Sample records for hg cn ga

  1. Cn

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

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  2. Ultrasensitive detection of Hg{sup 2+} using oligonucleotide-functionalized AlGaN/GaN high electron mobility transistor

    SciTech Connect (OSTI)

    Cheng, Junjie [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Division of Nanobiomedicine, Key Laboratory for Nano-Bio Interface Research, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Li, Jiadong; Miao, Bin; Wu, Dongmin, E-mail: dmwu2008@sinano.ac.cn [i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Wang, Jine; Pei, Renjun, E-mail: rjpei2011@sinano.ac.cn [Division of Nanobiomedicine, Key Laboratory for Nano-Bio Interface Research, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Wu, Zhengyan, E-mail: zywu@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China)

    2014-08-25T23:59:59.000Z

    An oligonucleotide-functionalized ion sensitive AlGaN/GaN high electron mobility transistor (HEMT) was fabricated to detect trace amounts of Hg{sup 2+}. The advantages of ion sensitive AlGaN/GaN HEMT and highly specific binding interaction between Hg{sup 2+} and thymines were combined. The current response of this Hg{sup 2+} ultrasensitive transistor was characterized. The current increased due to the accumulation of Hg{sup 2+} ions on the surface by the highly specific thymine-Hg{sup 2+}-thymine recognition. The dynamic linear range for Hg{sup 2+} detection has been determined in the concentrations from 10{sup ?14} to 10{sup ?8} M and a detection limit below 10{sup ?14} M level was estimated, which is the best result of AlGaN/GaN HEMT biosensors for Hg{sup 2+} detection till now.

  3. SF6432-CN Construction

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    under the tab titled "Forms" or obtained from the Control : SF 6432-CN Title: Standard Terms and Conditions for Firm-Fixed Price Commercial Construction Contracts Owner:...

  4. MERIT Hg System Design Update

    E-Print Network [OSTI]

    McDonald, Kirk

    of the Latest System · Circular sump tank - Drain at back - Ports for Hg fill, Hg extraction, cylinder vent & Hg discharge are same pipe · Drain & Hg inlet are same pipe · Lugs on cylinders not representative · Current: fused silica backed by lexan · Alternative: Sapphire instead of silica #12;12 OAK RIDGE NATIONAL

  5. High Power Hg Target Conceptual Design Review

    E-Print Network [OSTI]

    McDonald, Kirk

    LABORATORY U. S. DEPARTMENT OF ENERGY Conceptual Design Review 7-8 Feb 05 System Overview Solenoid Proton Alternative Hg Delivery System Hydraulic Fluid Cylinder (3000 psi) Hg Cylinder (1000 psi) Hg Discharge Hg concept & issues · Proposed new baseline delivery system · Hg flow analysis in new baseline system

  6. Supersymmetry and {sup 198}Hg

    SciTech Connect (OSTI)

    Bernards, Christian; Heinze, Stefan; Jolie, Jan; Fransen, Christoph; Linnemann, Andreas; Radeck, Desiree [Institut fuer Kernphysik, Universitaet zu Koeln, Zuelpicher Strasse 77, 50937 Koeln (Germany)

    2009-01-28T23:59:59.000Z

    The energy spectrum and electromagnetic transition properties of the supermultiplet members with two proton fermions can be constructed using the dynamical U{sub v}(6/12) x U{sub {pi}}(6/4) extended supersymmetry. In order to investigate predictions of the two proton fermion--four neutron boson supermultiplet member {sup 198}Hg, an experiment with the HORUS cube {gamma}-ray spectrometer at the Cologne TANDEM accelerator was performed using the {sup 196}Pt({alpha},2n){sup 198}Hg reaction. By analyzing {gamma}{gamma} coincidence spectra and {gamma}{gamma} angular correlations, the required experimental data--level and decay energies, level spins and multipole mixing ratios--could be obtained. For the low-energy states, the experimental data show good agreement with theory.

  7. The new barium zinc mercurides Ba{sub 3}ZnHg{sub 10} and BaZn{sub 0.6}Hg{sub 3.4} - Synthesis, crystal and electronic structure

    SciTech Connect (OSTI)

    Schwarz, Michael; Wendorff, Marco [Institut fuer Anorganische und Analytische Chemie, University of Freiburg, Albertstr. 21, D-79104 Freiburg (Germany)] [Institut fuer Anorganische und Analytische Chemie, University of Freiburg, Albertstr. 21, D-79104 Freiburg (Germany); Roehr, Caroline, E-mail: caroline@ruby.chemie.uni-freiburg.de [Institut fuer Anorganische und Analytische Chemie, University of Freiburg, Albertstr. 21, D-79104 Freiburg (Germany)] [Institut fuer Anorganische und Analytische Chemie, University of Freiburg, Albertstr. 21, D-79104 Freiburg (Germany)

    2012-12-15T23:59:59.000Z

    The title compounds Ba{sub 3}ZnHg{sub 10} and BaZn{sub 0.6}Hg{sub 3.4} were synthesized from stoichiometric ratios of the elements in Ta crucibles. Their crystal structures, which both represent new structure types, have been determined using single crystal X-ray data. The structure of Ba{sub 3}ZnHg{sub 10} (orthorhombic, oP28, space group Pmmn, a=701.2(3), b=1706.9(8), c=627.3(3)pm, Z=2, R1=0.0657) contains folded 4{sup 4} Hg nets, where the meshes form the bases of flat rectangular pyramids resembling the structure of BaAl{sub 4}. The flat pyramids are connected via Hg-Zn/Hg bonds, leaving large channels at the folds, in which Ba(1) and Hg(2) atoms alternate. Whereas the remaining Hg/Zn atoms form a covalent 3D network of three- to five-bonded atoms with short M-M distances (273-301 pm; CN 9-11), the Hg(2) atoms in the channels adopt a comparatively large coordination number of 12 and increased distances (317-348 pm) to their Zn/Hg neighbours. In the structure of BaZn{sub 0.6}Hg{sub 3.4} (cubic, cI320, space group I4{sup Macron }3d, a=2025.50(7) pm, Z=64, R1=0.0440), with a chemical composition not much different from that of Ba{sub 3}ZnHg{sub 10}, the Zn/Hg atoms of the mixed positions M(1/2) are arranged in an slightly distorted primitive cubic lattice with a 4 Multiplication-Sign 4 Multiplication-Sign 4 subcell relation to the unit cell. The 24 of the originating 64 cubes contain planar cis tetramers Hg(5,6){sub 4} with Hg in a nearly trigonal planar or tetrahedral coordination. In another 24 of the small cubes, two opposing faces are decorated by Hg(3,4){sub 2} dumbbells, two by Ba(2) atoms respectively. The third type of small cubes are centered by Ba(1) atoms only. The complex 3D polyanionic Hg/Zn network thus formed is compared with the Hg partial structure in Rb{sub 3}Hg{sub 20} applying a group-subgroup relation. Despite their different overall structures, the connectivity of the negatively charged Hg atoms, the rather metallic Zn bonding characteristic (as obtained from FP-LAPW band structure calculations) and the coordination number of 16 for all Ba cations relate the two title compounds. - Graphical abstract: Six of the 64 small sub-cubes of three types (A, B, C) forming the unit cell of the Hg-rich mercuride BaZn{sub 0.6}Hg{sub 3.4}. Highlights: Black-Right-Pointing-Pointer Two new Hg-rich Ba mercurides, both synthesized from the elements in pure phase. Black-Right-Pointing-Pointer BaZn{sub 0.6}HgG{sub 3.4} and Ba{sub 3}ZnHg{sub 10} with new complex structure types. Black-Right-Pointing-Pointer Structure relation to other complex cubic intermetallics. Black-Right-Pointing-Pointer Discussion of covalent and metallic bonding aspects, as found by the structure features and band structure calculations.

  8. Microsoft Word - Hg.doc

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOEThe Bonneville PowerCherries 82981-1cnHighandSWPA / SPRA / USACE SWPAURTeC:8CO6 Figureand

  9. Reactions of the CN Radical with Benzene and Toluene: Product Detection and Low-Temperature Kinetics

    E-Print Network [OSTI]

    Trevitt, Adam J.

