa Barbara, California 93106 (United States)

2010-09-13T23:59:59.000Z

171

GA Hot Cell D&D Closeout Report  

Office of Legacy Management (LM)

GENERAL ATOMICS GENERAL ATOMICS HOT CELL FACILITY DECONTAMINATION & DECOMMISSIONING PROJECT FINAL PROJECT CLOSEOUT REPORT prepared for GA HOT CELL D&D PROJECT CONTRACT NUMBERS DE-AC03-84SF11962 and DE-AC03-95SF20798 PBS VL-GA-0012 Approvals Prepared by: James Davis, III Date Project Manager, Oakland Environmental Programs Office Reviewed by: John Lee Date Deputy, Oakland Environmental Programs Office Approved by: Laurence McEwen Date Acting Director, Oakland Environmental Programs Office General Atomics Hot Cell Facility D&D Project Closeout Report Contents Page i CONTENTS CONTENTS.....................................................................................................................................

172

AlP/GaP distributed Bragg reflectors  

SciTech Connect

Distributed Bragg reflectors with high reflectivity bands centered at wavelengths from 530 to 690 nm (green to red) based on AlP/GaP quarter-wave stacks are prepared on (001)GaP using gas-source molecular-beam epitaxy. Additionally, the complex refractive index of AlP is measured using spectroscopic ellipsometry within the range of 330-850 nm in order to facilitate an accurate reflector design. Structures consisting of 15 quarter-wave stacks reach a peak reflectance between 95% and 98%, depending on the spectral position of the maximum.

Emberger, Valentin; Hatami, Fariba; Ted Masselink, W. [Department of Physics, Humboldt-Universitaet zu Berlin, Newtonstrasse 15, D-12489 Berlin (Germany); Peters, Sven [Sentech Instruments GmbH, Schwarzschildstr. 2, 12489 Berlin (Germany)

2013-07-15T23:59:59.000Z

173

Simple intrinsic defects in GaAs : numerical supplement.  

SciTech Connect

This Report presents numerical tables summarizing properties of intrinsic defects in gallium arsenide, GaAs, as computed by density functional theory. This Report serves as a numerical supplement to the results published in: P.A. Schultz and O.A. von Lilienfeld, 'Simple intrinsic defects in GaAs', Modelling Simul. Mater. Sci Eng., Vol. 17, 084007 (2009), and intended for use as reference tables for a defect physics package in device models. The numerical results for density functional theory calculations of properties of simple intrinsic defects in gallium arsenide are presented.

Schultz, Peter Andrew

2012-04-01T23:59:59.000Z

174

Electron Hall Mobility in GaAsBi  

Science Conference Proceedings (OSTI)

We present measurements of the electron Hall mobility in n-type GaAs{sub 1-x}Bi{sub x} epilayers. We observed no significant degradation in the electron mobility with Bi incorporation in GaAs, up to a concentration of 1.2%. At higher Bi concentration ({ge} 1.6%) some degradation of the electron mobility was observed, although there is no apparent trend. Temperature dependent Hall measurements of the electron mobility suggest neutral impurity scattering to be the dominant scattering mechanism.

Kini, R. N.; Bhusal, L.; Ptak, A. J.; France, R.; Mascarenhas, A.

2009-01-01T23:59:59.000Z

175

Analyzing the growth of In{sub x}Ga{sub 1-x}N/GaN superlattices in self-induced GaN nanowires by x-ray diffraction  

Science Conference Proceedings (OSTI)

Self-induced GaN nanowires are grown by plasma-assisted molecular beam epitaxy, with In{sub x}Ga{sub 1-x}N quantum wells inserted to form an axial superlattice. From the {omega}-2{theta} scans of a laboratory x-ray diffraction experiment, we obtain the superlattice period, the thickness of the quantum wells, and the In content in this layer. The axial growth rate of the In{sub x}Ga{sub 1-x}N quantum wells is significantly enhanced, which we attribute to increased Ga diffusion along the nanowire sidewalls in the presence of In.

Woelz, M.; Kaganer, V. M.; Brandt, O.; Geelhaar, L.; Riechert, H.

2011-06-27T23:59:59.000Z

176

Deep-Level Transient Spectroscopy in InGaAsN Lattice-Matched to GaAs: Preprint  

Science Conference Proceedings (OSTI)

This conference paper describes the deep-level transient spectroscopy (DLTS) measurements have been performed on the quaternary semiconductor InGaAsN. A series of as-grown, metal-organic chemical vapor deposited samples having varying composition were grown and measured. A GaAs sample was used as a baseline for comparison. After adding only In to GaAs, we did not detect significant additional defects; however, adding N and both N and In led to larger hole-trap peaks and additional electron-trap peaks in the DLTS data. The samples containing about 2% N, with and without about 6% In, had electron traps with activation energies of about 0.2 and 0.3 eV. A sample with 0.4% N had an electron trap with an activation energy of 0.37 eV.

Johnston, S. W.; Ahrenkiel, R. K.; Friedman, D. J.; Kurtz, S. R.

2002-05-01T23:59:59.000Z

177

Characteristics of InGaP/InGaAs pseudomorphic high electron mobility transistors with triple delta-doped sheets  

Science Conference Proceedings (OSTI)

Fundamental and insightful characteristics of InGaP/InGaAs double channel pseudomorphic high electron mobility transistors (DCPHEMTs) with graded and uniform triple {delta}-doped sheets are coomprehensively studied and demonstrated. To gain physical insight, band diagrams, carrier densities, and direct current characteristics of devices are compared and investigated based on the 2D semiconductor simulator, Atlas. Due to uniform carrier distribution and high electron density in the double InGaAs channel, the DCPHEMT with graded triple {delta}-doped sheets exhibits better transport properties, higher and linear transconductance, and better drain current capability as compared with the uniformly triple {delta}-doped counterpart. The DCPHEMT with graded triple {delta}-doped structure is fabricated and tested, and the experimental data are found to be in good agreement with simulated results.

Chu, Kuei-Yi [National Cheng-Kung University, Institute of Microelectronics, Department of Electrical Engineering (China); Chiang, Meng-Hsueh, E-mail: mhchiang@niu.edu.tw; Cheng, Shiou-Ying, E-mail: sycheng@niu.edu.tw [National II an University, Department of Electronic Engineering (China); Liu, Wen-Chau [National Cheng-Kung University, Institute of Microelectronics, Department of Electrical Engineering (China)

2012-02-15T23:59:59.000Z

178

An inverted AlGaAs/GaAs patterned-Ge tunnel junction cascade concentrator solar cell. Final subcontract report, 1 January 1991--31 August 1992  

DOE Green Energy (OSTI)

This report describes work to develop inverted-grown Al{sub 0.34}Ga{sub 0.66}As/GaAs cascades. Several significant developments are reported on as follows: (1) The AM1.5 1-sun total-area efficiency of the top Al{sub 0.34}Ga{sub 0.66}As cell for the cascade was improved from 11.3% to 13.2% (NREL measurement [total-area]). (2) The ``cycled`` organometallic vapor phase epitaxy growth (OMVPE) was studied in detail utilizing a combination of characterization techniques including Hall-data, photoluminescence, and secondary ion mass spectroscopy. (3) A technique called eutectic-metal-bonding (EMB) was developed by strain-free mounting of thin GaAs-AlGaAs films (based on lattice-matched growth on Ge substrates and selective plasma etching of Ge substrates) onto Si carrier substrates. Minority-carrier lifetime in an EMB GaAs double-heterostructure was measured as high as 103 nsec, the highest lifetime report for a freestanding GaAs thin film. (4) A thin-film, inverted-grown GaAs cell with a 1-sun AM1.5 active-area efficiency of 20.3% was obtained. This cell was eutectic-metal-bonded onto Si. (5) A thin-film inverted-grown, Al{sub 0.34}Ga{sub 0.66}As/GaAs cascade with AM1.5 efficiency of 19.9% and 21% at 1-sun and 7-suns, respectively, was obtained. This represents an important milestone in the development of an AlGaAs/GaAs cascade by OMVPE utilizing a tunnel interconnect and demonstrates a proof-of-concept for the inverted-growth approach.

Venkatasubramanian, R. [Research Triangle Inst., Research Triangle Park, NC (United States)

1993-01-01T23:59:59.000Z

179

Ultra High p-doping Material Research for GaN Based Light Emitters  

Science Conference Proceedings (OSTI)

The main goal of the Project is to investigate doping mechanisms in p-type GaN and AlGaN and controllably fabricate ultra high doped p-GaN materials and epitaxial structures. Highly doped p-type GaN-based materials with low electrical resistivity and abrupt doping profiles are of great importance for efficient light emitters for solid state lighting (SSL) applications. Cost-effective hydride vapor phase epitaxial (HVPE) technology was proposed to investigate and develop p-GaN materials for SSL. High p-type doping is required to improve (i) carrier injection efficiency in light emitting p-n junctions that will result in increasing of light emitting efficiency, (ii) current spreading in light emitting structures that will improve external quantum efficiency, and (iii) parameters of Ohmic contacts to reduce operating voltage and tolerate higher forward currents needed for the high output power operation of light emitters. Highly doped p-type GaN layers and AlGaN/GaN heterostructures with low electrical resistivity will lead to novel device and contact metallization designs for high-power high efficiency GaN-based light emitters. Overall, highly doped p-GaN is a key element to develop light emitting devices for the DOE SSL program. The project was focused on material research for highly doped p-type GaN materials and device structures for applications in high performance light emitters for general illumination P-GaN and p-AlGaN layers and multi-layer structures were grown by HVPE and investigated in terms of surface morphology and structure, doping concentrations and profiles, optical, electrical, and structural properties. Tasks of the project were successfully accomplished. Highly doped GaN materials with p-type conductivity were fabricated. As-grown GaN layers had concentration N{sub a}-N{sub d} as high as 3 x 10{sup 19} cm{sup -3}. Mechanisms of doping were investigated and results of material studies were reported at several International conferences providing better understanding of p-type GaN formation for Solid State Lighting community. Grown p-type GaN layers were used as substrates for blue and green InGaN-based LEDs made by HVPE technology at TDI. These results proved proposed technical approach and facilitate fabrication of highly conductive p-GaN materials by low-cost HVPE technology for solid state lighting applications. TDI has started the commercialization of p-GaN epitaxial materials.

Vladimir Dmitriev

2007-06-30T23:59:59.000Z

180

Using GA-ANN algorithm to predicate coal bump energy  

Science Conference Proceedings (OSTI)

A GA-ANN network was constructed for preidcating coal bump energy, based on the 300 training samples form simulated results with PFC2D software for different coal particle stiffness. It was tested that the average relative error of fitted-output value ... Keywords: artificial neural network, coal bump, energy, genetic algorithm, predication

Yunliang Tan; Tongbin Zhao; Zhigang Zhao

2009-06-01T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Properties of H, O and C in GaN  

DOE Green Energy (OSTI)

The electrical properties of the light ion impurities H, O and C in GaN have been examined in both as-grown and implanted material. H is found to efficiently passivate acceptors such as Mg, Ca and C. Reactivation occurs at {ge} 450 C and is enhanced by minority carrier injection. The hydrogen does not leave the GaN crystal until > 800 C, and its diffusivity is relatively high ({approximately} 10{sup {minus}11} cm{sup 2}/s) even at low temperatures (< 200 C) during injection by wet etching, boiling in water or plasma exposure. Oxygen shows a low donor activation efficiency when implanted into GaN, with an ionization level of 30--40 meV. It is essentially immobile up to 1,100 C. Carbon can produce low p-type levels (3 {times} 10{sup 17} cm{sup {minus}3}) in GaN during MOMBE, although there is some evidence it may also create n-type conduction in other nitrides.

Pearton, S.J.; Abernathy, C.R.; Lee, J.W. [Univ. of Florida, Gainesville, FL (United States)] [and others

1996-04-01T23:59:59.000Z

182

Optimization on Seawater Desulfurization Efficiency Based on LSSVM-GA  

Science Conference Proceedings (OSTI)

Seawater flue gas Desulfurization (SFGD) was adopted in many coal-fired power plants of littoral for its low cost and high desulfurization efficiency. Operating Parameters would seriously affect SFGD efficiency, the desulfurization efficiency can be ... Keywords: SFGD, desulfurization efficiency, LSSVM, GA, optimization

Liu Ding-ping; Li Xiao-wei

2010-10-01T23:59:59.000Z

183

Development of ZnO:Ga as an Ultrafast Scintillator  

DOE Green Energy (OSTI)

We report on several methods for synthesizing the ultra-fast scintillator ZnO(Ga), and measurements of the resulting products. This material has characteristics that make it an excellent alpha detector for tagging the time and direction of individual neutrons produced by t-d and d-d neutron generators (associated particle imaging). The intensity and decay time are strongly dependent on the method used for dopant incorporation. We compare samples made by diffusion of Ga metal to samples made by solid state reaction between ZnO and Ga2O3 followed by reduction in hydrogen. The latter is much more successful and has a pure, strong near-band-edge fluorescence and an ultra-fast decay time of the x-ray-excited luminescence. The luminescence increases dramatically as the temperature is reduced to 10K. We also present results of an alternate low-temperature synthesis that produces luminescent particles with a more uniform size distribution. We examine possible mechanisms for the bright near-band-edge scintillation and favor the explanation that it is due to the recombination of Ga3+ donor electrons with ionization holes trapped on H+ ion acceptors.

Bourret-Courchesne, E.D.; Derenzo, S.E.; Weber, M.J.

2008-12-10T23:59:59.000Z

184

Low cost high power GaSB photovoltaic cells  

Science Conference Proceedings (OSTI)

High power density and high capacity factor are important attributes of a thermophotovoltaics (TPV) system and GaSb cells are enabling for TPV systems. A TPV cogeneration unit at an off grid site will compliment solar arrays producing heat and electricity on cloudy days with the solar arrays generating electricity on sunny days. Herein

Lewis M. Fraas; Han X. Huang; Shi-Zhong Ye; She Hui; James Avery; Russell Ballantyne

1997-01-01T23:59:59.000Z

185

Low cost high power GaSb thermophotovoltaic cells  

Science Conference Proceedings (OSTI)

High power density and high capacity factor are important attributes of a TPV system and GaSb cells are enabling for TPV systems. A TPV cogeneration unit at an off grid site will compliment solar arrays producing heat and electricity on cloudy days with the solar arrays generating electricity on sunny days. Herein

Lewis M. Fraas; Han X. Huang; Shi-Zhong Ye; James Avery; Russell Ballantyne

1997-01-01T23:59:59.000Z

186

AlGaAsSb buffer/barrier on GaAs substrate for InAs channel devices with high electron mobility and practical reliability  

Science Conference Proceedings (OSTI)

Keywords: AlGaAsSb, Hall elements, InAs, Sb, buffer/barriers, deep quantum well, field effect transistors, reliability

S. Miya; S. Muramatsu; N. Kuze; K. Nagase; T. Iwabuchi; A. Ichii; M. Ozaki; I. Shibasaki

1996-03-01T23:59:59.000Z

187

Characterization and device performance of (AgCu)(InGa)Se2 absorber layers  

DOE Green Energy (OSTI)

The study of (AgCu)(InGa)Se2 absorber layers is of interest in that Ag-chalcopyrites exhibit both wider bandgaps and lower melting points than their Cu counterparts. (AgCu)(InGa)Se2 absorber layers were deposited over the composition range 0 < Ag/(Ag+Cu) < 1 and 0.3 < Ga/(In+Ga) < 1.0 using a variety of elemental co-evaporation processes. Films were found to be singlephase over the entire composition range, in contrast to prior studies. Devices with Ga content 0.3 < Ga/(In+Ga) <0.5 tolerated Ag incorporation up to Ag/(Ag+Cu) = 0.5 without appreciable performance loss. Ag-containing films with Ga/(In+Ga) = 0.8 showed improved device characteristics over Cu-only control samples, in particular a 30-40% increase in short-circuit current. An absorber layer with composition Ag/(Ag+Cu) = 0.75 and Ga/(In+Ga) = 0.8 yielded a device with VOC = 890 mV, JSC = 20.5mA/cm2, fill factor = 71.3%, and ? = 13.0%.

Hanket, Gregory; Boyle, Jonathan H.; Shafarman, William N.

2009-06-08T23:59:59.000Z

188

Optical and quantum efficiency analysis of (Ag,Cu)(In,Ga)Se2 absorber layers  

DOE Green Energy (OSTI)

(Ag,Cu)(In,Ga)Se2 thin films have been deposited by elemental co-evaporation over a wide range of compositions and their optical properties characterized by transmission and reflection measurements and by relative shift analysis of quantum efficiency device measurements. The optical bandgaps were determined by performing linear fits of (?h?)2 vs. h?, and the quantum efficiency bandgaps were determined by relative shift analysis of device curves with fixed Ga/(In+Ga) composition, but varying Ag/(Cu+Ag) composition. The determined experimental optical bandgap ranges of the Ga/(In+Ga) = 0.31, 0.52, and 0.82 groups, with Ag/(Cu+Ag) ranging from 0 to 1, were 1.19-1.45 eV, 1.32-1.56 eV, and 1.52-1.76 eV, respectively. The optical bowing parameter of the different Ga/(In+Ga) groups was also determined.

Boyle, Jonathan; Hanket, Gregory; Shafarman, William

2009-06-09T23:59:59.000Z

189

Dependence on proton energy of degradation of AlGaN/GaN high electron mobility transistors  

Science Conference Proceedings (OSTI)

The effects of proton irradiation energy on dc, small signal, and large signal rf characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) were investigated. AlGaN/GaN HEMTs were irradiated with protons at fixed fluence of 51015/cm2 and energies of 5, 10, and 15 MeV. Both dc and rf characteristics revealed more degradation at lower irradiation energy, with reductions of maximum transconductance of 11%, 22%, and 38%, and decreases in drain saturation current of 10%, 24%, and 46% for HEMTs exposed to 15, 10, and 5MeV protons, respectively. The increase in device degradation with decreasing proton energy is due to the increase in linear energy transfer and corresponding increase in nonionizing energy loss with decreasing proton energy in the active region of the HEMTs. After irradiation, both subthreshold drain leakage current and reverse gate current decreased more than 1 order of magnitude for all samples. The carrier removal rate was in the range 121 336 cm1 over the range of proton energies employed in this study

Liu, L. [University of Florida, Gainesville; Xi, Y. Y. [University of Florida, Gainesville; Wang, Y.l. [University of Florida; Ren, F. [University of Florida; Pearton, S. J. [University of Florida; Kim, H.-Y. [Korea University; Kim, J. [Korea University; Fitch, Robert C [Air Force Research Laboratory, Wright-Patterson AFB, OH; Walker, Dennis E [Air Force Research Laboratory, Wright-Patterson AFB, OH; Chabak, Kelson D [Air Force Research Laboratory, Wright-Patterson AFB, OH; Gillespie, James k [Air Force Research Laboratory, Wright-Patterson AFB, OH; Tetlak, Stephen E [Air Force Research Laboratory, Wright-Patterson AFB, OH; Via, Glen D [Air Force Research Laboratory, Wright-Patterson AFB, OH; Crespo, Antonio [Air Force Research Laboratory, Wright-Patterson AFB, OH; Kravchenko, Ivan I [ORNL

2013-01-01T23:59:59.000Z

190

Electroluminescence and Transmission Electron Microscopy Characterization of Reverse-Biased AlGaN/GaN Devices  

Science Conference Proceedings (OSTI)

Reverse-bias stress testing has been applied to a large set of more than 50 AlGaN/GaN high electron mobility transistors, which were fabricated using the same process but with different values of the AlN mole fraction and the AlGaN barrier-layer thickness, as well as different substrates (SiC and sapphire). Two sets of devices having different defect types and densities, related to the different growth conditions and the choice of nucleation layer, were also compared. When subjected to gate drain (or gate-to-drain and source short-circuited) reverse-bias testing, all devices presented the same time-dependent failure mode, consisting of a significant increase in the gate leakage current. This failure mechanism occurred abruptly during step-stress experiments when a certain negative gate voltage, or critical voltage, was exceeded or, during constant voltage tests, at a certain time, defined as time to breakdown. Electroluminescence (EL) microscopy was systematically used to identify localized damaged areas that induced an increase of gate reverse current. This current increase was correlated with the increase of EL intensity, and significant EL emission during tests occurred only when the critical voltage was exceeded. Focused-ion-beam milling produced cross-sectional samples suitable for electron microscopy observation at the sites of failure points previously identified by EL microscopy. In highdefectivity devices, V-defects were identified that were associated with initially high gate leakage current and corresponding to EL spots already present in untreated devices. Conversely, identification of defects induced by reverse-bias testing proved to be extremely difficult, and only nanometer-size cracks or defect chains, extending vertically from the gate edges through the AlGaN/GaN heterojunction, were found. No signs of metal/semiconductor interdiffusion or extended defective areas were visible.

Cullen, David A [ORNL; Smith, David J [Arizona State University; Passaseo, Adriana [Consiglio Nazionale delle Ricerche; Tasco, Vittorianna [Consiglio Nazionale delle Ricerche; Stocco, Antonio [Universita di Padova; Meneghini, Matteo [Universita di Padova; Meneghesso, Gaudenzio [Universita di Padova; Zanoni, Enrico [Universita di Padova

2013-01-01T23:59:59.000Z

191

GaSb substrates with extended IR wavelength for advanced space based applications  

SciTech Connect

GaSb substrates have advantages that make them attractive for implementation of a wide range of infrared (IR) detectors with higher operating temperatures for stealth and space based applications. A significant aspect that would enable widespread commercial application of GaSb wafers for very long wavelength IR (VLWIR) applications is the capability for transmissivity beyond 15 m. Due largely to the GaSb (antisite) defect and other point defects in undoped GaSb substrates, intrinsic GaSb is still slightly p-type and strongly absorbs in the VLWIR. This requires backside thinning of the GaSb substrate for IR transmissivity. An extremely low n-type GaSb substrate is preferred to eliminate thinning and provide a substrate solution for backside illuminated VLWIR devices. By providing a more homogeneous radial distribution of the melt solute to suppress GaSb formation and controlling the cooling rate, ultra low doped n:GaSb has been achieved. This study examines the surface properties and IR transmission spectra of ultra low doped GaSb substrates at both room and low temperatures. Atomic force microscopy (AFM), homoepitaxy by MBE, and infrared Fourier transform (FTIR) analysis was implemented to examine material quality. As compared with standard low doped GaSb, the ultra low doped substrates show over 50% transmission and consistent wavelength transparency past 23 m with improved %T at low temperature. Homoepitaxy and AFM results indicate the ultra low doped GaSb has a low thermal desorbtion character and qualified morphology. In summary, improvements in room temperature IR transmission and extended wavelength characteristics have been shown consistently for ultra low doped n:GaSb substrates.

Allen, Lisa P.; Flint, Patrick; Dallas, Gordon; Bakken, Daniel; Blanchat, Kevin; Brown, Gail J.; Vangala, Shivashankar R.; Goodhue, William D.; Krishnaswami, Kannan

2009-05-01T23:59:59.000Z

192

Two-color picosecond experiments on anti-Stokes photoluminescence in GaAs/AlGaAs asymmetric double quantum wells  

E-Print Network (OSTI)

quantum wells S. C. Hohng and D. S. Kima) Department of Physics and Condensed Matter Research Institute in GaAs/AlGaAs asymmetric double quantum wells. Direct evidence for forbidden absorption is shown heterojunctions and asymmetric double quan- tum wells was found and its origin is still being hotly de- bated

Hohng, Sung Chul

193

Light output enhancement of InGaN/GaN light-emitting diodes with contrasting indium tin-oxide nanopatterned structures  

Science Conference Proceedings (OSTI)

Various nanopatterns on the transparent conducting indium tin oxide (ITO) layer are investigated to enhance the light extraction efficiency of the InGaN/GaN light-emitting diodes (LEDs). Triangular, square, and circular nanohole patterns with the square ...

Sang Hyun Jung, Keun Man Song, Young Su Choi, Hyeong-Ho Park, Hyun-Beom Shin, Ho Kwan Kang, Jaejin Lee

2013-01-01T23:59:59.000Z

194

Optically pumped InxGa?â??xN/InyGa?â??yN multiple quantum well vertical cavity surface emitting laser operating at room temperature.  

E-Print Network (OSTI)

Room temperature vertical cavity lasing at the wavelength of 433nm has been successfully realized in InxGa?â??xN/InyGa?â??yN multiple quantum well without Bragg mirrors under photo-excitation. At high excitation intensity, ...

Chen, Zhen

195

Ultralow nonalloyed Ohmic contact resistance to self aligned N-polar GaN high electron mobility transistors by In(Ga)N regrowth  

Science Conference Proceedings (OSTI)

Ultralow Ohmic contact resistance and a self-aligned device structure are necessary to reduce the effect of parasitic elements and obtain higher f{sub t} and f{sub max} in high electron mobility transistors (HEMTs). N-polar (0001) GaN HEMTs, offer a natural advantage over Ga-polar HEMTs, in terms of contact resistance since the contact is not made through a high band gap material [Al(Ga)N]. In this work, we extend the advantage by making use of polarization induced three-dimensional electron-gas through regrowth of graded InGaN and thin InN cap in the contact regions by plasma (molecular beam epitaxy), to obtain an ultralow Ohmic contact resistance of 27 OMEGA mum to a GaN 2DEG.

Dasgupta, Sansaptak; Nidhi,; Brown, David F.; Wu, Feng; Keller, Stacia; Speck, James S.; Mishra, Umesh K. [Department of ECE, University of California, Santa Barbara, California 93106 (United States) and Department of Materials, University of California, Santa Barbara, California 93106 (United States)

2010-04-05T23:59:59.000Z

196

GaN Metal Oxide Semiconductor Field Effect Transistors  

SciTech Connect

A GaN based depletion mode metal oxide semiconductor field effect transistor (MOSFET) was demonstrated using Ga{sub 2}O{sub 3}(Gd{sub 2}O{sub 3}) as the gate dielectric. The MOS gate reverse breakdown voltage was > 35V which was significantly improved from 17V of Pt Schottky gate on the same material. A maximum extrinsic transconductance of 15 mS/mm was obtained at V{sub ds} = 30 V and device performance was limited by the contact resistance. A unity current gain cut-off frequency, f{sub {tau}}, and maximum frequency of oscillation, f{sub max} of 3.1 and 10.3 GHz, respectively, were measured at V{sub ds} = 25 V and V{sub gs} = {minus}20 V.

Ren, F.; Pearton, S.J.; Abernathy, C.R.; Baca, A.; Cheng, P.; Shul, R.J.; Chu, S.N.G.; Hong, M.; Lothian, J.R.; Schurman, M.J.

1999-03-02T23:59:59.000Z

197

Dynamic Model of Hydrogen in GaN  

NLE Websites -- All DOE Office Websites (Extended Search)

Dynamic Model of Hydrogen in GaN by S. M. Myers and A. F. Wright Motivation-Hydrogen is incorporated into p-type GaN during MOCVD growth, producing highly stable passivation of the Mg acceptors. Complete acceptor activation by thermal H release requires temperatures that threaten material integrity, prompting compromises in device processing. At lower temperatures, forward bias of p-n junctions or electron-beam irradiation produces a metastable, reversible activation without H release. To understand and control such effects, we are developing a mathematical model of H behavior wherein state energies from density-functional theory are employed in diffusion-reaction equations. Previously, we used the greatly simplifying assumptions of local equilibrium among states

198

A GaAs transceiver chip for optical data transmission  

SciTech Connect

The present article describes a transceiver VLSI chip for optical data transmission, at 1 Gbit/s (1.4 Gbit/s in selected production), made in GaAs technology. The transceiver makes the parallel-to-serial and serial-to-parallel conversion as well as the encoding and decoding of 32 bit data words. The circuit operates in a completely asynchronous mode, allowing the possibility of switching on-off the transmission in few nsec and of using the transceiver not only in point-to-point topologies, but also in flooding topologies (i.e. star connections). The radiation hardness and the relatively low power consumption, respect to TTL, of the GaAs, extend the use of the chip to a large number of applications in present and future high energy physics experimental apparatus.

Mirabelli, G.; Petrolo, E.; Valente, E. (Ist. Nazionale di Fisica Nucleare, Roma (Italy)); Cardarelli, R.; Santonico, R. (Sezione di Roma 2 and Univ. di Roma (Italy). Ist. Nazionale di Fisica Nucleare); Ferrer, M.L. (Lab. Nazionali di Frascati (Italy). Ist. Nazionale di Fisica Nucleare)

1993-08-01T23:59:59.000Z

199

Method of plasma etching Ga-based compound semiconductors  

SciTech Connect

A method of plasma etching Ga-based compound semiconductors includes providing a process chamber and a source electrode adjacent to the process chamber. The process chamber contains a sample comprising a Ga-based compound semiconductor. The sample is in contact with a platen which is electrically connected to a first power supply, and the source electrode is electrically connected to a second power supply. The method includes flowing SiCl.sub.4 gas into the chamber, flowing Ar gas into the chamber, and flowing H.sub.2 gas into the chamber. RF power is supplied independently to the source electrode and the platen. A plasma is generated based on the gases in the process chamber, and regions of a surface of the sample adjacent to one or more masked portions of the surface are etched to create a substantially smooth etched surface including features having substantially vertical walls beneath the masked portions.

Qiu, Weibin; Goddard, Lynford L.

2012-12-25T23:59:59.000Z

200

AlGaAs diode pumped tunable chromium lasers  

DOE Patents (OSTI)

An all-solid-state laser system is disclosed wherein the laser is pumped in the longwave wing of the pump absorption band. By utilizing a laser material that will accept unusually high dopant concentrations without deleterious effects on the crystal lattice one is able to compensate for the decreased cross section in the wing of the absorption band, and the number of pump sources which can be used with such a material increases correspondingly. In a particular embodiment a chromium doped colquiriite-structure crystal such as Cr:LiSrAlF.sub.6 is the laser material. The invention avoids the problems associated with using AlGaInP diodes by doping the Cr:LiSrAlF.sub.6 heavily to enable efficient pumping in the longwave wing of the absorption band with more practical AlGaAs diodes.

Krupke, William F. (Pleasanton, CA); Payne, Stephen A. (Castro Valley, CA)

1992-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

CsBr/GaN Heterojunction Photoelectron Source  

Science Conference Proceedings (OSTI)

Experimental results on a new CsBr/GaN heterojunction photocathode structure are presented. The results indicate a fourfold improvement in photoyield relative to CsBr/Cr photocathodes. A model is presented based on intraband states in CsBr and electron injection from the GaN (with 1% addition of indium) substrate to explain the observed photoyield enhancement. The photocathode lifetime at high current density (>40 A/cm{sup 2}) is limited by laser heating of the small illuminated area. Calculations are presented for sapphire and diamond substrates, indicating a factor of 20 reduction in temperature for the latter. The results are encouraging for the realization of a high photoyield photocathode operating at high current density with long lifetime.

Maldonado, J.R.; /Stanford U., Elect. Eng. Dept.; Liu, Z.; Sun, Y.; /SLAC, SSRL; Schuetter, S.; /Wisconsin U., Madison; Pianetta, P.; /SLAC, SSRL; Pease, R.F.W.; /Stanford U., Elect. Eng. Dept.

2009-04-30T23:59:59.000Z

202

Method of plasma etching GA-based compound semiconductors  

DOE Patents (OSTI)

A method of plasma etching Ga-based compound semiconductors includes providing a process chamber and a source electrode adjacent thereto. The chamber contains a Ga-based compound semiconductor sample in contact with a platen which is electrically connected to a first power supply, and the source electrode is electrically connected to a second power supply. SiCl.sub.4 and Ar gases are flowed into the chamber. RF power is supplied to the platen at a first power level, and RF power is supplied to the source electrode. A plasma is generated. Then, RF power is supplied to the platen at a second power level lower than the first power level and no greater than about 30 W. Regions of a surface of the sample adjacent to one or more masked portions of the surface are etched at a rate of no more than about 25 nm/min to create a substantially smooth etched surface.

Qiu, Weibin; Goddard, Lynford L.

2013-01-01T23:59:59.000Z

203

Materials physics and device development for improved efficiency of GaN HEMT high power amplifiers.  

SciTech Connect

GaN-based microwave power amplifiers have been identified as critical components in Sandia's next generation micro-Synthetic-Aperture-Radar (SAR) operating at X-band and Ku-band (10-18 GHz). To miniaturize SAR, GaN-based amplifiers are necessary to replace bulky traveling wave tubes. Specifically, for micro-SAR development, highly reliable GaN high electron mobility transistors (HEMTs), which have delivered a factor of 10 times improvement in power performance compared to GaAs, need to be developed. Despite the great promise of GaN HEMTs, problems associated with nitride materials growth currently limit gain, linearity, power-added-efficiency, reproducibility, and reliability. These material quality issues are primarily due to heteroepitaxial growth of GaN on lattice mismatched substrates. Because SiC provides the best lattice match and thermal conductivity, SiC is currently the substrate of choice for GaN-based microwave amplifiers. Obviously for GaN-based HEMTs to fully realize their tremendous promise, several challenges related to GaN heteroepitaxy on SiC must be solved. For this LDRD, we conducted a concerted effort to resolve materials issues through in-depth research on GaN/AlGaN growth on SiC. Repeatable growth processes were developed which enabled basic studies of these device layers as well as full fabrication of microwave amplifiers. Detailed studies of the GaN and AlGaN growth of SiC were conducted and techniques to measure the structural and electrical properties of the layers were developed. Problems that limit device performance were investigated, including electron traps, dislocations, the quality of semi-insulating GaN, the GaN/AlGaN interface roughness, and surface pinning of the AlGaN gate. Surface charge was reduced by developing silicon nitride passivation. Constant feedback between material properties, physical understanding, and device performance enabled rapid progress which eventually led to the successful fabrication of state of the art HEMT transistors and amplifiers.

Kurtz, Steven Ross; Follstaedt, David Martin; Wright, Alan Francis; Baca, Albert G.; Briggs, Ronald D.; Provencio, Paula Polyak; Missert, Nancy A.; Allerman, Andrew Alan; Marsh, Phil F.; Koleske, Daniel David; Lee, Stephen Roger; Shul, Randy John; Seager, Carleton Hoover; Tigges, Christopher P.

2005-12-01T23:59:59.000Z

204

X-ray diffraction analysis and scanning micro-Raman spectroscopy of structural irregularities and strains deep inside the multilayered InGaN/GaN heterostructure  

SciTech Connect

High-resolution X-ray diffraction analysis and scanning confocal Raman spectroscopy are used to study the spatial distribution of strains in the In{sub x}Ga{sub 1-x}N/GaN layers and structural quality of these layers in a multilayered light-emitting diode structure produced by metal-organic chemical vapor deposition onto (0001)-oriented sapphire substrates. It is shown that elastic strains almost completely relax at the heterointerface between the thick GaN buffer layer and In{sub x}Ga{sub 1-x}N/GaN buffer superlattice. It is established that the GaN layers in the superlattice are in a stretched state, whereas the alloy layers are in a compressed state. In magnitude, the stretching strains in the GaN layers are lower than the compressive strains in the InGaN layers. It is shown that, as compared to the buffer layers, the layers of the superlattice contain a smaller number of dislocations and the distribution of dislocations is more randomly disordered. In micro-Raman studies on scanning through the thickness of the multilayered structure, direct evidence is obtained for the asymmetric gradient distributions of strains and crystal imperfections of the epitaxial nitride layers along the direction of growth. It is shown that the emission intensity of the In{sub x}Ga{sub 1-x}N quantum well is considerably (more than 30 times) higher than the emission intensity of the GaN barrier layers, suggesting the high efficiency of trapping of charge carriers by the quantum well.

Strelchuk, V. V., E-mail: Strelch@isp.kiev.ua; Kladko, V. P.; Avramenko, E. A.; Kolomys, O. F.; Safryuk, N. V.; Konakova, R. V. [National Academy of Sciences of Ukraine, Lashkaryov Institute of Semiconductor Physics (Ukraine); Yavich, B. S., E-mail: byavich@soptel.ru [ZAO Svetlana-Optoelectronics (Russian Federation); Valakh, M. Ya.; Machulin, V. F.; Belyaev, A. E. [National Academy of Sciences of Ukraine, Lashkaryov Institute of Semiconductor Physics (Ukraine)

2010-09-15T23:59:59.000Z

205

UV-Photoassisted Etching of GaN in KOH  

SciTech Connect

The etch rate of GaN under W-assisted photoelectrochemical conditions in KOH solutions is found to be a strong function of illumination intensity, solution molarity, sample bias and material doping level. At low e-h pair generation rates, grain boundaries are selectively etched, while at higher illumination intensities etch rates for unintentionally doped (n - 3x 10^12Gcm-3) GaN are 2 1000 .min-l. The etching is diffusion limited under our conditions with an activation energy of - 0.8kCal.mol-1. The etched surfaces are rough, but retain their stoichiometry. PEC etching is found to selectively reveal grain boundaries in GaN under low light illumination conditions. At high lamp powers the rates increase with sample temperature and the application of bias to the PEC cell, while they go through a maximum with KOH solution molarity. The etching is diffusion-limited, producing rough surface morphologies that are suitable in a limited number of device fabrication steps. The surfaces however appear to remain relatively close to their stoichiometric composition.

Abernathy, C.R.; Auh, K.H.; Cho, H.; Donovan, S.M.; Han, J.; Lambers, E.S.; Pearton, S.J.; Ren F.; Shul, R.J.

1998-11-12T23:59:59.000Z

206

Comparative study of GaN growth process by MOVPE  

SciTech Connect

A comparative study of two different MOVPE reactors used for GaN growth is presented. Computational fluid dynamics (CFD) was used to determine common gas phase and fluid flow behaviors within these reactors. This paper focuses on the common thermal fluid features of these two MOVPE reactors with different geometries and operating pressures that can grow device-quality GaN-based materials. The study clearly shows that several growth conditions must be achieved in order to grow high quality GaN materials. The high-temperature gas flow zone must be limited to a very thin flow sheet above the susceptor, while the bulk gas phase temperature must be very low to prevent extensive pre-deposition reactions. These conditions lead to higher growth rates and improved material quality. A certain range of gas flow velocity inside the high-temperature gas flow zone is also required in order to minimize the residence time and improve the growth uniformity. These conditions can be achieved by the use of either a novel reactor structure such as a two-flow approach or by specific flow conditions. The quantitative ranges of flow velocities, gas phase temperature, and residence time required in these reactors to achieve high quality material and uniform growth are given.

Sun, J.; Redwing, J.M.; Kuech, T.F.

1999-07-01T23:59:59.000Z

207

Low-temperature magnetization of (Ga,Mn) As semiconductors  

E-Print Network (OSTI)

We report on a comprehensive study of the ferromagnetic moment per Mn atom in (Ga,Mn)As ferromagnetic semiconductors. Theoretical discussion is based on microscopic calculations and on an effective model of Mn local moments antiferromagnetically coupled to valence band hole spins. The validity of the effective model over the range of doping studied is assessed by comparing with microscopic tight-binding/coherent-potential approximation calculations. Using the virtual crystal k center dot p model for hole states, we evaluate the zero-temperature mean-field contributions to the magnetization from the hole kinetic and exchange energies, and magnetization suppression due to quantum fluctuations of Mn moment orientations around their mean-field ground state values. Experimental low-temperature ferromagnetic moments per Mn are obtained by superconducting quantum interference device and x-ray magnetic circular dichroism measurements in a series of (Ga,Mn)As semiconductors with nominal Mn doping ranging from similar to 2 to 8%. Hall measurements in as-grown and annealed samples are used to estimate the number of uncompensated substitutional Mn moments. Based on our comparison between experiment and theory we conclude that all these Mn moments in high quality (Ga,Mn)As materials have nearly parallel ground state alignment.

Jungwirth, T.; Masek, J.; Wang, KY; Edmonds, KW; Sawicki, M.; Polini, M.; Sinova, Jairo; MacDonald, AH; Campion, RP; Zhao, LX; Farley, NRS; Johal, TK; van der Laan, G.; Foxon, CT; Gallagher, BL.

2006-01-01T23:59:59.000Z

208

Substrate misorientation effects on epitaxial GaInAsSb  

DOE Green Energy (OSTI)

The effect of substrate misorientation on the growth of GaInAsSb was studied for epilayers grown lattice-matched to GaSb substrates by low-pressure organometallic vapor phase epitaxy. The substrates were (100) misoriented 2 or 6{degree} toward (110), (111)A, or (111)B. The surface is mirror-like and featureless for layers grown with a 6{degree} toward (111)B misorientation, while, a slight texture was observed for layers grown on all other misorientations. The optical quality of layers, as determined by the full width at half-maximum of photoluminescence spectra measured at 4K, is significantly better for layers grown on substrates with a 6{degree} toward (111)B misorientation. The incorporation of Zn as a p-type dopant in GaInAsSb is about 1.5 times more efficient on substrates with 6{degree} toward (111)B misorientation compared to 2{degree} toward (110) misorientation. The external quantum efficiency of thermophotovoltaic devices is not, however, significantly affected by substrate misorientation.

Wang, C.A.; Choi, H.K.; Oakley, D.C. [Massachusetts Inst. of Tech., Lexington, MA (United States). Lincoln Lab.; Charache, G.W. [Lockheed Martin Corp., Schenectady, NY (United States)

1997-12-01T23:59:59.000Z

209

Desferal (DFO) induced Ga-67 washout from normal tissue, tumor and abscess in experimental animals  

Science Conference Proceedings (OSTI)

In the experimental animal, desferal (DFO) given intravenously washes out Ga-67 from all tissues. This effect is not uniform: blood activity is reduced very markedly, while liver activity is less affected. Maximal effect of DFO occurs if given close to the Ga-67 injection. When the time interval between the two is increased, the absolute amount of Ga-67 excreted in the urine in excess of the spontaneous excretion is reduced. Administration of DFO does not effect Ga-67 gastrointestinal excretion. In three animal tumor models (EMT-6 sarcoma in Balb/c mice, spontaneous adenocarcinoma in mice, and spontaneous adenocarcinoma in the rabbit) and in sterile abscess-bearing rats, the administration of DFO 24 hrs after Ga-67-citrate improves significantly the target-to-nontarget ratio. Animals given 50 mg/kg DFO I.V. after Ga-67 citrate showed a significant reduction in the whole-body activity as seen in a one-week follow up.

Oster, Z.H.; Som, P.; Atkins, H.L.; Brill, A.B.

1980-01-01T23:59:59.000Z

210

Low energy electron beam induced vacancy activation in GaN  

Science Conference Proceedings (OSTI)

Experimental evidence on low energy electron beam induced point defect activation in GaN grown by metal-organic vapor phase epitaxy (MOVPE) is presented. The GaN samples are irradiated with a 5-20 keV electron beam of a scanning electron microscope and investigated by photoluminescence and positron annihilation spectroscopy measurements. The degradation of the band-to-band luminescence of the irradiated GaN films is associated with the activation of point defects. The activated defects were identified as in-grown Ga-vacancies. We propose that MOVPE-GaN contains a significant concentration of passive V{sub Ga}-H{sub n} complexes that can be activated by H removal during low energy electron irradiation.

Nykaenen, H.; Suihkonen, S.; Sopanen, M. [Department of Micro- and Nanosciences, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland); Kilanski, L. [Department of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto (Finland); Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/56, 02-668 Warsaw (Poland); Tuomisto, F. [Department of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto (Finland)

2012-03-19T23:59:59.000Z

211

Low-cost, high-efficiency solar cells utilizing GaAs-on-Si technology  

DOE Green Energy (OSTI)

This report describes work to develop technology to deposit GaAs on Si using a nucleation layer of atomic-layer-epitaxy-grown GaAs or AlAs on Si. This ensures two-dimensional nucleation and should lead to fewer defects in the final GaAs layer. As an alternative, we also developed technology for depositing GaAs on sawtooth-patterned Si. Preliminary studies showed that this material can have a very low defect density, [approximately] 1 [times] 10[sup 5] cm[sup [minus]5], as opposed to our conventionally grown GaAs on SL which has a typical defect density of over 1 [times]10[sup 7] cm[sup [minus]2]. Using these two now methods of GaAs-on-Si material growth, we made solar cells that are expected to show higher efficiencies than those of previous cells.

Vernon, S.M. (Spire Corp., Bedford, MA (United States))

1993-04-01T23:59:59.000Z

212

Ultra-shallow quantum dots in an undoped GaAs/AlGaAs two-dimensional electron gas  

SciTech Connect

We report quantum dots fabricated on very shallow 2-dimensional electron gases, only 30 nm below the surface, in undoped GaAs/AlGaAs heterostructures grown by molecular beam epitaxy. Due to the absence of dopants, an improvement of more than one order of magnitude in mobility (at 2 Multiplication-Sign 10{sup 11} cm{sup -2}) with respect to doped heterostructures with similar depths is observed. These undoped wafers can easily be gated with surface metallic gates patterned by e-beam lithography, as demonstrated here from single-level transport through a quantum dot showing large charging energies (up to 1.75 meV) and excited state energies (up to 0.5 meV).

Mak, W. Y.; Sfigakis, F.; Beere, H. E.; Farrer, I.; Griffiths, J. P.; Jones, G. A. C.; Ritchie, D. A. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom)] [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom); Das Gupta, K. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom) [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom); Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Klochan, O.; Hamilton, A. R. [School of Physics, University of New South Wales, Sydney (Australia)] [School of Physics, University of New South Wales, Sydney (Australia)

2013-03-11T23:59:59.000Z

213

Terrestrial Concentrator PV Modules Based on GaInP/GaAs/Ge TJ Cells and Minilens Panels  

SciTech Connect

This paper is a description of research activity in the field of cost-effective modules realizing the concept of very high solar concentration with small-aperture area Fresnel lenses and multijunction III-V cells. Structural simplicity and 'all-glass' design are the guiding principles of the corresponding development. The advanced concentrator modules are made with silicone Fresnel lens panels (from 8 up to 144 lenses, each lens is 4 times 4 cm{sup 2} in aperture area) with composite structure. GaInP/GaAs/Ge triple-junction cells with average efficiencies of 31.1 and 34.7% at 1000 suns were used for the modules. Conversion efficiency as high as 26.3% has been measured indoors in a test module using a newly developed large-area solar simulator.

Rumyantsev, V. D.; Sadchikov, N. A.; Chalov, A. E.; Ionova, E. A.; Friedman, D. J.; Glenn, G.

2006-01-01T23:59:59.000Z

214

Quaternary Bismide Alloy ByGa1-yAs1-xBix Lattice Matched to GaAs  

DOE Green Energy (OSTI)

We report on the lattice matched quaternary alloy, B{sub y}Ga{sub 1-y}As{sub 1-x}Bi{sub x} grown by molecular beam epitaxy at conditions conducive to bismuth incorporation. Incorporating a smaller atom (boron) along with the larger atom (bismuth) allows for a reduction of the epi-layer strain and lattice matching to GaAs for compositions of Bi:B{approx_equal}1.3:1. The addition of boron flux does not significantly affect the bismuth incorporation and no change in the band gap energy is observed with increasing boron content. However, excess, non-substitutional boron is incorporated which leads to an increase in hole density, as well as an increase in the density of shallow in-gap states as observed by the loss of localization of photo-excited excitons.

Deaton, D. A.; Ptak, A. J.; Alberi, K.; Mascarenhas, A.

2012-07-15T23:59:59.000Z

215

Impact of proton irradiation on dc performance of AlGaN/GaN high electron mobility transistors  

Science Conference Proceedings (OSTI)

The effects of proton irradiation dose on dc characteristics and the reliability of AlGaN/GaN high electron mobility transistors (HEMTs) were investigated. The HEMTs were irradiated with protons at a fixed energy of 5 MeV and doses ranging from 109 to 2 1014 cm-2. For the dc characteristics, there was only minimal degradation of saturation drain current (IDSS), transconductance (gm), electron mobility and sheet carrier concentration at doses below 2 1013 cm-2, while the reduction of these parameters were 15%, 9%, 41% and 16.6%, respectively, at a dose of 2 1014 cm-2. At this same dose condition, increases of 37% in drain breakdown voltage (VBR) and of 45% in critical voltage (Vcri) were observed. The improvement of device reliability was attributed to the modification of the depletion region due to the introduction of a higher density of defects after irradiation at a higher dose.

Liu, L. [University of Florida, Gainesville; Cuervo, C.V. [University of Florida, Gainesville; Xi, Y. Y. [University of Florida, Gainesville; Ren, F. [University of Florida; Pearton, S. J. [University of Florida; Kim, H.-Y. [Korea University; Kim, J. [Korea University; Kravchenko, Ivan I [ORNL

2013-01-01T23:59:59.000Z

216

Harmonic Responses in 2DEG AlGaAs/GaAs HEMT Devices Due to Plasma Wave Interaction  

Science Conference Proceedings (OSTI)

Plasma waves are oscillations of electron density in time and space, and in deep submicron field effect transistors, typical plasma frequencies, omega{sub p}, lie in the terahertz range and do not involve any quantum transitions. Hence, using plasma wave excitation for detection and/or generation of THz oscillations is a very promising approach. In this paper, the investigation of plasma wave interaction between the plasma waves propagating in a short-channel High-Electron-Mobility Transistor (HEMT) and the radiated electromagnetic waves was carried out. Experimentally, we have demonstrated the detection of the terahertz (THz) radiation by an AlGaAs/GaAs HEMT up to third harmonic at room temperature and their resonant responses show very good agreement with the calculated results.

Hashim, A. M.; Alias, Q. I. [Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Kasai, S.; Hasegawa, H. [Research Center for Integrated Quantum Electronics, Hokkaido University North 12 West 8, Sapporo 060-8628 (Japan)

2010-03-11T23:59:59.000Z

217

Subpicosecond spin relaxation in GaAsSb multiple quantum wells K. C. Hall,a)  

E-Print Network (OSTI)

Subpicosecond spin relaxation in GaAsSb multiple quantum wells K. C. Hall,a) S. W. Leonard, and H quantum wells are measured at 295 K using time-resolved circular dichroism induced by 1.5 m, 100 fs pulses times shorter than those in InGaAs and InGaAsP wells with similar band gaps. The shorter relaxation

Van Driel, Henry M.

218

Effect of Mg ionization efficiency on performance of Npn AlGaN/GaN heterojunction bipolar transistors  

SciTech Connect

A drift-diffusion transport model has been used to examine the performance capabilities of AlGaN/GaN Npn heterojunction bipolar transistors (HBTs). The Gummel plot from the first GaN-based HBT structure recently demonstrated is adjusted with simulation by using experimental mobility and lifetime reported in the literature. Numerical results have been explored to study the effect of the p-type Mg doping and its incomplete ionization in the base. The high base resistance induced by the deep acceptor level is found to be the cause of limiting current gain values. Increasing the operating temperature of the device activates more carriers in the base. An improvement of the simulated current gain by a factor of 2 to 4 between 25 and 300 C agrees well with the reported experimental results. A preliminary analysis of high frequency characteristics indicates substantial progress of predicted rf performances by operating the device at higher temperature due to a reduced extrinsic base resistivity.

MONIER,C.; PEARTON,S.J.; CHANG,PING-CHIH; BACA,ALBERT G.

2000-03-10T23:59:59.000Z

219

Plasma chemistries for dry etching GaN, AlN, InGaN and InAlN  

DOE Green Energy (OSTI)

Etch rates up to 7,000 {angstrom}/min. for GaN are obtained in Cl{sub 2}/H{sub 2}/Ar or BCl{sub 3}/Ar ECR discharges at 1--3mTorr and moderate dc biases. Typical rates with HI/H{sub 2} are about a factor of three lower under the same conditions, while CH{sub 4}/H{sub 2} produces maximum rates of only {approximately}2,000 {angstrom}/min. The role of additives such as SF{sub 6}, N{sub 2}, H{sub 2} or Ar to the basic chlorine, bromine, iodine or methane-hydrogen plasma chemistries are discussed. Their effect can be either chemical (in forming volatile products with N) or physical (in breaking bonds or enhancing desorption of the etch products). The nitrides differ from conventional III-V`s in that bond-breaking to allow formation of the etch products is a critical factor. Threshold ion energies for the onset of etching of GaN, InGaN and InAlN are {ge} 75 eV.

Pearton, S.J.; Vartuli, C.B.; Lee, J.W.; Donovan, S.M.; MacKenzie, J.D.; Abernathy, C.R. [Univ. of Florida, Gainesville, FL (United States); Shul, R.J. [Sandia National Labs., Albuquerque, NM (United States); McLane, G.F. [Army Research Lab., Fort Monmouth, NJ (United States); Ren, F. [AT and T Bell Labs., Murray Hill, NJ (United States)

1996-04-01T23:59:59.000Z

220

Reliability of GaN HEMTs: Electrical and Radiation-induced Failure ...  

Science Conference Proceedings (OSTI)

Symposium, Advanced Materials for Power Electronics, Power Conditioning, and Power Conversion II. Presentation Title, Reliability of GaN HEMTs: Electrical ...

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Thermoelectric Study of InGaN-Based Materials for Thermal Energy ...  

Science Conference Proceedings (OSTI)

Presentation Title, Thermoelectric Study of InGaN-Based Materials for Thermal ... Structural and Thermal Stability Properties of Cellulose Nanocomposites with ...

222

X-Ray Studies of GaN Film Grown on Si Using Electrochemical Deposition Techniques  

Science Conference Proceedings (OSTI)

This paper reports on the X-ray studies of GaN thin films deposited on Si (111) substrate at different current density using electrochemical deposition technique. The structural properties of GaN films were studied by X-ray diffraction (XRD). XRD analysis showed that hexagonal wurtzite and cubic zinc blende GaN phases were both deposited on Si (111). The lattice constants, the average size of h-GaN crystals and the in-plane (along a-axis) and out of plane (along c-axis) strains were calculated from XRD analysis.

Al-Heuseen, K.; Hashim, M. R. [Nano-Optoelectronics Research and Technology Laboratory School of Physics, Universiti Sains Malaysia (USM), 11800 Minden, Penang (Malaysia)

2011-03-30T23:59:59.000Z

223

M4, Semipolar AlGaN Buffers for Deep Ultraviolet Diode Lasers  

Science Conference Proceedings (OSTI)

On-axis reciprocal space mapping of the graded AlGaN showed tilt at each interface associated ..... New Concepts and Materials for Solar Power Conversion

224

Solidification and Microstructure Evaluation of the Ni-Ga and Co-Ni ...  

Science Conference Proceedings (OSTI)

Ni-Ga binary system is thus one of the basic binary system which forms the dominated ? ... The Effects of Natural and Marangoni Convection on the Resultant ...

225

Structure and Composition Peculiarities of GaN/AlN Multiple ...  

Science Conference Proceedings (OSTI)

Thickness of AlN and GaN layers in MQWs (multiple quantum wells) were ... InAs Quantum Dots by Ballistic Electron Emission Microscopy and Spectroscopy.

226

A Paleoenvironmental Study of the 2.7 GA Tumbiana Formation, Fortescue Basin, Western Australia.  

E-Print Network (OSTI)

??A paleoecological and paleoenvironmental study was conducted on the 2.7 Ga Meentheena Member of the Tumbiana Formation, Fortescue Basin, Western Australia. It involved the integrated… (more)

Coffey, Jessica

2011-01-01T23:59:59.000Z

227

Cu-Ga-Se Thin Films Prepared by a Combination of Electrodeposition and Evaporation Techniques  

Science Conference Proceedings (OSTI)

Cu-Ga-Se thin films were prepared using a combination of electrodeposition and evaporation techniques. A Cu-Se/Mo/glass precursor thin film was first prepared by galvanostatic electrodeposition. On top of this film three different thicknesses of Ga were deposited by evaporation. The Cu-Ga-Se thin films were formed by annealing the Ga/Cu-Se/Mo/glass thin film configuration in a tubular chamber with Se powder, at different temperatures. Thin films were characterized by X-ray diffraction (XRD), photocurrent spectroscopy (PS), inductively coupled plasma (ICP) analysis, and scanning electron microscopy (SEM). The detailed analysis from X-ray reveals that after annealing at 550 C the CuGaSe{sub 2} phase is formed when the thickness of Ga is 0.25 {mu}m, however at 0.5 {mu}m and 1.0 {mu}m Ga the formation of CuGa{sub 3}Se{sub 5} and CuGa{sub 5}Se{sub 8} phases is observed respectively. Band gap values were obtained using photocurrent spectroscopy.

Fernandez, A. M.; Turner, J. A.

2012-04-01T23:59:59.000Z

228

Electron and hole gas in modulation-doped GaAs/Al{sub 1-x}Ga{sub x}As radial heterojunctions  

Science Conference Proceedings (OSTI)

We perform self-consistent Schroedinger-Poisson calculations with exchange and correlation corrections to determine the electron and hole gas in a radial heterojunction formed in a GaAs/AlGaAs core-multi-shell nanowire, which is either n- or p-doped. We show that the electron and hole gases can be tuned to different localizations and symmetries inside the core as a function of the doping density/gate potential. Contrary to planar heterojunctions, conduction electrons do not form a uniform 2D electron gas (2DEG) localized at the GaAs/AlGaAs interface, but rather show a transition between an isotropic, cylindrical distribution deep in the GaAs core (low doping) and a set of six tunnel-coupled quasi-1D channels at the edges of the interface (high doping). Holes, on the other hand, are much more localized at the GaAs/AlGaAs interface. At low doping, they present an additional localization pattern with six separated 2DEGs strips. The field generated by a back-gate may easily deform the electron or hole gas, breaking the sixfold symmetry. Single 2DEGs at one interface or multiple quasi-1D channels are shown to form as a function of voltage intensity, polarity, and carrier type.

Bertoni, Andrea; Royo, Miquel; Mahawish, Farah; Goldoni, Guido [CNR-NANO S3, Istituto Nanoscienze, Via Campi 213/a, 41125 Modena (Italy); Department of Physics, University of Modena and Reggio Emilia and CNR-NANO S3, Istituto Nanoscienze, Via Campi 213/a, 41125 Modena (Italy)

2011-11-15T23:59:59.000Z

229

Relaxation and critical strain for maximum In incorporation in AlInGaN on GaN grown by metal organic vapour phase epitaxy  

Science Conference Proceedings (OSTI)

Quaternary AlInGaN layers were grown on conventional GaN buffer layers on sapphire by metal organic vapour phase epitaxy at different surface temperatures and different reactor pressures with constant precursor flow conditions. A wide range in compositions within 30-62% Al, 5-29% In, and 23-53% Ga was covered, which leads to different strain states from high tensile to high compressive. From high-resolution x-ray diffraction and Rutherford backscattering spectrometry, we determined the compositions, strain states, and crystal quality of the AlInGaN layers. Atomic force microscopy measurements were performed to characterize the surface morphology. A critical strain value for maximum In incorporation near the AlInGaN/GaN interface is presented. For compressively strained layers, In incorporation is limited at the interface as residual strain cannot exceed an empirical critical value of about 1.1%. Relaxation occurs at about 15 nm thickness accompanied by strong In pulling. Tensile strained layers can be grown pseudomorphically up to 70 nm at a strain state of 0.96%. A model for relaxation in compressively strained AlInGaN with virtual discrete sub-layers, which illustrates the gradually changing lattice constant during stress reduction is presented.

Reuters, Benjamin; Finken, M.; Wille, A.; Kalisch, H.; Vescan, A. [RWTH Aachen University, GaN Device Technology, Sommerfeldstrasse 24, 52074 Aachen (Germany); Juelich Aachen Research Alliance, JARA-FIT, Wilhelm-Johnen-Strasse, 52428 Juelich (Germany); Hollaender, B. [Juelich Aachen Research Alliance, JARA-FIT, Wilhelm-Johnen-Strasse, 52428 Juelich (Germany); Forschungszentrum Juelich GmbH, PGI9-IT, 52425 Juelich (Germany); Heuken, M. [RWTH Aachen University, GaN Device Technology, Sommerfeldstrasse 24, 52074 Aachen (Germany); AIXTRON SE, Kaiserstr. 98, 52134 Herzogenrath (Germany)

2012-11-01T23:59:59.000Z

230

Analysis of the GaInP/GaAs/1-eV/Ge Cell and Related Structures for Terrestrial Concentrator Application: Preprint  

DOE Green Energy (OSTI)

This conference paper describes the analysis of the potential of GaInP/GaAs/1-eV/Ge four-junction solar cell to improve on the efficiency of the state-of-the-art GaInP/GaAs/Ge benchmark. We emphasize three factors: (1) The newly proposed terrestrial concentrator spectrum has a lower ratio of red to blue light than does the old AM1.5 direct standard spectrum. (2) Standard two-layer antireflection coatings do not provide near-zero reflectance over the full spectral range of interest for these devices. (3) GaInNAs junctions used to date for the 1-eV junction have quantum efficiencies less than {approx}75%. These factors all limit the device current, adversely affecting the four-junction efficiency. We discuss strategies for ameliorating this problem, including going to alternate structures such as a GaInP/GaAs/0.9-eV three-junction device.

Friedman, D. J.; Kurtz, S. R.; Geisz, J. F.

2002-05-01T23:59:59.000Z

231

On-Sun Comparison of GaInP2/GaAs Tandem Cells with Top-Cell Thickness Varied  

DOE Green Energy (OSTI)

This study compares the on-sun performance of a set of GaInP2/GaAs tandem cells with different GaInP2 top-cell thicknesses. Because high-efficiency III-V cells are best suited to concentrating photovoltaic (CPV) applications, the cells were mounted on a two-axis tracker with the incident sunlight collimated to exclude all except the direct beam. Current-voltage (I-V) curves were taken throughout the course of several days, along with the direct solar spectrum. Our two major conclusions are: (1) GaInP2/GaAs tandem cells designed for an ''air mass 1.5 global'' (AM 1.5G) or a ''low aerosol optical depth'' (Low AOD) spectrum perform the best, and (2) a simple device model using the measured direct spectra as an input gives the same result. These results are equally valid for GaInP2/GaAs/Ge triple-junction cells.

McMahon, W. E.; Emery, K. A.; Friedman, D. J.; Ottoson, L.; Young, M. S.; Ward, J. S.; Kramer, C. M.; Duda, A.; Kurtz, S.

2005-01-01T23:59:59.000Z

232

The consequences of high injected carrier densities on carrier localisation and efficiency droop in InGaN/GaN quantum well structures  

E-Print Network (OSTI)

in the concentration of the randomly distributed In atoms on the optical properties of InGaN/GaN quantum wells. On the basis of this comparison of theory with experiment we attribute the reduction in the S- shape temperature dependence to the saturation... , the buffer layer was grown in a Thomas Swan 6x2” metalorganic vapour-phase epitaxy reactor using trimethyl gallium (TMG), silane (SiH4) and ammonia (NH3) as precursors, with hydrogen as the carrier gas. The GaN buffer layer was deposited at 1020 şC on a...

Hammersley, S; Watson-Parris, D; Dawson, P; Godfrey, M; Badcock, T; Kappers, M; McAleese, C; Oliver, R; Humphreys, C

2012-04-18T23:59:59.000Z

233

InGaAsN Solar Cells with 1.0eV Bandgap, Lattice Matched to GaAs  

DOE Green Energy (OSTI)

The design, growth by metal-organic chemical vapor deposition, and processing of an In{sub 0.07}Ga{sub 0.93}As{sub 0.98}N{sub 0.02} solar Al, with 1.0 ev bandgap, lattice matched to GaAs is described. The hole diffusion length in annealed, n-type InGaAsN is 0.6-0.8 pm, and solar cell internal quantum efficiencies > 70% arc obwined. Optical studies indicate that defects or impurities, from InGAsN doping and nitrogen incorporation, limit solar cell performance.

Allerman, A.A.; Banas, J.J.; Gee, J.M.; Hammons, B.E.; Jones, E.D.; Kurtz, S.R.

1998-11-24T23:59:59.000Z

234

K8, HVPE Homoepitaxy of p-Type GaN on n-Type Catalyst Free ...  

Science Conference Proceedings (OSTI)

We present the growth of p-type HVPE GaN using catalyst free GaN nitride nanowires as a lattice matched substrate. The nanowires were grown using plasma ...

235

Analisi dei processi di ricombinazione in diodi LED basati su GaN: caratterizzazione ottica e misure DLTS.  

E-Print Network (OSTI)

??In questo lavoro vengono analizzati i processi di ricombinazione nei diodi LED basati su GaN/InGaN mediante caratterizzazione ottica dei dispositivi e misure DLTS. In particolare… (more)

La Grassa, Marco

2013-01-01T23:59:59.000Z

236

Scattering and electron mobility in combination-doped HFET-structures AlGaAs/InGaAs/AlGaAs with high electron density  

Science Conference Proceedings (OSTI)

Molecular-beam epitaxy is used for growing structures differing in doping technique and doping level and having a high two-dimensional-electron concentration n{sub s} in the quantum well. The effect of doping combining uniform and {delta} doping on the electron-transport properties of heterostructures is investigated. A new type of structure with a two-sided silicon {delta} doping of GaAs transition layers located on the quantum-well boundaries is proposed. The largest value of electron mobility {mu}{sub H} = 1520 cm{sup 2}/(V s) is obtained simultaneously with a high electron density n{sub s} = 1.37 Multiplication-Sign 10{sup 13} cm{sup -2} at 300 K with such a doping. It is associated with decreasing electron scattering by an ionized impurity, which is confirmed by the carried out calculations.

Khabibullin, R. A., E-mail: khabibullin_r@mail.ru; Vasil'evskii, I. S. [MEPHI National Research Nuclear University (Russian Federation); Galiev, G. B.; Klimov, E. A. [Russian Academy of Sciences, Institute of Ultrahigh-Frequency Semiconductor Electronics (Russian Federation); Ponomarev, D. S. [MEPHI National Research Nuclear University (Russian Federation); Lunin, R. A.; Kulbachinskii, V. A. [Moscow State University (Russian Federation)

2011-10-15T23:59:59.000Z

237

Large energy absorption in Ni-Mn-Ga/polymer composites  

SciTech Connect

Ferromagnetic shape memory alloys can respond to a magnetic field or applied stress by the motion of twin boundaries and hence they show large hysteresis or energy loss. Ni-Mn-Ga particles made by spark erosion have been dispersed and oriented in a polymer matrix to form pseudo 3:1 composites which are studied under applied stress. Loss ratios have been determined from the stress-strain data. The loss ratios of the composites range from 63% to 67% compared to only about 17% for the pure, unfilled polymer samples.

Feuchtwanger, Jorge; Richard, Marc L.; Tang, Yun J.; Berkowitz, Ami E.; O'Handley, Robert C.; Allen, Samuel M. [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); University of California, San Diego, La Joya, California 92093 (United States); Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2005-05-15T23:59:59.000Z

238

Method of making V.sub.3 Ga superconductors  

DOE Patents (OSTI)

An improved method for producing a vanadium-gallium superconductor wire having aluminum as a component thereof is disclosed, said wire being encased in a gallium bearing copper sheath. The superconductors disclosed herein may be fabricated under normal atmospheres and room temperatures by forming a tubular shaped billet having a core composed of an alloy of vanadium and aluminum and an outer sheath composed of an alloy of copper, gallium and aluminum. Thereafter the entire billet is swage reduced to form a wire therefrom and heat treated to form a layer of V.sub.3 Ga in the interior of the wire.

Dew-Hughes, David (Bellport, NY)

1980-01-01T23:59:59.000Z

239

Lighting Enhancement of GaN LEDs by Applying p-Type Ni(P):SnO2 ...  

Science Conference Proceedings (OSTI)

About this Abstract. Meeting, Materials Science & Technology 2013. Symposium, Multifunctional Oxides. Presentation Title, Lighting Enhancement of GaN LEDs ...

240

A3, Depth Resolved Strain and Composition Studies on InGaN and ...  

Science Conference Proceedings (OSTI)

... devices due to its large spontaneous polarization and conduction band offset. ... 620°C with fixed beam fluxes of In and Ga under the same nitrogen plasma condition. ... Inexpensive, Non-Toxic Thermoelectric Materials for Waste Heat Recovery ..... Y5, Defect Characterization of InGaN Layer by Deep Level Transient and ...

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Development of a Low Cost Insulated Foil Substrate for Cu(InGaSe)2 Photovoltaics  

DOE Green Energy (OSTI)

The project validated the use of stainless steel flexible substrate coated with silicone-based resin dielectric, developed by Dow Corning Corporation, for Cu(InGa)Se2 based photovoltaics. The projects driving force was the high performance of Cu(InGa)Se2 based photovoltaics coupled with potential cost reduction that could be achieved with dielectric coated SS web substrate.

ERTEN ESER

2012-01-22T23:59:59.000Z

242

High efficiency light emitting diode with anisotropically etched GaN-sapphire interface  

E-Print Network (OSTI)

High efficiency light emitting diode with anisotropically etched GaN- sapphire interface M. H. Lo and optimization of a light-emitting diode projection micro-stereolithography three-dimensional manufacturingGaN micro-light emitting diodes Appl. Phys. Lett. 101, 231110 (2012) A bright cadmium-free, hybrid organic

243

Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution  

E-Print Network (OSTI)

Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution Aurélien David of photonic crystal PhC -assisted gallium nitride light-emitting diodes LEDs to the existence of unextracted a promising but challenging solution towards efficient solid-state lighting. Conventional GaN-based light-emitting

Recanati, Catherine

244

GaN light-emitting diodes with Archimedean lattice photonic crystals Aurlien David,a  

E-Print Network (OSTI)

GaN light-emitting diodes with Archimedean lattice photonic crystals Aurélien David,a Tetsuo Fujii 2005; published online 16 February 2006 We study GaN-based light emitting diodes incorporating light- emitting diodes LEDs , as they could extract the emitted light otherwise trapped inside

Recanati, Catherine

245

Cubic GaN Light Emitting Diode Grown by Metalorganic Vapor-Phase Epitaxy  

E-Print Network (OSTI)

this paper, we report on the doping characteristics of Si and Mg in the growth of cubic GaN by metalorganic vapor-phase epitaxy (MOVPE). We also report the growth of a p-n diode structure made of cubic GaN, and its characterization by electron-beam-induced-current (EBIC) and current injection measurements.

Hidenao Tanaka Member; Vapor-phase Epitaxy; Atsushi Nakadaira

2000-01-01T23:59:59.000Z

246

GaN membrane-supported UV photodetectors manufactured using nanolithographic processes  

Science Conference Proceedings (OSTI)

Membrane GaN metal-semiconductor-metal (MSM) photodetector structures using nanolithographic techniques have been manufactured for the first time. Very low dark currents and unexpected high values for the responsivity have been obtained. It seems that ... Keywords: GaN, Membrane, Nanolithography, Responsivity, SEM

A. Müller; G. Konstantinidis; M. Dragoman; D. Neculoiu; A. Dinescu; M. Androulidaki; M. Kayambaki; A. Stavrinidis; D. Vasilache; C. Buiculescu; I. Petrini; A. Kostopoulos; D. Dascalu

2009-02-01T23:59:59.000Z

247

The use of short-period InGaN/GaN superlattices in blue-region light-emitting diodes  

SciTech Connect

Optical and light-emitting diode structures with an active InGaN region containing short-period InGaN/GaN superlattices are studied. It is shown that short-period superlattices are thin two-dimensional layers with a relatively low In content that contain inclusions with a high In content 1-3 nm thick. Inclusions manifest themselves from the point of view of optical properties as a nonuniform array of quantum dots involved in a residual quantum well. The use of short-period superlattices in light-emitting diode structures allows one to decrease the concentration of nonradiative centers, as well as to increase the injection of carriers in the active region due to an increase in the effective height of the AlGaN barrier, which in general leads to an increase in the quantum efficiency of light-emitting diodes.

Sizov, V. S., E-mail: vsizov@mail.ioffe.ru; Tsatsulnikov, A. F.; Sakharov, A. V.; Lundin, W. V.; Zavarin, E. E.; Cherkashin, N. A. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Hytch, M. J. [National Center for Scientific Research (CNRS), Center for Material Elaboration and Structural Studies (CEMES) (France); Nikolaev, A. E. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Mintairov, A. M.; He Yan; Merz, J. L. [University of Notre Dame, EE Department (United States)

2010-07-15T23:59:59.000Z

248

Electron mobility and effective mass in composite InGaAs quantum wells with InAs and GaAs nanoinserts  

Science Conference Proceedings (OSTI)

The paper is concerned with the theoretical and experimental studies of the band structure and electrical properties of InAlAs/InGaAs/InAlAs/InP heterostructures containing a composite InGaAs quantum well with InAs and GaAs nanoinserts. From the Shubnikov-de Haas effect, the effective cyclotron mass m{sub c}* is determined experimentally and calculated with consideration for the nonparabolicity of the electron energy spectrum. An approach to estimation of the effective mass is proposed and tested. The approach is based on weighted averaging of the m{sub c}* of the composite quantum well's constituent materials. A first proposed heterostructure containing two InAs inserts symmetrically arranged in the quantum well makes a 26% reduction in m{sub c}* compared to m{sub c}* in the lattice-matched In{sub 0.53}Ga{sub 0.47}As quantum well possible.