    2010-01-01T23:59:59.000Z

    of the CN Radical with Benzene and Toluene: Productare measured for the CN + benzene and CN + toluene reactionsdetection. The CN + benzene reaction rate coefficient at

  10. Experimental and theoretical study of neutral AlmCn and AlmCnHx clusters

    E-Print Network [OSTI]

    Rocca, Jorge J.

    Cn clusters reacting with H2 gas in a fast flow reactor. The VIEs of AlmCnHx clusters are observed to vary ablation plasma-hydrocarbon reaction, an Al­C ablation plasma reacting with H2 gas, or through cold Alm

  11. Hg System Decommissioning V.B. Graves

    E-Print Network [OSTI]

    McDonald, Kirk

    respiratory protection at all times · Local ventilation in use · Estimate total overflow ~200 ml - Most cleaner storage canister and in plastic intermediate container · Vacuum cleaner and local ventilation · Prepared Hg vacuum cleaner, started cleanup of larger Hg pools then entire local area · Wiped equipment

  12. CERN Hg Jet System V.B. Graves

    E-Print Network [OSTI]

    McDonald, Kirk

    Collaboration Mtg 16 Feb 05 Alternative Hg Delivery System Hydraulic Fluid Cylinder (3000 psi) Hg Cylinder (1000 energy performed on piston = press*area*dist/time 11 Hyd Pump pump inefficiency 8 11 340 340 6 8 Piston Sized for 20sec jet Drain Hg Supply Hg Return Position Sensor Hydraulic Lines Hg Cylinder Vent Line #12

  13. HgTe-low-field Strained HgTe: a textbook 3D topological insulator

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    HgTe-low-field Strained HgTe: a textbook 3D topological insulator Cl´ement Bouvier, Tristan Meunier martyrs 38054 Grenoble Cedex 9, France (Dated: December 9, 2011) Topological insulators can be seen-conductors and topological- insulators, other contributions make transport data more difficult to unravel. This letter

  14. The circumstellar shell of the post-AGB star HD 56126: the $^{12}$CN/$^{13}$CN isotope ratio and fractionation

    E-Print Network [OSTI]

    Eric J. Bakker; David L. Lambert

    1997-11-15T23:59:59.000Z

    We have detected circumstellar absorption lines of the $^{12}$CN and $^{13}$CN Violet and Red System in the spectrum of the post-AGB star HD~56126. From a synthetic spectrum analysis, we derive a Doppler broadening parameter of $b=0.51\\pm0.04$ km~s$^{-1}$, $^{12}$CN/$^{13}$CN$=38\\pm2$, and a lower limit of $2000$ on $^{12}$CN/$^{14}$CN and $^{12}$C$^{14}$N/$^{12}$C$^{15}$N. A simple chemical model has been computed of the circumstellar shell surrounding HD~56126 that takes into account the gas-phase ion-molecule reaction between CN and C$^{+}$. From this we infer that this reaction leads to isotopic fractionation of CN. Taking into account the isotopic exchange reaction and the observed $^{12}$CN/$^{13}$CN we find $^{12}$C/$^{13}$C$\\sim 67$ (for $T_{\\rm kin}=25$ K). Our analysis suggests that $^{12}$CN has a somewhat higher rotational temperature than $^{13}$CN: $T_{\\rm rot}=11.5\\pm0.6$ and $8.0\\pm0.6$ K respectively. We identify possible causes for this difference in excitation temperature, among which the $N''$ dependence of the isotopic exchange reaction.

  15. CN Solar Co Ltd | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov You are beingZealand Jump to:EzfeedflagBiomassSustainable andBucoda,BurkeNebraska:CDMValencia JumpLtdCISCMERI Jump to:CN

  16. Microsoft Word - long-cn.doc

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  17. IAEA-F1-CN69.pdf

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    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOEThe Bonneville PowerCherries 82981-1cnHigh School footballHydrogen andHypernuclei in Hall CIn this

  18. Infrared spectra of ClCN{sup +}, ClNC{sup +}, and BrCN{sup +} trapped in solid neon

    SciTech Connect (OSTI)

    Jacox, Marilyn E.; Thompson, Warren E. [Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8441 (United States)

    2007-06-28T23:59:59.000Z

    When a mixture of ClCN or BrCN with a large excess of neon is codeposited at 4.3 K with a beam of neon atoms that have been excited in a microwave discharge, the infrared spectrum of the resulting solid includes prominent absorptions of the uncharged isocyanide, ClNC or BrNC, and of the corresponding cation, ClCN{sup +} or BrCN{sup +}. The NC-stretching fundamentals of the isocyanides trapped in solid neon lie close to the positions for their previously reported argon-matrix counterparts. The CN-stretching absorptions of ClCN{sup +} and BrCN{sup +} and the CCl-stretching absorption of ClCN{sup +} appear very close to the gas-phase band centers. Absorptions of two overtones and one combination band of ClCN{sup +} are identified. Reversible photoisomerization of ClCN{sup +} to ClNC{sup +} occurs. The two stretching vibrational fundamentals and several infrared and near infrared absorptions associated with electronic transitions of ClNC{sup +} are observed. Minor infrared peaks are attributed to the vibrational fundamental absorptions of the CX and CX{sup +} species (X=Cl,Br)

  19. Dipole Bands in {sup 196}Hg

    SciTech Connect (OSTI)

    Lawrie, J. J.; Lawrie, E. A.; Newman, R. T.; Sharpey-Schafer, J. F.; Smit, F. D. [iThemba LABS, PO Box 722, Somerset West 7129 (South Africa); Msezane, B. [iThemba LABS, PO Box 722, Somerset West 7129 (South Africa); Physics Department, University of Zululand, Private Bag X1001, Kwadlangezwa 3886 (South Africa); Benatar, M.; Mabala, G. K.; Mutshena, K. P. [iThemba LABS, PO Box 722, Somerset West 7129 (South Africa); Physics Department, University of Cape Town, Rondebosch 7700 (South Africa); Federke, M.; Mullins, S. M. [Physics Department, University of Cape Town, Rondebosch 7700 (South Africa); Ncapayi, N. J.; Vymers, P. [iThemba LABS, PO Box 722, Somerset West 7129 (South Africa); Physics Department, University of the Western Cape, Private Bag X17, Belleville 7535 (South Africa)

    2011-10-28T23:59:59.000Z

    High spin states in {sup 196}Hg have been populated in the {sup 198}Pt({alpha},6n) reaction at 65 MeV and the level scheme has been extended. A new dipole band has been observed and a previously observed dipole has been confirmed. Excitation energies, spins and parities of these bands were determined from DCO ratio and linear polarization measurements. Possible quasiparticle excitations responsible for these structures are discussed.

  20. Observation of superdeformation in sup 191 Hg

    SciTech Connect (OSTI)

    Moore, E.F.; Janssens, R.V.F.; Chasman, R.R.; Ahmad, I.; Khoo, T.L.; Wolfs, F.L.H. (Argonne National Laboratory, Argonne, Illinois 60439 (US)); Ye, D. (Argonne National Laboratory, Argonne, Illinois 60439 (US)); Beard, K.B. (Argonne National Laboratory, Argonne, Illinois 60439 (US)); Garg, U. (University of Notre Dame, Notre Dame, Indiana 46556); Drigert, M.W. (Idaho National Engineering Laboratory, EG G Idaho Inc., Idaho Falls, Idaho 83415); and others

    1989-07-24T23:59:59.000Z

    The first observation of superdeformation in the mass region {ital A}{congruent}190 is reported. A rotational band of twelve transitions with an average energy spacing of 37 keV, an average moment of inertia {ital scrF}{sup (2)} of 110 {h bar}{sup 2} MeV{sup {minus}1}, and an average quadrupole moment of 18{plus minus}3 {ital e} b has been observed in {sup 191}Hg; this band persists at low rotational frequency. These results are in excellent agreement with a calculation that predicts an ellipsoidal axis ratio of 1.65:1 for the superdeformed shape in this nucleus.

  1. Process of [sup 196]Hg enrichment

    DOE Patents [OSTI]

    Grossman, M.W.; Mellor, C.E.

    1993-04-27T23:59:59.000Z

    A simple rate equation model shows that by increasing the length of the photochemical reactor and/or by increasing the photon intensity in said reactor, the feedstock utilization of [sup 196]Hg will be increased. Two preferred embodiments of the present invention are described, namely (1) long reactors using long photochemical lamps and vapor filters; and (2) quartz reactors with external UV reflecting films. These embodiments have each been constructed and operated, demonstrating the enhanced utilization process dictated by the mathematical model (also provided).