Ponomarev, D. S., E-mail: ponomarev_dmitr@mail.ru; Vasil'evskii, I. S. [National Nuclear Research University 'Moscow Engineering Physics Institute (MEPhI)' (Russian Federation); Galiev, G. B.; Klimov, E. A. [Russian Academy of Sciences, Institute of Ultrahigh-Frequency Semiconductor Electronics (Russian Federation); Khabibullin, R. A. [National Nuclear Research University 'Moscow Engineering Physics Institute (MEPhI)' (Russian Federation); Kulbachinskii, V. A.; Uzeeva, N. A. [Moscow State University (Russian Federation)

2012-04-15T23:59:59.000Z

249

Power Conversion Efficiency of AlGaAs/GaAs Schottky Diode for Low-Power On-Chip Rectenna Device Application  

Science Conference Proceedings (OSTI)

A Schottky diode has been designed and fabricated on n-AlGaAs/GaAs high-electron-mobility-transistor (HEMT) structure. Current-voltage (I-V) measurements show good device rectification with a Schottky barrier height of 0.4349 eV for Ni/Au metallization. The differences of Schottky barrier height from theoretical value are due to the fabrication process and smaller contact area. The RF signals up to 1 GHz are well rectified by the fabricated Schottky diodes and stable DC output voltage is obtained. Power conversion efficiency up to 50% is obtained at 1 GHz with series connection between diode and load. The fabricated the n-AlGaAs/GaAs Schottky diode provide conduit for breakthrough designs for ultra-low power on-chip rectenna device technology to be integrated in nanosystems.

Mustafa, Farahiyah; Hashim, Abdul Manaf; Rahman, Shaharin Fadzli Abd [Material Innovations and Nanoelectronics Research Group, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 Skudai (Malaysia); Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, 81310 Skudai Johor Malaysia (Malaysia); Osman, Mohd Nizam [Telekom Research and Development, TM Innovation Centre, 63000 Cyberjaya (Malaysia)

2011-05-25T23:59:59.000Z

250

Identification of the Parasitic Chemical Reactions during AlGaN OMVPE  

NLE Websites -- All DOE Office Websites (Extended Search)

Identification of the Parasitic Chemical Reactions during AlGaN OMVPE Identification of the Parasitic Chemical Reactions during AlGaN OMVPE by J. R. Creighton, M. E. Coltrin, and W. G. Breiland Motivation-GaN and AlGaN alloys are ex- tremely important materials with widespread applications for optoelectronics (e.g. solid state lighting) and high power electronics. Or- ganometallic vapor phase epitaxy (OMVPE) is the primary deposition methodology, but it suf- fers from several growth chemistry anomalies. Growth rate and alloy composition are often a sensitive function of temperature and other reac- tor variables. These factors make the AlGaN OMVPE process difficult to control and in- crease the cost of the material. Conventional wisdom has been that the non-ideal OMVPE behavior is due to parasitic "pre-reactions" be-

251

The quantum efficiency of InGaAsSb thermophotovoltaic diodes  

DOE Green Energy (OSTI)

Uncoated InGaAsSb/GaSb thermophotovoltaic (TPV) diodes with 0.56 eV (2.2 {micro}m) bandgaps exhibit external quantum efficiencies of 59% at 2 {micro}m, which corresponds to an internal quantum efficiency of 95%. The structures were grown by molecular-beam epitaxy. The devices have electron diffusion lengths as long as 29 {micro}m in 8-{micro}m-wide p-InGaAsSb layers and hole diffusion lengths of 3 {micro}m in 6-{micro}m-wide n-InGaAsSb layers. The electron and hole diffusion lengths appear to increase with increasing p- and n-layer widths, respectively. These excellent minority carrier transport properties of InGaAsSb are well-suited to efficient TPV diode operation.

Martinelli, R.U.; Garbuzov, D.Z.; Lee, H.; Morris, N.; Odubanjo, T.; Taylor, G.C.; Connolly, J.C. [Sarnoff Corp., Princeton, NJ (United States)

1997-10-01T23:59:59.000Z

252

Magnetically active vacancy related defects in irradiated GaN layers  

Science Conference Proceedings (OSTI)

We present the studies of magnetic properties of 2 MeV {sup 4}He{sup +}-irraadiated GaN grown by metal-organic chemical-vapor deposition. Particle irradiation allowed controllable introduction of Ga-vacancy in the samples. The magnetic moments with concentrations changing between 4.3 and 8.3 Multiplication-Sign 10{sup 17}cm{sup -3} showing superparamagnetic blocking at room temperature are observed. The appearance of clear hysteresis curve at T=5K with coercive field of about H{sub C} Almost-Equal-To 270 Oe suggests that the formation of more complex Ga vacancy related defects is promoted with increasing Ga vacancy content. The small concentration of the observed magnetically active defects with respect to the total Ga-vacancy concentration suggests that the presence of the oxygen/hydrogen-related vacancy complexes is the source of the observed magnetic moments.

Kilanski, L.; Tuomisto, F. [Department of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto Espoo (Finland); Szymczak, R. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Kruszka, R. [Institute of Electron Technology, Al. Lotnikow 46, 02-668 Warsaw (Poland)

2012-08-13T23:59:59.000Z

253

Electron Traps Detected in p-type GaAsN Using Deep Level Transient Spectroscopy  

DOE Green Energy (OSTI)

The GaAsN alloy can have a band gap as small as 1.0 eV when the nitrogen composition is about 2%. Indium can also be added to the alloy to increase lattice matching to GaAs and Ge. These properties are advantageous for developing a highly-efficient, multi-junction solar cell. However, poor GaAsN cell properties, such as low open-circuit voltage, have led to inadequate performance. Deep-level transient spectroscopy of p-type GaAsN has identified an electron trap having an activation energy near 0.2 eV and a trap density of at least 1016 cm-3. This trap level appears with the addition of small amounts of nitrogen to GaAs, which also corresponds to an increased drop in open-circuit voltage.

Johnston, S.; Kurtz, S.; Friedman, D.; Ptak, A.; Ahrenkiel, R.; Crandall, R.

2005-01-01T23:59:59.000Z

254

Cr-Ga-N materials for negative electrodes in Li rechargeable batteries : structure, synthesis and electrochemical performance  

E-Print Network (OSTI)

Electrochemical performances of two ternary compounds (Cr2GaN and Cr3GaN) in the Cr-Ga-N system as possible future anode materials for lithium rechargeable batteries were studied. Motivation for this study was dealt in ...

Kim, Miso

2007-01-01T23:59:59.000Z

255

Micro-Photoluminescence Characterization of Low Density Droplet GaAs Quantum Dots for Single Photon Sources  

Science Conference Proceedings (OSTI)

The GaAs quantum dots in AlGaAs barriers were grown by droplet epitaxy, emitting around 700 nm in wavelength which is compatible with low cost Si based detectors. The excitation power dependent and time resolved micro-photoluminescence measurements identified optical characteristics of exciton and biexciton states which are attributed to good quantum confinements in GaAs QDs.

Ha, S.-K.; Song, J. D.; Lim, J. Y.; Choi, W. J.; Han, I. K.; Lee, J. I. [Nano Convergence Devices Center, KIST, Seoul 136-791 (Korea, Republic of); Bounouar, S.; Donatini, F.; Dang, L. S.; Poizat, J. P. [CEA/CNRS/UJF team 'Nanophysics and semiconductors', Institute Neel/CNRS-UJF, 38042 Grenoble (France); Kim, J. S. [Department of Physics, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of)

2011-12-23T23:59:59.000Z

256

The effects of quantum dot coverage in InAs/(In)GaAs nanostructures for long wavelength emission  

Science Conference Proceedings (OSTI)

We present a study on the effects of quantum dot coverage on the properties of InAs dots embedded in GaAs and in metamorphic In0.15Ga0.85As confining layers grown by molecular beam epitaxy on GaAs substrates. We show that redshifted ... Keywords: Long wavelength emission, Molecular beam epitaxy, Quantum dot ripening, Quantum dots

G. Trevisi; L. Seravalli; P. Frigeri; M. Prezioso; J. C. Rimada; E. Gombia; R. Mosca; L. Nasi; C. Bocchi; S. Franchi

2009-03-01T23:59:59.000Z

257

Junction temperature, spectral shift, and efficiency in GaInN-based blue and green light emitting diodes  

E-Print Network (OSTI)

Keywords: GaInN/GaN Light emitting diode temperature Micro-Raman Photoluminescence Electroluminescence well light emitting diode (LED) dies is analyzed by micro-Raman, photoluminescence, cathodoluminescenceJunction temperature, spectral shift, and efficiency in GaInN-based blue and green light emitting

Wetzel, Christian M.

258

Influence of post deposition annealing on Y2O3-gated GaAs MOS capacitors and their reliability issues  

Science Conference Proceedings (OSTI)

The feasibility of employing yttrium oxide (Y"2O"3) as high-k gate dielectrics for GaAs metal-oxide-semiconductor (MOS) devices has been investigated. MOS capacitors were fabricated using RF-sputtered deposited Y"2O"3 films on NH"4OH treated n-GaAs substrate. ... Keywords: GaAs, TDDB, Trapping centroid, Y2O3

P. S. Das; A. Biswas

2011-03-01T23:59:59.000Z

259

Direct measurement of interfacial structure in epitaxial Gd2O3 on GaAs (001) using scanning tunneling microscopy  

Science Conference Proceedings (OSTI)

The epitaxial growth of Gd"2O"3 on GaAs (001) has given a low interfacial density of states, resulting in the demonstration of the first inversion-channel GaAs metal-oxide-semiconductor field-effect transistor. Motivated by the significance of this discovery, ... Keywords: Electronic information, GaAs, Gd2O3, Interfacial stacking, Scanning tunneling microscopy

Y. P. Chiu; M. C. Shih; B. C. Huang; J. Y. Shen; M. L. Huang; W. C. Lee; P. Chang; T. H. Chiang; M. Hong; J. Kwo

2011-07-01T23:59:59.000Z

260

Improving light output power of InGaN-based light emitting diodes with pattern-nanoporous p-type GaN:Mg surfaces  

SciTech Connect

InGaN-based light emitting diodes (LEDs) with a top pattern-nanoporous p-type GaN:Mg surface were fabricated by using a photoelectrochemical (PEC) process. The peak wavelengths of electroluminescence (EL) and operating voltages were measured as 461.2 nm (3.1 V), 459.6 nm (9.2 V), and 460.1 nm (3.3 V) for conventional, nanoporous, and pattern-nanoporous LEDs using 20 mA operation current. The EL spectrum of the nanoporous LED had a larger blueshift phenomenon as a result of a partial compression strain release in the InGaN active layer through the formation of a top nanoporous surface. The light output power had 12.1% and 26.4% enhancements for the nanoporous and the pattern-nanoporous LEDs compared with conventional LEDs. The larger operating voltage of the nanoporous LED was due to the non-ohmic contact on the PEC treated p-type GaN:Mg surface. By using a pattern-nanoporous p-type GaN:Mg structure, the operating voltage of the pattern-nanoporous LED was reduced to 3.3 V. A lower compression strain in the InGaN active layer and a higher light extraction efficiency at the top nanoporous surface were observed in pattern-nanoporous LEDs for higher efficiency nitride-based LED applications.

Yang, C.C.; Lin, C.F.; Lin, C.M.; Chang, C.C.; Chen, K.T.; Chien, J.F.; Chang, C.Y. [Department of Materials Engineering, National Chung Hsing University, Taichung 402, Taiwan (China)

2008-11-17T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Indium and impurity incorporation in InGaN films on polar, nonpolar, and semipolar GaN orientations grown by ammonia molecular beam epitaxy  

SciTech Connect

The effects of NH{sub 3} flow, group III flux, and substrate growth temperature on indium incorporation and surface morphology have been investigated for bulk InGaN films grown by ammonia molecular beam epitaxy. The incorporation of unintentional impurity elements (H, C, O) in InGaN films was studied as a function of growth temperature for growth on polar (0001) GaN on sapphire templates, nonpolar (1010) bulk GaN, and semipolar (1122), (2021) bulk GaN substrates. Enhanced indium incorporation was observed on both (1010) and (2021) surfaces relative to c-plane, while reduced indium incorporation was observed on (1122) for co-loaded conditions. Indium incorporation was observed to increase with decreasing growth temperature for all planes, while being relatively unaffected by the group III flux rates for a 1:1 Ga:In ratio. Indium incorporation was found to increase at the expense of a decreased growth rate for higher ammonia flows; however, smooth surface morphology was consistently observed for growth on semipolar orientations. Increased concentrations of oxygen and hydrogen were observed on semipolar and nonpolar orientations with a clear trend of increased hydrogen incorporation with indium content.

Browne, David A.; Young, Erin C.; Lang, Jordan R.; Hurni, Christophe A.; Speck, James S. [Materials Department, University of California Santa Barbara, Santa Barbara, California 93106 (United States)

2012-07-15T23:59:59.000Z

262

Local structure and vibrational properties of alpha'-Pu martensitein Ga-stabilized delta-Pu  

Science Conference Proceedings (OSTI)

Extended x-ray absorption fine structure spectroscopy (EXAFS) is used to investigate the local atomic environment and vibrational properties of plutonium and gallium atoms in the {alpha}{prime} and {delta} phases of a mixed phase Pu-Ga alloy. EXAFS results measured at low temperature compare the structure of the mixed phase sample with a single-phase {delta}-Pu sample. EXAFS spectral components attributed to both {alpha}{prime}-Pu and {delta}-Pu were observed in the mixed phase sample. Ga K-edge EXAFS spectra indicate local atomic environments similar to the Pu LIII-edge EXAFS results, which suggests that Ga is substitutional for Pu atoms in both the monoclinic {alpha}{prime}-Pu and the fcc {delta}-Pu structures. In {delta}-Pu, we measure a Ga-Pu bond length contraction of 0.11 Angstroms with respect to the Pu-Pu bond length. The corresponding bond-length contraction around Ga in {alpha}{prime}-Pu is only 0.03 Angstroms. Results from temperature-dependent Pu LIII-edge EXAFS measurements are fit to a correlated Debye model, and a large difference in the Pu-Pu bond Debye temperature is observed for the {alpha}{prime} and {delta} phases: {theta}{sub cD}({alpha}{prime})=159{+-}13 K versus {theta}{sub cD}({delta})=120{+-}3 K. The corresponding analysis for the Ga K EXAFS determines a Ga-Pu bond Debye temperature of {theta}{sub cD}({delta})=188{+-}12 K in the {delta}-Pu phase. These results are related to the observed solubility of Ga in {delta}-Pu, the ''stabilization'' of {delta}-Pu by Ga at room temperature, and the insolubility of Ga in {alpha}{prime}-Pu.

Nelson, E.J.; Blobaum, K.J.M.; Wall, M.A.; Allen, P.G.; Schwartz,A.J.; Booth, C.H.

2003-02-26T23:59:59.000Z

263

GaInAsSb materials for thermophotovoltaics  

DOE Green Energy (OSTI)

Ga{sub 1{minus}x}In{sub x}As{sub 1{minus}y}Sb{sub y} (0.06 < x < 0.2, 0.05 < y < 0.18) epilayers were grown lattice-matched to GaSb substrates by organometallic vapor phase epitaxy (OMVPE) and molecular beam epitaxy (MBE). For lattice-matched alloys, mirror-like surface morphologies were obtained by both OMVPE and MBE. The 4K photoluminescence (PL) of all layers had a full-width at half-maximum (FWHM) of less than 10 meV for PL peak emission < 1.9 {micro}m. PL FWHM increased to 30 meV for peak emission {approximately}2.12 {micro}m for OMVPE-grown layers. Nominally undoped layers are p-type with typical 300 K hole concentration of {approximately}9 {times} 10{sup 15} cm{sup {minus}3} and hole mobility {approximately}450 to 580 cm{sup 2}/V-s for OMVPE-grown layers, p- and n-type doping is reported for layers grown with either technique. The ideality factor of diode structures is {approximately}2 for both techniques.

Wang, C.A.; Turner, G.W.; Manfra, M.J.; Choi, H.K.; Spears, D.L. [Massachusetts Inst. of Tech., Lexington, MA (United States). Lincoln Lab.

1996-12-01T23:59:59.000Z

264

Ga-doped ZnO grown by pulsed laser deposition in H2: the roles of Ga and H  

DOE Green Energy (OSTI)

Highly conductive thin films of ZnO doped with Ga were grown by pulsed-laser deposition (PLD) with 10 mTorr of H2 in the growth chamber. Compared with a more conventional method of producing conductive films of ZnO, i.e., growth in O2 followed by annealing in forming gas (5% H2 in Ar), the H2 method requires no post-growth anneal and also produces higher carrier concentrations and lower resistivities with better depth uniformity. As an example, a 65-nm-thick sample had a room-temperature mobility of 32 cm2/V-s, a concentration of 6.8 x 1020 cm-3, and a resistivity of 2.9 x 10^-4 ohm-cm. From a scattering model, the donor and acceptor concentrations were calculated as 8.9 x 1020 and 2.1 x 10^20 cm-3, respectively, as compared to the Ga and H concentrations of 11 x 10^20 and 1 x 10^20 cm-3. Thus, H does not play a significant role as a donor in this type of ZnO

Look, David; Droubay, Timothy; McCloy, John S.; Zhu, Zihua; Chambers, Scott A.

2011-01-11T23:59:59.000Z

265

Transmission electron microscopy characterization of electrically stressed AlGaN/GaN high electron mobility transistor devices  

Science Conference Proceedings (OSTI)

A set of AlGaN/GaN high electron mobility transistor devices has been investigated using step-stress testing, and representative samples of undegraded, source-side-degraded, and drain-side-degraded devices were examined using electron microscopy and microanalysis. An unstressed reference sample was also examined. All tested devices and their corresponding transmission electron microscopy samples originated from the same wafer and thus received nominally identical processing. Step-stressing was performed on each device and the corresponding current voltage characteristics were generated. Degradation in electrical performance, specifically greatly increased gate leakage current, was shown to be correlated with the presence of crystal defects near the gate edges. However, the drain-side-degraded device showed a surface pit on the source side, and another region of the same device showed no evidence of damage. Moreover, significant metal diffusion into the barrier layer from the gate contacts was also observed, as well as thin amorphous oxide layers below the gate metal contacts, even in the unstressed sample. Overall, these observations emphasize that gate-edge defects provide only a partial explanation for device failure.

Johnson, Michael [Arizona State University; Cullen, David A [ORNL; Liu, Lu [University of Florida; Kang, Tsung Sheng [University of Florida, Gainesville; Ren, F. [University of Florida; Chang, C. Y. [University of Florida; Pearton, S. J. [University of Florida; Jang, Soohwan [University of Florida, Gainesville; Johnson, Wayne J. [Kopin Corporation, Taunton, MA; Smith, David J [Arizona State University

2012-01-01T23:59:59.000Z

266

IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 55, NO. 6, DECEMBER 2008 3633 Radiation Effects on InGaN Quantum Wells  

E-Print Network (OSTI)

GaN Quantum Wells and GaN Simultaneously Probed by Ion Beam-Induced Luminescence J. W. Tringe, Member, IEEE, A. Stevens, and C. Wetzel, Member, IEEE Abstract--InGaN quantum well structures on GaN epilayers were exposed of the epilayer and wells. Performance was estimated by the intensity of ion-beam induced luminescence. Two

Wetzel, Christian M.

267

Enhanced quality thin film Cu(In,Ga)Se.sub.2 for semiconductor device applications by vapor-phase recrystallization  

DOE Patents (OSTI)

Enhanced quality thin films of Cu.sub.w (In,Ga.sub.y)Se.sub.z for semiconductor device applications are fabricated by initially forming a Cu-rich, phase-separated compound mixture comprising Cu(In,Ga):Cu.sub.x Se on a substrate to form a large-grain precursor and then converting the excess Cu.sub.x Se to Cu(In,Ga)Se.sub.2 by exposing it to an activity of In and/or Ga, either in vapor In and/or Ga form or in solid (In,Ga).sub.y Se.sub.z. Alternatively, the conversion can be made by sequential deposition of In and/or Ga and Se onto the phase-separated precursor. The conversion process is preferably performed in the temperature range of about 300.degree.-600.degree. C., where the Cu(In,Ga)Se.sub.2 remains solid, while the excess Cu.sub.x Se is in a liquid flux. The characteristic of the resulting Cu.sub.w (In,Ga).sub.y Se.sub.z can be controlled by the temperature. Higher temperatures, such as 500.degree.-600.degree. C., result in a nearly stoichiometric Cu(In,Ga)Se.sub.2, whereas lower temperatures, such as 300.degree.-400.degree. C., result in a more Cu-poor compound, such as the Cu.sub.z (In,Ga).sub.4 Se.sub.7 phase.

Tuttle, John R. (Denver, CO); Contreras, Miguel A. (Golden, CO); Noufi, Rommel (Golden, CO); Albin, David S. (Denver, CO)

1994-01-01T23:59:59.000Z

268

Highly Responsive Ultrathin GaS Nanosheet Photodetectors on Rigid and Flexible Substrates  

Science Conference Proceedings (OSTI)

The first GaS nanosheet-based photodetectors are demonstrated on both mechanically rigid and flexible substrates. Highly-crystalline, exfoliated GaS nanosheets are promising for optoelectronics due to strong absorption in the UV-visible wavelength region. Photocurrent measurements of GaS nanosheet photodetectors made on SiO2/Si substrates and flexible polyethylene terephthalate (PET) substrates exhibit a photo-responsivity at 254nm up to 4.2 AW-1 and 19.2 AW-1, respectively, which exceeds that of graphene, MoS2, or other 2D materials-based devices. Additionally, the linear dynamic range of the devices on SiO2/Si and PET substrates are 97.7dB and 78.73 dB, respectively. Both surpass that of currently-exploited InGaAs photodetectors (66 dB). Theoretical modeling of the electronic structures indicates that the reduction of the effective mass at the valence band maximum (VBM) with decreasing sheet thickness enhances the carrier mobility of the GaS nanosheets, contributing to the high photocurrents. Double-peak VBMs are theoretically predicted for ultrathin GaS nanosheets (thickness less than 5 monolayers), which is found to promote photon absorption. These theoretical and experimental results show that GaS nanosheets are promising materials for high performance photodetectors on both conventional silicon and flexible substrates.

Hu, Prof Pingan [Harbin Institute of Technology; Wang, Lifeng [Harbin Institute of Technology; Yoon, Mina [ORNL; Zhang, Jia [Harbin Institute of Technology; Feng, Wei [Harbin Institute of Technology; Wang, Xiaona [Harbin Institute of Technology; Wen, Zhenzhong [Harbin Institute of Technology; Idrobo Tapia, Juan C [ORNL; Miyamoto, Yoshiyuki [National Institute of Advanced Industrial Science and Technology, Japan; Geohegan, David B [ORNL; Xiao, Kai [ORNL

2013-01-01T23:59:59.000Z

269

Polarity inversion of N-face GaN using an aluminum oxide interlayer  

Science Conference Proceedings (OSTI)

The polarity of GaN grown by plasma-assisted molecular beam epitaxy was inverted from N-face to Ga-face by inserting a composite AlN/aluminum oxide (AlO{sub x}) interlayer structure at the inversion interface. The change in polarity was verified in situ by reflection high energy electron diffraction via intensity transients and postgrowth surface reconstructions, and ex situ by convergent beam electron diffraction and etch studies in an aqueous potassium hydroxide solution. The inverted materials showed smooth surfaces and good electrical properties. AlGaN/GaN high electron mobility transistors fabricated on the inverted epilayers showed good dc and high frequency performance. A current-gain cutoff frequency (f{sub T}) of 21 GHz and maximum oscillation frequency (f{sub max}) of 61 GHz were measured in devices with a gate length of 0.7 {mu}m. These data compare favorably to those of Ga-face AlGaN/GaN devices with a similar structure grown on Si-face SiC substrates.

Wong, Man Hoi; Mishra, Umesh K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106-9560 (United States); Wu, Feng; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States)

2010-12-15T23:59:59.000Z

270

Thermoelectric properties of epitaxial TbAs:InGaAs nanocomposites  

SciTech Connect

InGaAs lattice-matched to InP was grown by molecular beam epitaxy with randomly distributed TbAs nanoparticles for thermoelectric power generation applications. TbAs:InGaAs is expected to have a large thermoelectric figure of merit, ZT, particularly at high temperatures, owing to energy band alignment between the nanoparticles and their surrounding matrix. Here, the room temperature thermoelectric properties were measured as a function of TbAs concentration, revealing a maximum thermoelectric power factor of 2.38 W/mK{sup 2} and ZT of 0.19 with 0.2% TbAs. Trends in the thermoelectric properties closely resemble those found in comparable ErAs:InGaAs nanocomposite materials. However, nanoparticles were not observed by scanning transmission electron microscopy in the highest ZT TbAs:InGaAs sample, unlike the highest ZT ErAs:InGaAs sample (0.2% ErAs) and two higher concentration TbAs:InGaAs samples examined. Consistent with expectations concerning the positioning of the Fermi level in these materials, ZT was enhanced by TbAs incorporation largely due to a high Seebeck coefficient, whereas ErAs provided InGaAs with higher conductivity but a lower Seebeck coefficient than that of TbAs:InGaAs. Thermal conductivity was reduced significantly from that of intrinsic thin-film InGaAs only with TbAs concentrations greater than {approx}1.7%.

Clinger, Laura E.; Zide, Joshua M. O. [Materials Science and Engineering Department, University of Delaware, Newark, Delaware 19716 (United States); Pernot, Gilles; Shakouri, Ali [Electrical Engineering Department, University of California, Santa Cruz, California 95064 (United States); Buehl, Trevor E.; Burke, Peter G.; Gossard, Arthur C. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Palmstroem, Christopher J. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

2012-05-01T23:59:59.000Z

271

Direct evidence of the fermi-energy-dependent formation of Mn interstitials in modulation doped Ga1-yAlyAs/Ga1-xMnxAs/Ga1-yAlyAs heterostructures  

SciTech Connect

Using ion channeling techniques, we investigate the lattice locations of Mn in Ga{sub 1-x}Mn{sub x}As quantum wells between Be-doped Ga{sub 1-y}Al{sub y}As barriers. The earlier results showed that the Curie temperature T{sub C} depends on the growth sequence of the epitaxial layers. A lower T{sub C} was found in heterostructures in which the Ga{sub 1-x}Mn{sub x}As layer is grown after the modulation-doped barrier. Here we provide direct evidence that this reduction in T{sub C} is directly correlated with an increased formation of magnetically inactive Mn interstitials. The formation of interstitials is induced by a shift of the Fermi energy as a result of the transfer of holes from the barrier to the quantum well during the growth.

Yu, K.M.; Walukiewicz, W.; Wojtowicz, T.; Lim, W.L.; Liu, X.; Dobrowolska, M.; Furdyna, J.K.

2004-01-30T23:59:59.000Z

272

Growth and development of GaInAsP for use in high-efficiency solar cells  

DOE Green Energy (OSTI)

This report describes work done during Phase II of the subcontract. Goals for Phase II include the following: (1) Optimize the GaInAsP cell on GaAs and demonstrate a 500-sun at air mass (AM) 1.5 efficiency of >23%. (2) Develop a window layer, including the evaluation of AlGaAs, GaInP, AlGaAsP, AlGaInP, and GaP. (3) Develop a front-surface contact, with a grid designed for 500-sun concentration, and a goal of a contact resistivity of [approximately]10[sup 5] ohm-cm[sup 2]. (4) Grow GaInAsP cells on Ge, with a goal of a 1-sun (AM 1.5) efficiency of >15%. Accomplishments reported herein include (1) the fabrication of p-on-n and n-on-p GaInAsP cells on GaAs, with the n-on-p cell demonstrating a 10-sun (AM 1.5) active-area efficiency of 23.4% as measured at NREL (2) the evaluation of Al[sub x]Ga([sub 1-x])As, GaInP[sub 2], and AlInP[sub 2] window layers; and (3) the fabrication of GaInAsP cells on Ge, with the demonstration of a p-on-n GaInAsP cell grown on Ge with a 1-sun (AM 1.5) active-area efficiency of 14.4%.

Sharps, P.R. (Research Triangle Inst., Research Triangle Park, NC (United States))

1993-04-01T23:59:59.000Z

273

Ferromagnetism in GaN: Gd: A density functional theory study  

SciTech Connect

First principle calculations of the electronic structure and magnetic interaction of GaN:Gd have been performed within the Generalized Gradient Approximation (GGA) of the density functional theory (DFT) with the on-site Coulomb energy U taken into account (also referred to as GGA+U). The ferromagnetic p-d coupling is found to be over two orders of magnitude larger than the s-d exchange coupling. The experimental colossal magnetic moments and room temperature ferromagnetism in GaN:Gd reported recently are explained by the interaction of Gd 4f spins via p-d coupling involving holes introduced by intrinsic defects such as Ga vacancies.

Stevenson, Cynthia; Stevenson, Cynthia

2008-02-04T23:59:59.000Z

274

Low Cost Production of InGaN for Next-Generation Photovoltaic Devices  

SciTech Connect

The goal of this project is to develop a low-cost and low-energy technology for production of photovoltaic devices based on InGaN materials. This project builds on the ongoing development by Structured Materials Industries (SMI), of novel thin film deposition technology for Group III-Nitride materials, which is capable of depositing Group-III nitride materials at significantly lower costs and significantly lower energy usage compared to conventional deposition techniques. During this project, SMI demonstrated deposition of GaN and InGaN films using metalorganic sources, and demonstrated compatibility of the process with standard substrate materials and hardware components.

Nick M. Sbrockey, Shangzhu Sun, Gary S. Tompa,

2012-07-09T23:59:59.000Z

275

Development of a Multifilament PIT V3Ga Conductor for Fusion Applications  

SciTech Connect

Previous studies on V{sub 3}Ga assert its suitability for use in proposed fusion reactors. V{sub 3}Ga may outperform Nb{sub 3}Sn in a fusion reactor environment based on its relatively flat critical-current profile in the 15 T-20 T range, resilience to applied strain, and reduced risk of induced radioactivity. A multifilament powder-in-tube V{sub 3}Ga conductor was designed, fabricated and tested with a focus on evaluating critical current versus applied field and applied strain performance, wire drawing difficulties, heat-treatment optimization, and overall feasibility of the concept.

Distin, J.S.; Ghosh, A.; Motowidlo, L.R.; Lee, P.J.; Larbalestier, D.C.; Lu, X.F.; Cheggour, N.; Stauffer, T.C.; Goodrich, L.F.

2011-08-03T23:59:59.000Z

276

Low-energy positron diffraction from GaAs(110)  

Science Conference Proceedings (OSTI)

Intensities of 16 beams of near normal incidence positrons have been measured at {ital T}=120 K and analyzed using a multiple scattering model of the low-energy positron diffraction (LEPD) process. Excellent correspondence between the measured and calculated intensities is obtained for a reconstruction that is primarily a bond-length-conserving rotation of the top layer, with As relaxed outward and Ga inward with a tilt angle {omega}{sub 1} = 28.6 {plus minus} 3{degree}, confirming the results of previous structure analyses for this surface. The quality of the description of the measured intensities, as measured by the x-ray {ital R} factor, is significantly better for LEPD than for low-energy electron diffraction. This result is attributed to the repulsive character of the positron-ion core potential and a resulting more surface sensitive diffraction process for LEPD.

Lessor, D.L. (Pacific Northwest Laboratory, K5-17 ISB-1, Richland, Washington 99352 (United States)); Duke, C.B. (Xerox Webster Research Center, 800 Phillips Road, 0114-38D, Webster, New York 14580 (United States)); Chen, X.M.; Brandes, G.R.; Canter, K.F. (Department of Physics, Brandeis University, Waltham, Massachusetts 02254 (United States)); Ford, W.K. (Advanced Materials Center and Department of Physics, Montana State University, Bozeman, Montana 59717 (United States))

1992-07-01T23:59:59.000Z

277

GaN directional couplers for integrated quantum photonics  

SciTech Connect

Large cross-section GaN waveguides are proposed as a suitable architecture to achieve integrated quantum photonic circuits. Directional couplers with this geometry have been designed with aid of the beam propagation method and fabricated using inductively coupled plasma etching. Scanning electron microscopy inspection shows high quality facets for end coupling and a well defined gap between rib pairs in the coupling region. Optical characterization at 800 nm shows single-mode operation and coupling-length-dependent splitting ratios. Two photon interference of degenerate photon pairs has been observed in the directional coupler by measurement of the Hong-Ou-Mandel dip [C. K. Hong, et al., Phys. Rev. Lett. 59, 2044 (1987)] with 96% visibility.

Zhang Yanfeng; McKnight, Loyd; Watson, Ian M.; Gu, Erdan; Calvez, Stephane; Dawson, Martin D. [Institute of Photonics, SUPA, University of Strathclyde, Glasgow G4 0NW (United Kingdom); Engin, Erman; Cryan, Martin J.; Thompson, Mark G.; O'Brien, Jeremy L. [Centre for Quantum Photonics, H. H. Wills Physics Laboratory and Department of Electrical and Electronic Engineering, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB (United Kingdom)

2011-10-17T23:59:59.000Z

278

Growth of cubic GaN quantum dots  

SciTech Connect

Zinc-blende GaN quantum dots were grown on 3C-AlN(001) by two different methods in a molecular beam epitaxy system. The quantum dots in method A were fabricated by the Stranski-Krastanov growth process. The quantum dots in method B were fabricated by droplet epitaxy, a vapor-liquid-solid process. The density of the quantum dots was controllable in a range of 10{sup 8} cm{sup -2} to 10{sup 12} cm{sup -2}. Reflection high energy electron diffraction analysis confirmed the zinc-blende crystal structure of the QDs. Photoluminescence spectroscopy revealed the optical activity of the QDs, the emission energy was in agreement with the exciton ground state transition energy of theoretical calculations.

Schupp, T.; Lischka, K.; As, D. J. [Universitaet Paderborn, Department Physik, Warburger Str.100, 33095 Paderborn (Germany); Meisch, T.; Neuschl, B.; Feneberg, M.; Thonke, K. [Institut fuer Quantenmaterie, Universitaet Ulm, 89069 Ulm (Germany)

2010-11-01T23:59:59.000Z

279

0.7-eV GaInAs Junction for a GaInP/GaAs/GaInAs(1-eV)/GaInAs(0.7-eV) Four-Junction Solar Cell: Preprint  

DOE Green Energy (OSTI)

We discuss recent developments in III-V multijunction solar cells, focusing on adding a fourth junction to the Ga0.5In0.5P/GaAs/Ga0.75In0.25As inverted three-junction cell. This cell, grown inverted on GaAs so that the lattice-mismatched Ga0.75In0.25As third junction is the last one grown, has demonstrated 38% efficiency, and 40% is likely in the near future. To achieve still further gains, a lower-bandgap GaxIn1-xAs fourth junction could be added to the three-junction structure for a four-junction cell whose efficiency could exceed 45% under concentration. Here, we present the initial development of the GaxIn1-xAs fourth junction. Junctions of various bandgaps ranging from 0.88 to 0.73 eV were grown, in order to study the effect of the different amounts of lattice mismatch. At a bandgap of 0.88 eV, junctions were obtained with very encouraging {approx}80% quantum efficiency, 57% fill factor, and 0.36 eV open-circuit voltage. The device performance degrades with decreasing bandgap (i.e., increasing lattice mismatch). We model the four-junction device efficiency vs. fourth junction bandgap to show that an 0.7-eV fourth-junction bandgap, while optimal if it could be achieved in practice, is not necessary; an 0.9-eV bandgap would still permit significant gains in multijunction cell efficiency while being easier to achieve than the lower-bandgap junction.

Friedman, D. J.; Geisz, J. F.; Norman, A. G.; Wanlass, M. W.; Kurtz, S. R.

2006-05-01T23:59:59.000Z

280

InGaAs monolithic interconnected modules (MIM)  

DOE Green Energy (OSTI)

A monolithic interconnected module (MIM) structure has been developed for thermophotovoltaic (TPV) applications. The MIM device consists of many individual InGaAs cells series-connected on a single semi-insulating (S.I.) InP substrate. An infrared (IR) back surface reflector (BSR), placed on the rear surface of the substrate, returns the unused portion of the TPV radiator output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Also, the use of a BSR obviates the need to use a separate filtering element. As a result, MIMs are exposed to the entire emitter output, thereby maximizing output power density. MIMs with an active area of 1 x 1-cm were comprised of 15 cells monolithically connected in series. Both lattice-matched and lattice-mismatched InGaAs/InP devices were produced, with bandgaps of 0.74 and 0.55 eV, respectively. The 0.74-eV modules demonstrated an open-circuit voltage (Voc) of 6.158 V and a fill factor of 74.2% at a short-circuit current (Jsc) of 842 mA/cm{sup 2}, under flashlamp testing. The 0.55-eV modules demonstrated a Voc of 4.849 V and a fill factor of 57.8% at a Jsc of 3.87 A/cm{sup 2}. IR reflectance measurements (i.e., {lambda} > 2 {micro}m) of these devices indicated a reflectivity of {ge} 83%. Latest electrical and optical performance results for the MIMs will be presented.

Fatemi, N.S.; Jenkins, P.P.; Weizer, V.G.; Hoffman, R.W. Jr. [Essential Research, Inc., Cleveland, OH (United States); Wilt, D.M.; Scheiman, D.; Brinker, D. [National Aeronautics and Space Administration, Cleveland, OH (United States). Lewis Research Center; Murray, C.S.; Riley, D. [Westinghouse Electric Corp., West Mifflin, PA (United States)

1997-12-31T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

K2, Photoluminescence of Bandgap-Graded InGaN Wires Grown by ...  

Science Conference Proceedings (OSTI)

I4, Electrical Spin Injection in a Hybrid Organic/Inorganic Spin-Polarized Light Emitting Diode (Spin-LED) · I5, Properties of MnAs/GaMnAs/MnAs Magnetic ...

282

Price of Elba Island, GA Natural Gas LNG Imports from Equatorial...  

Gasoline and Diesel Fuel Update (EIA)

Equatorial Guinea (Dollars per Thousand Cubic Feet) Price of Elba Island, GA Natural Gas LNG Imports from Equatorial Guinea (Dollars per Thousand Cubic Feet) Decade Year-0 Year-1...

283

Price of Elba Island, GA Natural Gas LNG Imports from Nigeria...  

Annual Energy Outlook 2012 (EIA)

Nigeria (Nominal Dollars per Thousand Cubic Feet) Price of Elba Island, GA Natural Gas LNG Imports from Nigeria (Nominal Dollars per Thousand Cubic Feet) Decade Year-0 Year-1...

284

Metalorganic Vapor-Phase Epitaxial Growth and Characterization of Quaternary AlGaInN  

SciTech Connect

In this letter we report the growth (by MOVPE) and characterization of quaternary AlGaInN. A combination of PL, high-resolution XRD, and RBS characterizations enables us to explore and delineate the contours of equil-emission energy and lattice parameters as functions of the quaternary compositions. The observation of room temperature PL emission as short as 351nm (with 20% Al and 5% In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GdnN MQW heterostructures have also been grown; both x-ray diffraction and PL measurement suggest the possibility of incorporating this quaternary into optoelectronic devices.

BANAS, MICHAEL ANTHONY; CRAWFORD, MARY H.; FIGIEL, JEFFREY J.; HAN, JUNG; LEE, STEPHEN R.; MYERS JR., SAMUEL M.; PETERSON, GARY D.

1999-09-27T23:59:59.000Z

285

Correlation of doping, structure, and carrier dynamics in a single GaN nanorod  

E-Print Network (OSTI)

We report the nanoscale optical investigation of a single GaN p-n junction nanorod by cathodoluminescence (CL) in a scanning transmission electron microscope. CL emission characteristic of dopant-related transitions was ...

Zhou, Xiang

286

II2, GaN/AlN Heterostructures on Vertical {111} Fin Facets of Si (110)  

Science Conference Proceedings (OSTI)

I4, Electrical Spin Injection in a Hybrid Organic/Inorganic Spin-Polarized Light Emitting Diode (Spin-LED) · I5, Properties of MnAs/GaMnAs/MnAs Magnetic ...

287

Terahertz waveguide spectroscopy of two-dimensional plasmons in GaAs  

E-Print Network (OSTI)

The electrical characteristics of high-mobility, two-dimensional electron gas (2DEG) systems, such as GaAs quantum wells, have been well-studied at low frequencies and in extreme conditions of high magnetic fields and ...

Harris, C. Thomas (Charles Thomas)

2010-01-01T23:59:59.000Z

288

Millimeter-wave GaN high electron mobility transistors and their integration with silicon electronics  

E-Print Network (OSTI)

In spite of the great progress in performance achieved during the last few years, GaN high electron mobility transistors (HEMTs) still have several important issues to be solved for millimeter-wave (30 ~ 300 GHz) applications. ...

Chung, Jinwook W. (Jinwook Will)

2011-01-01T23:59:59.000Z

289

RF Power Degradation of GaN High Electron Mobility Transistors  

E-Print Network (OSTI)

We have developed a versatile methodology to systematically investigate the RF reliability of GaN High-Electron Mobility Transistors. Our technique utilizes RF and DC figures of merit to diagnose the degradation of RF ...

Joh, Jungwoo

290

G3, Improvement of InGaZnO 4 TFT Device Performance on Glass ...  

Science Conference Proceedings (OSTI)

I4, Electrical Spin Injection in a Hybrid Organic/Inorganic Spin-Polarized Light Emitting Diode (Spin-LED) · I5, Properties of MnAs/GaMnAs/MnAs Magnetic ...

291

Lattice-Matched GaNPAs-On-Silicon Tandem Solar Cells  

DOE Green Energy (OSTI)

A two-junction device consisting of a 1.7-eV GaNPAs junction on a 1.1-eV silicon junction has the theoretical potential to achieve nearly optimal efficiency for a two-junction tandem cell. We have demonstrated a monolithic III-V-on-silicon tandem solar cell in which most of the III-V layers are nearly lattice-matched to the silicon substrate. The cell includes a 1.8 eV GaNPAs top cell, a GaP-based tunnel junction (TJ), and a diffused silicon junction formed during the epitaxial growth of GaNP on the silicon substrate. This tandem on silicon has a Voc of 1.53 V and an AM1.5G efficiency of 5.2% without any antireflection coating. Low currents in the top cell are the primary limitation to higher efficiency at this point.

Geisz, J. F.; Olson, J. M.; Friedman, D. J.; Jones, K. M.; Reedy, R. C.; Romero, M. J.

2005-02-01T23:59:59.000Z

292

Mexico FL GA SC AL MS LA TX AR TN TN  

NLE Websites -- All DOE Office Websites (Extended Search)

2005 Hurricanes on the Natural Gas Industry in the Gulf of Mexico Region Mexico FL GA SC AL MS LA TX AR TN TN Katrina - Cumulative wind > 39 mph Katrina - Cumulative wind > 73 mph...

293

Microsoft Word - gmc GA21 AOCS Report -final 9-10-07.doc  

Science Conference Proceedings (OSTI)

Certified Reference Materials AOCS 0407-A and AOCS 0407-B Report of the certification process for Conventional and Event GA21 Maize (corn) Kernel Certified Reference Materials G. Clapper and R. Cantrill

294

2013-2014 Student Health Services Health Promotion GA IMPACT Program Instructor  

E-Print Network (OSTI)

schedule. · Ability to conduct research and work on program development2013-2014 Student Health Services ­ Health Promotion GA IMPACT Program Description The IMPACT program seeks to provide students with education and feedback

Tullos, Desiree

295

Anisotropic intermediate valence in Yb2M3Ga9 (M = Rh, Ir)  

SciTech Connect

The intermediate valence compounds Yb{sub 2}M{sub 3}Ga{sub 9} (M = Rh, Ir) exhibit an anisotropic magnetic susceptibility. We report measurements of the temperature dependence of the 4f occupation number, n{sub f}(T), for Yb{sub 2}M{sub 3}Ga{sub 9} as well as the magnetic inelastic neutron scattering spectrum S{sub mag}({Delta}E) at 12 and 300 K for Yb{sub 2}Rh{sub 3}Ga{sub 9}. Both n{sub f}(T) and S{sub mag}({Delta}E) were calculated for the Anderson impurity model with crystal field terms within an approach based on the non-crossing approximation. These results corroborate the importance of crystal field effects in these materials; they also suggest that Anderson lattice effects are important to the physics of Yb{sub 2}M{sub 3}Ga{sub 9}.

Christianson, A.D.; Lawrence, J.M.; Lobos, A.M.; Aligia, A.A.; Bauer, E.D.; Moreno, N.O.; Booth, C.H.; Goremychkin, E.A.; Sarrao, J.L.; Thompson, J.D.; Batista, C.D.; Trouw, F.R.; Hehlen, M.P.

2005-04-26T23:59:59.000Z

296

In situ studies of the effect of silicon on GaN growth modes.  

SciTech Connect

We present real-time X-ray scattering studies of the influence of silicon on the homoepitaxial growth mode of GaN grown by metal-organic vapor-phase epitaxy. Both annealing of Si-doped GaN and surface dosing of GaN with disilane are shown to change the mode of subsequent growth from step-flow to layer-by-layer. By comparing the growth behavior induced by doped layers which have been annealed to that induced by surface dosing, we extract an approximate diffusion coefficient for Si in GaN of 3.5 x 10{sup -18} cm{sup 2}/s at 810{sup o}C.

Munkholm, A.; Stephenson, G. B.; Eastman, J. A.; Auciello, O.; Murty, M. V. R.; Thompson, C.; Fini, P.; Speck, J. S.; DenBaars, S. P.; Northern Illinois Univ.; Univ. of California at Santa Barbara

2000-12-01T23:59:59.000Z

297

Prediction of plasma enhanced deposition process using GA-Optimized GRNN  

Science Conference Proceedings (OSTI)

A genetic algorithm (GA)-based optimization of generalized regression neural network (GRNN) was presented and evaluated with statistically characterized plasma deposition data. The film characteristics to model were deposition rate and positive charge ...

Byungwhan Kim; Dukwoo Lee; Seung Soo Han

2006-05-01T23:59:59.000Z

298

Electroluminescense from InGaN Quantum Dots, in a Monolithically ...  

Science Conference Proceedings (OSTI)

We present an electrically driven structure based on a monolithically GaN/AlInN cavity with a single quantum dot layer grown by MOVPE. The device was grown ...

299

GA 200-500 (VSD): Oil-injected rotary screw compressors, 200 ...  

U.S. Energy Information Administration (EIA)

GA 200-500 (VSD): Oil-injected rotary screw compressors, 200-500 kW / 268-670 hp.,Kunshan CompAirs Machinery Plant Co.,Ltd is the leading air ...

300

MOCVD growth of In GaP-based heterostructures for light emitting devices  

E-Print Network (OSTI)

In this work, we examine fundamental materials processes in the growth of indium gallium phosphide (InGaP) via metalorganic chemical vapor deposition (MOCVD). In particular, we realize improvements in the epitaxial integration ...

McGill, Lisa Megan, 1975-

2004-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

JJ3, Anisotropic Carrier Mobility in GaN Quantum Well  

Science Conference Proceedings (OSTI)

L6, PECVD-SiN, Si or Si/Al2O3-Capped ED-Mode AlN/GaN Inverters · Hide details for [

302

LATE NEWS: L7, Molecular Beam Epitaxy of N-Polar InGaN  

Science Conference Proceedings (OSTI)

L6, PECVD-SiN, Si or Si/Al2O3-Capped ED-Mode AlN/GaN Inverters · Hide details for [

303

Y5, Electrochemical Etching of GaN and Its Applications  

Science Conference Proceedings (OSTI)

L6, PECVD-SiN, Si or Si/Al2O3-Capped ED-Mode AlN/GaN Inverters · Hide details for [

304

Collapse for Higher Gate Voltages in N-Polar GaN  

Science Conference Proceedings (OSTI)

L6, PECVD-SiN, Si or Si/Al2O3-Capped ED-Mode AlN/GaN Inverters · Hide details for [

305

K7, Self-Assembled GaN/AlN Nanowire Superlattices on Si toward ...  

Science Conference Proceedings (OSTI)

L6, PECVD-SiN, Si or Si/Al2O3-Capped ED-Mode AlN/GaN Inverters · Hide details for [

306

N7, Olefin Metathesis Reaction on GaN (0001) Surfaces  

Science Conference Proceedings (OSTI)

L6, PECVD-SiN, Si or Si/Al2O3-Capped ED-Mode AlN/GaN Inverters · Hide details for [

307

Temperature dependence and current transport mechanisms in Al{sub x}Ga{sub 1-x}N Schottky rectifiers  

SciTech Connect

GaN and Al{sub 0.25}Ga{sub 0.75}N lateral Schottky rectifiers were fabricated either with (GaN) or without (AlGaN) edge termination. The reverse breakdown voltage V{sub B} (3.1 kV for GaN; 4.3 kV for AlGaN) displayed a negative temperature coefficient of -6.0{+-}0.4 V K{sup -1} for both types of rectifiers. The reverse current originated from contact periphery leakage at moderate bias, while the forward turn-on voltage at a current density of 100 A cm-2 was {approx}5 V for GaN and {approx}7.5 V for AlGaN. The on-state resistances, R{sub ON}, were 50 m{omega} cm2 for GaN and 75 m{omega} cm2 for AlGaN, producing figures-of-merit (V{sub RB}){sup 2}/R{sub ON} of 192 and 246 MW cm-2, respectively. The activation energy of the reverse leakage was 0.13 eV at moderate bias. (c) 2000 American Institute of Physics.

Zhang, A. P. [Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States)] [Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States); Dang, G. [Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States)] [Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States); Ren, F. [Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States)] [Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States); Han, J. [Sandia National Laboratories, Albuquerque, New Mexico 87195 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87195 (United States); Polyakov, A. Y. [Institute of Rare Metals, Moscow 109017, Russia (Russian Federation)] [Institute of Rare Metals, Moscow 109017, Russia (Russian Federation); Smirnov, N. B. [Institute of Rare Metals, Moscow 109017, Russia (Russian Federation)] [Institute of Rare Metals, Moscow 109017, Russia (Russian Federation); Govorkov, A. V. [Institute of Rare Metals, Moscow 109017, Russia (Russian Federation)] [Institute of Rare Metals, Moscow 109017, Russia (Russian Federation); Redwing, J. M. [Epitronics, Phoenix, Arizona 85027 (United States)] [Epitronics, Phoenix, Arizona 85027 (United States); Cho, H. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States)] [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Pearton, S. J. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States)] [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States)

2000-06-19T23:59:59.000Z

308

Development of 1.25 eV InGaAsN for triple junction solar cells  

DOE Green Energy (OSTI)

Development of next generation high efficiency space monolithic multifunction solar cells will involve the development of new materials lattice matched to GaAs. One promising material is 1.05 eV InGaAsN, to be used in a four junction GaInP{sub 2}/GaAs/InGaAsN/Ge device. The AMO theoretical efficiency of such a device is 38--42%. Development of the 1.05 eV InGaAsN material for photovoltaic applications, however, has been difficult. Low electron mobilities and short minority carrier lifetimes have resulted in short minority carrier diffusion lengths. Increasing the nitrogen incorporation decreases the minority carrier lifetime. The authors are looking at a more modest proposal, developing 1.25 eV InGaAsN for a triple junction GaInP{sub 2}/InGaAsN/Ge device. The AMO theoretical efficiency of this device is 30--34%. Less nitrogen and indium are required to lower the bandgap to 1.25 eV and maintain the lattice matching to GaAs. Hence, development and optimization of the 1.25 eV material for photovoltaic devices should be easier than that for the 1.05 eV material.

LI,N.Y.; SHARPS,P.R.; HILLS,J.S.; HOU,H.; CHANG,PING-CHIH; BACA,ALBERT G.

2000-05-16T23:59:59.000Z

309

High external quantum efficiency and fill-factor InGaN/GaN heterojunction solar cells grown by NH{sub 3}-based molecular beam epitaxy  

SciTech Connect

High external quantum efficiency (EQE) p-i-n heterojunction solar cells grown by NH{sub 3}-based molecular beam epitaxy are presented. EQE values including optical losses are greater than 50% with fill-factors over 72% when illuminated with a 1 sun AM0 spectrum. Optical absorption measurements in conjunction with EQE measurements indicate an internal quantum efficiency greater than 90% for the InGaN absorbing layer. By adjusting the thickness of the top p-type GaN window contact layer, it is shown that the short-wavelength (<365 nm) quantum efficiency is limited by the minority carrier diffusion length in highly Mg-doped p-GaN.

Lang, J. R.; Hurni, C. A.; Cruz, S. C.; Matioli, E.; Speck, J. S. [Department of Materials, University of California, Santa Barbara, California 93106 (United States); Neufeld, C. J.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

2011-03-28T23:59:59.000Z

310

Electrically active Er doping in InAs, In{sub 0.53}Ga{sub 0.47}As, and GaAs  

SciTech Connect

The electron concentration in dilute alloys of Er in GaAs, In{sub 0.53}Ga{sub 0.47}As, and InAs grown by molecular beam epitaxy is studied as a function of Er concentration and In content. Using first-principles calculations based on hybrid density functional theory, we attribute an observed increase in conduction electron concentration to Er incorporation on interstitial sites. Er also incorporates on substitutional sites where it is isovalent and electrically inactive. The formation energy of interstitial Er in InAs is significantly smaller than in GaAs, allowing for more electrically active Er in InAs. The results provide insight into characteristics of rare-earth elements as dopants in semiconductors.

Burke, Peter G.; Ismer, Lars; Lu Hong; Frantz, Elan; Janotti, Anderson; Van de Walle, Chris G.; Bowers, John E.; Gossard, Arthur C. [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States)

2012-12-03T23:59:59.000Z

311

GaInNAs Junctions for Next-Generation Concentrators: Progress and Prospects  

DOE Green Energy (OSTI)

We discuss progress in the development of GaInNAs junctions for application in next-generation multijunction concentrator cells. A significant development is the demonstration of near-100% internal quantum efficiencies in junctions grown by molecular-beam epitaxy. Testing at high currents validates the compatibility of these devices with concentrator operation. The efficiencies of several next-generation multijunction structures incorporating these state-of-the-art GaInNAs junctions are projected.

Friedman, D. J.; Ptak, A. J.; Kurtz, S. R.; Geisz, J. F.; Kiehl, J.

2005-08-01T23:59:59.000Z

312

Single-event phenomena in GaAs devices and circuits  

Science Conference Proceedings (OSTI)

The single-event upset (SEU) characteristics of GaAs devices and circuits are reviewed. GaAs FET-based integrated circuits (IC`s) are susceptible to upsets from both cosmic-ray heavy ions and protons trapped in the Earth`s radiation belts. The origin of the SEU sensitivity of GaAs IC`s is discussed in terms of both device-level and circuit-level considerations. At the device level, efficient charge-enhancement mechanisms through which more charge can be collected than is deposited by the ion have a significant negative impact on the SEU characteristics of GaAs IC`s. At the circuit level, different GaAs digital logic topologies exhibit different levels of sensitivity to SEU because of variations in parameters, including logic levels, capacitances, and the degree of gate or peripheral isolation. The operational and SEU characteristics of several different GaAs logic families are discussed. Recent advances in materials and processing that provide possible solutions to the SEU problem are addressed.

McMorrow, D.; Melinger, J.S.; Campbell, A.B. III; Weatherford, T.R. [Naval Research Lab., Washington, DC (United States); Buchner, S.; Knudson, A.R.; Tran, L.H. [SFA Inc., Landover, MD (United States)

1996-04-01T23:59:59.000Z

313

GaN CVD Reactions: Hydrogen and Ammonia Decomposition and the Desorption of Gallium  

DOE Green Energy (OSTI)

Isotopic labeling experiments have revealed correlations between hydrogen reactions, Ga desorption, and ammonia decomposition in GaN CVD. Low energy electron diffraction (LEED) and temperature programmed desorption (TPD) were used to demonstrate that hydrogen atoms are available on the surface for reaction after exposing GaN(0001) to deuterium at elevated temperatures. Hydrogen reactions also lowered the temperature for Ga desorption significantly. Ammonia did not decompose on the surface before hydrogen exposure. However, after hydrogen reactions altered the surface, N15H3 did undergo both reversible and irreversible decomposition. This also resulted in the desorption of N2 of mixed isotopes below the onset of GaN sublimation, This suggests that the driving force of the high nitrogen-nitrogen bond strength (226 kcal/mol) can lead to the removal of nitrogen from the substrate when the surface is nitrogen rich. Overall, these findings indicate that hydrogen can influence G-aN CVD significantly, being a common factor in the reactivity of the surface, the desorption of Ga, and the decomposition of ammonia.

Bartram, Michael E.; Creighton, J. Randall

1999-05-26T23:59:59.000Z

314

1-MeV-Electron Irradiation of GaInAsN Cells: Preprint  

DOE Green Energy (OSTI)

This conference paper describes the GaInAsN cells that are measured to retain 933% and 894% of their original efficiency after exposure to 5 X 1014 and 1 X 1015 cm-2 1-MeV electrons, respectively. The rate of degradation is not correlated with the performance at beginning of life (BOL). The depletion width remains essentially unchanged, increasing by< 1%. Temperature-coefficient data for GaInAsN cells are also presented. These numbers are used to project the efficiency of GaInAsN-containing multijunction cells. The GaInAsN junction is not currently predicted to increase the efficiencies of the multijunction cells. Nevertheless, GaInAsN-containing multijunction cell efficiencies are predicted to be comparable to those of the conventional structures, and even small improvements in the GaInAsN cell may lead to higher multijunction cell efficiencies, especially for high-radiation applications and when cell operating temperature is low.

Kurtz, S.; King, R. R.; Edmondson, K. M.; Friedman, D. J.; Karam, N. H.

2002-05-01T23:59:59.000Z

315

GaNPAs Solar Cells that Can Be Lattice-Matched to Silicon  

DOE Green Energy (OSTI)

III-V semiconductors grown on silicon substrates are very attractive for lower-cost, high-efficiency multijunction solar cells, but lattice-mismatched alloys that result in high dislocation densities have been unable to achieve satisfactory performance. GaNxP1-x-yAsy is a direct-gap III-V alloy that can be grown lattice-matched to Si when y= 4.7x - 0.1. We have proposed the use of lattice-matched GaNPAs on silicon for high-efficiency multijunction solar cells. We have grown GaNxP1-x-yAsy on GaP (with a similar lattice constant to silicon) by metal-organic chemical vapor phase epitaxy with direct bandgaps in the range of 1.5 to 2.0 eV. We have demonstrated the performance of single-junction GaNxP1-x-yAsy solar cells grown on GaP substrates and shown improvements in material quality by reducing carbon and hydrogen impurities through optimization of growth conditions. We have achieved quantum efficiencies (QE) in these cells as high as 60% and PL lifetimes as high as 3.0 ns.

Geisz, J. F.; Friedman, D. J.; McMahon, W. E.; Ptak, A. J.; Kibbler, A. E.; Olson, J. M.; Kurtz, S.; Kramer, C.; Young, M.; Duda, A.; Reedy, R. C.; Keyes, B. M.; Dippo, P.; Metzger, W. K.

2003-05-01T23:59:59.000Z

316

2 {mu}m laterally coupled distributed-feedback GaSb-based metamorphic laser grown on a GaAs substrate  

SciTech Connect

We report a type-I GaSb-based laterally coupled distributed-feedback (DFB) laser grown on a GaAs substrate operating continuous wave at room temperature. The laser structure was designed to operate near a wavelength of 2 {mu}m and was grown metamorphically with solid-source molecular beam epitaxy. The device was fabricated using a 6th-order deep etch grating structure as part of the sidewalls of the narrow ridge waveguide. The DFB laser emits total output power of up to 40 mW in a single longitudinal mode operation at a heat-sink temperature of 20 Degree-Sign C.

Apiratikul, P.; He, L.; Richardson, C. J. K. [Laboratory for Physical Sciences, 8050 Greenmead Drive, College Park, Maryland 20740 (United States)] [Laboratory for Physical Sciences, 8050 Greenmead Drive, College Park, Maryland 20740 (United States)

2013-06-10T23:59:59.000Z

317

Critical film thickness dependence on As flux in In{sub 0.27}Ga{sub 0.73}As/GaAs(001) films  

SciTech Connect

The transition between planar and nonplanar growth is examined for compressively strained In{sub 0.27}Ga{sub 0.73}As/GaAs(001) films using reflection high energy electron diffraction, atomic force microscopy, and scanning tunneling microscopy (STM). For a narrow range of temperature and composition, the critical thickness (t{sub SK}) is strongly dependent on As flux. For high values of As flux, t{sub SK} increases by more than a factor of 2. The morphology of three-dimensional islands formed during the initial stages of nonplanar growth is also characterized by high resolution STM.

Riposan, A.; Mirecki Millunchick, J.; Pearson, Chris [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Department of Computer Science, Engineering Science, and Physics, University of Michigan-Flint, Flint, Michigan 48502 (United States)

2007-02-26T23:59:59.000Z

318

Theoretical And Experimental Studies Of The Effects Of Rapid Thermal Annealing In GaAs/AlGaAs Quantum Dots Grown By Droplet Epitaxy  

Science Conference Proceedings (OSTI)

We fabricated low-density GaAs/AlGaAs quantum dots for single photon source by droplet epitaxy. We investigated the emission energies of the dots and underlying superlattice by using photoluminescence and cathodoluminescence measurements. By forming a mesa etched structure, we distinguished the transitions from the superlattice and the dots. And we calculated the diffusion length in this system from the peak shift of the superlattice, and applied the diffusion to the dots to investigate the emission energy shift of the QDs.z

Moon, P. [Nano Convergence Devices Center, Korea Institute of Science and Technology, Seoul (Korea, Republic of); School of Materials Science, Japan Advanced Institute of Science and Technology, Ishikawa (Japan); Ha, S.-K.; Song, J. D.; Lim, J. Y.; Choi, W. J.; Han, I. K.; Lee, J. I. [Nano Convergence Devices Center, Korea Institute of Science and Technology, Seoul (Korea, Republic of); Bounouar, S.; Donatini, F.; Dang, L. S.; Poizat, J. P. [CEA/CNRS/UJF team 'Nanophysics and semiconductors', Institute Neel/CNRS-UJF, Grenoble (France); Kim, J. S. [Department of Physics, Yeungnam University, Gyeonsan (Korea, Republic of)

2011-12-23T23:59:59.000Z

319

Performance improvement of Ge-Sb-Te material by GaSb doping for phase change memory  

SciTech Connect

Effects of GaSb doping on phase change characteristics of Ge-Sb-Te material are investigated by in situ resistance and x-ray diffraction measurement, optical spectroscopy, and x-ray photoelectron spectroscopy. The crystallization temperature and data retention of Ge-Sb-Te material increase significantly by the addition of GaSb, which results from the high thermal stability of amorphous GaSb. In addition, GaSb-doped Ge-Sb-Te material exhibits faster crystallization speed due to the change in electronic states as a result of the formation of chemical bonds with Ga element. Incorporation of GaSb is highly effective way to enhance the comprehensive performance of Ge-Sb-Te material for phase change memory.

Lu, Yegang [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China) [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Faculty of Information Science and Engineering, Ningbo University, Ningbo 315211 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Zhonghua; Song, Sannian; Cheng, Limin; Song, Zhitang [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)] [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Shen, Xiang; Wang, Guoxiang; Dai, Shixun [Faculty of Information Science and Engineering, Ningbo University, Ningbo 315211 (China)] [Faculty of Information Science and Engineering, Ningbo University, Ningbo 315211 (China)

2013-06-17T23:59:59.000Z

320

Computational Thermodynamics of CoNiGa High Temperature Shape Memory Alloys  

E-Print Network (OSTI)

Shape Memory Alloys (SMAs) are advanced materials with interesting properties such as pseudoelasticity (PE) and the shape memory effect (SME). Recently, the CoNiGa system has emerged as the basis for very promising High Temperature Shape Memory Alloys (HTSMAs), with possible applications in the aerospace and automotive industries. Although the CoNiGa system shows significant promise for its use as HTSMAs, limited studies are available on them. Hence, a more intensive investigation of these alloys is necessary to understand their phase stability over a wide range of temperature and compositions in order for further development of CoNiGabased HTSMAs and future use of the model in alloy design. This formed the basis of motivation for the present work. In this work, a thermodynamic model of the ternary system is calculated based on the CALPHAD approach, to investigate the thermodynamic properties, phase stability and shape memory properties of these alloys. The CALPHAD approach is a computational method that enables the calculations of thermodynamic properties of systems. This method uses all available experimental and theoretical data in order to calculate the Gibbs energies of the phases in the system. The software used to carry out the calculations is "ThermoCalc," which is a computational software using CALPHAD principles, based on the minimization of Gibbs energy, and is enhanced by a global minimization technique on the system. The stability of the beta phase at high temperatures was enforced accurately by remodeling the CoGa system. The binary CoGa system that makes up the ternary was remodeled, as the beta phase (which is very important as it dominates the central region of the ternary CoNiGa system where the shape memory effect is observed), re-stabilizes as the temperature increases above the liquidus in the CoGa system. Phase relations and thermodynamic properties of the CoNiGa system based on all experimental information were evaluated. Different properties like enthalpies, activities, sublattice site fraction of vacancies and phase fractions calculated in the system matched well compared to the experimental information used to model the system. Also, the phase equilibria among the gamma (fcc), beta, gamma'(Ni3Ga), delta (Ni5Ga3) and epsilon (Ni13Ga9) were determined at various temperatures.

Chari, Arpita

2011-08-01T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

Photoluminescence study of the 1.047 eV emission in GaN K. Pressela)  

E-Print Network (OSTI)

GaN/ AlGaN blue green light emitting diode, which has a much higher quantum efficiency than the SiC blue light emitting diode, became possible.2 Presently the wide bandgap semi- conductor GaN is intensively. Especially the 1.19 eV is very intense. Thus one can think of developing a light emitting diode in the near

Nabben, Reinhard

322

GaAs ohmic contacts for high temperature devices  

DOE Green Energy (OSTI)

Instrumentation requirements for geothermal wells, jet engines, and nuclear reactors have exceeded the high temperature capability of silicon devices. As one part of a program to develop high temperature compound semiconductor devices, four basic ohmic contact systems for n-type GaAs have been evaluated for contact resistance as a function of temperature (24 to 350/sup 0/C) and time (at 300/sup 0/C): Ni/AuGe; Ag/Si and Ag/Ni/Si; Al/Ge and Al/AlGe; and Au/Nb/Si and Pt/Nb/Si. Optimization of processing parameters produced viable high temperature contacts with all but the Al/Ge systems. Aging at 300/sup 0/C changed the contact resistivity in only the Ag/Ni/Si contacts. Film adhesion was excellent for the Al/Ge, Ni/AuGe, and Ag/Si systems as measured with ultrasonic Al wire bond pull strengths. Lower adhesion was noticed with Nb/Si systems measured with gold wire bond pull strengths.

Coquat, J.A.; Palmer, D.W.

1980-01-01T23:59:59.000Z

323

Heavy ion SEU immunity of a GaAs complementary HIGFET circuit fabricated on a low temperature grown buffer layer  

SciTech Connect

The authors compare dynamic SEU characteristics of GaAs complementary HIGFET devices fabricated on conventional semi-insulating substrates versus low temperature grown GaAs (LT GaAs) buffer layers. Heavy ion test results on shift register and flip-flop devices from the same process lot demonstrate that the LT GaAs layer provides immunity from upsets, even at an LET value of 90 MeV {center_dot} cm{sup 2}/mg. This result is also consistent with pulsed laser measurements performed on the same flip-flop circuits used in the ion test.

Marshall, P.W.; Weatherford, T.; Carts, M. [Naval Research Lab., Washington, DC (United States)]|[SFA, Inc., Landover, MD (United States); Dale, C.J.; McMorrow, D. [Naval Research Lab., Washington, DC (United States); Peczalski, A.; Baier, S.; Nohava, J.; Skogen, J. [Honeywell Systems and Research Center, Bloomington, MN (United States)

1995-12-01T23:59:59.000Z

324

Analysis of mechanisms of carrier emission in the p-i-n structures with In(Ga)As quantum dots  

SciTech Connect

With the help of the photocurrent spectroscopy, the mechanism of emission of charge carriers from energy levels of the (In,Ga)As/(Al,Ga)As quantum dots of different design are studied. Thermal activation is shown to be the main mechanism of carrier emission from the quantum dots for the isolated layer of quantum dots separated by wide (Al,Ga)As spacer layers. At a small width of the (Al,Ga)As spacer layer, when electron binding of separate layers of the quantum dots in the vertical direction takes place, the role of the tunneling mechanism of carrier emission between the vertically coupled quantum dots increases.

Shatalina, E. S., E-mail: Shatalina@mail.ioffe.ru; Blokhin, S. A.; Nadtochy, A. M.; Payusov, A. S.; Savelyev, A. V.; Maximov, M. V.; Zhukov, A. E. [St. Petersburg Academic University, Nanotechnology Research and Education Centre (Russian Federation); Ledentsov, N. N. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Kovsh, A. R.; Mikhrin, S. S.; Ustinov, V. M. [Innolume GmbH (Germany)

2010-10-15T23:59:59.000Z

325

Novel InGaAsN pn Junction for High-Efficiency Multiple-Junction Solar Cells  

DOE Green Energy (OSTI)

We report the application of a novel material, InGaAsN, with bandgap energy of 1.05 eV as a junction in an InGaP/GaAs/InGaAsN/Ge 4-junction design. Results of the growth and structural, optical, and electrical properties were demonstrated, showing the promising perspective of this material for ultra high efficiency solar cells. Photovoltaic properties of an as-grown pn diode structure and improvement through post growth annealing were also discussed.

Allerman, A.A.; Chang, P.C.; Gee, J.M.; Hammons, B.E.; Hou, H.Q.; Jones, E.D.; Kurtz, S.R.; Reinhardt, K.C.

1999-03-26T23:59:59.000Z

326

Reduction of Crosshatch Roughness and Threading Dislocation Density in Metamorphic GaInP Buffers and GaInAs Solar Cells  

Science Conference Proceedings (OSTI)

Surface crosshatch roughness typically develops during the growth of lattice-mismatched compositionally graded buffers and can limit misfit dislocation glide. In this study, the crosshatch roughness during growth of a compressive GaInP/GaAs graded buffer is reduced by increasing the phosphine partial pressure throughout the metamorphic growth. Changes in the average misfit dislocation length are qualitatively determined by characterizing the threading defect density and residual strain. The decrease of crosshatch roughness leads to an increase in the average misfit dislocation glide length, indicating that the surface roughness is limiting dislocation glide. Growth rate is also analyzed as a method to reduce surface crosshatch roughness and increase glide length, but has a more complicated relationship with glide kinetics. Using knowledge gained from these experiments, high quality inverted GaInAs 1 eV solar cells are grown on a GaInP compositionally graded buffer with reduced roughness and threading dislocation density. The open circuit voltage is only 0.38 V lower than the bandgap potential at a short circuit current density of 15 mA/cm{sup 2}, suggesting that there is very little loss due to the lattice mismatch.

France, R. M.; Geisz, J. F.; Steiner, M. A.; To, B.; Romero, M. J.; Olavarria, W. J.; King, R. R.

2012-05-15T23:59:59.000Z

327

As-grown deep-level defects in n-GaN grown by metal-organic chemical vapor deposition on freestanding GaN  

SciTech Connect

Traps of energy levels E{sub c}-0.26 and E{sub c}-0.61 eV have been identified as as-grown traps in n-GaN grown by metal-organic chemical vapor deposition by using deep level transient spectroscopy of the Schottky contacts fabricated by resistive evaporation. The additional traps of E{sub c}-0.13 and E{sub c}-0.65 eV have been observed in samples whose contacts are deposited by electron-beam evaporation. An increase in concentration of the E{sub c}-0.13 and E{sub c}-0.65 eV traps when approaching the interface between the contact and the GaN film supports our argument that these traps are induced by electron-beam irradiation. Conversely, the depth profiles of as-grown traps show different profiles between several samples with increased or uniform distribution in the near surface below 50 nm. Similar profiles are observed in GaN grown on a sapphire substrate. We conclude that the growth process causes these large concentrations of as-grown traps in the near-surface region. It is speculated that the finishing step in the growth process should be an essential issue in the investigation of the surface state of GaN.

Chen Shang; Ishikawa, Kenji; Hori, Masaru [Nagoya University, Chikusa, Nagoya 464-8603 (Japan); Honda, Unhi; Shibata, Tatsunari; Matsumura, Toshiya; Tokuda, Yutaka [Aichi Institute of Technology, Yakusa, Toyota 470-0392 (Japan); Ueda, Hiroyuki; Uesugi, Tsutomu; Kachi, Tetsu [Toyota Central R and D Laboratories, Inc., Yokomichi, Nagakute 480-1192 (Japan)

2012-09-01T23:59:59.000Z

328

Compositional tuning of ferromagnetism in Ga1-xMnxP  

SciTech Connect

We report the magnetic and transport properties of Ga{sub 1-x}Mn{sub x}P synthesized via ion implantation followed by pulsed laser melting over a range of x, namely 0.018 to 0.042. Like Ga{sub 1-x}Mn{sub x}As, Ga{sub 1-x}Mn{sub x}P displays a monotonic increase of the ferromagnetic Curie temperature with x associated with the hole-mediated ferromagnetic phase while thermal annealing above 300 C leads to a quenching of ferromagnetism that is accompanied by a reduction of the substitutional fraction of Mn. However, contrary to observations in Ga{sub 1-x}Mn{sub x}As, Ga{sub 1-x}Mn{sub x}P is non-metallic over the entire composition range. At the lower temperatures over which the films are ferromagnetic, hole transport occurs via hopping conduction in a Mn-derived band; at higher temperatures it arises from holes in the valence band which are thermally excited across an energy gap that shrinks with x.

Farshchi, R.; Scarpulla, M.A.; Stone, P.R.; Yu, K.M.; Sharp,I.D.; Beeman, J.W.; Silvestri, H.H.; Reichertz, L.A.; Haller E.E.; Dubon,O.D.