  2. Process of .sup.196 Hg enrichment

    DOE Patents [OSTI]

    Grossman, Mark W. (Belmont, MA); Mellor, Charles E. (Salem, MA)

    1993-01-01T23:59:59.000Z

    A simple rate equation model shows that by increasing the length of the photochemical reactor and/or by increasing the photon intensity in said reactor, the feedstock utilization of .sup.196 Hg will be increased. Two preferred embodiments of the present invention are described, namely (1) long reactors using long photochemical lamps and vapor filters; and (2) quartz reactors with external UV reflecting films. These embodiments have each been constructed and operated, demonstrating the enhanced utilization process dictated by the mathematical model (also provided).

  3. U01HG004279 (D.M.M.), U01HG004261 (E.L.), U01HG004274 (S.H.), and U41HG004269 (L.S.). Awards

    E-Print Network [OSTI]

    .T.N.), the Indiana Genomics Initiative (T.C.K.), H. Smith and the NIDDK genomics core laboratory (B.O.), NIH R01HG

  4. Improved InGaN/GaN light-emitting diodes with a p-GaN/n-GaN/p-GaN/n-GaN/p-GaN current-

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Improved InGaN/GaN light-emitting diodes with a p-GaN/n-GaN/p-GaN/n-GaN/p-GaN current- spreading experimental and theoretical studies on the InGaN/GaN light-emitting diodes (LEDs) with optical output power and external quantum efficiency (EQE) levels substantially enhanced by incorporating p-GaN/n-GaN/p-GaN/n-GaN/p-GaN

  5. THE LIFETIMES OF NITRILES (CN) AND ACIDS (COOH) DURING ULTRAVIOLET PHOTOLYSIS AND THEIR SURVIVAL IN SPACE

    E-Print Network [OSTI]

    ) versus acetonitrile (CH3CN) and glycine (H2NCH2COOH) versus aminoacetonitrile (H2NCH2CN). We findCOOH) versus acetonitrile (CH3CN) and glycine (H2NCH2COOH) versus amino- acetonitrile (H2NCH2CN). We

  6. lingyy@ruc.edu.cn Web Web Web

    E-Print Network [OSTI]

    DEEP WEB 100872 lingyy@ruc.edu.cn Web Web Web Deep Web Deep Web Deep Web; Web TP391 Entity Identification for Deep Web Data Integration Ling Yan-Yan, Liu Wei, Wang Zhong-Yuan, Ai Nowadays, growing number of Web Databases emerge from the web with their contents duplicated. Two or more

  7. C-DBLPhttp://www.cdblp.cn Web 2008 10 863

    E-Print Network [OSTI]

    C-DBLP: C-DBLPhttp://www.cdblp.cn Web 2008 10 863 "" 2007AA01Z155 Web C-DBLP Community Academic Community Information Management DBLP Computer Science Bibliography DBLP WAMDM 2000 Web Web Web DBLP 2008 WAMDM Web 11 NDBC2000 2008 5 C-DBLP 2008 10 C-DBLP 1 1 C

  8. Abundance analysis of SB2 binary stars with HgMn primaries

    E-Print Network [OSTI]

    T. Ryabchikova

    1998-05-06T23:59:59.000Z

    We present a short review of the abundances in the atmospheres of SB2 systems with Mercury-Manganese (HgMn) primaries. Up to now a careful study has been made for both components of 8 out of 17 known SB2 binaries with orbital periods shorter than 100 days and mass ratio ranging from 1.08 to 2.2. For all eight systems we observe a lower Mn abundance in the secondary's atmospheres than in the primary's. Significant difference in the abundances is also found for some peculiar elements such as Ga, Xe, Pt. All secondary stars with effective temperatures less than 10000 K show abundance characteristics typical of the metallic-line stars.

  9. Compositional depth profiling of TaCN thin films

    SciTech Connect (OSTI)

    Adelmann, Christoph; Conard, Thierry; Franquet, Alexis; Brijs, Bert; Munnik, Frans; Burgess, Simon; Witters, Thomas; Meersschaut, Johan; Kittl, Jorge A.; Vandervorst, Wilfried; Van Elshocht, Sven [Imec, B-3001 Leuven (Belgium); Forschungszentrum Dresden-Rossendorf, D-01314 Dresden (Germany); Oxford Instruments NanoAnalysis, High Wycombe, HP12 3SE (United Kingdom); Imec, B-3001 Leuven (Belgium); Imec, B-3001 Leuven, Belgium and Instituut voor Kern- en Stralingsfysica, Katholieke Universiteit Leuven, B-3001 Leuven (Belgium); Imec, B-3001 Leuven (Belgium)

    2012-07-15T23:59:59.000Z

    The composition profiling of thin TaCN films was studied. For the composition profile determination using x-ray photoemission spectrometry (XPS) in combination with Ar sputtering, preferential sputtering effects of N with respect to Ta and C were found to lead to inaccurate elemental concentrations. Sputter yield calculations for the given experimental conditions allowed for the correction of a part of the error, leading to fair accuracy by reference-free measurements. Further improvement of the accuracy was demonstrated by the calibration of the XPS compositions against elastic recoil detection analysis (ERDA) results. For Auger electron spectrometry (AES) in combination with Ar sputtering, accurate results required the calibration against ERDA. Both XPS and AES allowed for a reliable and accurate determination of the compositional profiles of TaCN-based thin films after calibration. Time-of-flight secondary-ion mass spectrometry was also used to assess the composition of the TaCN films. However, the analysis was hampered by large matrix effects due to small unintentional oxygen contents in the films. Energy-dispersive x-ray spectrometry is also discussed, and it is shown that an accurate reference-free measurement of the average film concentration can be achieved.

  10. Active transport, substrate specificity, and methylation of Hg(II) in anaerobic bacteria

    SciTech Connect (OSTI)

    Schasfer, Jeffra [Princeton University; Rocks, Sara [Princeton University; Zheng, Wang [ORNL; Liang, Liyuan [ORNL; Gu, Baohua [ORNL; Morel, Francois M [ORNL

    2011-01-01T23:59:59.000Z

    The formation of methylmercury (MeHg), which is biomagnified in aquatic food chains and poses a risk to human health, is effected by some iron- and sulfate-reducing bacteria (FeRB and SRB) in anaerobic environments. However, very little is known regarding the mechanism of uptake of inorganic Hg by these organisms, in part because of the inherent difficulty in measuring the intracellular Hg concentration. By using the FeRB Geobacter sulfurreducens and the SRB Desulfovibrio desulfuricans ND132 as model organisms, we demonstrate that Hg(II) uptake occurs by active transport. We also establish that Hg(II) uptake by G. sulfurreducens is highly dependent on the characteristics of the thiols that bind Hg(II) in the external medium, with some thiols promoting uptake and methylation and others inhibiting both. The Hg(II) uptake system of D. desulfuricans has a higher affinity than that of G. sulfurreducens and promotes Hg methylation in the presence of stronger complexing thiols. We observed a tight coupling between Hg methylation and MeHg export from the cell, suggesting that these two processes may serve to avoid the build up and toxicity of cellular Hg. Our results bring up the question of whether cellular Hg uptake is specific for Hg(II) or accidental, occurring via some essential metal importer. Our data also point at Hg(II) complexation by thiols as an important factor controlling Hg methylation in anaerobic environments.

  11. HgMn Stars as apparent X-ray emitters

    E-Print Network [OSTI]

    Hubrig, S; Mathys, G

    1998-01-01T23:59:59.000Z

    In the ROSAT all-sky survey 11 HgMn stars were detected as soft X-ray emitters (Berghoefer, Schmitt & Cassinelli 1996). Prior to ROSAT, X-ray observations with the Einstein Observatory had suggested that stars in the spectral range B5-A7 are devoid of X-ray emission. Since there is no X-ray emitting mechanism available for these stars (also not for HgMn stars), the usual argument in the case of an X-ray detected star of this spectral type is the existence of an unseen low-mass companion which is responsible for the X-ray emission. The purpose of the present work is to use all available data for our sample of X-ray detected HgMn stars and conclude on the nature of possible companions.

  12. On the effect of N-GaN/P-GaN/N-GaN/P-GaN/N-GaN built-in junctions in the n-GaN layer for

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    On the effect of N-GaN/P-GaN/N-GaN/P-GaN/N- GaN built-in junctions in the n-GaN layer for InGaN/GaN: N-GaN/P-GaN/N-GaN/P-GaN/N-GaN (NPNPN-GaN) junctions embedded between the n-GaN region and multiple the performance of InGaN/GaN light emitting diodes (LEDs) in this work. In the proposed architecture, each thin P-GaN

  13. trans-K3[TcO2(CN)4

    SciTech Connect (OSTI)

    Chatterjee, Sayandev; Del Negro, Andrew S.; Edwards, Matthew K.; Twamley, Brendan; Krause, Jeanette A.; Bryan, Samuel A.

    2010-07-14T23:59:59.000Z

    The dioxotetracyanotechnetate anion, [TcO2(CN)4]3-, of the title complex has octahedral symmetry. The technetium is located on a center of inversion and is bound by two oxygen atoms and four cyano ligands. The Tc?O bond distance of 1.7721 (12) Å is consistent with double bond character. The potassium cations [located on special (1/2,0,1) and general positions] reside in octahedral or tetrahedral environments; interionic K···O and K···N interactions occur in the 2.7877 (19)-2.8598 (15) Å range.

  14. Pyrolysis and Combustion of Acetonitrile (CH{sub 3}CN)

    SciTech Connect (OSTI)

    Britt, P.F.

    2002-05-22T23:59:59.000Z

    Acetonitrile (CH{sub 3}CN) is formed from the thermal decomposition of a variety of cyclic, noncyclic, and polymeric nitrogen-containing compounds such as pyrrole and polyacrylonitrile. The pyrolysis and combustion of acetonitrile have been studied over the past 30 years to gain a more detailed understanding of the complex mechanisms involved in the release of nitrogen-containing compounds such as hydrogen cyanide (HCN) in fires and nitrogen oxides (NOx) in coal combustion. This report reviews the literature on the formation of HCN and NOx from the pyrolysis and combustion of acetonitrile and discusses the possible products found in an acetonitrile fire.

  15. IAEA-CN-94/EX/C4-6

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    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOEThe Bonneville PowerCherries 82981-1cnHigh School footballHydrogen andHypernuclei in Hall CIn this issueNews

  16. The new Hg-rich barium indium mercurides BaIn{sub x}Hg{sub 7?x} (x=3.1) and BaIn{sub x}Hg{sub 11?x} (x=0–2.8)

    SciTech Connect (OSTI)

    Wendorff, Marco; Schwarz, Michael; Röhr, Caroline, E-mail: caroline@ruby.chemie.uni-freiburg.de

    2013-07-15T23:59:59.000Z

    The title compounds BaIn{sub x}Hg{sub 7?x} (x=3.1(1)) and BaIn{sub x}Hg{sub 11?x} (x=0–2.8) were synthesized from stoichiometric ratios of the elements in Ta crucibles. Their crystal structures have been determined using single crystal X-ray data. BaIn{sub x}Hg{sub 7?x} (x=3.1(1)) crystallizes in a new structure type (orthorhombic, oC16, space group Cmmm: a=512.02(1), b=1227.68(3), c=668.61(2) pm, Z=2, R1=0.0311). In the structure, the atoms of the three crystallographically different mixed In/Hg positions form planar nets of four-, six- and eight-membered rings. These nets are shifted against each other such that the four-membered rings form empty distorted cubes. The cubes are connected via common edges, corners and folded ladders, which are also found in BaIn{sub 2}/BaHg{sub 2} (KHg{sub 2} structure type) and BaIn (?-NaHg type). The Ba atoms are centered in the eight-membered rings and exhibit an overall coordination number of 20. The [BaM{sub 20}] polyhedra and twice as many distorted [M{sub 8}] cubes tesselate the space. BaIn{sub 2.8}Hg{sub 8.2} (cubic, cP36, space group Pm3{sup ¯}m, a=961.83(1) pm, Z=3, R1=0.0243) is the border compound of the phase width BaIn{sub x}Hg{sub 11?x} of the rare BaHg{sub 11} structure type. In the structure, ideal [M{sub 8}] cubes (at the corners of the unit cell) and BaM{sub 20} polyhedra (at the edges of the unit cell) represent the building blocks comparable to the other new In mercuride. In accordance with the increased In/Hg content, additional M-pure regions appear: the center of the unit cell contains a huge [Hg(1)M(2){sub 12}M(3,4){sub 32}] polyhedron, a Hg-centered cuboctahedron of In/Hg atoms surrounded by a capped cantellated cube of 32 additional M atoms. For both structure types, the bonding situation and the ‘coloring’, i.e. the In/Hg distribution of the polyanionic network, are discussed considering the different sizes of the atoms and the charge distribution (Bader AIM charges), which have been calculated within the framework of FP-LAPW density functional theory. - Graphical abstract: BaIn{sub 2.6}Hg{sub 4.4}: distorted cubes [(In/Hg){sub 8}] (green, like in BaHg{sub 11}), folded ladders (violet, like in BaIn, BaHg{sub 2} and BaIn{sub 2}) and Ba coordination polyhedra [Ba(In/Hg){sub 20}] (blue, like in BaHg{sub 11}). - Highlights: • The Hg-rich In-mercuride BaIn{sub 3.1}Hg{sub 3.9} crystallizes with a singular structure type. • The phase width of the BaHg{sub 11} structure in BaIn{sub x}Hg{sub 11-x} ends at x=2.8. • The relations of both compounds with other alkaline-earth mercurides are outlined. • The Hg/In coloring of the polyanion is discussed considering the structure features. • Bonding aspects are explored using band structure calculations.

  17. Coadsorption of sulfate/bisulfate anions with Hg cations during Hg underpotential deposition on Au(111): An in situ x-ray diffraction study

    SciTech Connect (OSTI)

    Li, J.; Abruna, H.D. [Cornell Univ., Ithaca, NY (United States)] [Cornell Univ., Ithaca, NY (United States)

    1997-01-09T23:59:59.000Z

    The first stage of mercury underpotential deposition on Au(111) electrodes in 0.10 M H{sub 2}SO{sub 4} containing 1.0 mM Hg{sup 2+} has been studied by synchrotron X-ray scattering techniques including grazing incidence X-ray diffraction and specular crystal truncation rod measurements. An ordered coadsorbed structure of sulfate/bisulfate anions and Hg cations was found at potentials between the first and second Hg UPD peaks (+0.80 V > E > +0.88 V vs Ag/AgCl(3 M KCl)). The coadsorption structure was found to consist of a compressed Hg honeycomb lattice with the honeycomb centers occupied by sulfate or bisulfate anions. The compression of the lattice is likely due to the formation of mercurous (Hg{sub 2}{sup 2+}) ions which have a much shorter Hg-Hg distance than that in frozen bulk Hg crystals. The net charge transferred under the first Hg UPD peak suggests that the chemical state of the species in the coadsorbed structure is likely Hg{sub 2}SO{sub 4}. Our results indicate that both the chemical state of the mercury cations and the nature of the anions are important in the resulting electrodeposited structures. 38 refs., 8 figs., 1 tab.

  18. Photoinduced Oxidation of Hg0 in the Waters from the St.

    E-Print Network [OSTI]

    Morel, François M. M.

    -A induced reactions. Doubling UV irradiation did not increase the reaction rate of Hg0 photooxidation food chain. Understanding the parameters that govern Hg0 oxidation is therefore crucial to assess

  19. On-line method of determining utilization factor in Hg-196 photochemical separation process

    DOE Patents [OSTI]

    Grossman, Mark W. (Belmont, MA); Moskowitz, Philip E. (Peabody, MA)

    1992-01-01T23:59:59.000Z

    The present invention is directed to a method for determining the utilization factor [U] in a photochemical mercury enrichment process (.sup.196 Hg) by measuring relative .sup.196 Hg densities using absorption spectroscopy.

  20. Theoretical performance of very long wavelength InAs/InxGa1 xSb superlattice based infrared detectors

    E-Print Network [OSTI]

    Flatte, Michael E.