2006-05-23T23:59:59.000Z

329

Tunnel-injection GaN quantum dot ultraviolet light-emitting diodes  

SciTech Connect

We demonstrate a GaN quantum dot ultraviolet light-emitting diode that uses tunnel injection of carriers through AlN barriers into the active region. The quantum dot heterostructure is grown by molecular beam epitaxy on AlN templates. The large lattice mismatch between GaN and AlN favors the formation of GaN quantum dots in the Stranski-Krastanov growth mode. Carrier injection by tunneling can mitigate losses incurred in hot-carrier injection in light emitting heterostructures. To achieve tunnel injection, relatively low composition AlGaN is used for n- and p-type layers to simultaneously take advantage of effective band alignment and efficient doping. The small height of the quantum dots results in short-wavelength emission and are simultaneously an effective tool to fight the reduction of oscillator strength from quantum-confined Stark effect due to polarization fields. The strong quantum confinement results in room-temperature electroluminescence peaks at 261 and 340 nm, well above the 365 nm bandgap of bulk GaN. The demonstration opens the doorway to exploit many varied features of quantum dot physics to realize high-efficiency short-wavelength light sources.

Verma, Jai; Kandaswamy, Prem Kumar; Protasenko, Vladimir; Verma, Amit; Grace Xing, Huili; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)] [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)

2013-01-28T23:59:59.000Z

330

Optical stability of shape-engineered InAs/InAlGaAs quantum dots  

SciTech Connect

The optical properties of shape-engineered InAs/InAlGaAs quantum dots (SEQDs) were investigated by temperature-dependent and excitation-power-dependent photoluminescence (PL) spectroscopy and compared with those of the conventionally grown InAs QDs (CQDs). The emission wavelength of the InAs/InAlGaAs SEQDs at 240 K was redshifted by 18 nm from that at 15 K, which was relatively smaller than that of the InAs CQDs (97 nm). The PL yield at 240 K was reduced to 1/86 and 1/65 of that measured at 15 K for the InAs CQDs and the InAs/InAlGaAs SEQDs, respectively. The emission wavelength for the InAs CQDs was blueshifted by 76 nm with increasing excitation power from 0.56 to 188 mW, compared to only by 7 nm for the InAs/InAlGaAs SEQDs. These results indicated that the InAs/InAlGaAs SEQDs were optically more stable than the InAs CQDs mainly due to the enhancement of the carrier confinement in the vertical direction and the improvement in the size uniformity.

Yang, Youngsin; Jo, Byounggu; Kim, Jaesu; Lee, Cheul-Ro; Kim, Jin Soo [Division of Advanced Materials Engineering, Research Center of Advanced Materials Development (RCAMD), Chonbuk National University, Jeonju, Chonbuk 561-756 (Korea, Republic of); Oh, Dae Kon [Electronics and Telecommunication Research Institute (ETRI), Daejeon 305-350 (Korea, Republic of); Kim, Jong Su [Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Leem, Jae-Young [School of Nano Engineering, Inje University, Gimhae 621-749 (Korea, Republic of)

2009-03-01T23:59:59.000Z

331

Lattice-registered growth of GaSb on Si (211) with molecular beam epitaxy  

Science Conference Proceedings (OSTI)

A GaSb film was grown on a Si(211) substrate using molecular beam epitaxy indicating full lattice relaxation as well as full lattice registration and dislocation-free growth in the plane perpendicular to the [01 - 1]-direction. Heteroepitaxy of GaSb on a Si(211) substrate is dominated by numerous first order and multiple higher order micro-twins. The atomic-resolved structural study of GaSb films by high-angle annular dark-field scanning transmission electron microscopy reveals that slight tilt, along with twinning, favors the lattice registry to Si(211) substrates. Preferential bonding of impinging Ga and Sb atoms at the interface due to two distinctive bonding sites on the Si(211) surface enables growth that is sublattice-ordered and free of anti-phase boundaries. The role of the substrate orientation on the strain distribution of GaSb epilayers is further elucidated by investigating the local change in the lattice parameter using the geometric phase analysis method and hence effectiveness of the lattice tilting in reducing the interfacial strain was confirmed further.

Hosseini Vajargah, S.; Botton, G. A. [Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Canadian Centre for Electron Microscopy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Ghanad-Tavakoli, S. [Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Preston, J. S.; Kleiman, R. N. [Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)

2012-11-01T23:59:59.000Z

332

Self-cleaning and surface recovery with arsine pretreatment in ex situ atomic-layer-deposition of Al2O3 on GaAs  

E-Print Network (OSTI)

. heavily doped GaAs 001 substrates at 650 °C with TMG Ga CH3 3 and arsine AsH3 V/III=23 with disilane Si2H6

333

Epitaxial Growth of GaN-based LEDs on Simple Sacrificial Substrates  

SciTech Connect

The objective of this project is to produce alternative substrate technologies for GaN-based LEDs by developing an ALD interlayer of Al{sub 2}O{sub 3} on sacrificial substrates such as ZnO and Si. A sacrificial substrate is used for device growth that can easily be removed using a wet chemical etchant leaving only the thin GaN epi-layer. After substrate removal, the GaN LED chip can then be mounted in several different ways to a metal heat sink/reflector and light extraction techniques can then be applied to the chip and compared for performance. Success in this work will lead to high efficiency LED devices with a simple low cost fabrication method and high product yield as stated by DOE goals for its solid state lighting portfolio.

Ian Ferguson; Chris Summers

2009-12-31T23:59:59.000Z

334

Room-temperature diluted magnetic semiconductors p-(Ga,Ni)N  

SciTech Connect

High concentration (5 at. %) Ni was incorporated into a chemical vapor deposition-grown GaN film by using a thin protecting Ni layer on top of the GaN film during ion implantation. After etching off the protecting layer, subsequent annealing up to 800 deg. C under flowing N{sub 2} resulted in a p-type GaN with apparent ferromagnetic behavior up to {approx}320 K. In addition, the ferromagnetic behavior became more manifest with increasing annealing temperature that increases hole concentration. No presence of any other second phases nor clusters in the Ni-implanted region was identifiable, at least to the 0.2 nm point-to-point resolution of high resolution transmission electron microscopy. This novel indirect implantation process that being easy to implement appears promising for attaining room-temperature diluted magnetic semiconductors which are applicable to magnetotransport, magneto-optical and spintronics devices, among others.

Huang, R.-T.; Hsu, C.-F.; Kai, J.-J.; Chen, F.-R.; Chin, T.-S. [Department of Engineering and System Science, National Tsing-Hua University, Hsinchu 300, Taiwan (China); Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 300, Taiwan (China)

2005-11-14T23:59:59.000Z

335

Structural Characterization of Doped GaSb Single Crystals by X-ray Topography  

Science Conference Proceedings (OSTI)

We characterized GaSb single crystals containing different dopants (Al, Cd and Te), grown by the Czochralski method, by x-ray topography and high angular resolution x-ray diffraction. Lang topography revealed dislocations parallel and perpendicular to the crystal's surface. Double-crystal GaSb 333 x-ray topography shows dislocations and vertical stripes than can be associated with circular growth bands. We compared our high-angular resolution x-ray diffraction measurements (rocking curves) with the findings predicted by the dynamical theory of x-ray diffraction. These measurements show that our GaSb single crystals have a relative variation in the lattice parameter ({Delta}d/d) on the order of 10{sup -5}. This means that they can be used as electronic devices (detectors, for example) and as x-ray monochromators.

Honnicke, M.G.; Mazzaro, I.; Manica, J.; Benine, E.; M da Costa, E.; Dedavid, B. A.; Cusatis, C.; Huang, X. R.

2009-09-13T23:59:59.000Z

336

Optically-pumped UV Lasing from a GaN-based VCSEL  

NLE Websites -- All DOE Office Websites (Extended Search)

Optically-pumped UV Lasing from a GaN-based VCSEL Optically-pumped UV Lasing from a GaN-based VCSEL by J. Han, K. E. Waldrip, J. J. Figiel, S. R. Lee, and A. J. Fischer* Motivation-Compact ultraviolet sources are required for advanced chemical and biological sensors, high density optical storage, and as pump sources for phosphors used in solid-state white lighting. Although GaN-based edge- emitting lasers operating near 400 nm are available commercially, shorter wavelengths as well as other lasing geometries have remained a challenge. In particular, electrically-injected vertical-cavity surface-emitting lasers (VCSELs) have not been demonstrated in the III-Nitrides. VCSELs have unique advantages due to their low cost, compact size, and well- defined circular output beam. Optoelectronic sources based on UV VCSELS will be the

337

Coincident site lattice-matched InGaN on (111) spinel substrates  

Science Conference Proceedings (OSTI)

Coincident site lattice-matched wurtzite (0001) In{sub 0.31}Ga{sub 0.69}N, emitting in the important green wavelength region, is demonstrated by molecular beam epitaxy on a cubic (111) MgAl{sub 2}O{sub 4} spinel substrate. The coincident site lattice matching condition involves a 30 deg. rotation between the lattice of the InGaN epitaxial layer and the lattice of the spinel. This work describes an alternative approach towards realizing more compositionally homogenous InGaN films with low dislocation density emitting in the ''green gap'' of low efficiency currently observed for semiconductor light emitting diodes (LEDs). This approach could lead to higher efficiency green LEDs presently of great interest for solid-state lighting applications.

Norman, A. G.; Dippo, P. C.; Moutinho, H. R.; Simon, J.; Ptak, A. J. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

2012-04-09T23:59:59.000Z

338

Coincident Site Lattice Matched InGaN on (111) Spinel Substrates  

Science Conference Proceedings (OSTI)

Coincident site lattice-matched wurtzite (0001) In{sub 0.31}Ga{sub 0.69}N, emitting in the important green wavelength region, is demonstrated by molecular beam epitaxy on a cubic (111) MgAl{sub 2}O{sub 4} spinel substrate. The coincident site lattice matching condition involves a 30{sup o} rotation between the lattice of the InGaN epitaxial layer and the lattice of the spinel. This work describes an alternative approach towards realizing more compositionally homogenous InGaN films with low dislocation density emitting in the 'green gap' of low efficiency currently observed for semiconductor light emitting diodes (LEDs). This approach could lead to higher efficiency green LEDs presently of great interest for solid-state lighting applications.

Norman, A. G.; Dippo, P. C.; Moutinho, H. R.; Simon, J.; Ptak, A. J.

2012-04-09T23:59:59.000Z

339

Single-event dynamics of high-performance HBTs and GaAs MESFETs  

SciTech Connect

Picosecond charge-collection transients measured for GaAs/AlGaAs HBTs following 3.0 MeV [alpha]-particle and 620 nm picosecond laser excitation reveal charge-collection efficiencies up to twenty-eight times smaller than for GaAs MESFETs, with [approximately]90% of the charge collected within 75 ps of the ionizing event. The small charge-collection efficiency of the HBTs is a consequence of the ultrafast charge-collection dynamics in these devices. The authors show that picosecond laser excitation reproduces nicely the ion-induced transients, providing a valuable tool for the investigation of charge-collection and SEU phenomena in these devices.

McMorrow, D.; Melinger, J.S.; Campbell, A.B. (Naval Research Lab., Washington, DC (United States)); Weatherford, T.; Knudson, A.R.; Tran, L.H.

1993-12-01T23:59:59.000Z

340

Ga{sub 1-x}Mn{sub x}N epitaxial films with high magnetization  

Science Conference Proceedings (OSTI)

We report on the fabrication of pseudomorphic wurtzite Ga{sub 1-x}Mn{sub x}N grown on GaN with Mn concentrations up to 10% using molecular beam epitaxy. According to Rutherford backscattering, the Mn ions are mainly at the Ga-substitutional positions, and they are homogeneously distributed according to depth-resolved Auger-electron spectroscopy and secondary-ion mass-spectroscopy measurements. A random Mn distribution is indicated by transmission electron microscopy, and no Mn-rich clusters are present for optimized growth conditions. A linear increase of the c-lattice parameter with increasing Mn concentration is found using x-ray diffraction. The ferromagnetic behavior is confirmed by superconducting quantum-interference measurements showing saturation magnetizations of up to 150 emu/cm{sup 3}.

Kunert, G.; Kruse, C.; Figge, S.; Hommel, D. [Semiconductor Epitaxy, Institute of Solid State Physics, University of Bremen, D-28359 Bremen (Germany); Dobkowska, S.; Jakiela, R.; Stefanowicz, W.; Sawicki, M. [Institute of Physics, Polish Academy of Science, PL-02-668 Warszawa (Poland); Li, Tian; Bonanni, A. [Institute for Semiconductor and Solid State Physics, Johannes Kepler University Linz, A 4040 Linz (Austria); Reuther, H.; Grenzer, J.; Borany, J. von [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstrasse 400, 01328 Dresden (Germany); Dietl, T. [Institute of Physics, Polish Academy of Science, PL-02-668 Warszawa (Poland); Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, PL-00-681 Warszawa (Poland)

2012-07-09T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

Low-lying structure of neutron-rich Zn and Ga isotopes  

Science Conference Proceedings (OSTI)

Low-lying states of even-even Zn and odd-mass Ga nuclei with neutron numbers between 42 and 50 have been calculated within the framework of the SDG-pair approximation of the nuclear shell model. We employ a monopole and quadrupole pairing plus quadrupole-quadrupole interaction with optimized parameters, which are assumed to be constants for nuclei with the same proton number or neutron number. We calculate low-lying level schemes, electric quadrupole and magnetic dipole moments, and E2 and M1 transition rates. Reasonable agreement is achieved between the calculated results and experimental data. Dominant configurations in the ground states of odd-mass Ga nuclei are discussed in terms of pair correlations. The weak-coupling picture for some states of odd-mass Ga nuclei is studied.

Jiang, H. [School of Arts and Sciences, Shanghai Maritime University, Shanghai 200135 (China); Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China); Fu, G. J.; Arima, A. [Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China); Zhao, Y. M. [Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China); Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator, Lanzhou 730000 (China); CCAST, World Laboratory, P.O. Box 8730, Beijing 100080 (China)

2011-09-15T23:59:59.000Z

342

Radiation-induced surface degradation of GaAs and high electron mobility transistor structures  

Science Conference Proceedings (OSTI)

Transistor heterostructures with high-carrier-mobility have been studied. It is shown that, as the {gamma}-irradiation dose {Phi} increases, their degradation occurs in the following sequence. (i) At {Phi} 0.2-eV decrease in the diffusion energy of intrinsic defects and, probably, atmospheric oxygen. (ii) At {Phi} > 10{sup 7} rad, highly structurally disordered regions larger than 1 {mu}m are formed near microscopic defects or dislocations. (iii) At {Phi} > 10{sup 8} rad, there occurs degradation of the internal AlGaAs/InGaAs/GaAs interfaces and the working channel. An effective method for studying the degradation processes in heterostructures is to employ a set of structural diagnostic methods to analyze processes of radiation-induced and aging degradation, in combination with theoretical simulation of the occurring processes.

Bobyl, A. V.; Konnikov, S. G.; Ustinov, V. M.; Baidakova, M. V.; Maleev, N. A.; Sakseev, D. A. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Konakova, R. V., E-mail: konakova@isp.kiev.ua; Milenin, V. V.; Prokopenko, I. V. [National Academy of Sciences of Ukraine, Lashkaryov Institute of Semiconductor Physics (Ukraine)

2012-06-15T23:59:59.000Z

343

Band offsets in HfO{sub 2}/InGaZnO{sub 4} heterojunctions  

SciTech Connect

The valence band discontinuity ({Delta}E{sub V}) of sputter deposited HfO{sub 2}/InZnGaO{sub 4} (IGZO) heterostructures was obtained from x-ray photoelectron spectroscopy measurements. The HfO{sub 2} exhibited a bandgap of 6.07 eV from absorption measurements. A value of {Delta}E{sub V} = 0.48 {+-} 0.025 eV was obtained by using the Ga 2p{sub 3/2}, Zn 2p{sub 3/2}, and In 3d{sub 5/2} energy levels as references. This implies a conduction band offset {Delta}E{sub C} of 2.39 eV in HfO{sub 2}/InGaZnO{sub 4} heterostructures and a nested interface band alignment.

Cho, Hyun [Department of Nanomechatronics Engineering, Pusan National University, Gyeongnam 627-706 (Korea, Republic of); Douglas, E. A.; Gila, B. P.; Craciun, V.; Lambers, E. S.; Pearton, S. J. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Ren Fan [Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States)

2012-01-02T23:59:59.000Z

344

Current injection efficiency induced efficiency-droop in InGaN quantum well light-emitting diodes  

E-Print Network (OSTI)

Current injection efficiency induced efficiency-droop in InGaN quantum well light-emitting diodes]. The detail of the model for current injection model for quantum well heterostructure is described in Ref. [18 Keywords: III-Nitride InGaN QWs Light-emitting diodes Efficiency-droop a b s t r a c t Current injection

Gilchrist, James F.

345

Heteroepitaxial growth of InAs on GaAs(001) by in situ STM located inside MBE growth chamber  

Science Conference Proceedings (OSTI)

The growth of InAs on GaAs(001) is of great interest primarily due to the self-assembly of arrays of quantum dots (QDs) with excellent opto-electronic properties. However, a basic understanding of their spontaneous formation is lacking. Advanced experimental ... Keywords: GaAs, InAs, Molecular beam epitaxy, Quantum dots, Scanning tunneling microscopy

S. Tsukamoto; G. R. Bell; Y. Arakawa

2006-12-01T23:59:59.000Z

346

The Effect of Periodic Silane Burst on the Properties of GaN on Si (111) Substrates  

E-Print Network (OSTI)

The periodic silane burst technique was employed during metalorganic chemical vapor deposition of epitaxial GaN on AlN buffer layers grown on Si (111). Periodic silicon delta doping during growth of both the AlN and GaN ...

Zang, Keyan

347

Simulation of H behavior in p-GaN(Mg) at elevated temperatures  

DOE Green Energy (OSTI)

The behavior of H in p-GaN(Mg) at temperatures >400 C is modeled by using energies and vibrational frequencies from density-functional theory to parameterize transport and reaction equations. Predictions agree semiquantitatively with experiment for the solubility, uptake, and release of the H when account is taken of a surface barrier. Hydrogen is introduced into GaN during growth by metal-organic chemical vapor deposition (MOCVD) and subsequent device processing. This impurity affects electrical properties substantially, notably in p-type GaN doped with Mg where it reduces the effective acceptor concentration. Application of density-functional theory to the zincblende and wurtzite forms of GaN has indicated that dissociated H in interstitial solution assumes positive, neutral, and negative charge states. The neutral species is found to be less stable than one or the other of the charged states for all Fermi energies. Hydrogen is predicted to form a bound neutral complex with Mg, and a local vibrational mode ascribed to this complex has been observed. The authors are developing a unified mathematical description of the diffusion, reactions, uptake, and release of H in GaN at the elevated temperatures of growth and processing. Their treatment is based on zero-temperature energies from density functional theory. One objective is to assess the consistency of theory with experiment at a more quantitative level than previously. A further goal is prediction of H behavior pertinent to device processing. Herein is discussed aspects relating to p-type GaN(Mg).

Myers, S.M. Jr.; Wright, A.F.; Petersen, G.A.; Seager, C.H.; Crawford, M.H.; Wampler, W.R.; Han, J.

1999-12-07T23:59:59.000Z

348

Synthesis, structure and theoretical studies of a new ternary non-centrosymmetric beta-LaGaS{sub 3}  

SciTech Connect

New ternary beta-LaGaS{sub 3} has been synthesized from the stoichiometric mixture of elements by a conventional solid-state reaction at 1100 deg. C and annealed at 820 deg. C. This compound represents a new structure type that crystallizes in a non-centrosymmetric orthorhombic space group Pna2{sub 1} (No.33) with a=10.405(1) A, b=21.984(2) A, c=6.0565(5) A, and Z=12, and features the wavy GaS{sub 4} tetrahedron chains that are separated by La{sup 3+} cations. Detailed structural differences between the title compound and its isomer, monoclinic alpha-LaGaS{sub 3}, are discussed. With the aid of WIEN2k package, the absorption spectra and electronic structures as well as the refractive indexes, absorption coefficients and reflectivities of two types of LaGaS{sub 3} have been calculated. The calculated band gap and the absorption edge of beta-LaGaS{sub 3} agree well with the experimental measurements. And a weak NLO response of beta-LaGaS{sub 3} has been detected. - Graphical abstract: New non-centrosymmeteic ternary lanthanum gallium sulfide, beta-LaGaS{sub 3}, features the wavy GaS{sub 4} tetrahedron chains that are separated by La{sup 3+} cations has been synthesized by a solid state reaction. Such an orthorhombic beta-LaGaS{sub 3} is isomeric with the monoclinic alpha-LaGaS{sub 3}. Detailed structural differences between the title compound and its isomer, monoclinic alpha-LaGaS{sub 3}, are discussed. The absorption spectra and electronic structures of both types of LaGaS{sub 3} have been calculated with the aid of WIEN2k package as well as the refractive indexes, absorption coefficients and reflectivities. The calculated band gap and absorption edge of beta-LaGaS{sub 3} agree well with the experimental measurements. And a weak NLO response of beta-LaGaS{sub 3} has been detected.

Li Peng; Li Longhua [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences Fuzhou, Fujian 350002 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Chen Ling [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences Fuzhou, Fujian 350002 (China); Wu Liming, E-mail: liming_wu@fjirsm.ac.c [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences Fuzhou, Fujian 350002 (China)

2010-02-15T23:59:59.000Z

349

Development of polycrystal GaAs solar cells. Quarterly technical progress report No. 1, January 15-April 30, 1979  

DOE Green Energy (OSTI)

The objective of this program is to develop a thin film GaAs solar cell technology with the potential of yielding cells with 12 to 15% efficiency and to develop thin film growth techniques which are compatible with the low cost production goal of $500/kW-peak. Progress is reported on a study of junction formation in large grain polycrystal GaAs; characterization of the electronic properties of polycrystal GaAs grown by MBE on low cost foreign substrates; optimizing the structure of AlGaAs-GaAs heterojunction Schottky barrier solar cells; and a variety of grain boundary measurements, including Scanning Light Microscopy (SLM), Deep Level Transient Spectroscopy (DLTS), SIMS, and temperature dependent resistivity.

Miller, D.L.; Cohen, M.J.; Harris, J.S. Jr.; Ballantyne, J.; Hoyte, A.; Stefanakos, E.

1979-05-01T23:59:59.000Z

350

Growth of high Bi concentration GaAs{sub 1-x}Bi{sub x} by molecular beam epitaxy  

Science Conference Proceedings (OSTI)

The incorporation of Bi is investigated in the molecular beam epitaxy growth of GaAs{sub 1-x}Bi{sub x}. Bi content increases rapidly as the As{sub 2}:Ga flux ratio is lowered to 0.5 and then saturates for lower flux ratios. Growth under Ga and Bi rich conditions shows that Bi content increases strongly with decreasing temperature. A model is proposed where Bi from a wetting layer incorporates through attachment to Ga-terminated surface sites. The weak Ga-Bi bond can be broken thermally, ejecting Bi back into the wetting layer. Highly crystalline films with up to 22% Bi were grown at temperatures as low as 200 Degree-Sign C.

Lewis, R. B. [Department of Physics and Astronomy, University of British Columbia, V6T 1Z1 Vancouver (Canada); Department of Electrical and Computer Engineering, University of Victoria, V8W 3P6 Victoria (Canada); Masnadi-Shirazi, M. [Department of Electrical and Computer Engineering, University of Victoria, V8W 3P6 Victoria (Canada); Department of Electrical and Computer Engineering, University of British Columbia, V6T 1Z4 Vancouver (Canada); Tiedje, T. [Department of Electrical and Computer Engineering, University of Victoria, V8W 3P6 Victoria (Canada)

2012-08-20T23:59:59.000Z

351

Effects of low-temperature buffer-layer thickness and growth temperature on the SEE sensitivity of GaAs HIGFET circuits  

Science Conference Proceedings (OSTI)

Heavy-ion Single Event Effects (SEE) test results reveal the role of growth temperature and buffer layer thickness in the use of a low-temperature grown GaAs (LT GaAs) buffer layer for suppressing SEE sensitivity in GaAs HIGFET circuits.

Weatherford, T.R.; Fouts, D.J. [Naval Postgraduate School, Monterey, CA (United States); Marshall, P.W. [Naval Research Lab., Washington, DC (United States)]|[SFA, Inc., Largo, MD (United States); Marshall, C.J. [Naval Research Lab., Washington, DC (United States); Mathes, B.; LaMacchia, M. [Motorola Government Systems, Scottsdale, AZ (United States)

1997-12-01T23:59:59.000Z

352

The control of size and areal density of InAs self-assembled quantum dots in selective area molecular beam epitaxy on GaAs (001) surface  

Science Conference Proceedings (OSTI)

The growth of InAs quantum dots (QDs) on GaAs (001) substrates by selective area molecular beam epitaxy (SA-MBE) with dielectric mask is investigated. The GaAs polycrystals on the mask, which is formed during growth due to low GaAs selectivity between ... Keywords: InAs quantum dots, Molecular beam epitaxy, Selective area epitaxy

J. C. Lin; P. W. Fry; R. A. Hogg; M. Hopkinson; I. M. Ross; A. G. Cullis; R. S. Kolodka; A. I. Tartakovskii; M. S. Skolnick

2006-12-01T23:59:59.000Z

353

Wet chemical synthesis and characterization of AgGaSe{sub 2} nanoparticles  

SciTech Connect

AgGaSe{sub 2} compound semiconductor nanoparticles were synthesized by wet chemical method using mercaptoacetic acid as a capping agent at room temperature. The synthesized powders belong to chalcopyrite structure confirmed by powder XRD. The surface morphology and crystalline size were observed by high resolution scanning electron microscope (HR-SEM). The stoichiometric composition of AgGaSe{sub 2} nanoparticles was confirmed by Energy dispersive X-ray (EDX) analysis. Different functional group vibrations of mercaptoacetic acid capped nanoparticles were studied using FT-IR spectrum. The absorbance and optical bandgap of the nanoparticles were determined using diffuse reflectance spectroscopy (DRS).

Sugan, S.; Dhanasekaran, R. [Crystal Growth Centre, Anna University, Chennai- 600 025 (India)

2013-06-03T23:59:59.000Z

354

Polarized Emission from Single GaN Quantum Dots Grown by Molecular Beam Epitaxy  

Science Conference Proceedings (OSTI)

Polarization resolved microphotoluminescence measurements of single MBE-grown GaN/Al(Ga)N quantum dots (QDs) have been performed. The exciton and biexciton peaks with full width at half maximum as narrow as dots, resulting in different built-in electric field. Moreover, a strongly linearly polarized emission is observed for the investigated dots with a degree of linear polarization of about 0.9, interpreted as the valence-band mixing induced by in-plane anisotropy due to strain and/or QD shape.

Amloy, S. [Department of Physics, Chemistry, and Biology (IFM), Linkoeping University, S-58183 Linkoeping (Sweden); Department of Physics, Faculty of Science, Thaksin University, 93110 Phattalung (Thailand); Yu, K. H.; Karlsson, K. F.; Holtz, P. O. [Department of Physics, Chemistry, and Biology (IFM), Linkoeping University, S-58183 Linkoeping (Sweden); Farivar, R.; Andersson, T. G. [Applied Semiconductor Physics, Department of Microtechnology and Nanoscience, Chalmers University of Technology, S-41296 Goeteborg (Sweden)

2011-12-23T23:59:59.000Z

355

Structure of droplet-epitaxy-grown InAs/GaAs quantum dots  

Science Conference Proceedings (OSTI)

We have used a direct x-ray phasing method, coherent Bragg rod analysis, to obtain sub-angstrom resolution electron density maps of the InAs/GaAs dot system. The dots were grown by the droplet heteroepitaxy (DHE) technique and their structural and compositional properties are compared with those of dots grown by the strain-driven Stranski-Krastanov method. Our results show that the Ga diffusion into the DHE-grown dots is somewhat larger; however, other characteristics such as the composition of the dots uppermost layers, the interlayer spacing, and the bowing of the atomic layers are similar.

Cohen, Eyal; Yochelis, Shira; Westreich, Ohad; Shusterman, Sergey; Kumah, Divine P.; Clarke, Roy; Yacoby, Yizhak; Paltiel, Yossi (Michigan); (Hebrew); (Soreq NRC, Israel)

2011-09-06T23:59:59.000Z

356

Charge Separation of Wurtzite/Zinc-blende Heterojunction GaN Nanowires  

DOE Green Energy (OSTI)

The electronic properties of wurtzite/zinc-blende (WZ/ZB) heterostructure GaN are investigated using first-principles methods. A small component of ZB stacking formed along the growth direction in the WZ GaN nanowires does not show a significant effect on the electronic property, whereas a charge separation of electrons and holes occurs along the directions perpendicular to the growth direction in the ZB stacking. The later case provides an efficient way to separate the charge through controlling crystal structure. These results should have significant implications for most state of the art excitonic solar cells and the tuning region in tunable laser diodes.

Wang, Zhiguo; Li, Jingbo; Gao, Fei; Weber, William J.

2010-08-27T23:59:59.000Z

357

An intentionally positioned (In,Ga)As quantum dot in a micron sized light emitting diode  

SciTech Connect

We have integrated individual (In,Ga)As quantum dots (QDs) using site-controlled molecular beam epitaxial growth into the intrinsic region of a p-i-n junction diode. This is achieved using an in situ combination of focused ion beam prepatterning, annealing, and overgrowth, resulting in arrays of individually electrically addressable (In,Ga)As QDs with full control on the lateral position. Using microelectroluminescence spectroscopy we demonstrate that these QDs have the same optical quality as optically pumped Stranski-Krastanov QDs with random nucleation located in proximity to a doped interface. The results suggest that this technique is scalable and highly interesting for different applications in quantum devices.

Mehta, M.; Michaelis de Vasconcellos, S.; Zrenner, A.; Meier, C. [Department of Physics and Center for Optoelectronics and Photonics Paderborn (CeOPP), University of Paderborn, Warburger Street 100, 33098 Paderborn (Germany); Reuter, D.; Wieck, A. D. [Applied Solid State Physics, Ruhr-University of Bochum, Universitaetsstr. 150, 44780 Bochum (Germany)

2010-10-04T23:59:59.000Z

358

Lattice location of deuterium in plasma and gas charged Mg doped GaN  

SciTech Connect

The authors have used ion channeling to examine the lattice configuration of deuterium in Mg doped GaN grown by MOCVD. The deuterium is introduced both by exposure to deuterium gas and to ECR plasmas. A density functional approach including lattice relaxation, was used to calculate total energies for various locations and charge states of hydrogen in the wurtzite Mg doped GaN lattice. Computer simulations of channeling yields were used to compare results of channeling measurements with calculated yields for various predicted deuterium lattice configurations.

Wampler, W.R.; Barbour, J.C.; Seager, C.H.; Myers, S.M. Jr.; Wright, A.F.; Han, J.

1999-12-02T23:59:59.000Z

359

THz laser based on quasi-periodic AlGaAs superlattices  

SciTech Connect

The use of quasi-periodic AlGaAs superlattices as an active element of a quantum cascade laser of terahertz range is proposed and theoretically investigated. A multi-colour emission, having from three to six peaks of optical gain, is found in Fibonacci, Thue-Morse, and figurate superlattices in electric fields of intensity F = 11 - 13 kV cm{sup -1} in the frequency range f = 2 - 4 THz. The peaks depend linearly on the electric field, retain the height of 20 cm{sup -1}, and strongly depend on the thickness of the AlGaAs-layers. (lasers)

Malyshev, K V [N.E. Bauman Moscow State Technical University, Moscow (Russian Federation)

2013-06-30T23:59:59.000Z

360

Transport and strain relaxation in wurtzite InAs-GaAs core-shell heterowires  

Science Conference Proceedings (OSTI)

Indium-arsenide-gallium-arsenide (InAs-GaAs) core-shell, wurtzite nanowires have been grown on GaAs (001) substrates. The core-shell geometries (core radii 11 to 26 nm, shell thickness >2.5 nm) exceeded equilibrium critical values for strain relaxation via dislocations, apparent from transmission electron microscopy. Partial axial relaxation is detected in all nanowires increasing exponentially with size, while radial strain relaxation is >90%, but undetected in nanowires with both smaller core radii electron field-effect mobility compared to bare InAs nanowires.

Kavanagh, Karen L. [Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); Salfi, Joe; Savelyev, Igor; Blumin, Marina; Ruda, Harry E. [Centre for Advanced Nanotechnology, University of Toronto, 170 College Street, Toronto, Ontario M5S 3E4 (Canada)

2011-04-11T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Role of nanoscale AlN and InN for the microwave characteristics of AlGaN/(Al,In)N/GaN-based HEMT  

Science Conference Proceedings (OSTI)

A new AlGaN/GaN-based high electron mobility transistor (HEMT) is proposed and its micro-wave characteristics are discussed by introducing a nanoscale AlN or InN layer to study the potential improvement in their high frequency performance. The 2DEG transport mechanism including various sub-band calculations for both (Al,In) N-based HEMTs are also discussed in the paper. Apart from direct current characteristics of the proposed HEMT, various microwave parameters such as transconductance, unit current gain (h{sub 21} = 1) cut-off frequency (f{sub t}), high power-gain frequency (f{sub max}). Masons available/stable gain and masons unilateral gain are also discussed for both devices to understand its suitable deployment in microwave frequency range.

Lenka, T. R., E-mail: trlenka@gmail.com; Panda, A. K., E-mail: akpanda62@hotmail.com [National Institute of Science and Technology (India)

2011-09-15T23:59:59.000Z

362

Evolution of the deformation state and composition as a result of changes in the number of quantum wells in multilayered InGaN/GaN structures  

Science Conference Proceedings (OSTI)

The methods of high-resolution X-ray diffraction have been used to study the multilayered structures in an In{sub x}Ga{sub 1-x}N/GaN system grown by the method of metal-organic chemical-vapor deposition. A correlation between the strain state (relaxation) of the system, the indium content within quantum wells, the ratio of the barrier/well thicknesses, and the number of quantum wells in the active superlattice is established. It is shown that partial relaxation is observed even in a structure with one quantum well. The results we obtained indicate that the relaxation processes are bound to appreciably affect the optical characteristics of devices.

Kladko, V. P., E-mail: kladko@isp.kiev.ua; Kuchuk, A. V.; Safriuk, N. V.; Machulin, V. F.; Belyaev, A. E.; Konakova, R. V. [National Academy of Sciences of Ukraine, Lashkaryov Institute of Semiconductor Physics (Ukraine); Yavich, B. S. [ZAO Svetlana-Optoelectronics (Russian Federation); Ber, B. Ya.; Kazantsev, D. Yu. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

2011-06-15T23:59:59.000Z

363

SF{sub 6}/O{sub 2} plasma effects on silicon nitride passivation of AlGaN/GaN high electron mobility transistors  

SciTech Connect

The effects of various plasma and wet chemical surface pretreatments on the electrical characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) passivated with plasma-deposited silicon nitride were investigated. The results of pulsed IV measurements show that samples exposed to various SF{sub 6}/O{sub 2} plasma treatments have markedly better rf dispersion characteristics compared to samples that were either untreated or treated in wet buffered oxide etch prior to encapsulation. The improvement in these characteristics correlates with the reduction of carbon on the semiconductor surface as measured with x-ray photoelectron spectroscopy. HEMT channel sheet resistance was also affected by varying silicon nitride deposition parameters.

Meyer, David J.; Flemish, Joseph R.; Redwing, Joan M. [Materials Science and Engineering Department, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2006-11-27T23:59:59.000Z

364

Microstructural stability in LPE Ga{sub x}In{sub (1{minus}x)}As{sub y}Sb{sub (1{minus}y)}/GaSb heterostructures  

DOE Green Energy (OSTI)

The morphological and structural characteristics associated with the growth of lattice matched In{sub x}Ga{sub (1{minus}x)}As{sub y}Sb{sub (1{minus}y)}/GaSb (100) heterostructures is presented. The experiments focused on studying the effect of growth on vicinal surfaces tilted from the exact (100) orientation as well as variations in epilayer chemistry. It was found that variations in these process parameters had very strong effects on both the nucleation characteristics of the epilayer and the atomistic scale homogeneity of the alloy. The <100> and <110> variants in compositional modulation/phase separation were detected, as well as the evolution of weak (110) ordering. These results are discussed in the context of other studies on phase stability in III-V epitaxial structures, especially in terms of surface reconstruction and kinetic effects near conditions of spinodal decomposition.

Chen, C.Y.; Bucklen, V.; Rajan, K. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Materials Science and Engineering; Freeman, M.; Cardines, R.P. [Lockheed-Martin, Inc., Schenectady, NY (United States)

1998-06-01T23:59:59.000Z

365

X-ray reciprocal space mapping of dislocation-mediated strain relaxation during InGaAs/GaAs(001) epitaxial growth  

Science Conference Proceedings (OSTI)

Dislocation-mediated strain relaxation during lattice-mismatched InGaAs/GaAs(001) heteroepitaxy was studied through in situ x-ray reciprocal space mapping (in situ RSM). At the synchrotron radiation facility SPring-8, a hybrid system of molecular beam epitaxy and x-ray diffractometry with a two-dimensional detector enabled us to perform in situ RSM at high-speed and high-resolution. Using this experimental setup, four results in terms of film properties were simultaneously extracted as functions of film thickness. These were the lattice constants, the diffraction broadenings along in-plane and out-of-plane directions, and the diffuse scattering. Based on correlations among these results, the strain relaxation processes were classified into four thickness ranges with different dislocation behavior. In addition, the existence of transition regimes between the thickness ranges was identified. Finally, the dominant dislocation behavior corresponding to each of the four thickness ranges and transition regimes was noted.