    , and satellite-based surveillance. Present day infrared detection technology based on bulk Hg1 xCdxTe MCT alloys is facing significant challenges in this spectral region due to i a sensitive dependence of the energy gap tunneling currents. An alter- native infrared system, based on InAs/InxGa1 xSb superlat- tices SLs , shows

  1. Anthropogenic and Natural Emissions of Mercury (Hg) in the northeastern United Jeffrey MacAdam Sigler

    E-Print Network [OSTI]

    Lee, Xuhui

    Abstract Anthropogenic and Natural Emissions of Mercury (Hg) in the northeastern United States impact may depend on the emission rate. Anthropogenic Hg emissions in the United States are poorly characterized. Natural Hg emissions are poorly understood worldwide, due to lack of data or measurement systems

  2. A formula representing Magnetic Berezin Transformsas functions of the Laplacian on Cn

    E-Print Network [OSTI]

    Nour Eddine Askour; Ahmed Intissar; Zouhair Mouayn

    2010-04-17T23:59:59.000Z

    We give a formula that express magnetic Berezin transforms associated with generalized Bargmann-Fock spaces as functions of the Euclidean Laplacian on Cn.

  3. THE SPATIAL DISTRIBUTION OF OH AND CN RADICALS IN THE COMA OF COMET ENCKE

    SciTech Connect (OSTI)

    Ihalawela, Chandrasiri A.; Pierce, Donna M.; Dorman, Garrett R. [Department of Physics and Astronomy, Mississippi State University, P.O. Box 5167, Mississippi State, MS 39762-5167 (United States); Cochran, Anita L., E-mail: cai11@msstate.edu, E-mail: ci856509@ohio.edu, E-mail: dmp149@msstate.edu, E-mail: grd33@msstate.edu, E-mail: anita@barolo.as.utexas.edu [McDonald Observatory, University of Texas at Austin, 1 University Station, C1402, Austin, TX 78712-0259 (United States)

    2011-11-10T23:59:59.000Z

    Multiple potential parent species have been proposed to explain CN abundances in comet comae, but the parent has not been definitively identified for all comets. This study examines the spatial distribution of CN radicals in the coma of comet Encke and determines the likelihood that CN is a photodissociative daughter of HCN in the coma. Comet Encke is the shortest orbital period (3.3 years) comet known and also has a low dust-to-gas ratio based on optical observations. Observations of CN were obtained from 2003 October 22 to 24, using the 2.7 m telescope at McDonald Observatory. To determine the parent of CN, the classical vectorial model was modified by using a cone shape in order to reproduce Encke's highly aspherical and asymmetric coma. To test the robustness of the modified model, the spatial distribution of OH was also modeled. This also allowed us to obtain CN/OH ratios in the coma. Overall, we find the CN/OH ratio to be 0.009 {+-} 0.004. The results are consistent with HCN being the photodissociative parent of CN, but we cannot completely rule out other possible parents such as CH{sub 3}CN and HC{sub 3}N. We also found that the fan-like feature spans {approx}90 Degree-Sign , consistent with the results of Woodney et al..

  4. Synthesis and growth of HgI{sub 2} nanocrystals in a glass matrix: Heat treatment

    SciTech Connect (OSTI)

    Condeles, J. F., E-mail: condeles@fisica.uftm.edu.br, E-mail: ricssilva@yahoo.com.br; Silva, R. S., E-mail: condeles@fisica.uftm.edu.br, E-mail: ricssilva@yahoo.com.br [Departamento de Física, Instituto de Ciências Exatas, Naturais e Educação, Universidade Federal do Triângulo Mineiro, 38025-180, Uberaba, MG (Brazil); Silva, A. C. A.; Dantas, N. O. [Laboratório de Novos Materiais Isolantes e Semicondutores (LNMIS), Instituto de Física, Universidade Federal de Uberlandia, 38400-902, Uberlândia, MG (Brazil)

    2014-08-14T23:59:59.000Z

    Mercury iodide (HgI{sub 2}) nanocrystals (NCs) were successfully grown in a barium phosphate glass matrix synthesized by fusion. Growth control of HgI{sub 2} NCs was investigated by Atomic Force Microscopy (AFM), Optical Absorption (OA), Fluorescence (FL), and X-ray diffraction (XRD). AFM images reveal the formation of HgI{sub 2} nanocrystals in host glass matrix. HgI{sub 2} NCs growth was evidenced by an OA and FL band red-shift with increasing annealing time. XRD measurements revealed the ? crystalline phase of the HgI{sub 2} nanocrystals.

  5. Carrier recombination mechanisms and efficiency droop in GaInN/GaN light-emitting diodes

    SciTech Connect (OSTI)

    Dai, Qi; Shan, Qifeng; Wang, Jing; Chhajed, Sameer; Cho, Jaehee; Schubert, E. Fred; Crawford, Mary H.; Koleske, Daniel D.; Kim, Min-Ho; Park, Yongjo

    2010-01-01T23:59:59.000Z

    We model the carrier recombination mechanisms in GaInN/GaN light-emitting diodes as R=An+Bn{sup 2} +Cn{sup 3} +f(n) , where f(n) represents carrier leakage out of the active region. The term f(n) is expanded into a power series and shown to have higher-than-third-order contributions to the recombination. The total third-order nonradiative coefficient (which may include an f(n) leakage contribution and an Auger contribution) is found to be 8×10{sup ?29} ?cm{sup 6} ?s{sup ?1} . Comparison of the theoretical ABC+f(n) model with experimental data shows that a good fit requires the inclusion of the f(n) term.

  6. CN-Cycle Solar Neutrinos and Sun's Primordial Core Metalicity

    E-Print Network [OSTI]

    W. C. Haxton; A. M. Serenelli

    2008-05-14T23:59:59.000Z

    We argue that it may be possible to exploit neutrinos from the CN cycle and pp chain to determine the primordial solar core abundances of C and N at an interesting level of precision. Such a measurement would allow a comparison of the Sun's deep interior composition with it surface, testing a key assumption of the standard solar model (SSM), a homogeneous zero-age Sun. It would also provide a cross-check on recent photospheric abundance determinations that have altered the once excellent agreement between the SSM and helioseismology. As further motivation, we discuss a speculative possibility in which photospheric abundance/helioseismology puzzle is connected with the solar-system metal differentiation that accompanied formation of the gaseous giant planets. The theoretical relationship between core C and N and the 13N and 15O solar neutrino fluxes can be made more precise (and more general) by making use of the Super-Kamiokande and SNO 8B neutrino capture rates, which calibrate the temperature of the solar core. The primordial C and N abundances can then be obtained from these neutrino fluxes and from a product of nuclear rates, with little residual solar model dependence. We describe some of the recent experimental advances that could allow this comparison to be made (theoretically) at about the 9% level, and note that this uncertainty may be reduced further due to ongoing work on the S-factor for 14N(p,gamma). The envisioned measurement might be possible in deep, large-volume detectors using organic scintillator, e.g., Borexino or SNO+

  7. Advantages of the Blue InGaN/GaN Light-Emitting Diodes with an AlGaN/GaN/AlGaN Quantum Well Structured Electron Blocking Layer

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Advantages of the Blue InGaN/GaN Light-Emitting Diodes with an AlGaN/GaN/AlGaN Quantum Well ABSTRACT: InGaN/GaN light-emitting diodes (LEDs) with p-(AlGaN/GaN/AlGaN) quantum well structured electron. The proposed QWEBL LED structure, in which a p-GaN QW layer is inserted in the p-AlGaN electron blocking layer

  8. Expanded Prussian Blue Analogues Incorporating [Re6Se8(CN)6]3-/4-Clusters: Adjusting Porosity via Charge Balance

    E-Print Network [OSTI]

    Shores, Matthew P.

    Expanded Prussian Blue Analogues Incorporating [Re6Se8(CN)6]3-/4- Clusters: Adjusting Porosity via of octahedral [M(CN)6]3-/4- complexes for the synthesis of microporous Prussian blue type solids with adjustable to be a direct expansion of Prussian blue (Fe4[Fe(CN)6]3,14H2O), with [Re6Se8(CN)6]4- clusters connected through

  9. Micromechanical resonators fabricated from lattice-matched and etch-selective GaAs/InGaP/GaAs heterostructures

    E-Print Network [OSTI]

    Micromechanical resonators fabricated from lattice-matched and etch-selective GaAs/InGaP September 2007 Utilizing lattice-matched GaAs/InGaP/GaAs heterostructures, clean micromechanical resonators are fabricated and characterized. The nearly perfect selectivity of GaAs/InGaP is demonstrated by realizing

  10. Ga nanoparticle-enhanced photoluminescence of GaAs

    SciTech Connect (OSTI)

    Kang, M.; Al-Heji, A. A.; Jeon, S.; Wu, J. H. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Lee, J.-E.; Saucer, T. W.; Zhao, L.; Sih, V. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)] [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States); Katzenstein, A. L. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, Eckerd College, St. Petersburg, Florida 33711-4744 (United States); Sofferman, D. L. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, Adelphi University, Garden City, New York 11530-0701 (United States); Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)

    2013-09-02T23:59:59.000Z

    We have examined the influence of surface Ga nanoparticles (NPs) on the enhancement of GaAs photoluminescence (PL) efficiency. We have utilized off-normal focused-ion-beam irradiation of GaAs surfaces to fabricate close-packed Ga NP arrays. The enhancement in PL efficiency is inversely proportional to the Ga NP diameter. The maximum PL enhancement occurs for the Ga NP diameter predicted to maximize the incident electromagnetic (EM) field enhancement. The PL enhancement is driven by the surface plasmon resonance (SPR)-induced enhancement of the incident EM field which overwhelms the SPR-induced suppression of the light emission.

  11. Processes prevent detrimental effects from As and Hg in feedstocks

    SciTech Connect (OSTI)

    Sarrazin, P.; Cameron, C.J.; Barthel, Y. (Institut Francais du Petrole (IFP), 92 - Rueil-Malmaison (France)); Morrison, M.E. (IFP Enterprises Texas Inc., Houston, TX (United States))

    1993-01-25T23:59:59.000Z

    The wide range of mercury and arsenic species sometimes present in raw condensates or crude oils can cause major problems such as corrosion and reduced catalyst life. This paper reports on simple, low-investment, feedstock treatment procedures which have been developed that eliminate both As and Hg impurities with very high efficiencies. During the past 20 years, refiners and petrochemical producers have experienced a serious increase in catalyst poisoning caused by mercury and arsenic. This phenomenon may be partically explained by the diversification of the feedstock supply resulting from the need to optimize the profitability of refining and petrochemical operations. The utilization of a more diverse feedstock supply containing metal impurities has led to operating problems such as corrosion of aluminum alloys in steam cracker cold boxes.

  12. Optical characteristics of a HgBr excilamp

    SciTech Connect (OSTI)

    Malinina, A A; Malinin, A N; Shuaibov, A K [Uzhgorod National University, Uzhgorod (Ukraine)

    2013-08-31T23:59:59.000Z

    Optical characteristics of a coaxial HgBr excilamp on multicomponent mercury dibromide vapour mixtures with helium, nitrogen and sulfur hexafluoride are investigated under pumping by a pulse-periodic barrier discharge. Stable excilamp operation was demonstrated at a pump pulse repetition rate of 3 – 9 kHz. The component composition of the working system was determined, which provides a maximal average and pulsed specific radiation power of 48.8 mW cm{sup -3} and 40.6 W cm{sup -3}, respectively, at the efficiency of 7.3 % in the blue-green spectral range with the maximal radiation intensity at the wavelength of 502 nm. The reduction in the radiation power after 2.5 × 10{sup 6} shots is 5 %. Interpretation is given for the results of optimisation of excilamp characteristics. (optical radiation sources)

  13. trans-K3[TcO2(CN)4]. | EMSL

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    range. Citation: Chatterjee S, AS Del Negro, MK Edwards, B Twamley, JA Krause, and SA Bryan.2010."trans-K3TcO2(CN)4."Acta Crystallographica. Section E 66(8):i61 - i62....

  14. AlGaN/GaN-based power semiconductor switches

    E-Print Network [OSTI]

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

    2013-01-01T23:59:59.000Z

    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 ...

  15. GaAs/InGaP/AlGaAs quantum-well infrared photodetectors

    SciTech Connect (OSTI)

    Keshagupta, P.; Radpour, F. [Univ. of Cincinnati, OH (United States)

    1994-12-31T23:59:59.000Z

    In this paper, a new quantum-well infrared photodetector (QWIP) based on bound-to-miniband transitions in a GaAs/InGaP quantum well with GaAs/AlGaAs short superlattice barriers is presented and compared with the conventional GaAs/InGaP QWIPs. Results of the theoretical calculations of the detector parameters and the preliminary fabrication results of an embedded-well to miniband (EWTMB) GaAs/InGaP/AlGaAs quantum well/superlattice detector are presented. The advantages of the proposed design include improvement of the material quality, ability to adjust the peak wavelength in 8--12 {micro}m range, and in the lower dark current.

  16. Siemens AG, CT IC 4, H.-G. Zimmermann1 CORPORATETECHNOLOGY

    E-Print Network [OSTI]

    Schmidhuber, Juergen

    © Siemens AG, CT IC 4, H.-G. Zimmermann1 CORPORATETECHNOLOGY System Identification & Forecasting with Advanced Neural Networks Principles, Techniques, Applications Hans Georg Zimmermann Siemens AG Email : Hans_Georg.Zimmermann@siemens.com © Siemens AG, CT IC 4, H.-G. Zimmermann2 CORPORATETECHNOLOGY . . . . ! " i ii wxw 0 w1 wn xn x1 Distinct

  17. Frequency Ratio of ${}^{199}$Hg and ${}^{87}$Sr Optical Lattice Clocks beyond the SI Limit

    E-Print Network [OSTI]

    Yamanaka, Kazuhiro; Ushijima, Ichiro; Takamoto, Masao; Katori, Hidetoshi

    2015-01-01T23:59:59.000Z

    We report on a frequency ratio measurement of a ${}^{199}$Hg-based optical lattice clock referencing a ${}^{87}$Sr-based clock. Evaluations of lattice light shift, including atomic-motion-dependent shift, enable us to achieve a total systematic uncertainty of $7.2 \\times 10^{-17}$ for the Hg clock. The frequency ratio is measured to be $\

  18. INELASTIC NEUTRON SCATTERING SELECTION RULES OF 03B1 HgI2 M. SIESKIND

    E-Print Network [OSTI]

    Boyer, Edmond

    899 INELASTIC NEUTRON SCATTERING SELECTION RULES OF 03B1 HgI2 M. SIESKIND Laboratoire de The inelastic neutron scattering selection rules of 03B1 HgI2 in the directions 0394, 03A3 and 039B are derived Abstracts 63.20D Introduction. - Inelastic neutron scattering is a powerful technique for the determination

  19. SmartHG: Energy Demand Aware Open Services for Smart Grid Intelligent Automation

    E-Print Network [OSTI]

    Tronci, Enrico

    solar panels)], for each time slot (say each hour) the DNO price policy defines an interval of energySmartHG: Energy Demand Aware Open Services for Smart Grid Intelligent Automation Enrico Tronci.prodanovic,jorn.gruber, barry.hayes}@imdea.org I. INTRODUCTION The SmartHG project [1], [2] has the goal of developing

  20. Carrier spin relaxation in GaInNAsSb/GaNAsSb/GaAs quantum well

    SciTech Connect (OSTI)

    Asami, T.; Nosho, H.; Tackeuchi, A. [Department of Applied Physics, Waseda University, Shinjuku, Tokyo 169-8555 (Japan); Li, L. H.; Harmand, J. C. [Laboratory for Photonics and Nanostructures-CNRS, Site Alcatel de Marcoussis, Route de Nozay, 91460 Marcoussis (France); Lu, S. L. [Suzhou Institute of Nano-tech and Nano-bionics, CAS, Dushu, Lake Higher Education Town, Ruoshui Road 398, Suzhou Industrial Park, Suzhou 215125 (China)

    2011-12-23T23:59:59.000Z

    We have investigated the carrier spin relaxation in GaInNAsSb/GaNAsSb/GaAs quantum well (QW) by time-resolved photoluminescence (PL) measurement. The sample consists of an 8-nm-thick GaIn{sub 0.36}N{sub 0.006}AsSb{sub 0.015} well, 5-nm-thick GaN{sub 0.01}AsSb{sub 0.11} intermediate barriers and 100-nm-thick GaAs barriers grown by molecular beam epitaxy on a GaAs(100) substrate. The spin relaxation time and recombination lifetime at 10 K are measured to be 228 ps and 151 ps, respectively. As a reference, we have also obtained a spin relaxation time of 125 ps and a recombination lifetime of 63 ps for GaInNAs/GaNAs/GaAs QW. This result shows that crystal quality is slightly improved by adding Sb, although these short carrier lifetimes mainly originate from a nonradiative recombination. These spin relaxation times are longer than the 36 ps spin relaxation time of InGaAs/InP QWs and shorter than the 2 ns spin relaxation time of GaInNAs/GaAs QW.