Sasaki, Takuo; Ohshita, Yoshio; Kamiya, Itaru; Yamaguchi, Masafumi [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya 468-8511 (Japan); Suzuki, Hidetoshi [University of Miyazaki, 1-1 Gakuen, Kibanadai-nishi, Miyazaki 889-2154 (Japan); Takahasi, Masamitu [Japan Atomic Energy Agency, 1-1-1 Koto, Sayo, Hyogo 679-5148 (Japan)

2011-12-01T23:59:59.000Z

366

Improvement of near-infrared absorption linewidth in AlGaN/GaN superlattices by optimization of delta-doping location  

Science Conference Proceedings (OSTI)

We report a systematic study of the near-infrared intersubband absorption in AlGaN/GaN superlattices grown by plasma-assisted molecular-beam epitaxy as a function of Si-doping profile with and without {delta}-doping. The transition energies are in agreement with theoretical calculations including many-body effects. A dramatic reduction of the intersubband absorption linewidth is observed when the {delta}-doping is placed at the end of the quantum well. This reduction is attributed to the improvement of interface roughness. The linewidth dependence on interface roughness is well reproduced by a model that considers the distribution of well widths measured with transmission electron microscopy.

Edmunds, C.; Cervantes, M.; Malis, O. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Tang, L.; Shao, J.; Li, D. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, West Lafayette, Indiana 47907 (United States); Gardner, G. [Birck Nanotechnology Center, West Lafayette, Indiana 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Zakharov, D. N. [Birck Nanotechnology Center, West Lafayette, Indiana 47907 (United States); Manfra, M. J. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, West Lafayette, Indiana 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

2012-09-03T23:59:59.000Z

367

New Thin Film CuGaSe2/Cu(In,Ga)Se2 Bifacial, Tandem Solar Cell with Both Junctions Formed Simultaneously  

Science Conference Proceedings (OSTI)

Thin films of CuGaSe2 and Cu(In,Ga)Se2 were evaporated by the 3-stage process onto opposite sides of a single piece of soda-lime glass, coated bifacially with an n+/-TCO. Junctions were formed simultaneously with each of the p-type absorbers by depositing thin films of n-CdS via chemical bath deposition (CBD) at 60C. The resulting four-terminal device is a non-mechanically stacked, two-junction tandem. The unique growth sequence protects the temperature-sensitive p/n junctions. The initial device (h= 3.7%, Voc= 1.1 V[AM1.5]) suffered from low quantum efficiencies. Initial results are also presented from experiments with variations in growth sequence and back reflectors.

Young, D. L.; Abu-Shama, J.; Noufi, R.; Li, X.; Keane, J.; Gessert, T. A.; Ward, J. S.; Contreas, M.; Symko-Davies, M.; Coutts, T. J.

2002-05-01T23:59:59.000Z

368

Comparative study of InGaP/GaAs high electron mobility transistors with upper and lower delta-doped supplied layers  

Science Conference Proceedings (OSTI)

Influence corresponding to the position of {delta}-doped supplied layer on InGaP/GaAs high electron mobility transistors is comparatively studied by two-dimensional simulation analysis. The simulated results exhibit that the device with lower {delta}-doped supplied layer shows a higher gate potential barrier height, a higher saturation output current, a larger magnitude of negative threshold voltage, and broader gate voltage swing, as compared to the device with upper {delta}-doped supplied layer. Nevertheless, it has smaller transconductance and inferior high-frequency characteristics in the device with lower {delta}-doped supplied layer. Furthermore, a knee effect in current-voltage curves is observed at low drain-to-source voltage in the two devices, which is investigated in this article.

Tsai, Jung-Hui, E-mail: jhtsai@nknucc.nknu.edu.tw; Ye, Sheng-Shiun [National Kaohsiung Normal University, Department of Electronic Engineering, Taiwan (China); Guo, Der-Feng [Air Force Academy, Kaohsiung, Department of Electronic Engineering, Taiwan (China); Lour, Wen-Shiung [National Taiwan Ocean University, Department of Electrical Engineering, Taiwan (China)

2012-04-15T23:59:59.000Z

369

Improved Off-State Stress Critical Voltage on AlGaN/GaN High Electron Mobility Transistors Utilizing Pt/Ti/Au Based Gate Metallization  

Science Conference Proceedings (OSTI)

The critical voltage for degradation of AlGaN/GaN high electron mobility transistors (HEMTs) employed with the Pt/Ti/Au gate metallization instead of the commonly used Ni/Au was significantly increased during the off-state stress. The typical critical voltage for HEMTs with Ni/Au gate metallization was around -60V. By sharp contrast, no critical voltage was observed for the HEMTs with Pt/Ti/Au gate metallization, even up to -100V, which was the instrumental limitation in this experiment. Both Schottky forward and reverse gate characteristics of the Ni/Au degraded once the gate voltage passed the critical voltage of around -60V. There was no degradation exhibited for the HEMTs with Pt-gated HEMTs.

Lo, C. F. [University of Florida; Liu, L. [University of Florida, Gainesville; Kang, Tsung Sheng [University of Florida, Gainesville; Davies, Ryan [University of Florida; Gila, Brent P. [University of Florida, Gainesville; Pearton, S. J. [University of Florida; Kravchenko, Ivan I [ORNL; Laboutin, O. [Kopin Corporation, Taunton, MA; Cao, Yu [Kopin Corporation, Taunton, MA; Johnson, Wayne J. [Kopin Corporation, Taunton, MA; Ren, F. [University of Florida

2011-01-01T23:59:59.000Z

370

Real-time x-ray response of biocompatible solution gate AlGaN/GaN high electron mobility transistor devices  

Science Conference Proceedings (OSTI)

We present the real-time x-ray irradiation response of charge and pH sensitive solution gate AlGaN/GaN high electron mobility transistors. The devices show stable and reproducible behavior under and following x-ray radiation, including a linear integrated response with dose into the muGy range. Titration measurements of devices in solution reveal that the linear pH response and sensitivity are not only retained under x-ray irradiation, but an irradiation response could also be measured. Since the devices are biocompatible, and can be simultaneously operated in aggressive fluids and under hard radiation, they are well-suited for both medical radiation dosimetry and biosensing applications.

Hofstetter, Markus; Funk, Maren; Paretzke, Herwig G.; Thalhammer, Stefan [Helmholtz Zentrum Muenchen, Ingolstaedter Landstrasse 1, 85764 Neuherberg (Germany); Howgate, John; Sharp, Ian D.; Stutzmann, Martin [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, 85748 Garching (Germany)

2010-03-01T23:59:59.000Z

371

Optical modulation at around 1550 nm in a InGaAlAs optical waveguide containing a InGaAs/AlAs resonant tunnelling diode  

E-Print Network (OSTI)

We report electro-absorption modulation of light at around 1550 nm in a unipolar InGaAlAs optical waveguide containing a InGaAs/AlAs double-barrier resonant tunneling diode (DB-RTD). The RTD peak-to-valley transition increases the electric field across the waveguide, which shifts the core material absorption band-edge to longer wavelengths via the Franz-Keldysh effect, thus changing the light-guiding characteristics of the waveguide. Low-frequency characterisation of a device shows modulation up to 28 dB at 1565 nm. When dc biased close to the negative differential conductance (NDC) region, the RTD optical waveguide behaves as an electro-absorption modulator integrated with a wide bandwidth electrical amplifier, offering a potential advantage over conventional pn modulators.

Figueiredo, J M L; Stanley, C R; Ironside, C N; McMeekin, S G; Leite, A M P

1999-01-01T23:59:59.000Z

372

Strain control of AlGaN/GaN high electron mobility transistor structures on silicon (111) by plasma assisted molecular beam epitaxy  

Science Conference Proceedings (OSTI)

This paper reports on the use of plasma assisted molecular beam epitaxy of AlGaN/GaN-based high electron mobility transistor structures grown on 4 in. Si (111) substrates. In situ measurements of wafer curvature during growth proved to be a very powerful method to analyze the buffer layer's thickness dependent strain. The Ga/N ratio at the beginning of growth of the GaN buffer layer is the critical parameter to control the compressive strain of the entire grown structure. An engineered amount of compressive strain must be designed into the structure to perfectly compensate for the tensile strain caused by differences in the thermal expansion coefficient between the epi-layer and substrate during sample cool down from growth temperatures. A maximum film thickness of 4.2 {mu}m was achieved without the formation of any cracks and a negligible bow of the wafers below 10 {mu}m. Measurement of the as-grown wafers revealed depth profiles of the charge carrier concentration comparable to values achieved on SiC substrates and mobility values of the two dimensional electron gas in the range 1230 to 1350 cm{sup 2}/Vs at a charge carrier concentration of 6.5-7 10{sup 12}/cm{sup 2}. First results on processed wafers with 2 {mu}m thick buffer layer indicate very promising results with a resistance of the buffer, measured on 200 {mu}m long contacts with 15 {mu}m pitch, in the range of R > 10{sup 9}{Omega} at 100 V and breakdown voltages up to 550 V.

Aidam, Rolf; Diwo, Elke; Rollbuehler, Nicola; Kirste, Lutz; Benkhelifa, Fouad [Fraunhofer-Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg (Germany)

2012-06-01T23:59:59.000Z

373

Issues associated with the metalorganic chemical vapor deposition of ScGaN and YGaN alloys.  

SciTech Connect

The most energy efficient solid state white light source will likely be a combination of individually efficient red, green, and blue LED. For any multi-color approach to be successful the efficiency of deep green LEDs must be significantly improved. While traditional approaches to improve InGaN materials have yielded incremental success, we proposed a novel approach using group IIIA and IIIB nitride semiconductors to produce efficient green and high wavelength LEDs. To obtain longer wavelength LEDs in the nitrides, we attempted to combine scandium (Sc) and yttrium (Y) with gallium (Ga) to produce ScGaN and YGaN for the quantum well (QW) active regions. Based on linear extrapolation of the proposed bandgaps of ScN (2.15 eV), YN (0.8 eV) and GaN (3.4 eV), we expected that LEDs could be fabricated from the UV (410 nm) to the IR (1600 nm), and therefore cover all visible wavelengths. The growth of these novel alloys potentially provided several advantages over the more traditional InGaN QW regions including: higher growth temperatures more compatible with GaN growth, closer lattice matching to GaN, and reduced phase separation than is commonly observed in InGaN growth. One drawback to using ScGaN and YGaN films as the active regions in LEDs is that little research has been conducted on their growth, specifically, are there metalorganic precursors that are suitable for growth, are the bandgaps direct or indirect, can the materials be grown directly on GaN with a minimal defect formation, as well as other issues related to growth. The major impediment to the growth of ScGaN and YGaN alloys was the low volatility of metalorganic precursors. Despite this impediment some progress was made in incorporation of Sc and Y into GaN which is detailed in this report. Primarily, we were able to incorporate up to 5 x 10{sup 18} cm{sup -3} Y atoms into a GaN film, which are far below the alloy concentrations needed to evaluate the YGaN optical properties. After a no-cost extension was granted on this program, an additional more 'liquid-like' Sc precursor was evaluated and the nitridation of Sc metals on GaN were investigated. Using the Sc precursor, dopant level quantities of Sc were incorporated into GaN, thereby concluding the growth of ScGaN and YGaN films. Our remaining time during the no-cost extension was focused on pulsed laser deposition of Sc metal films on GaN, followed by nitridation in the MOCVD reactor to form ScN. Finally, GaN films were deposited on the ScN thin films in order to study possible GaN dislocation reduction.

Koleske, Daniel David; Knapp, James Arthur; Lee, Stephen Roger; Crawford, Mary Hagerott; Creighton, James Randall; Cross, Karen Charlene; Thaler, Gerald

2009-07-01T23:59:59.000Z

374

Atomic-layer-deposited Al2O3 and HfO2 on GaN: A comparative study on interfaces and electrical characteristics  

Science Conference Proceedings (OSTI)

Al"2O"3, HfO"2, and composite HfO"2/Al"2O"3 films were deposited on n-type GaN using atomic layer deposition (ALD). The interfacial layer of GaON and HfON was observed between HfO"2 and GaN, whereas the absence of an interfacial layer at Al"2O"3/GaN ... Keywords: Al2O3, Atomic-layer-deposition (ALD), GaN, HfO2, High k dielectric, MOS

Y. C. Chang; M. L. Huang; Y. H. Chang; Y. J. Lee; H. C. Chiu; J. Kwo; M. Hong

2011-07-01T23:59:59.000Z

375

Ga NMR/NQR study of the kagom compound Nd This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-Print Network (OSTI)

29 Si NMR and 69,71 Ga NMR/NQR study of the kagomé compound Nd 3 Ga 5 SiO 14 This article has been Contact us My IOPscience #12;29 Si NMR and 69,71 Ga NMR/NQR study of the kagom´e compound Nd3Ga5SiO14.zorko@ijs.si Abstract. We report a comprehensive 29 Si NMR and 69,71 Ga NMR/NQR study of the large- spin magnetically

Paris-Sud 11, Université de

376

A novel approach for the improvement of open circuit voltage and fill factor of InGaAsSb/GaSb thermophotovoltaic cells  

DOE Green Energy (OSTI)

Heterojunction n-Al{sub 0.25}Ga{sub 0.75}As{sub 0.02}Sb{sub 098}/p-In{sub 0.16}Ga{sub 0.84}As{sub 0.04}Sb{sub 0.96} thermophotovoltaic (TPV) cells were grown by molecular-beam epitaxy on n-GaSb-substrates. In the spectral range from 1 {micro}m to 2.1 {micro}m these cells, as well as homojunction n-p-In{sub 0.16}Ga{sub 0.84}As{sub 0.04}Sb{sub 0.96} cells, have demonstrated internal quantum efficiencies exceeding 80%, despite about a 200 meV barrier in the conduction band at the heterointerface. Estimation shows that the thermal emission of the electrons photogenerated in p-region over this barrier can provide high efficiency for hetero-cells if the electron recombination time in p-In{sub 0.16}Ga{sub 0.84}As{sub 0.04}Sb{sub 0.96}is longer than 10 ns. Keeping the same internal efficiency as homojunction cells, hetero-cells provide a unique opportunity to decrease the dark forward current and thereby increase open circuit voltage (V{sub {proportional_to}}) and fill factor at a given illumination level. It is shown that the decrease of the forward current in hetero-cells is due to the lower recombination rate in n-type wider-bandgap space-charge region and to the suppression of the hole component of the forward current. The improvement in V{sub {proportional_to}} reaches 100% at illumination level equivalent to 1 mA/cm{sup 2} and it decreases to 5% at the highest illumination levels (2--3 A/cm{sup 2}), where the electron current component dominates in both the homo- and heterojunction cells. Values of V{sub {proportional_to}} as high as 310 meV have been obtained for a hetero-cell at illumination levels of 3 A/cm{sup 2}. Under this condition, the expected fill factor value is about 72% for a hetero-cell with improved series resistance. The heterojunction concept provides excellent prospects for further reduction of the dark forward current in TPV cells.

Garbuzov, D.Z.; Martinelli, R.U.; Khalfin, V.; Lee, H.; Morris, N.A.; Taylor, G.C.; Connolly, J.C. [Sarnoff Corp., Princeton, NJ (United States); Charache, G.W.; DePoy, D.M. [Lockheed-Martin, Inc., Schenectady, NY (United States)

1997-10-01T23:59:59.000Z

377

Growth and Electronic Properties of GaN/ZnO Solid Solution Nanowires  

Science Conference Proceedings (OSTI)

We have grown single-crystal (Ga{sub 1-x}Zn{sub x})(N{sub 1-x}O{sub x}) solid-solution nanowires using nanostructured ZnGa{sub 2}O{sub 4} precursor prepared by a sol-gel method. From electrical transport measurements in individual nanowire field-effect transistors, we have identified the conduction as n-type and obtained a background carrier density (-10{sup 19} cm{sup -3}) and an electron mobility (-1 cm{sup 2}/V s) that are consistent with chemical disorder and a large number of charge traps, as confirmed by the devices photocurrent response. From the dependence of the device photoresponse on incident light wavelength, we have determined the energy band gap of (Ga{sub 0.88}Zn{sub 0.12})(N{sub 0.88}O{sub 0.12}) to be as much as -0.6 eV lower than that of GaN or ZnO.

Han, W.Q.; Zhang, Y.; Nam, C.-Y.; Black, C.T.; Mendez, E.E.

2010-08-23T23:59:59.000Z

378

W and WSi(x) Ohmic Contacts on p- And n-Type GaN  

SciTech Connect

W and WSi ohmic contacts on both p- and n-type GaN have been annealed at temperatures from 300-1000 *C. There is minimal reaction (< 100 ~ broadening of the metal/GaN interface) even at 1000 *C. Specific contact resistances in the 10-5 f2-cm2 range are obtained for WSiX on Si-implanted GaN with a peak doping concentration of- 5 x 1020 cm-3, after annealing at 950 `C. On p-GaN, leaky Schottky diode behavior is observed for W, WSiX and Ni/Au contacts at room temperature, but true ohmic characteristics are obtained at 250 - 300 *C, where the specific contact resistances are typically in the 10-2 K2-cm2 range. The best contacts for W and WSiX are obtained after 700 *C annealing for periods of 30- 120 sees. The formation of &WzN interracial phases appear to be important in determining the contact quality.

Abernathy, C.R.; Cao, X.A.; Eizenberg, M.; Han, J.; Lothian, J.R.; Pearton, S.J.; Ren, F.; Shul, R.J.; Zeitouny, A.; Zolper, J.C.

1998-10-13T23:59:59.000Z

379

Method of extracting thermally stable optical signals from a GaAlAs LED source  

SciTech Connect

A self-compensating scheme is described that eliminates the need for temperature control devices employed in many LED-based optical test and measurement instruments to ensure optical signal stability. Thermal behavior of GaAlAs LED sources is exploited to provide an optical wavelength band signal with 0.1%/C power level stability.

Murtaza, G.; Senior, J.M. [Manchester Metropolitan Univ. (United Kingdom). Faculty of Science and Engineering

1995-05-01T23:59:59.000Z

380

Photoconductivity and luminescence in GaSe crystals at high levels of optical excitation  

Science Conference Proceedings (OSTI)

The photoconductivity and luminescence of GaSe layered crystals at high levels of optical excitation are studied experimentally. The specific features observed in the photoconductivity and photoluminescence spectra are controlled by the nonlinear optical absorption in the region of excitonic resonance.

Kyazym-zade, A. G.; Salmanov, V. M., E-mail: vagif_salmanov@yahoo.com; Salmanova, A. A. [Baku State University (Azerbaijan); Alieva, A. M.; Ibaeva, R. Z. [National Academy of Sciences, Institute of Physics (Azerbaijan)

2010-03-15T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Critical Voltage for Electrical Reliability of GaN High Electron Mobility Transistors on Si Substrate  

E-Print Network (OSTI)

We have evaluated the electrical reliability of GaN HEMTs on Si by carrying out V[subscript DS] = 0 V step-stress experiments. We have found that these devices show a degradation pattern that is very similar to that of ...

Demirtas, Sefa

382

Siting and sizing of distributed generation units using GA and OPF  

Science Conference Proceedings (OSTI)

This paper deals with the important task of finding the optimal siting and sizing of Distributed Generation (DG) units for a given distribution network so that the cost of active and reactive power generation can be minimized. The optimization technique ... Keywords: distributed generation, genetic alghorithm(GA), optimal power flow(OPF)

M. Hosseini Aliabadi; M. Mardaneh; B. Behbahan

2008-01-01T23:59:59.000Z

383

Electron Beam-induced Light Emission and Transport in GaN Nanowires  

SciTech Connect

We report observations of electron beam-induced light from GaN nanowires grown by chemical vapor deposition. GaN nanowires were modified in-situ with deposited opaque platinum coatings to estimate the extent to which light is channeled to the ends of nanowires. Some evidence of light channeling was found, but wire microstructure and defects play an important role in light scattering and transport, limiting the extent to which light is confined. Optical interconnects are powerful components presently applied for high bandwidth communications among high-performance processors. Future circuits based on nanometer-scale components could similarly benefit from optical information transfer among processing blocks. Strong light channeling (and even lasing) has been observed in GaN nanowires, suggesting that these structures could be useful building blocks in a future networked electro-optical processor. However, the extent to which defects and microstructure control optical performance in nanowire waveguides has not been measured. In this study, we use electron microscopy and in-situ modification of individual nanowires to begin to correlate wire structure with light transport efficiency through GaN nanowires tens of microns long.

Tringe, J W; MoberlyChan, W J; Stevens, C G; Davydov, A V; Motayed, A

2006-05-10T23:59:59.000Z

384

Formation of manganese {delta}-doped atomic layer in wurtzite GaN  

Science Conference Proceedings (OSTI)

We describe the formation of a {delta}-doped manganese layer embedded within c-plane wurtzite gallium nitride using a special molecular beam epitaxy growth process. Manganese is first deposited on the gallium-poor GaN (0001) surface, forming a {radical}(3) Multiplication-Sign {radical}(3)-R30 Degree-Sign reconstructed phase. This well-defined surface reconstruction is then nitrided using plasma nitridation, and gallium nitride is overgrown. The manganese content of the {radical}(3) Multiplication-Sign {radical}(3)-R30 Degree-Sign phase, namely one Mn per each {radical}(3) Multiplication-Sign {radical}(3)-R30 Degree-Sign unit cell, implies that the MnGaN alloy layer has a Mn concentration of up to 33%. The structure and chemical content of the surface are monitored beginning from the initial growth stage up through the overgrowth of 20 additional monolayers (MLs) of GaN. An exponential-like drop-off of the Mn signal with increasing GaN monolayers, as measured by Auger electron spectroscopy, indicates that the highly concentrated Mn layer remains at the {delta}-doped interface. A model of the resultant {delta}-doped structure is formulated based on the experimental data, and implications for possible spintronic applications are discussed.

Shi Meng; Chinchore, Abhijit; Wang Kangkang; Mandru, Andrada-Oana; Liu Yinghao; Smith, Arthur R. [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States)

2012-09-01T23:59:59.000Z

385

Optimal study of distributed generation impact on electrical distribution networks using GA and generalized reduced gradient  

Science Conference Proceedings (OSTI)

This paper presents the effect of Distributed Generators (DG) existence in the electrical power distribution networks taking IEEE 14 and IEEE 30 bus test feeders as proposed systems. The analysis is done to examine the effect on the overall system losses ... Keywords: IEEE 14 bus system, IEEE 30 bus system and optimization, distributed generator (DG), generalized reduced gradient (GRG), genetic algorithms (GA)

Samuel Raafat Fahim; Walid Helmy; Hany M. Hasanien; M. A. L. Badr

2011-03-01T23:59:59.000Z

386

Design of GA thermochemical water-splitting process for the Mirror Advanced Reactor System  

DOE Green Energy (OSTI)

GA interfaced the sulfur-iodine thermochemical water-splitting cycle to the Mirror Advanced Reactor System (MARS). The results of this effort follow as one section and part of a second section to be included in the MARS final report. This section describes the process and its interface to the reactor. The capital and operating costs for the hydrogen plant are described.

Brown, L.C.

1983-04-01T23:59:59.000Z

387

GA-GPU: extending a library-based global address spaceprogramming model for scalable heterogeneouscomputing systems  

Science Conference Proceedings (OSTI)

Scalable heterogeneous computing (SHC) architectures are emerging as a response to new requirements for low cost, power efficiency, and high performance. For example, numerous contemporary HPC systems are using commodity Graphical Processing Units (GPU) ... Keywords: armci, ga, gas, global address space, global arrays, gpu, nwchem, pgas

Vinod Tipparaju; Jeffrey S. Vetter

2012-05-01T23:59:59.000Z

388

GA based energy loss minimization approach for optimal sizing & placement of distributed generation  

Science Conference Proceedings (OSTI)

Distributed Generators (DG) provide the lowest cost solution to handle low voltage or overload problems. In conjunction with such problems, a technique of energy saving is introduced by placement of distributed generation (DG) in distribution systems. ... Keywords: Distributed generation (DG), energy saving, genetic algorithms (GA), optimal sizing and placement

Deependra Singh; Devender Singh; K. S. Verma

2008-04-01T23:59:59.000Z

389

Confocal microphotoluminescence of InGaN-based light-emitting diodes Koichi Okamoto,a  

E-Print Network (OSTI)

for conventional incandescent and fluorescent light bulbs.5 However, luminous efficacies of commercial white LEDsConfocal microphotoluminescence of InGaN-based light-emitting diodes Koichi Okamoto,a Akio Kaneta-well-structured light-emitting diodes LEDs with a yellow-green light 530 nm and an amber light 600 nm was measured

Okamoto, Koichi

390

Particle-induced mitigation of SEU sensitivity in high data rate GaAs HIGFET technologies  

Science Conference Proceedings (OSTI)

Proton and heavy ion data on two GaAs HIGFET logic families, one source coupled (SCFL) and the other complementary (C-HIGFET), show the importance of dynamic testing and develop a new technique for mitigating SEU sensitivity by minimizing charge enhancement effects.

Marshall, P.W.; Weatherford, T.R. [Naval Research Lab., Washington, DC (United States)]|[SFA, Inc., Landover, MD (United States); Dale, C.J. [Naval Research Lab., Washington, DC (United States); La Macchia, M. [Motorola, Inc., Phoenix, AZ (United States); LaBel, K.A. [National Aeronautics and Space Administration, Greenbelt, MD (United States)

1995-12-01T23:59:59.000Z

391

Pulsed laser-induced charge collection in GaAs MESFETs  

Science Conference Proceedings (OSTI)

Pulsed picosecond lasers with variable wavelength have been used to investigate the details of charge collection in GaAs MESFETs. In short gate-length devices, charge collection at the drain may be much larger than at the gate and greater than the charge produced by the laser pulses.

Knudson, A.R.; Campbell, A.B.; McMorrow (Naval Research Lab., Washington, DC (USA)); Buchner, S.; Kang, K. (Martin Marietta Labs., Baltimore, MD (USA)); Weatherford, T. (SFA Inc., Landover, MD (US)); Srinivas, V.; Swartzlander, G.A. Jr.; Chen, Y.J. (Maryland Univ., Baltimore, MD (USA))

1990-12-01T23:59:59.000Z

392

Modulation on Ni{sub 2}MnGa(001) surface  

SciTech Connect

We report periodic modulation on (001) surface of Ni2MnGa ferromagnetic shape memory alloy. For the stoichiometric surface, analysis of the low energy electron diffraction (LEED) spot profiles shows that the modulation is incommensurate. The modulation appears at 200 K, concomitant with the first order structural transition to the martensitic phase.

D'Souza, S. W.; Rai, Abhishek; Nayak, J.; Maniraj, M.; Dhaka, R. S.; Barman, S. R.; Schlagel, D. L.; Lograsso, T. A. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore, 452001, Madhya Pradesh (India); Ames Laboratory U. S. DOE, Iowa State University, Ames, Iowa 50011-3020 (United States)

2011-07-15T23:59:59.000Z

393

Time response of the high-field electron distribution function in GaAs  

Science Conference Proceedings (OSTI)

Numerical calculations have been made of the high-field electron distribution function for GaAs, its small-signal frequency response and its behavior in large sinusoidal electric fields-The response speed is limited by the low scattering rate within ...

H. D. Rees

1969-09-01T23:59:59.000Z

394

HH7, Degradation of Ohmic and Schottky Contacts on InGaAs ...  

Science Conference Proceedings (OSTI)

In order to study the device reliability and failure mechanisms, both high ... InAlAs /InGaAs MHEMTs, obtained from a vendor, were stressed for 36 hours at a drain voltage of 3V. ... Transmission line method (TLM) structures were also stressed under similar .... Epitaxial Graphene: Designing a New Electronic Material.

395

Time-resolved resonance and linewidth of an ultrafast switched GaAs/AlAs microcavity  

E-Print Network (OSTI)

We explore a planar GaAs/AlAs photonic microcavity using pump-probe spectroscopy. Free carriers are excited in the GaAs with short pump pulses. The time-resolved reflectivity is spectrally resolved short probe pulses. We show experimentally that the cavity resonance and its width depend on the dynamic refractive index of both the lambda-slab and the lambda/4 GaAs mirrors. We clearly observe a double exponential relaxation of both the the cavity resonance and its width, which is due to the different recombination timescales in the lambda-slab and the mirrors. In particular, the relaxation time due to the GaAs mirrors approaches the photon storage time of the cavity, a regime for which nonlinear effects have been predicted. The strongly non-single exponential behavior of the resonance and the width is in excellent agreement to a transfer-matrix model taking into account two recombination times. The change in width leads to a change in reflectivity modulation depth. The model predicts an optimal cavity Q for any...

Harding, Philip J; Hartsuiker, Alex; Nowicki-Bringuier, Yoanna-Reine; Gerard, Jean-Michel; Vos, Willem L

2009-01-01T23:59:59.000Z

396

The stock index forecast based on dynamic recurrent neural network trained with GA  

E-Print Network (OSTI)

neural networks applied in forecasting stock price, at present, the most widely used neural network is BPThe stock index forecast based on dynamic recurrent neural network trained with GA Fang Yixian1In order to forecast the stock market more accurately, according to the dynamic property for the stock

397

Enhancement of Radiative Efficiency with Staggered InGaN Quantum Well Light Emitting Diodes  

SciTech Connect

The technology on the large overlap InGaN QWs developed in this program is currently implemented in commercial technology in enhancing the internal quantum efficiency in major LED industry in US and Asia. The scientific finding from this work supported by the DOE enabled the implementation of this step-like staggered quantum well in the commercial LEDs.

Tansu, Nelson; Dierolf, Volkmar; Huang, Gensheng; Penn, Samson; Zhao, Hongping; Liu, Guangyu; Li, Xiaohang; Poplawsky, Jonathan

2011-07-14T23:59:59.000Z

398

Entanglement in GaAs and CdSe quantum dots: Exact calculations and DFT approximations  

Science Conference Proceedings (OSTI)

We consider two electrons confined in spherical GaAs and CdSe quantum dots and calculate their ground-state spatial entanglement exactly within a parabolic confinement model. We propose a perturbative scheme to approximate the above entanglement within ... Keywords: Density-functional theory, Entanglement, Quantum dots, Quantum information, Semiconductors

J. P. Coe; A. Sudbery; I. D'Amico

2009-03-01T23:59:59.000Z

399

LATE NEWS: KK3, Non-Catalytic Synthesis of GaN Nanostructures ...  

Science Conference Proceedings (OSTI)

We have observed the synthesis of gallium nitride (GaN) nanopowders on boron ... as 400°C. The synthesis process is based on the reaction between gallium atoms from the decomposition of gallium acetylacetonate and ammonia gas molecules. ... the crystal structure and growth mechanism of the grown nanostructures.

400

Fine structure of AlN/AlGaN superlattice grown by pulsed atomic-layer epitaxy for dislocation filtering  

SciTech Connect

We report the detailed structure analysis of our AlN/AlGaN superlattice (SL) grown by pulsed atomic-layer epitaxy (PALE) for dislocation filtering. Due to the nature of PALE, the AlGaN well material itself in the SL was found to be composed actually of an Al{sub x}Ga{sub 1-x}N/Al{sub y}Ga{sub 1-y}N short-period superlattice (SPSL), with the periodicity of 15.5 A ({approx_equal}6 monolayer), determined consistently from high-resolution x-ray diffraction and high-resolution transmission electron microscopy measurements. The SPSL nature of the AlGaN layers is believed to benefit from the AlN/AlGaN SL's coherent growth, which is important in exerting compressive strain for the thick upper n-AlGaN film, which serves to eliminate cracks. Direct evidence is presented which indicates that this SL can dramatically reduce the screw-type threading dislocation density.

Sun, W.H.; Zhang, J.P.; Yang, J.W.; Maruska, H.P.; Khan, M. Asif; Liu, R.; Ponce, F.A. [Department of Electrical Engineering, University of South Carolina, Columbia, South Carolina 29208 (United States); Department of Physics and Astronomy, Arizona State University, Tempe, Arizona 85287 (United States)

2005-11-21T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

Method of fabricating high-efficiency Cu(In,Ga)(Se,S){sub 2} thin films for solar cells  

DOE Patents (OSTI)

A process for producing a slightly Cu-poor thin film of Cu(In,Ga)(Se,S){sub 2} comprises depositing a first layer of (In,Ga){sub x} (Se,S){sub y} followed by depositing just enough Cu+(Se,S) or Cu{sub x} (Se,S) to produce the desired slightly Cu-poor material. In a variation, most, but not all, (about 90 to 99%) of the (In,Ga){sub x} (Se,S){sub y} is deposited first, followed by deposition of all the Cu+(Se,S) or Cu{sub x} (Se,S) to go near stoichiometric, possibly or even preferably slightly Cu-rich, and then in turn followed by deposition of the remainder (about 1 to 10%) of the (In,Ga){sub x} (Se,S){sub y} to end with a slightly Cu-poor composition. In yet another variation, a small portion (about 1 to 10%) of the (In,Ga){sub x} (Se,S){sub y} is first deposited as a seed layer, followed by deposition of all of the Cu+(Se,S) or Cu{sub x} (Se,S) to make a very Cu-rich mixture, and then followed deposition of the remainder of the (In,Ga){sub x} (Se,S){sub y} to go slightly Cu-poor in the final Cu(In,Ga)(Se,S){sub 2} thin film. 5 figs.

Noufi, R.; Gabor, A.M.; Tuttle, J.R.; Tennant, A.L.; Contreras, M.A.; Albin, D.S.; Carapella, J.J.

1995-08-15T23:59:59.000Z

402

Method of fabricating high-efficiency Cu(In,Ga)(SeS).sub.2 thin films for solar cells  

DOE Patents (OSTI)

A process for producing a slightly Cu-poor thin film of Cu(In,Ga)(Se,S).sub.2 comprises depositing a first layer of (In,Ga).sub.x (Se,S).sub.y followed by depositing just enough Cu+(Se,S) or Cu.sub.x (Se,S) to produce the desired slightly Cu-poor material. In a variation, most, but not all, (about 90 to 99%) of the (In,Ga).sub.x (Se,S).sub.y is deposited first, followed by deposition of all the Cu+(Se,S) or Cu.sub.x (Se,S) to go near stoichiometric, possibly or even preferably slightly Cu-rich, and then in turn followed by deposition of the remainder (about 1 to 10%) of the (In,Ga).sub.x (Se,S).sub.y to end with a slightly Cu-poor composition. In yet another variation, a small portion (about 1 to 10%) of the (In,Ga).sub.x (Se,S).sub.y is first deposited as a seed layer, followed by deposition of all of the Cu+(Se,S) or Cu.sub.x (Se,S) to make a very Cu-rich mixture, and then followed deposition of the remainder of the (In,Ga).sub.x (Se,S).sub.y to go slightly Cu-poor in the final Cu(In,Ga)(Se,S).sub.2 thin film.

Noufi, Rommel (Golden, CO); Gabor, Andrew M. (Boulder, CO); Tuttle, John R. (Denver, CO); Tennant, Andrew L. (Denver, CO); Contreras, Miguel A. (Golden, CO); Albin, David S. (Denver, CO); Carapella, Jeffrey J. (Evergreen, CO)

1995-01-01T23:59:59.000Z

403

Final report on LDRD project : outstanding challenges for AlGaInN MOCVD.  

Science Conference Proceedings (OSTI)

The AlGaInN material system is used for virtually all advanced solid state lighting and short wavelength optoelectronic devices. Although metal-organic chemical vapor deposition (MOCVD) has proven to be the workhorse deposition technique, several outstanding scientific and technical challenges remain, which hinder progress and keep RD&A costs high. The three most significant MOCVD challenges are: (1) Accurate temperature measurement; (2) Reliable and reproducible p-doping (Mg); and (3) Low dislocation density GaN material. To address challenge (1) we designed and tested (on reactor mockup) a multiwafer, dual wavelength, emissivity-correcting pyrometer (ECP) for AlGaInN MOCVD. This system simultaneously measures the reflectance (at 405 and 550 nm) and emissivity-corrected temperature for each individual wafer, with the platen signal entirely rejected. To address challenge (2) we measured the MgCp{sub 2} + NH{sub 3} adduct condensation phase diagram from 65-115 C, at typical MOCVD concentrations. Results indicate that it requires temperatures of 80-100 C in order to prevent MgCp{sub 2} + NH{sub 3} adduct condensation. Modification and testing of our research reactor will not be complete until FY2005. A new commercial Veeco reactor was installed in early FY2004, and after qualification growth experiments were conducted to improve the GaN quality using a delayed recovery technique, which addresses challenge (3). Using a delayed recovery technique, the dislocation densities determined from x-ray diffraction were reduced from 2 x 10{sup 9} cm{sup -2} to 4 x 10{sup 8} cm{sup -2}. We have also developed a model to simulate reflectance waveforms for GaN growth on sapphire.