  1. Reactions of the CN Radical with Benzene and Toluene: Product Detection and Low-Temperature Kinetics

    SciTech Connect (OSTI)

    Trevitt, Adam J.; Goulay, Fabien; Taatjes, Craig A.; Osborn, David L.; Leone, Stephen R.

    2009-12-23T23:59:59.000Z

    Low temperature rate coefficients are measured for the CN + benzene and CN + toluene reactions using the pulsed Laval nozzle expansion technique coupled with laser-induced fluorescence detection. The CN + benzene reaction rate coefficient at 105, 165 and 295 K is found to be relatively constant over this temperature range, 3.9 - 4.9 x 10-10 cm3 molecule-1 s-1. These rapid kinetics, along with the observed negligible temperature dependence, are consistent with a barrierless reaction entrance channel and reaction efficiencies approaching unity. The CN + toluene reaction is measured to have a slower rate coefficient of 1.3 x 10-10 cm3 molecule-1 s-1 at 105 K. At room temperature, non-exponential decay profiles are observed for this reaction that may suggest significant back-dissociation of intermediate complexes. In separate experiments, the products of these reactions are probed at room temperature using synchrotron VUV photoionization mass spectrometry. For CN + benzene, cyanobenzene (C6H5CN) is the only product recorded with no detectable evidence for a C6H5 + HCN product channel. In the case of CN + toluene, cyanotoluene (NCC6H4CH3) constitutes the only detected product. It is not possible to differentiate among the ortho, meta and para isomers of cyanotoluene because of their similar ionization energies and the ~;; 40 meV photon energy resolution of the experiment. There is no significant detection of benzyl radicals (C6H5CH2) that would suggest a H-abstraction or a HCN elimination channel is prominent at these conditions. As both reactions are measured to be rapid at 105 K, appearing to have barrierless entrance channels, it follows that they will proceed efficiently at the temperatures of Saturn?s moon Titan (~;;100 K) and are also likely to proceed at the temperature of interstellar clouds (10-20 K).

  2. Pressure dependence of the superconducting critical temperature of HgBa 2Ca 2Cu 3O 8 y and HgBa 2Ca 3Cu 4O 10 y up to 30 GPa

    E-Print Network [OSTI]

    Wijngaarden, Rinke J.

    Pressure dependence of the superconducting critical temperature of HgBa 2Ca 2Cu 3O 8 y and HgBa 2Ca of the reported pressure- induced Tc values well above 150 K in the mercury-based high-Tc superconductors has been superconducting transition temperature Tc have been observed in HgBa2Ca2Cu3O8 y Hg-1223 samples under very high

  3. Compositionally-graded InGaAsInGaP alloys and GaAsSb alloys for metamorphic InP on GaAs

    E-Print Network [OSTI]

    Compositionally-graded InGaAs­InGaP alloys and GaAsSb alloys for metamorphic InP on GaAs Li Yang a of tandem graded layers of InGaAs and InGaP with compositional grading of the In concentration. This tandem

  4. Legacy Hg-Cu Contamination of Active Stream Sediments in the Gold Hill Mining District, North Carolina

    E-Print Network [OSTI]

    Lecce, Scott A.

    geoquímicos secundarios, y fuentes de meteorización de minerales. Más del 45 por ciento de la variación de Hg

  5. Low frequency noise in AlGaN/InGaN/GaN double heterostructure field effect transistors

    E-Print Network [OSTI]

    Pala, Nezih

    Torr and consisted of a 1.4 lm undoped GaN buffer layer on i-SiC substrate, * Corresponding authorLow frequency noise in AlGaN/InGaN/GaN double heterostructure field effect transistors N. Pala a November 2002 Abstract Low-frequency noise in AlGaN/InGaN/GaN double heterostructure field effect

  6. Polarization-engineered GaN/InGaN/GaN tunnel diodes

    E-Print Network [OSTI]

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

    2010-08-24T23:59:59.000Z

    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.

  7. MEASURED ENERGY PERFORMANCE OF ENERGY-EFFICIENT NEW COMMERCIAL BUILDINGS: RESULTS FROM THE BECA-CN DATA COMPILATION

    E-Print Network [OSTI]

    Piette, M.A.

    2010-01-01T23:59:59.000Z

    owners to share energy consumption data. In the future wecompare BECA-CN to energy consumption data for conventionalABSTRACT Measured energy consumption data have been compiled

  8. Violet to deep-ultraviolet InGaN/GaN and GaN/AlGaN quantum structures for UV electroabsorption modulators

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Violet to deep-ultraviolet InGaN/GaN and GaN/AlGaN quantum structures for UV electroabsorption In this paper, we present four GaN based polar quantum structures grown on c-plane embedded in p-i-n diode GaN/AlGaN quantum structures for operation in the deep-UV spectral region and the other three

  9. Luminescence Efficiency of InGaN/GaN Quantum Wells on Bulk GaN Substrate M. Dworzak1

    E-Print Network [OSTI]

    Nabben, Reinhard

    Luminescence Efficiency of InGaN/GaN Quantum Wells on Bulk GaN Substrate M. Dworzak1 , T. Stempel1/37, 01-142 Warsaw, Poland ABSTRACT Time-integrated and time-resolved photoluminescence measurements on InGaN quantum wells grown by MOCVD on two different substrates (sapphire and GaN) show that the lumines- cence

  10. Analysis of InGaN light-emitting diodes with GaN-AlGaN and AlGaN-GaN composition-graded barriers

    SciTech Connect (OSTI)

    Yang, Yujue; Wang, Junxi; Li, Jinmin; Zeng, Yiping, E-mail: ypzeng@semi.ac.cn [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

    2014-06-21T23:59:59.000Z

    The effects of InGaN-based light-emitting diodes (LEDs) with Al composition increasing and decreasing GaN-AlGaN barriers along the growth direction are studied numerically. Simulation results suggest that the LEDs with GaN-AlGaN composition-decreased barriers show more significant enhancement of light-output power and internal quantum efficiency than LEDs with composition-increasing GaN-AlGaN barriers when compared with the conventional LED with GaN barriers, due to the improvement in hole injection efficiency and electron blocking capability. Moreover, the optical performance is further improved by replacing GaN-AlGaN barriers with AlGaN-GaN barriers of the same Al composition-decreasing range, which are mainly attributed to the modified band diagrams. In addition, the major causes of the different efficiency droop behaviors for all the designed structures are explained by the electron leakage current and the different increase rates of hole concentration with injection current.

  11. Design and fabrication of InGaN/GaN heterojunction bipolar transistors for microwave power amplifiers

    E-Print Network [OSTI]

    Keogh, David Martin

    2006-01-01T23:59:59.000Z

    T. Henderson, “High- Speed InGaP/GaAs HBT’s Using a SimpleA typical AlGaAs/GaAs HBT or InGaP/GaAs HBT has the opposite

  12. Tailored Macroporous SiCN and SiC Structures for High-Temperature Fuel Reforming**

    E-Print Network [OSTI]

    Kenis, Paul J. A.