Mitchell, Christine Charlotte; Follstaedt, David Martin; Russell, Michael J.; Cross, Karen Charlene; Wang, George T.; Creighton, James Randall; Allerman, Andrew Alan; Koleske, Daniel David; Lee, Stephen Roger; Coltrin, Michael Elliott

2005-03-01T23:59:59.000Z

404

Surface science analysis of GaAs photocathodes following sustained electron beam delivery  

DOE Green Energy (OSTI)

Degradation of the photocathode materials employed in photoinjectors represents a challenge for sustained operation of nuclear physics accelerators and high power Free Electron Lasers (FEL). Photocathode quantum efficiency (QE) degradation is due to residual gasses in the electron source vacuum system being ionized and accelerated back to the photocathode. These investigations are a first attempt to characterize the nature of the photocathode degradation, and employ multiple surface and bulk analysis techniques to investigate damage mechanisms including sputtering of the Cs-oxidant surface monolayer, other surface chemistry effects, and ion implantation. Surface and bulk analysis studies were conducted on two GaAs photocathodes, which were removed from the JLab FEL DC photoemission gun after delivering electron beam, and two control samples. The analysis techniques include Helium Ion Microscopy (HIM), Rutherford Backscattering Spectrometry (RBS), Atomic Force Microscopy (AFM) and Secondary Ion Mass Spectrometry (SIMS). In addition, two high-polarization strained superlattice GaAs photocathode samples, one removed from the Continuous Electron Beam Accelerator Facility (CEBAF) photoinjector and one unused, were also analyzed using Transmission Electron Microscopy (TEM) and SIMS. It was found that heat cleaning the FEL GaAs wafer introduces surface roughness, which seems to be reduced by prolonged use. The bulk GaAs samples retained a fairly well organized crystalline structure after delivering beam but shows evidence of Cs depletion on the surface. Within the precision of the SIMS and RBS measurements the data showed no indication of hydrogen implantation or lattice damage from ion back bombardment in the bulk GaAs wafers. In contrast, SIMS and TEM measurements of the strained superlattice photocathode show clear crystal damage in the wafer from ion back bombardment.

Carlos Hernandez-Garcia, Fay Hannon, Marcy Stutzman, V. Shutthanandan, Z. Zhu, M. Nandasri, S. V. Kuchibhatla, S. Thevuthasan, W. P. Hess

2012-06-01T23:59:59.000Z

405

Heteroepitaxial growth of GaN/Si (111) junctions in ammonia-free atmosphere: Charge transport, optoelectronic, and photovoltaic properties  

Science Conference Proceedings (OSTI)

We report the catalyst-free growth of gallium nitride (GaN) nanostructures on n-Si (111) substrates using physical vapor deposition via thermal evaporation of GaN powder at 1150 Degree-Sign C in the absence of NH{sub 3} gas. Scanning electron microscopy and energy dispersive x-ray analysis indicate that the growth rate of GaN nanostructures varies with deposition time. Photoluminescence spectra showed the suppression of the UV emission and the enhancement of the visible band emission with increasing the deposition time. The fabricated GaN nanostructures exhibited p-type behavior at the GaN/Si interface, which can be related to the diffusion of Ga into the Si substrate. The obtained lowest reflection and highest transmittance over a wide wavelength range (450-750 nm) indicate the high quality of the fabricated GaN films. Hall-effect measurements showed that all fabricated films have p-type behavior with decreasing electron concentration from 10{sup 21} to 10{sup 12} cm{sup -3} and increasing the electron mobility from 50 to 225 cm{sup 2}/V s with increasing the growth time. The fabricated solar cell based on the 1 h-deposited GaN nanostructures on n-Si (111) substrate showed a well-defined rectifying behavior with a rectification ratio larger than 8.32 Multiplication-Sign 10{sup 3} in dark. Upon illumination (30 mW/cm{sup 2}), the 1 h-deposited heterojunction solar cell device showed a conversion efficiency of 5.78%. The growth of GaN in the absence of NH{sub 3} gas has strong effect on the morphological, optical, and electrical properties and consequently on the efficiency of the solar cell devices made of such layers.

Saron, K. M. A.; Hashim, M. R. [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, Penang 11800 (Malaysia); Allam, Nageh K. [Energy Materials Laboratory (EML), Department of Physics, School of Sciences and Engineering, The American University in Cairo, New Cairo 11835 (Egypt)

2013-03-28T23:59:59.000Z

406

Multi-junction, monolithic solar cell using low-band-gap materials lattice matched to GaAs or Ge  

DOE Patents (OSTI)

A multi-junction, monolithic, photovoltaic solar cell device is provided for converting solar radiation to photocurrent and photovoltage with improved efficiency. The solar cell device comprises a plurality of semiconductor cells, i.e., active p/n junctions, connected in tandem and deposited on a substrate fabricated from GaAs or Ge. To increase efficiency, each semiconductor cell is fabricated from a crystalline material with a lattice constant substantially equivalent to the lattice constant of the substrate material. Additionally, the semiconductor cells are selected with appropriate band gaps to efficiently create photovoltage from a larger portion of the solar spectrum. In this regard, one semiconductor cell in each embodiment of the solar cell device has a band gap between that of Ge and GaAs. To achieve desired band gaps and lattice constants, the semiconductor cells may be fabricated from a number of materials including Ge, GaInP, GaAs, GaInAsP, GaInAsN, GaAsGe, BGaInAs, (GaAs)Ge, CuInSSe, CuAsSSe, and GaInAsNP. To further increase efficiency, the thickness of each semiconductor cell is controlled to match the photocurrent generated in each cell. To facilitate photocurrent flow, a plurality of tunnel junctions of low-resistivity material are included between each adjacent semiconductor cell. The conductivity or direction of photocurrent in the solar cell device may be selected by controlling the specific p-type or n-type characteristics for each active junction.

Olson, Jerry M. (Lakewood, CO); Kurtz, Sarah R. (Golden, CO); Friedman, Daniel J. (Lakewood, CO)

2001-01-01T23:59:59.000Z

407

Growth and development of GaInAsP for use in high-efficiency solar cells. Annual subcontract report, 1 July 1991--30 June 1992  

DOE Green Energy (OSTI)

This report describes work done during Phase II of the subcontract. Goals for Phase II include the following: (1) Optimize the GaInAsP cell on GaAs and demonstrate a 500-sun at air mass (AM) 1.5 efficiency of >23%. (2) Develop a window layer, including the evaluation of AlGaAs, GaInP, AlGaAsP, AlGaInP, and GaP. (3) Develop a front-surface contact, with a grid designed for 500-sun concentration, and a goal of a contact resistivity of {approximately}10{sup 5} ohm-cm{sup 2}. (4) Grow GaInAsP cells on Ge, with a goal of a 1-sun (AM 1.5) efficiency of >15%. Accomplishments reported herein include (1) the fabrication of p-on-n and n-on-p GaInAsP cells on GaAs, with the n-on-p cell demonstrating a 10-sun (AM 1.5) active-area efficiency of 23.4% as measured at NREL (2) the evaluation of Al{sub x}Ga({sub 1-x})As, GaInP{sub 2}, and AlInP{sub 2} window layers; and (3) the fabrication of GaInAsP cells on Ge, with the demonstration of a p-on-n GaInAsP cell grown on Ge with a 1-sun (AM 1.5) active-area efficiency of 14.4%.

Sharps, P.R. [Research Triangle Inst., Research Triangle Park, NC (United States)

1993-04-01T23:59:59.000Z

408

A search for spin-polarized photoemission from GaAs using light with orbital angular momentum  

Science Conference Proceedings (OSTI)

Laser light with photon energy near the bandgap of GaAs and with different amounts of orbital angular momentum was used to produce photoemission from unstrained GaAs. The degree of electron spin polarization was measured using a micro-Mott polarimeter and found to be consistent with zero with an upper limit of ~3% for light with up to ±5{bar h} of orbital angular momentum. In contrast, the degree of spin polarization was 32.32 ± 1.35% using circularly-polarized laser light at the same wavelength, which is typical of bulk GaAs.

Nathan Clayburn, James McCarter, Joan Dreiling, Bernard Poelker, Dominic Ryan, Timothy Gay

2013-01-01T23:59:59.000Z

409

The Surface Activation Layer of GaAs Negative Electron Affinity Photocathode Activated by Cs, Li and NF3  

Science Conference Proceedings (OSTI)

The lifetime of GaAs photocathodes can be greatly improved by introducing Li in the Cs+NF{sub 3} activation process. The surface activation layer of such photocathodes is studied by synchrotron radiation photoemission and is compared with GaAs photocathodes activated without Li. The charge distributions of N, F and Cs experience significant changes when Li is added in the activation. In addition, the presence of Li causes NF{sub x} molecules to take an orientation with F atoms on top. All these changes induced by Li hold the key for the lifetime improvement of GaAs photocathodes.

Sun, Yun; /SLAC, SSRL; Kirby, R.E.; /Saxet Surface Sci.; Maruyama, T.; /SLAC; Mulhollan, G.A.; Bierman, J.C.; /Saxet Surface Sci.; Pianetta, P.; /SLAC, SSRL

2009-12-11T23:59:59.000Z

410

Measurement of the absorption coefficient for light laterally propagating in light-emitting diode structures with In{sub 0.2}Ga{sub 0.8}N/GaN quantum wells  

SciTech Connect

A procedure for measuring the absorption coefficient for light propagating parallel to the surface of a GaN-based light emitting diode chip on a sapphire substrate is suggested. The procedure implies the study of emission from one end face of the chip as the opposite end face is illuminated with a light emitting diode. The absorption coefficient is calculated from the ratio between the intensities of emission emerging from the end faces of the sapphire substrate and the epitaxial layer. From the measurements for chips based on p-GaN/In{sub 0.2}Ga{sub 0.8}N/n-GaN structures, the lateral absorption coefficient is determined at a level of (23 {+-} 3)cm{sup -1} at a wavelength of 465 nm. Possible causes for the discrepancy between the absorption coefficients determined in the study and those reported previously are analyzed.

Lelikov, Yu. S.; Bochkareva, N. I.; Gorbunov, R. I.; Martynov, I. A.; Rebane, Yu. T.; Tarkin, D. V.; Shreter, Yu. G. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)], E-mail: YShreter@mail.ioffe.ru

2008-11-15T23:59:59.000Z

411

Magneto-optical study of excitonic states in In0.045Ga0.955AsGaAs multiple coupled quantum wells T. Wang,* M. Bayer, A. Forchel, N. A. Gippius, and V. Kulakovskii  

E-Print Network (OSTI)

Magneto-optical study of excitonic states in In0.045Ga0.955AsĂ?GaAs multiple coupled quantum wells T consisting of i quantum wells (i 1,2,3,4) with 7.5 nm well thickness. For a 2.5 nm barrier thickness between the wells, the electronic states are strongly coupled. Because of the coupling, the heavy-hole exciton nshh

412

High-Efficiency Non-Polar GaN-Based LEDs  

SciTech Connect

Inlustra Technologies with subcontractor U.C. Santa Barbara conducted a project with the principle goal of demonstrating high internal quantum efficiency blue (430 nm) and green (540nm) light emitting diodes (LEDs) on low-defect density non-polar GaN wafers. Inlustra pursued the fabrication of smooth thick a-plane and m-plane GaN films, as well as defect reduction techniques such as lateral epitaxial overgrowth (LEO) to uniformly lower dislocation density in these films. Limited free-standing wafers were produced as well. By the end of the reporting period, Inlustra had met its milestone of dislocation reduction to < 5 x 10{sup 6} cm{sup -2}. Stacking faults were still present in appreciable density ({approx} 1 x 10{sup 5} cm{sup -1}), but were not the primary focus of defect reduction since there have been no published studies establishing their detrimental effects on LED performance. Inlustra's LEO progress built a solid foundation upon which further commercial development of GaN substrates will occur. UCSB encountered multiple delays in its LED growth and fabrication efforts due to unavoidable facilities outages imposed by ongoing construction in an area adjacent to the metalorganic chemical vapor deposition (MOCVD) laboratory. This, combined with the large amount of ab initio optimization required for the MOCVD system used during the project, resulted in unsatisfactory LED progress. Although numerous blue-green photoluminescence results were obtained, only a few LED structures exhibited electroluminescence at appreciable levels. UCSB also conducting extensive modeling (led by Prof. Van de Walle) on the problem of non-radiative Auger recombination in GaN-based LED structures, which has been posited to contribute to LED efficiency 'droop' at elevated current density. Unlike previous modeling efforts, UCSB's approach was truly a first-principles ab initio methodology. Building on solid numerical foundations, the Auger recombination rates of In{sub x}Ga{sub 1-x}N alloys were calculated from first-principles density-functional and many-body-perturbation theory. The differing mechanisms of inter- and intra-band recombination were found to affect different parts of the emission spectrum. In the blue to green spectral region and at room temperature the Auger coefficient was calculated to be as large as 2 x 10{sup -30} cm{sup 6} s{sup -1}; in the infrared it is even larger. These results indicated that Auger recombination may be responsible for the loss of quantum efficiency that affects InGaN-based light emitters, whether on non-polar or polar crystal planes.

Paul Fini

2010-11-30T23:59:59.000Z

413

High-Efficiency Non-Polar GaN-Based LEDs  

Science Conference Proceedings (OSTI)

Inlustra Technologies with subcontractor U.C. Santa Barbara conducted a project with the principle goal of demonstrating high internal quantum efficiency blue (430 nm) and green (540nm) light emitting diodes (LEDs) on low-defect density non-polar GaN wafers. Inlustra pursued the fabrication of smooth thick a-plane and m-plane GaN films, as well as defect reduction techniques such as lateral epitaxial overgrowth (LEO) to uniformly lower dislocation density in these films. Limited free-standing wafers were produced as well. By the end of the reporting period, Inlustra had met its milestone of dislocation reduction to LED performance. Inlustra's LEO progress built a solid foundation upon which further commercial development of GaN substrates will occur. UCSB encountered multiple delays in its LED growth and fabrication efforts due to unavoidable facilities outages imposed by ongoing construction in an area adjacent to the metalorganic chemical vapor deposition (MOCVD) laboratory. This, combined with the large amount of ab initio optimization required for the MOCVD system used during the project, resulted in unsatisfactory LED progress. Although numerous blue-green photoluminescence results were obtained, only a few LED structures exhibited electroluminescence at appreciable levels. UCSB also conducting extensive modeling (led by Prof. Van de Walle) on the problem of non-radiative Auger recombination in GaN-based LED structures, which has been posited to contribute to LED efficiency 'droop' at elevated current density. Unlike previous modeling efforts, UCSB's approach was truly a first-principles ab initio methodology. Building on solid numerical foundations, the Auger recombination rates of In{sub x}Ga{sub 1-x}N alloys were calculated from first-principles density-functional and many-body-perturbation theory. The differing mechanisms of inter- and intra-band recombination were found to affect different parts of the emission spectrum. In the blue to green spectral region and at room temperature the Auger coefficient was calculated to be as large as 2 x 10{sup -30} cm{sup 6} s{sup -1}; in the infrared it is even larger. These results indicated that Auger recombination may be responsible for the loss of quantum efficiency that affects InGaN-based light emitters, whether on non-polar or polar crystal planes.

Paul Fini

2010-11-30T23:59:59.000Z

414

A model for the critical voltage for electrical degradation of GaN high electron mobility transistors  

E-Print Network (OSTI)

We have found that there is a critical drain-to-gate voltage beyond which GaN high-electron mobility transistors start to degrade in electrical-stress experiments. The critical voltage depends on the detailed voltage biasing ...

Joh, Jungwoo

415

Aluminum nitride transitional layer for reducing dislocation density and cracking of AlGaN epitaxial films  

DOE Patents (OSTI)

A denticulated Group III nitride structure that is useful for growing Al.sub.xGa.sub.1-xN to greater thicknesses without cracking and with a greatly reduced threading dislocation (TD) density.

Allerman, Andrew A.; Crawford, Mary H.; Lee, Stephen R.

2013-01-08T23:59:59.000Z

416

Local Built-in Potential on Grain Boundary of Cu(In,Ga)Se2 Thin Films  

DOE Green Energy (OSTI)

We report on a direct measurement of two-dimensional potential distribution on the surface of Cu(In,Ga)Se2 (CIGS) thin films using a nanoscale electrical characterization of scanning Kelvin probe microscopy (SKPM). The potential measurement reveals a higher surface potential or a smaller work function on grain boundaries (GBs) of the film than on the grain surfaces. This demonstrates the existence of a local built-in potential on GBs and that the GB is positively charged. The role of the built-in potential in device performance was further examined by tuning Ga content or band gap of the film. With increasing Ga content, the GB potential drops sharply in a Ga range of 28%-38%. Comparing the change in the built-in potential to the theoretical and experimental photoconversion efficiencies, we conclude that the potential plays a significant role in the device conversion efficiency of NREL's three-stage CIGS device.

Jiang, C.-S.; Noufi, R.; Ramanathan, K.; AbuShama, J. A.; Moutinho, H. R.; Al-Jassim, M. M.

2005-01-01T23:59:59.000Z

417

Mg doping of GaN grown by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions  

SciTech Connect

Acceptor doping of GaN with Mg during plasma-assisted molecular beam epitaxy, under N-rich conditions and a relatively high growth temperature of 740 deg. C, was investigated. The p-doping level steadily increases with increasing Mg flux. The highest doping level achieved, determined from Hall measurements, is 2.1x10{sup 18} cm{sup -3}. The corresponding doping efficiency and hole mobility are approx4.9% and 3.7 cm{sup 2}/V s at room temperature. Cross-sectional transmission electron microscopy and photoluminescence measurements confirm good crystalline and optical quality of the Mg-doped layers. An InGaN/GaN quantum dot light emitting diode (lambda{sub peak}=529 nm) with p-GaN contact layers grown under N-rich condition exhibits a low series resistance of 9.8 OMEGA.

Zhang Meng; Bhattacharya, Pallab; Guo Wei; Banerjee, Animesh [Department of Electrical Engineering and Computer Science, Solid-State Electronics Laboratory, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States)

2010-03-29T23:59:59.000Z

418

CuIn(1-x)Ga(x)Se-Based Solar Cells prepared from Electrodeposited and Electroless-Deposited Precursors  

DOE Green Energy (OSTI)

Three devices were fabricated from electrodeposited (ED) and electroless-deposited (EL) precursors. Compositions were adjusted with additional In and Ga by physical vapor deposition (PVD) for an ED and an EL device.

Batchelor, W. K.; Bhattacharya, R. N.

2000-01-01T23:59:59.000Z

419

Growth and development of GaInAsP for use in high-efficiency solar cells. Final subcontract report, 1 July 1991--30 December 1993  

DOE Green Energy (OSTI)

This report describes accomplishments during Phase 3 of this subcontract. The overall goals of the subcontract were (1) to develop the necessary technology to grow high-efficiency GaInAsP layers that are lattice-matched to GaAs and Ge; (2) to demonstrate highefficiency GaInAsP single-junction solar cells; and (3) to demonstrate GaInAsP/Ge cascade solar cells suitable for operation under concentrated (500X) sunlight. The major accomplishments during Phase 3 include (1) demonstrating a GaInAsP tunnel diode for use as an interconnect in the GaInAsP/Ge cascade cell, and (2) demonstrating a GaInAsP/Ge cascade cell. The development of the GaInAsP tunnel diode is a major accomplishment because it allows for the GaInAsP and Ge cells to be connected without optical losses for the bottom Ge cell, such as a Ge tunnel diode would cause. The GaInAsP/Ge cascade cell development is significant because of the demonstration of a cascade cell with a new materials system.

Sharps, P.R. [Research Triangle Inst., Research Triangle Park, NC (United States)

1994-10-01T23:59:59.000Z

420

Rare-earth chromium gallides RE{sub 4}CrGa{sub 12} (RE=Tb-Tm)  

Science Conference Proceedings (OSTI)

The ternary rare-earth-metal chromium gallides RE{sub 4}CrGa{sub 12} (RE=Tb-Tm) have been prepared by reactions of the elements at 1000 Degree-Sign C in the presence of excess gallium used as a self-flux. Their structures are derived by inserting Cr atoms into a quarter of the empty Ga{sub 6} octahedral clusters found in the parent binary gallides REGa{sub 3} (AuCu{sub 3}-type), although single-crystal X-ray diffraction studies suggest that complex superstructures may be adopted. An ideal ordered Y{sub 4}PdGa{sub 12}-type structure was successfully refined for a crystal of Dy{sub 4}CrGa{sub 12} (Pearson symbol cI34, space group Im3{sup Macron }m, Z=2, a=8.572(1) A). Magnetic measurements on single-crystal samples reveal ferromagnetic or possibly ferrimagnetic ordering for the Tb, Dy, and Er members (T{sub C}=22, 15, and 2.8 K, respectively) and antiferromagnetic ordering for the Ho member (T{sub N}=7.5 K). Band structure calculations on a hypothetical 'Y{sub 4}CrGa{sub 12}' model suggest that the Cr atoms carry no local magnetic moment. - Graphical abstract: RE{sub 4}CrGa{sub 12} is derived by inserting Cr atoms into empty Ga{sub 6} octahedral clusters present in the parent binary gallides REGa{sub 3}. Highlights: Black-Right-Pointing-Pointer RE{sub 4}MGa{sub 12} (previously known for M=Fe, Ni, Pd, Pt, Ag) has been extended to M=Cr. Black-Right-Pointing-Pointer RE{sub 4}CrGa{sub 12} compounds show predominantly ferromagnetic ordering. Black-Right-Pointing-Pointer Band structure calculations suggest that Cr atoms carry no local magnetic moment.

Slater, Brianna R.; Bie, Haiying; Stoyko, Stanislav S. [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada)] [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada); Bauer, Eric D.; Thompson, Joe D. [Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)] [Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Mar, Arthur, E-mail: arthur.mar@ualberta.ca [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada)] [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada)

2012-12-15T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

Perturbation potential produced by a monolayer of InAs on GaAs,,100... Z. Barticevic,1  

E-Print Network (OSTI)

, using the linear muffin-tin orbital tight-binding method, for the potential of an InAs 001 monolayerAs sand- wiched in bulk 001 -GaAs. This result evidences the impor- tance of excitonic effects in InAs ML of InAs in bulk GaAs 001 have been done mainly using the sp3 s* tight-binding TB method. In spite of its

Vargas, Patricio

422

GaN-Ready Aluminum Nitride Substrates for Cost-Effective, Very Low Dislocation Density III-Nitride LED's  

SciTech Connect

The objective of this project was to develop and then demonstrate the efficacy of a costeffective approach for a low defect density substrate on which AlInGaN LEDs can be fabricated. The efficacy of this “GaN-ready” substrate would then be tested by growing high efficiency, long lifetime InxGa1-xN blue LEDs. The approach used to meet the project objectives was to start with low dislocation density AlN single-crystal substrates and grow graded AlxGa1-xN layers on top. Pseudomorphic AlxGa1-xN epitaxial layers grown on bulk AlN substrates were used to fabricate light emitting diodes and demonstrate better device performance as a result of the low defect density in these layers when benched marked against state-of-the-art LEDs fabricated on sapphire substrates. The pseudomorphic LEDs showed excellent output powers compared to similar wavelength devices grown on sapphire substrates, with lifetimes exceeding 10,000 hours (which was the longest time that could reliably be estimated). In addition, high internal quantum efficiencies were demonstrated at high driving current densities even though the external quantum efficiencies were low due to poor photon extraction. Unfortunately, these pseudomorphic LEDs require high Al content so they emit in the ultraviolet. Sapphire based LEDs typically have threading dislocation densities (TDD) > 108 cm-2 while the pseudomorphic LEDs have TDD ? 105 cm-2. The resulting TDD, when grading the AlxGa1-xN layer all the way to pure GaN to produce a “GaN-ready” substrate, has varied between the mid 108 down to the 106 cm-2. These inconsistencies are not well understood. Finally, an approach to improve the LED structures on AlN substrates for light extraction efficiency was developed by thinning and roughening the substrate.

Sandra Schujman; Leo Schowalter

2010-10-15T23:59:59.000Z

423

Photonic crystal laser lift-off GaN light-emitting diodes Aurlien David,a  

E-Print Network (OSTI)

Photonic crystal laser lift-off GaN light-emitting diodes Aurélien David,a Tetsuo Fujii,b Brendan March 2006 We report on the fabrication and study of laser lift-off GaN-based light-emitting diodes-state lighting. However, as is the case for any light-emitting diode LED , light tends to be trapped in the high

Recanati, Catherine

424

Efficiency-improvement study for GaAs solar cells. Final report, March 31, 1980-September 30, 1981  

DOE Green Energy (OSTI)

High-yield fabrication of good quality AlGaAs/GaAs concentration solar cells has been a limiting factor in widespread utilization of these high conversion efficiency (22 to 24%) photovoltaic cells. Reported is a series of investigations to correlate solar cell yield with substrate quality, growth techniques, layer composition, and metallization processes. In addition, several diagnostic techniques are described to aid in device characterization.

Cape, J.A.; Oliver, J.R.; Zehr, S.W.

1982-04-01T23:59:59.000Z

425

Ultra-low resistance ohmic contacts to GaN with high Si doping concentrations grown by molecular beam epitaxy  

Science Conference Proceedings (OSTI)

Ti/Al/Ni/Au ohmic contacts were formed on heavily doped n{sup +} metal-polar GaN samples with various Si doping concentrations grown by molecular beam epitaxy. The contact resistivity (R{sub C}) and sheet resistance (R{sub sh}) as a function of corresponding GaN free carrier concentration (n) were measured. Very low R{sub C} values (electron mobility transistors.

Afroz Faria, Faiza; Guo Jia; Zhao Pei; Li Guowang; Kumar Kandaswamy, Prem; Wistey, Mark; Xing Huili; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)

2012-07-16T23:59:59.000Z

426

Spin-Resolved Electronic Structure of Ultrathin Epitaxial Fe Films on Vicinal and Singular GaAs(100) Substrates  

SciTech Connect

Recently there has been considerable interest in the study of spin injection at ferromagnetic semiconductor heterojunctions and ferromagnetic metal--semiconductor contacts. Studies of ntype semiconductors have demonstrated spin-coherent transport over large distances5 and the persistence of spin coherence over a sizeable time scale. Clearly such investigations have been stimulated by the potential of the development of ''spintronics'', electronic devices utilizing the information of the electron spin states. To understand and improve the magnetic properties of ultrathin Fe films on GaAs has been the aim of many research groups over recent years. The interest in this system has both technological and fundamental scientific motivations. Technologically, Fe on GaAs may serve to realize spin electronic devices. From a fundamental science point of view, Fe on GaAs serves as a prototype for studies of the interplay between the crystalline structure and morphology of an ultrathin film, its electronic structure and the long range magnetic order it exhibits. Furthermore, it is well known that an oxidized Cs layer on GaAs substantially alters the work-function of the GaAs surface, which plays a very important role in the application of GaAs as a spin polarized electron source.

Morton, S A; Waddill, G D; Spangenberg, M; Seddon, E A; Neal, J; Shen, T; Tobin, J G

2003-03-10T23:59:59.000Z

427

The Crystallization Behavior of Stochiometric and Off-stochiometric Ga-Sb-Te Materials for Phase-Change Memory  

Science Conference Proceedings (OSTI)

The stoichiometric Ga{sub 4}Sb{sub 6}Te{sub 3} and Ga-Sb materials were systematically studied. The alloy Ga{sub 4}Sb{sub 6}Te{sub 3} shows a fast crystallization speed, very high crystallization temperature, T{sub x}, and high electrical contrast. Although stoichiometric GaSb has similar performance and even faster crystallization speed, the electrical contrast is much lower. The other off-stoichiometric compounds we studied all have higher T{sub x} than Ge{sub 2}Sb{sub 2}Te{sub 5} indicating a good amorphous stability. By raising the Sb/Te ratio with GaSb incorporation, T{sub x} and the recrystallization time of melt-quenched, amorphous samples can be effectively increased. The stoichiometric Ga{sub 4}Sb{sub 6}Te{sub 3} with less likelihood of phase-segregation compared to nonstoichiometric compounds is a promising candidate for phase-change memory.

H Cheng; S Raoux; J Jordan-Sweet

2011-12-31T23:59:59.000Z

428

Mid-infrared InAs/AlGaSb superlattice quantum-cascade lasers  

SciTech Connect

We report on the demonstration of mid-infrared InAs/AlGaSb superlattice quantum-cascade lasers operating at 10 {mu}m. The laser structures are grown on n-InAs (100) substrate by solid-source molecular-beam epitaxy. An InAs/AlGaSb chirped superlattice structure providing a large oscillator strength and fast carrier depopulation is employed as the active part. The observed minimum threshold current density at 80 K is 0.7 kA/cm{sup 2}, and the maximum operation temperature in pulse mode is 270 K. The waveguide loss of an InAs plasmon waveguide is estimated, and the factors that determine the operation temperature are discussed.

Ohtani, K.; Fujita, K.; Ohno, H. [Laboratory for Nanoelectronics and Semiconductor Spintronics, Research Institute of Electrical Communication, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai (Japan)

2005-11-21T23:59:59.000Z

429

Optical transitions in MnGa{sub 2}Se{sub 4}  

Science Conference Proceedings (OSTI)

The dependence of the absorption coefficient on incident photon energy in a MnGa{sub 2}Se{sub 4} single crystal has been investigated in the temperature range 110-295 K. Using group-theory analysis of the electron state symmetry and comparison of the symmetry of the energy spectrum of MnGa{sub 2}Se{sub 4} and its isoelectronic analogs, a conclusion about the character of optical transitions has been drawn. It is shown that the features observed at 2.31 and 2.45 eV are related to the intracenter transitions {sup 6}A{sub 1}{sup 1} {yields} {sup 4}T{sub 2}({sup 4}G) and {sup 6}A{sub 1}{sup 2} {yields} {sup 4}T{sub 2}({sup 4}G). The {sup 6}A{sub 1} state is split by the crystal field.

Tagiev, B. G.; Kerimova, T. G., E-mail: ktaira@physics.ab.az; Tagiev, O. B.; Asadullayeva, S. G.; Mamedova, I. A. [National Academy of Sciences of Azerbaijan, Institute of Physics (Azerbaijan)

2012-06-15T23:59:59.000Z

430

File:USDA-CE-Production-GIFmaps-GA.pdf | Open Energy Information  

Open Energy Info (EERE)

GA.pdf GA.pdf Jump to: navigation, search File File history File usage Georgia Ethanol Plant Locations Size of this preview: 776 × 600 pixels. Full resolution ‎(1,650 × 1,275 pixels, file size: 410 KB, MIME type: application/pdf) Description Georgia Ethanol Plant Locations Sources United States Department of Agriculture Related Technologies Biomass, Biofuels, Ethanol Creation Date 2010-01-19 Extent State Countries United States UN Region Northern America States Georgia External links http://www.nass.usda.gov/Charts_and_Maps/Ethanol_Plants/ File history Click on a date/time to view the file as it appeared at that time. Date/Time Thumbnail Dimensions User Comment current 16:12, 27 December 2010 Thumbnail for version as of 16:12, 27 December 2010 1,650 × 1,275 (410 KB) MapBot (Talk | contribs) Automated bot upload

431

Pulsed atomic layer epitaxy of quaternary AlInGaN layers  

Science Conference Proceedings (OSTI)

In this letter, we report on a material deposition scheme for quaternary Al{sub x}In{sub y}Ga{sub 1-x--y}N layers using a pulsed atomic layer epitaxy (PALE) technique. The PALE approach allows accurate control of the quaternary layer composition and thickness by simply changing the number of aluminum, indium, and gallium pulses in a unit cell and the number of unit cell repeats. Using PALE, AlInGaN layers with Al mole fractions in excess of 40% and strong room-temperature photoluminescence peaks at 280 nm can easily be grown even at temperatures lower than 800{sup o}C. {copyright} 2001 American Institute of Physics.

Zhang, J.; Kuokstis, E.; Fareed, Q.; Wang, H.; Yang, J.; Simin, G.; Asif Khan, M.; Gaska, R.; Shur, M.

2001-08-13T23:59:59.000Z

432

Structural controlled magnetic anisotropy in Heusler L1{sub 0}-MnGa epitaxial thin films  

Science Conference Proceedings (OSTI)

Ferromagnetic L1{sub 0}-MnGa thin films have been epitaxially grown on GaN, sapphire, and MgO substrates using molecular beam epitaxy. Using diffraction techniques, the epitaxial relationships are determined. It is found that the crystalline orientation of the films differ due to the influence of the substrate. By comparing the magnetic anisotropy to the structural properties, a clear correlation could be established indicating that the in-plane and out-of-plane anisotropy is directly determined by the crystal orientation of the film and could be controlled via selection of the substrates. This result could be helpful in tailoring magnetic anisotropy in thin films for spintronic applications.

Wang Kangkang; Lu Erdong; Smith, Arthur R. [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States); Knepper, Jacob W.; Yang Fengyuan [Department of Physics, Ohio State University, 191 Woodruff Ave., Columbus, Ohio 43210 (United States)

2011-04-18T23:59:59.000Z

433

Improved InGaN epitaxy yield by precise temperature measurement :yearly report 1.  

SciTech Connect

This Report summarizes the first year progress (October 1, 2004 to September 30, 2005) made under a NETL funded project entitled ''Improved InGaN Epitaxy Yield by Precise Temperature Measurement''. This Project addresses the production of efficient green LEDs, which are currently the least efficient of the primary colors. The Project Goals are to advance IR and UV-violet pyrometry to include real time corrections for surface emissivity on multiwafer MOCVD reactors. Increasing wafer yield would dramatically reduce high brightness LED costs and accelerate the commercial manufacture of inexpensive white light LEDs with very high color quality. This work draws upon and extends our previous research (funded by DOE) that developed emissivity correcting pyrometers (ECP) based on the high-temperature GaN opacity near 400 nm (the ultraviolet-violet range, or UVV), and the sapphire opacity in the mid-IR (MIR) near 7.5 microns.

Koleske, Daniel David; Creighton, James Randall; Russell, Michael J.; Fischer, Arthur Joseph

2006-08-01T23:59:59.000Z

434

Single event induced charge transport modeling of GaAs MESFETs  

SciTech Connect

Previous studies examining single event charge collection in GaAs MESFETs have revealed enhanced charge collection, in which the drain charge collection can be as high as 8 times the amount of charge deposited in the device. The understanding of these charge amplifying mechanisms requires correlation between experimental and simulation analysis. Two-dimensional computer simulations of charge collection phenomena in GaAs MESFETs have been performed for alpha and laser ionization. In both cases more charge is collected than is created by the ionizing event. The simulations indicate that a bipolar transport mechanism (t < 60 ps) and a channel modulation mechanism (t > 40 ps) are responsible for this enhanced charge collection.

Weatherford, T.R.; Knudson, A.R. (SFA Inc., Landover, MD (United States)); McMorrow, D.; Campbell, A.B. (Naval Research Lab., Washington, DC (United States)); Curtice, W.R. (W.R. Curtice Consulting, Princeton Junction, NJ (United States))

1993-12-01T23:59:59.000Z

435

Heavy ion and proton analysis of a GaAs C-HIGFET SCRAM  

Science Conference Proceedings (OSTI)

The authors present heavy ion and proton upset measurements, including total dose, and displacement damage on a one micron, GaAs, complementary-heterostructure insulated-gate FET (C-HIGFET) 1k x 1 SRAM. SEU characteristics show a two order of magnitude improvement over GaAs MESFET technology. Heavy-ion upset equilibrium measurements show that all cells upset with equal probability at the five percent LET threshold. This indicates that for this device the shape of the cross section versus LET curve is a result of a probability distribution that applies to all cells and is not the result of variations in cell sensitivities. The data set also indicates that the traditional two-dimensional cos([theta]) normalization to LET and fluence are not applicable to this technology.

Cutchin, J.H.; Marshall, P.W.; Weatherford, T.R. (SFA Inc., Landover, MD (United States) Naval Research Lab., Washington, DC (United States)); Langworthy, J.; Petersen, E.L.; Campbell, A.B. (Naval Research Lab., Washington, DC (United States)); Hanka, S.; Peczalski, A. (Honeywell, Inc., Minneapolis, MN (United States))

1993-12-01T23:59:59.000Z

436

SEU rate prediction and measurement of GaAs SRAMs onboard the CRRES satellite  

SciTech Connect

The Combined Release and Radiation Effects Satellite (CRRES) launched in July of 1990 included experiments to study effects of Single Event Upset (SEU) on various microelectronic ICs. The MicroElectronics Package (MEP) subsection of the satellite experiments monitored upset rates on 65 devices over a 15 month period. One of the purposes of the SEU experiments was to determine if the soft error modeling techniques were of sufficient accuracy to predict error rates, and if not, to determine where the deficiencies existed. An analysis is presented on SPICE predicted, SEU ground tested, and CRRES observed heavy ion and proton soft error rates of GaAs SRAMs. Upset rates overestimated the susceptibility of the GaAs SRAMs. Differences are accounted to several factors.

Weatherford, T.R.; McDonald, P.T. (SFA, Inc., Landover, MD (United States) Naval Research Lab., Washington, DC (United States)); Campbell, A.B.; Langworthy, J.B. (Naval Research Lab., Washington, DC (United States))

1993-12-01T23:59:59.000Z

437

Formation of ohmic contacts to MOCVD grown p-GaN by controlled activation of Mg  

DOE Green Energy (OSTI)

We report on the formation of low resistivity ohmic contacts to p-GaN, r{sub c} < 10{sup {minus}4}{Omega}cm{sup 2}, by increasing the concentration of the active Mg in the subcontact zone, via Zr-mediated release of hydrogen. We have investigated the process of evolution of hydrogen from MOCVD grown p-GaN via Zr-based metallization, and determined the optimum processing conditions (temperature and gas ambient) for fabrication of low resistance ohmic contacts. When the process is conducted in N{sub 2} flow, the metallization remains stable at temperatures required to achieve the ohmic behavior, and the morphology of the metal/semiconductor interface is unaltered by such a heat treatment. The processing in O{sub 2}, on the contrary, causes the interdiffusion of metallization constituents and the incorporation of oxygen into the semiconductor subcontact region, which could be responsible for increased resistivity of these contacts.

Kaminska, E.; Piotrowska, A.; Barcz, A.; Bour, D.; Zielinski, M.; Jasinski, J.

2000-11-27T23:59:59.000Z

438

Effects of atomic hydrogen and deuterium exposure on high polarization GaAs photocathodes  

DOE Green Energy (OSTI)

Strained-layer GaAs and strained-superlattice GaAs photocathodes are used at Jefferson Laboratory to create high average current beams of highly spin-polarized electrons. High electron yield, or quantum efficiency (QE), is obtained only when the photocathode surface is atomically clean. For years, exposure to atomic hydrogen or deuterium has been the photocathode cleaning technique employed at Jefferson Laboratory. This work demonstrates that atomic hydrogen cleaning is not necessary when precautions are taken to ensure that clean photocathode material from the vendor is not inadvertently dirtied while samples are prepared for installation inside photoemission guns. Moreover, this work demonstrates that QE and beam polarization can be significantly reduced when clean high-polarization photocathode material is exposed to atomic hydrogen from an rf dissociator-style atomic hydrogen source. Surface analysis provides some insight into the mechanisms that degrade QE and polarization due to atomic hydrogen cleaning.

M. Baylac; P. Adderley; J. Brittian; J. Clark; T. Day; J. Grames; J. Hansknecht; M. Poelker; M. Stutzman; A. T. Wu; A. S. Terekhov

2005-12-01T23:59:59.000Z

439

Thermoelectric properties of AgGaTe$_2$ and related chalcopyrite structure materials  

Science Conference Proceedings (OSTI)

We present an analysis of the potential thermoelectric performance of p-type AgGaTe$_{2}$, which has already shown a $ZT$ of 0.8 with partial optimization, and observe that the same band structure features, such as a mixture of light and heavy bands and isotropic transport, that lead to this good performance are present in certain other ternary chalcopyrite structure semiconductors. We find that optimal performance of AgGaTe$_2$ will be found for hole concentrations between 4 $\\times 10^{19}$ and 2 $\\times 10^{20}$cm$^{-3}$ at 900 K, and 2 $\\times 10^{19}$ and 10$^{20}$ cm$^{-3}$ at 700 K, and that certain other chalcopyrite semiconductors might show good thermoelectric performance at similar doping ranges and temperatures if not for higher lattice thermal conductivity.

Parker, David S [ORNL; Singh, David J [ORNL

2012-01-01T23:59:59.000Z

440

Band offsets in ZrO{sub 2}/InGaZnO{sub 4} heterojunction  

SciTech Connect

X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band ( White-Up-Pointing-Triangle E{sub V}) of amorphous InGaZnO{sub 4} (a-IGZO)/ZrO{sub 2} heterostructure deposited by DC and RF sputtering at room temperature, respectively. A value of White-Up-Pointing-Triangle E{sub V}= 0 eV was obtained by using the Ga and Zn 2p{sup 3} and In 3d{sup 3} energy levels as references. Given the experimental band gap of 3.1 eV and 5.8 eV for the a-IGZO and ZrO{sub 2}, respectively, this would indicate a conduction band offset of 2.7 eV in the system.

Yao Jianke [School of Computer and Information Engineering, Shenzhen Graduate School, Peking University, Shenzhen 518055 (China); Zhang Shengdong [School of Computer and Information Engineering, Shenzhen Graduate School, Peking University, Shenzhen 518055 (China); Institute of Microelectronics, Peking University, Beijing 100871 (China); Gong Li [Instrumental Analysis and Research Center, Sun Yat-Sen University, Guangzhou 510275 (China)

2012-08-27T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

Ar plasma induced deep levels in epitaxial n-GaAs  

SciTech Connect

Ar plasma etching of n-type (Si doped) GaAs introduces several electron traps (E{sub c} - 0.04 eV, E{sub c} - 0.07 eV, E{sub c} - 0.19 eV, E{sub c} - 0.31 eV, E{sub c} - 0.53 eV, and E{sub c} - 0.61 eV). The trap, E{sub c} - 0.04 eV, labelled E1' and having a trap signature similar to irradiation induced defect E1, appears to be metastable. E{sub c} - 0.31 eV and E{sub c} - 0.61 eV are metastable too and they are similar to the M3/M4 defect configuration present in hydrogen plasma exposed n-GaAs.

Venter, A.; Nyamhere, C.; Botha, J. R. [Department of Physics, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Auret, F. D.; Janse van Rensburg, P. J.; Meyer, W. E.; Coelho, S. M. M. [Department of Physics, University of the Pretoria, Lynnwood Road, Pretoria 0002 (South Africa); Kolkovsky, V. l. [Technische Universitaet, Dresden, 01062 Dresden (Germany)

2012-01-01T23:59:59.000Z

442

Triggering GaAs lock-on switches with laser diode arrays  

Science Conference Proceedings (OSTI)

Many of the applications that require the unique capabilities of Photoconductive Semiconductor Switches (PCSS) demand a compact package. We have been able to demonstrate that GaAs switches operated in the high gain mode called lock-on'' meet the required electrical switching parameters of several such applications using small switch sizes. The only light source that has enough power to trigger a PCSS and is compatible with a small package is a laser diode. This paper will describe the progress that leads to the triggering of high power PCSS switches with laser diodes. Our goal is to switch up to 5 kA in a single shot mode and up to 100 MW repetitively at up to 10 kHz. These goals are feasible since the switches can be used in parallel or in series. Low light level triggering became possible after the discovery of a high electric field, high gain switching mode in GaAs (and later in InP). At electric fields below 3 kV/cm GaAs switches are activated by creation of, at most, only one conduction electron- valence hole pair per photon absorbed in the sample. This linear mode demands high laser power and, after the light is extinguished, the carriers live for only a few nanoseconds. At higher electric fields GaAs behaves as a light activated Zener diode. The laser light generates carriers as in the linear mode and the field induces gain such that the amount of light required to trigger the switch is reduced by a factor of up to 500. The gain continues until the field across the sample drops to a material dependent lock-on field. At this point the switch will carry as much current as, and for as long as, the circuit can maintain the lock-on field. The gain in the switch allows for the use of laser diodes. 8 refs., 11 figs.

Loubriel, G.M.; Helgeson, W.D.; McLaughlin, D.L.; O'Malley, M.W.; Zutavern, F.J. (Sandia National Labs., Albuquerque, NM (USA)); Rosen, A.; Stabile, P.J. (David Sarnoff Research Center, Princeton, NJ (USA))

1990-01-01T23:59:59.000Z

443

Growth and optical characterization of multilayers of InGaN quantum dots  

E-Print Network (OSTI)

(QDs) have recently attracted much attention for a variety of optoelectronic applications and for exploration of their fundamental physics [1] . By using a high density of uniformly distributed self-assembled QDs, laser diodes (LDs) have been r... [ 11] and microdisks [ 12] , which allows more efficient light extraction from the QD layer. In this paper, we investigated the growth of multilayers of InGaN QDs using the modified droplet epitaxy approach. It is hoped that this could lead...

Zhu, Tontong; El-Ella, Haitham; Reid, Benjamin; Holmes, Mark; Taylor, Robert; Kappers, Menno; Oliver, Rachel

2012-01-01T23:59:59.000Z

444

Proton and heavy ion upsets in GaAs MESFET devices  

Science Conference Proceedings (OSTI)

This paper reports on proton and heavy SEU data that has been obtained for devices made by several GaAs MESFET manufacturers. Proton energy dependence and proton and heavy ion upset cross sections are reported. Measurements of charge collection from latches designed with various gate widths show that charge collection depths appear deeper than the 1 {mu}m depth expected. Critical charge does not scale linearly with area. Proton upset cross sections are reduced with increased device width.

Weatherford, T.R.; Tran, L. (Sachs/Freeman Associates, Inc., Bowie, MD (United States)); Stapor, W.J.; Petersen, E.L.; Langworthy, J.B.; McMorrow, D. (Naval Research Lab., Washington, DC (United States)); Abdel-Kader, W.G.; McNulty, P.J. (Clemson Univ., SC (United States). Dept. of Physics and Astronomy)

1991-12-01T23:59:59.000Z

445

Mn deposition on Ni{sub 2}MnGa(100)  

Science Conference Proceedings (OSTI)

We report the study of Mn adlayers on a Mn deficient Ni{sub 2}MnGa(100) surface by using low energy electron diffraction (LEED). The spot profile analysis indicates that after 0.2 monolayer (ML) deposition, the LEED spots become very sharp. This pattern indicates the removal of Mn vacancies formed on the surface due to Mn deficiency. But with further growth of Mn layers on this surface, the LEED spots become broad.

Nayak, J.; Rai, Abhishek; D'Souza, S. W.; Maniraj, M.; Barman, S. R. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore, 452001, M.P. (India)

2012-06-05T23:59:59.000Z

446

Superlattice-like stacking fault array in ion-irradiated GaN  

SciTech Connect

Controlling defects in crystalline solids is of technological importance for realizing desirable materials properties. Irradiation with energetic particles is useful for designing the spatial distribution and concentration of defects in materials. Here, we performed ion irradiation into hexagonal GaN with the wurtzite structure and demonstrated the spontaneous formation of superlattice-like stacking fault arrays. It was found that the modulation period can be controlled by irradiation conditions and post-irradiation heat treatments.

Ishimaru, Dr. Manabu [Osaka University; Usov, Igor Olegovich [ORNL; Zhang, Yanwen [ORNL; Weber, William J [ORNL

2012-01-01T23:59:59.000Z

447

New limits on the ordered moments in ?-Pu and Ga-stabilized ?-Pu  

E-Print Network (OSTI)

We present the first µSR measurements ever performed on elemental Pu, and set the most stringent upper limits to date on the magnitude of the ordered moment µord in ?-Pu and ?-stabilized Pu (alloyed with 4.3 at. % Ga). Assuming a nominal hyperfine coupling field of 1 kOe/µB we find µord ? 10 ?3 µB at T ? = 4 K. Key words: plutonium magnetism, f-electron, µSR 1.

R. H. Heffner A; G. D. Morris A

2005-01-01T23:59:59.000Z

448

Temperature-dependent excitonic absorption in long-period multiple In{sub x}Ga{sub 1-x}As/GaAs quantum well structures  

Science Conference Proceedings (OSTI)

Temperature variations in the fundamental absorption edge of long-period In{sub x}Ga{sub 1-x}As/GaAs structures are studied for samples with different numbers of quantum wells and similar periods. The quantum wells were close in composition and width. Experimental data are interpreted in the model of exciton-polariton light transfer involving localized excitons in confined structures with a finite number of quantum wells. The experimentally observed low-temperature anomaly of the integrated absorption coefficient is attributed to reemission of resonance localized excitons along a finite chain of quantum wells, with no excitonic transfer. The radiative decay time of an exciton in a single quantum well is estimated from the experimental data. It is demonstrated that, at low temperatures, the major contribution to the width of the experimentally observed absorption line corresponding to the ground heavy-hole exciton state is made by inhomogeneous broadening of the line by the field of potential fluctuations associated with the compositional disorder of the alloy. At low temperatures, the inhomogeneous broadening is much more pronounced than the broadening governed by the true radiative and nonradiative dissipative decay.

Vaganov, S. A., E-mail: sv.exciton@mail.ioffc.ru; Seisyan, R. P. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

2011-01-15T23:59:59.000Z

449

Real-time observation of anisotropic strain relaxation by three-dimensional reciprocal space mapping during InGaAs/GaAs (001) growth  

Science Conference Proceedings (OSTI)

Real-time three-dimensional reciprocal space mapping (3D-RSM) measurement during In{sub 0.12}Ga{sub 0.88}As/GaAs(001) molecular beam epitaxial growth has been performed to investigate anisotropy in relaxation processes along [110] and [110] directions caused by alpha and beta misfit dislocations (MDs). Anisotropies, strain relaxation, and crystal quality in both directions were simultaneously evaluated via the position and broadness of 022 diffraction in 3D-RSM. In the small-thickness region, strain relaxation caused by alpha-MDs is higher than that caused by beta-MDs, and therefore crystal quality along [110] is worse than that along [110]. Rapid relaxation along both [110] and [110] directions occurs at almost the same thickness. After rapid relaxation, anisotropy in strain relaxation gradually decreases, whereas crystal quality along [110] direction, presumably due to beta-MDs, becomes better that along [110] direction and the ratio does not decay with thickness.

Suzuki, Hidetoshi; Sasaki, Takuo; Sai, Akihisa; Ohshita, Yoshio; Kamiya, Itaru; Yamaguchi, Masafumi [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468-8511 (Japan); Takahasi, Masamitu; Fujikawa, Seiji [Synchrotron Radiation Research Center, Japan Atomic Energy Agency, Hyogo 679-5148 (Japan)

2010-07-26T23:59:59.000Z

450

Intermixing of InGaAs/GaAs quantum wells and quantum dots using sputter-deposited silicon oxynitride capping layers  

SciTech Connect

Various approaches can be used to selectively control the amount of intermixing in III-V quantum well and quantum dot structures. Impurity-free vacancy disordering is one technique that is favored for its simplicity, however this mechanism is sensitive to many experimental parameters. In this study, a series of silicon oxynitride capping layers have been used in the intermixing of InGaAs/GaAs quantum well and quantum dot structures. These thin films were deposited by sputter deposition in order to minimize the incorporation of hydrogen, which has been reported to influence impurity-free vacancy disordering. The degree of intermixing was probed by photoluminescence spectroscopy and this is discussed with respect to the properties of the SiO{sub x}N{sub y} films. This work was also designed to monitor any additional intermixing that might be attributed to the sputtering process. In addition, the high-temperature stress is known to affect the group-III vacancy concentration, which is central to the intermixing process. This stress was directly measured and the experimental values are compared with an elastic-deformation model.

McKerracher, Ian; Fu Lan; Hoe Tan, Hark; Jagadish, Chennupati [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

2012-12-01T23:59:59.000Z

451

Comparison of dc performance of Pt/Ti/Au- and Ni/Au-Gated AlGaN/GaN High Electron Mobility Transistors  

Science Conference Proceedings (OSTI)

We have demonstrated significant improvements of AlGaN/GaN High Electron Mobility Transistors (HEMTs) dc performance by employing Pt/Ti/Au instead of the conventional Ni/Au gate metallization. During off-state bias stressing, the typical critical voltage for HEMTs with Ni/Au gate metallization was ~ -45 to -65V. By sharp contrast, no critical voltage was observed for HEMTs with Pt/Ti/Au gate metallization, even up to -100V, which was the instrumental limitation in this experiment. After the off-state stressing, the drain current of Ni/Au gated-HEMTs decreased by~ 15%. For the Pt-gate HEMTs, no degradation of the drain current occurred and there were minimal changes in the Schottky gate characteristics for both forward and reverse bias conditions. The HEMTs with Pt/Ti/Au metallization showed an excellent drain on/off current ratio of 1.5 108. The on/off drain current ratio of Ni-gated HEMTs was dependent on the drain bias voltage and ranged from 1.2 107 at Vds=5V and 6 105

Liu, L. [University of Florida, Gainesville; Lo, C. F. [University of Florida; Kang, Tsung Sheng [University of Florida, Gainesville; Pearton, S. J. [University of Florida; Kravchenko, Ivan I [ORNL; Laboutin, O. [Kopin Corporation, Taunton, MA; Johnson, Wayne J. [Kopin Corporation, Taunton, MA; Ren, F. [University of Florida

2011-01-01T23:59:59.000Z

452

Ohmic contacts to Si-implanted and un-implanted n-type GaN  

SciTech Connect

We report on ohmic contacts to Si-implanted and un-implanted n-type GaN on sapphire. A ring shaped contact design avoids the need to isolate the contact structures by additional implantation or etching. Metal layers of Al and Ti/Al were investigated. On un-implanted GaN, post metalization annealing was performed in an RTA for 30 seconds in N{sub 2} at 700, 800, and 900 C. A minimum specific contact resistance (r{sub c}) of 1.4{times}10{sup -5} {Omega}{minus}cm{sup 2} was measured for Ti/Al at an annealing temperature of 800 C. Although these values are reasonably low, variations of 95% in specific contact resistance were measured within a 500 {mu}m distance on the wafer. These results are most likely caused by the presence of compensating hydrogen. Specific contact resistance variation was reduced from 95 to 10% by annealing at 900 C prior to metalization. On Si-implanted GaN, un-annealed ohmic contacts were formed with Ti/Al metalization. The implant activation anneal of 1120 C generates nitrogen vacancies that leave the surface heavily n-type, which makes un-annealed ohmic contacts with low contact resistivity possible.

Brown, J; Ramer, J.; Zheng, L.F.; Hersee, S.D. [New Mexico Univ., Albuquerque, NM (United States). Center for High Technology Materials; Zolper, J. [Sandia National Labs., Albuquerque, NM (United States)

1996-02-01T23:59:59.000Z

453

High-performance, lattice-mismatched InGaAs/InP monolithic interconnected modules (MIMs)  

SciTech Connect

High performance, lattice-mismatched p/n InGaAs/lnP monolithic interconnected module (MIM) structures were developed for thermophotovoltaic (TPV) applications. A MIM device consists of several individual InGaAs photovoltaic (PV) cells series-connected on a single semi-insulating (S.I.) InP substrate. Both interdigitated and conventional (i.e., non-interdigitated) MIMs were fabricated. The energy bandgap (Eg) for these devices was 0.60 eV. A compositionally step-graded InPAs buffer was used to accommodate a lattice mismatch of 1.1% between the active InGaAs cell structure and the InP substrate. 1x1-cm, 15-cell, 0.60-eV MIMs demonstrated an open-circuit voltage (Voc) of 5.2 V (347 mV per cell) and a fill factor of 68.6% at a short-circuit current density (Jsc) of 2.0 A/cm{sup 2}, under flashlamp testing. The reverse saturation current density (Jo) was 1.6x10{sup {minus}6} A/cm{sup 2}. Jo values as low as 4.1x10{sup {minus}7} A/cm{sup 2} were also observed with a conventional planar cell geometry.

Fatemi, Navid S.; Wilt, David M.; Hoffman, Richard W., Jr.; Stan, Mark S.; Weizer, Victor G.; Jenkins, Phillip P.; Khan, Osman S.; Murray, Christopher S.; Scheiman, David; Brinker, David

1998-10-01T23:59:59.000Z

454

Performance status of 0.55 eV InGaAs thermophotovoltaic cells  

DOE Green Energy (OSTI)

Data on {approximately} 0.55 eV In{sub 0.72}Ga{sub 0.28}As cells with an average open-circuit voltage (Voc) of 298 mV (standard deviation 7 mV) at an average short-circuit current density of 1.16 A/cm{sup 2} (sdev. 0.1 A/cm{sup 2}) and an average fill-factor of 61.6% (sdev. 2.8%) is reported. The absorption coefficient of In{sub 0.72}Ga{sub 0.28}As was measured by a differential transmission technique. The authors use a numerical integration of the absorption data to determine the radiative recombination coefficient for In{sub 0.72}Ga{sub 0.28}As. Using this absorption data and simple one-dimensional analytical formula the above cells are modeled. The models show that the cells may be limited more by Auger recombination rather than Shockley-Read-Hall (SRH) recombination at dislocation centers caused by the 1.3% lattice mismatch of the cell to the host InP wafer.

Wojtczuk, S.; Colter, P. [Spire Corp., Bedford, MA (United States); Charache, G.; DePoy, D. [Lockheed Martin Inc., Schenectady, NY (United States)

1998-10-01T23:59:59.000Z

455

Electronic properties and deep traps in electron-irradiated n-GaN  

Science Conference Proceedings (OSTI)

The study is concerned with the effect of electron irradiation (with the energies E = 7 and 10 MeV and doses D = 10{sup 16}-10{sup 18} cm{sup -2}) and subsequent heat treatments in the temperature range 100-1000 Degree-Sign C on the electrical properties and the spectrum of deep traps of undoped (concentration of electrons n = 1 Multiplication-Sign 10{sup 14}-1 Multiplication-Sign 10{sup 16} cm{sup -3}), moderately Si-doped (n = (1.2-2) Multiplication-Sign 10{sup 17} cm{sup -3}), and heavily Si-doped (n = (2-3.5) Multiplication-Sign 10{sup 18} cm{sup -3}) epitaxial n-GaN layers grown on Al{sub 2}O{sub 3} substrates by metal-organic chemical vapor deposition. It is found that, on electron irradiation, the resistivity of n-GaN increases, this is due to a shift of the Fermi level to the limiting position close to E{sub c} -0.91 eV. The spectrum of deep traps is studied for the initial and electron-irradiated n-GaN. It is shown that the initial properties of the irradiated material are restored in the temperature range 100-1000 Degree-Sign C, with the main stage of the annealing of radiation defects at about 400 Degree-Sign C.

Brudnyi, V. N., E-mail: brudnyi@mail.tsu.ru [Tomsk State University (Russian Federation); Verevkin, S. S. [Karpov Institute of Physical Chemistry (Russian Federation); Govorkov, A. V. [Joint Stock Company 'Federal State Research and Design Institute of Rare Metal Industry (Giredmet)' (Russian Federation); Ermakov, V. S.; Kolin, N. G.; Korulin, A. V. [Karpov Institute of Physical Chemistry (Russian Federation); Polyakov, A. Ya.; Smirnov, N. B. [Joint Stock Company 'Federal State Research and Design Institute of Rare Metal Industry (Giredmet)' (Russian Federation)

2012-04-15T23:59:59.000Z

456

Observation of Band Alignment Transition in InAs/GaAsSb Quantum Dots by Photoluminescence  

Science Conference Proceedings (OSTI)

The band alignment of InAs quantum dots (QDs) embedded in GaAsSb barriers with various Sb compositions is investigated by photoluminescence (PL) measurements. InAs/GaAsSb samples with 13% and 15% Sb compositions show distinct differences in emission spectra as the PL excitation power increases. Whilst no discernible shift is seen for the 13% sample, a blue-shift of PL spectra following a 1/3 exponent of the excitation power is observed for the 15% sample suggesting a transition from a type I to type II band alignment. Time-resolved PL data show a significant increase in carrier lifetime as the Sb composition increases between 13% and 15% implying that the transformation from a type I to type II band alignment occurs between 13% and 15% Sb compositions. These results taken together lead to the conclusion that a zero valence band offset (VBO) can be achieved for the InAs/GaAsSb system in the vicinity of 14% Sb composition.

Ban, K. Y.; Kuciauskas, D.; Bremner, S. P.; Honsberg, C. B.

2012-05-15T23:59:59.000Z

457

Structural evolution and characterization of heteroepitaxial GaSb thin films on Si(111) substrates  

Science Conference Proceedings (OSTI)

This paper describes the structural evolution and characterization of heteroepitaxial GaSb thin films on Si(111) substrates. The growth process used a combination of atomic sources which included the rf sputtering of Sb and the thermal effusion of Ga. The formation of crystalline GaSb thin films required that initially a monolayer thick Sb buffer layer be applied directly to a clean H-passivated Si(111) substrate surface. The resulting film was characterized by high resolution x-ray diffraction, Rutherford backscattering spectrometry, transmission electron microscopy, secondary ion mass spectroscopy, and atomic force microscopy (AFM). The AFM images were taken from the material after several periods of growth to determine the evolution of crystal structure with thickness. Atomic force microscopy images of the film surface showed that the heteroepitaxial layers were formed via the Stranski-Krastanov growth mechanism. This result is consistent with the heteroepitaxial growth of systems representing large differences in lattice constant. The hole mobility and carrier concentration in the deposited material were determined by the Hall measurement, performed at room temperature and on a 140 nm thick sample, to be 66 cm{sup 2}/V sec and 3x10{sup 19} cm{sup -3}, respectively. The carrier mobility was relatively low as expected for measurements taken at room temperature.

Nguyen, Thang; Varhue, Walter; Cross, Michael; Pino, Robinson; Adams, Edward; Lavoie, Mark; Lee, Jaichan [School of Engineering, University of Vermont, Burlington, Vermont 05405 (United States); IBM Corporation, Essex Junction, Vermont 05452 (United States); Department of Materials Science and Engineering, Sung Kyun Kwan University, Suwon 440-746 (Korea, Republic of)

2007-04-01T23:59:59.000Z

458

Rapid liquid phase epitaxial growth studies of GaAs: Final report, July 1984-June 1987  

Science Conference Proceedings (OSTI)

Single crystal layers of gallium arsenide have been grown on (111) and (100) oriented GaAs substrates from a flowing, GaAs saturated, gallium solution with a few degrees temperature differential across the liquid/solid interface. Very high growth rates, on the order of 8..mu..m per minute, have been observed. Such rates are in agreement with the growth theory developed as part of this program, and are about two orders greater than those typically achieved in conventional, static solution, liquid phase epitaxy. Both undoped and p-doped (Si) GaAs layers have been grown and some of their material properties measured. Good crystallinity was inferred from the narrowness of x-ray diffraction lines and from the intensities of the photoluminescence responses of all specimens sampled. While these results do not prove that the epi material is of photovoltaic quality, they indicate both a high crystallographic perfection and a low density of life-time poisoning impurities; conditions which are usually necessary for PV device development. Thus far, smooth surfaces have not been produced directly by the rapid liquid phase epitaxy (RLPE) process. The rough surface morphologies are due, at least in part, to incomplete wipe off of the liquid when the substrate is withdrawn at the end of the growth cycle. Another potential source is growth instabilities which will be discussed later. This report summarizes the three year research program of the RLPE process sponsored by DOE-SOLERAS.

Gerritsen, H.J.; Crisman, E.E.

1987-01-01T23:59:59.000Z

459

NEUTRON DIFFRACTION STUDY OF A NON-STOICHIOMETRIC Ni-Mn-Ga MSM ALLOY  

SciTech Connect

The structure and chemical order of a Heusler alloy of non-stoichiometric composition Ni-Mn-Ga were studied using constant-wavelength (1.538 ) neutron diffraction at 363K and the diffraction pattern was refined using the FullProf software. At this temperature the structure is austenite (cubic) with Fm-3m space group and lattice constant of a = 5.83913(4) [ ]. The chemical order is of critical importance in these alloys, as Mn becomes antiferromagnetic when the atoms are closer than the radius of the 3d shell. In the studied alloy the refinement of the site occupancy showed that the 4b (Ga site) contained as much as 22% Mn; that significantly alters the distances between the Mn atoms in the crystal and, as a result, also the exchange energy between some of the Mn atoms. Based on the refinement, the composition was determined to be Ni1.91Mn1.29Ga0.8

Ari-Gur, Pnina [Western Michigan University; Garlea, Vasile O [ORNL

2013-01-01T23:59:59.000Z

460

Low-cost, high-efficiency solar cells utilizing GaAs-on-Si technology. Annual subcontract report, 1 August 1991--31 July 1992  

DOE Green Energy (OSTI)

This report describes work to develop technology to deposit GaAs on Si using a nucleation layer of atomic-layer-epitaxy-grown GaAs or AlAs on Si. This ensures two-dimensional nucleation and should lead to fewer defects in the final GaAs layer. As an alternative, we also developed technology for depositing GaAs on sawtooth-patterned Si. Preliminary studies showed that this material can have a very low defect density, {approximately} 1 {times} 10{sup 5} cm{sup {minus}5}, as opposed to our conventionally grown GaAs on SL which has a typical defect density of over 1 {times}10{sup 7} cm{sup {minus}2}. Using these two now methods of GaAs-on-Si material growth, we made solar cells that are expected to show higher efficiencies than those of previous cells.

Vernon, S.M. [Spire Corp., Bedford, MA (United States)

1993-04-01T23:59:59.000Z

Note: This page contains sample records for the topic "ga ga cooperative" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


461

Chemically-assisted ion-beam etching of (AIGa)As/GaAa: Lattice damage and removal by in-situ Cl2 treatment  

Science Conference Proceedings (OSTI)

Keywords: (ALGa)As/GaAs-SQW structures, chemically-assisted ion-beam etching, dry etching, in-situ Cl2 treatment, lattice damage, semiconductor

J. Daleiden; R. Kiefer; S. Klußmann; M. Kunzer; C. Manz; M. Wailher; J. Braunstein; G. Weimann

1999-02-01T23:59:59.000Z

462

The Hybridization of CdSe/ZnS Quantum Dot on InGaN Light-Emitting Diodes for Color Conversion  

Science Conference Proceedings (OSTI)

We have demonstrated the fabrication and characterization of hybrid CdSe/ZnS quantum dot (QD)-InGaN blue LEDs. The chemically synthesized red light (lambda = 623 nm) QD solutions with different concentrations were dropped onto the blue InGaN LEDs with ... Keywords: CdSe/ZnS quantum dots, CdSe/ZnS quantum dots (QDs), InGaN quantum well and hybrid LEDs, InGaN quantum well and hybrid light-emitting diodes

Ying-Chih Chen; Chun-Yuan Huang; Yan-Kuin Su; Wen-Liang Li; Chia-Hsien Yeh; Yu-Cheng Lin

2008-07-01T23:59:59.000Z

463

Impact of defects on the electrical transport, optical properties and failure mechanisms of GaN nanowires.  

SciTech Connect

We present the results of a three year LDRD project that focused on understanding the impact of defects on the electrical, optical and thermal properties of GaN-based nanowires (NWs). We describe the development and application of a host of experimental techniques to quantify and understand the physics of defects and thermal transport in GaN NWs. We also present the development of analytical models and computational studies of thermal conductivity in GaN NWs. Finally, we present an atomistic model for GaN NW electrical breakdown supported with experimental evidence. GaN-based nanowires are attractive for applications requiring compact, high-current density devices such as ultraviolet laser arrays. Understanding GaN nanowire failure at high-current density is crucial to developing nanowire (NW) devices. Nanowire device failure is likely more complex than thin film due to the prominence of surface effects and enhanced interaction among point defects. Understanding the impact of surfaces and point defects on nanowire thermal and electrical transport is the first step toward rational control and mitigation of device failure mechanisms. However, investigating defects in GaN NWs is extremely challenging because conventional defect spectroscopy techniques are unsuitable for wide-bandgap nanostructures. To understand NW breakdown, the influence of pre-existing and emergent defects during high current stress on NW properties will be investigated. Acute sensitivity of NW thermal conductivity to point-defect density is expected due to the lack of threading dislocation (TD) gettering sites, and enhanced phonon-surface scattering further inhibits thermal transport. Excess defect creation during Joule heating could further degrade thermal conductivity, producing a viscous cycle culminating in catastrophic breakdown. To investigate these issues, a unique combination of electron microscopy, scanning luminescence and photoconductivity implemented at the nanoscale will be used in concert with sophisticated molecular-dynamics calculations of surface and defect-mediated NW thermal transport. This proposal seeks to elucidate long standing material science questions for GaN while addressing issues critical to realizing reliable GaN NW devices.

Armstrong, Andrew M.; Aubry, Sylvie; Shaner, Eric Arthur; Siegal, Michael P.; Li, Qiming; Jones, Reese E.; Westover, Tyler; Wang, George T.; Zhou, Xiao Wang; Talin, Albert Alec; Bogart, Katherine Huderle Andersen; Harris, C. Thomas; Huang, Jian Yu

2010-09-01T23:59:59.000Z

464

Polarization-balanced design of AlN/GaN heterostructures: Application to double-barrier structures  

E-Print Network (OSTI)

Inversion- and depletion- regions generally form at the interfaces between doped leads (cladding layers) and the active region in wurtzite c-plane AlN/GaN heterostructures. The band bending in the depletion region can seriously impede perpendicular electronic transport. To counter the formation of these regions, we consider polarization-balanced designs of AlN/GaN heterostructures based on matching the applied bias to the internal voltage drop arising from spontaneous and piezeolectric fields. To retain freedom of design we use alloyed Al$_{\\tilde{x}}$Ga$_{1-\\tilde{x}}$N leads. Use of pure GaN leads requires huge voltage drops which severely restricts design. The alloy concentration $\\tilde{x}$ tunes the internal voltage drop over the structure. For short active regions comprised of AlN and GaN layers, we derive a simple relation between the applied bias, average alloy composition of the active region, and the alloy concentration of the leads. We study polarization-balanced designs for AlN barriers structures...

Berland, Kristian; Hyldgaard, Per

2011-01-01T23:59:59.000Z

465

Correlation between Ga-O signature and midgap states at the Al{sub 2}O{sub 3}/In{sub 0.53}Ga{sub 0.47}As interface  

SciTech Connect

Al{sub 2}O{sub 3}/In{sub 0.53}Ga{sub 0.47}As gate stacks were fabricated using different concentrations of NH{sub 4}OH as a pre-deposition treatment. Increased NH{sub 4}OH concentrations significantly reduced the C-V weak inversion hump and the measured near midgap interface states density (D{sub it}). X-ray photoelectron spectroscopy (XPS) studies revealed that these changes in the electrical properties were accompanied by a reduction in the amount of the Ga-O bonding while As-As dimers as well as other XPS detected InGaAs surface species did not correlate with the observed D{sub it} trend. Possible explanations for these findings are suggested.

Krylov, Igor [Russell Berrie Nanotechnology Institute, Technion - Israel Institute of Technology, Haifa 32000 (Israel); Gavrilov, Arkady [Department of Electrical Engineering, Technion - Israel Institute of Technology, Haifa 32000 (Israel); Eizenberg, Moshe [Russell Berrie Nanotechnology Institute, Technion - Israel Institute of Technology, Haifa 32000 (Israel); Department of Materials Engineering, Technion - Israel Institute of Technology, Haifa 32000 (Israel); Ritter, Dan [Russell Berrie Nanotechnology Institute, Technion - Israel Institute of Technology, Haifa 32000 (Israel); Department of Electrical Engineering, Technion - Israel Institute of Technology, Haifa 32000 (Israel)

2012-08-06T23:59:59.000Z

466

Drift velocity of electrons in quantum wells of selectively doped In{sub 0.5}Ga{sub 0.5}As/Al{sub x}In{sub 1-x}As and In{sub 0.2}Ga{sub 0.8}As/Al{sub x}Ga{sub 1-x}As heterostructures in high electric fields  

Science Conference Proceedings (OSTI)

The field dependence of drift velocity of electrons in quantum wells of selectively doped In{sub 0.5}Ga{sub 0.5}As/Al{sub x}In{sub 1-x}As and In{sub 0.2}Ga{sub 0.8}As/Al{sub x}Ga{sub 1-x}As heterostructures is calculated by the Monte Carlo method. The influence of varying the molar fraction of Al in the composition of the Al{sub x}Ga{sub 1-x}As and Al{sub x}In{sub 1-x}As barriers of the quantum well on the mobility and drift velocity of electrons in high electric fields is studied. It is shown that the electron mobility rises as the fraction x of Al in the barrier composition is decreased. The maximum mobility in the In{sub 0.5}Ga{sub 0.5}As/In{sub 0.8}Al{sub 0.2}As quantum wells exceeds the mobility in a bulk material by a factor of 3. An increase in fraction x of Al in the barrier leads to an increase in the threshold field E{sub th} of intervalley transfer (the Gunn effect). The threshold field is E{sub th} = 16 kV/cm in the In{sub 0.5}Ga{sub 0.5}As/Al{sub 0.5}In{sub 0.5}As heterostructures and E{sub th} = 10 kV/cm in the In{sub 0.2}Ga{sub 0.8}As/Al{sub 0.3}Ga{sub 0.7}As heterostructures. In the heterostructures with the lowest electron mobility, E{sub th} = 2-3 kV/cm, which is lower than E{sub th} = 4 kV/cm in bulk InGaAs.

Pozela, J., E-mail: pozela@pfi.lt; Pozela, K.; Raguotis, R.; Juciene, V. [Center for Physical Sciences and Technology, Semiconductor Physics Institute (Lithuania)

2011-06-15T23:59:59.000Z

467