    Tailored Macroporous SiCN and SiC Structures for High-Temperature Fuel Reforming** By In-Kyung Sung such as the reforming of hydrocarbon fuels (e.g., die- sel or JP-8) into hydrogen for use in portable power sources the reaction rate of endothermic reactions (such as the steam reforming of hydrocarbons), at the macroscale

  13. Dating the Glass Lake Dugout by Dendrochronology (NY State Museum #CN-37516)

    E-Print Network [OSTI]

    Manning, Sturt

    Dating the Glass Lake Dugout by Dendrochronology (NY State Museum #CN-37516) Carol Griggs, Dendrochronology Lab, Cornell University, cbg4@cornell.edu The Glass Lake Dugout was found at the bottom of Glass for the Glass Lake Dugout (Figure 2B). The series was compared with other site and regional white pine

  14. F1-CN64/GP-2 DEVELOPMENT OF INNOVATIVE FUELLING SYSTEMS

    E-Print Network [OSTI]

    F1-CN64/GP-2 DEVELOPMENT OF INNOVATIVE FUELLING SYSTEMS FOR FUSION ENERGY SCIENCE M. J. Gouge,1 D Development of Innovative Fuelling Systems for Fusion Energy Science Abstract The development of innovative's) complex fuelling needs. For ITER [1] and fusion power plants, the fuelling system has to provide deuterium

  15. C ISOTOPE GRADIENT DERIVED FROM MILLIMETER TRANSITIONS OF CN: THE CASE FOR GALACTIC CHEMICAL EVOLUTION

    E-Print Network [OSTI]

    Ziurys, Lucy M.

    THE 12 C/13 C ISOTOPE GRADIENT DERIVED FROM MILLIMETER TRANSITIONS OF CN: THE CASE FOR GALACTIC kinetic temperature, suggests that chemical fractionation and isotope-selective photodissociation both do be a result of 13 C enrichment since the formation of the solar system, as predicted by recent models. Subject

  16. Pedosphere 20(1): 114, 2010 ISSN 1002-0160/CN 32-1315/P

    E-Print Network [OSTI]

    Ellis, Erle C.

    Published by Elsevier Limited and Science Press Land Use and Soil Organic Carbon in China's Village. Q., Li, H. X. and Ellis, E. C. 2010. Land use and soil organic carbon in China's village landscapesPedosphere 20(1): 1­14, 2010 ISSN 1002-0160/CN 32-1315/P c 2010 Soil Science Society of China

  17. CRADA Identification Number: CN-FY-XXXX Collaborator: [Insert Company Name

    E-Print Network [OSTI]

    CRADA Identification Number: CN-FY-XXXX Collaborator: [Insert Company Name] CRADA Template 10.21.13 Article 1. INTRODUCTION This Cooperative Research and Development Agreement (CRADA) between the National of the Parties in the course of this CRADA is detailed in the Technical Statement of Work (SoW) which is attached

  18. ISSN 1000-9825, CODEN RUXUEW E-mail: jos@iscas.ac.cn Journal of Software, Vol.19, No.2, February 2008, pp.179-193 http://www.jos.org.cn

    E-Print Network [OSTI]

    -10-62562563 © 2008 by Journal of Software. All rights reserved. Web , + , ( , 100872) A Graph-Based Approach for Web Database Sampling LIU Wei, MENG Xiao-Feng+ , LING Yan-Yan (School of Information, Renmin@ruc.edu.cn, http://idke.ruc.edu.cn/xfmeng/ Liu W, Meng XF, Ling YY. A graph-based approach for Web database

  19. Investigation of the GaN-on-GaAs interface for vertical power device applications

    SciTech Connect (OSTI)

    Möreke, Janina, E-mail: janina.moereke@bristol.ac.uk; Uren, Michael J.; Kuball, Martin [H.H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Novikov, Sergei V.; Foxon, C. Thomas [Department of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Hosseini Vajargah, Shahrzad; Wallis, David J.; Humphreys, Colin J. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Haigh, Sarah J. [Super STEM Laboratory, STFC Daresbury Campus, Keckwick Lane, Daresbury WA4 4AD (United Kingdom); School of Materials, University of Manchester, Manchester M13 9PL (United Kingdom); Al-Khalidi, Abdullah; Wasige, Edward; Thayne, Iain [School of Engineering, University of Glasgow, Rankine Bldg, Oakfield Avenue, Glasgow G12 8LT (United Kingdom)

    2014-07-07T23:59:59.000Z

    GaN layers were grown onto (111) GaAs by molecular beam epitaxy. Minimal band offset between the conduction bands for GaN and GaAs materials has been suggested in the literature raising the possibility of using GaN-on-GaAs for vertical power device applications. I-V and C-V measurements of the GaN/GaAs heterostructures however yielded a rectifying junction, even when both sides of the junction were heavily doped with an n-type dopant. Transmission electron microscopy analysis further confirmed the challenge in creating a GaN/GaAs Ohmic interface by showing a large density of dislocations in the GaN layer and suggesting roughening of the GaN/GaAs interface due to etching of the GaAs by the nitrogen plasma, diffusion of nitrogen or melting of Ga into the GaAs substrate.

  20. Ga NMR spectra and relaxation in wurtzite GaN M. Corti and A. Gabetta

    E-Print Network [OSTI]

    Svane, Axel Torstein

    69,71 Ga NMR spectra and relaxation in wurtzite GaN M. Corti and A. Gabetta Department of Physics properties of wurtzite GaN are studied by Ga nuclear magnetic resonance NMR in a GaN bulk crystal containing GaN is a wide band-gap semiconductor which crystallizes in the hexagonal wurtzite structure

  1. Cross-sectional Scanning Tunneling Microscopy and Spectroscopy of InGaP/GaAs Heterojunctions

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Cross-sectional Scanning Tunneling Microscopy and Spectroscopy of InGaP/GaAs Heterojunctions Y Abstract Compositionally abrupt InGaP/GaAs heterojunctions grown by gas-source molecular beam epitaxy have the InGaP layer show non-uniform In and Ga distribution. About 1.5 nm of transition region

  2. Role of Electrochemical Reactions in the Degradation Mechanisms of AlGaN/GaN HEMTs

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    Role of Electrochemical Reactions in the Degradation Mechanisms of AlGaN/GaN HEMTs Feng Gao1, USA tpalacios@mit.edu; (617) 324-2395 Keywords: AlGaN/GaN HEMTs, reliability, moisture, electro-chemical reactions Abstract The nature of structural degradation in AlGaN/GaN high electron mobility transistors

  3. Dopant-Free GaN/AlN/AlGaN Radial Nanowire Heterostructures as High

    E-Print Network [OSTI]

    Li, Yat

    Dopant-Free GaN/AlN/AlGaN Radial Nanowire Heterostructures as High Electron Mobility Transistors, 2006 ABSTRACT We report the rational synthesis of dopant-free GaN/AlN/AlGaN radial nanowire-organic chemical vapor deposition (MOCVD). Transmission electron microscopy (TEM) studies reveal that the GaN/ AlN/AlGaN

  4. Speciation, characterization, and mobility of As, Se, and Hg in flue gas desulphurization residues

    SciTech Connect (OSTI)

    Souhail R. Al-Abed; Gautham Jegadeesan; Kirk G. Scheckel; Thabet Tolaymat [United States Environmental Protection Agency, Cincinnati, OH (United States). National Risk Management Research Laboratory

    2008-03-01T23:59:59.000Z

    Flue gas from coal combustion contains significant amounts of volatile toxic trace elements such as arsenic (As), selenium (Se), and mercury (Hg). The capture of these elements in the flue gas desulphurization (FGD) scrubber unit has resulted in generation of a metal-laden residue. With increasing reuse of the FGD residues in beneficial applications, it is important to determine metal speciation and mobility to understand the environmental impact of its reuse. In this paper, we report the solid phase speciation of As, Se, and Hg in FGD residues using X-ray absorption spectroscopy (XAS), X-ray fluorescence spectroscopy (XRF), and sequential chemical extraction (SCE) techniques. The SCE results combined with XRF data indicated a strong possibility of As association with iron oxides, whereas Se was distributed among all geochemical phases. Hg appeared to be mainly distributed in the strong-complexed phase. XRF images also suggested a strong association of Hg with Fe oxide materials within FGD residues. XAS analysis indicated that As existed in its oxidized state (As(V)), whereas Se and Hg was observed in primarily reduced states as selenite (Se(IV)) and Hg(I), respectively. The results from the SCE and variable pH leaching tests indicated that the labile fractions of As, Se, and Hg were fairly low and thus suggestive of their stability in the FGD residues. However, the presence of a fine fraction enriched in metal content in the FGD residue suggested that size fractionation is important in assessing the environmental risks associated with their reuse. 34 refs., 3 figs., 4 tabs.

  5. Beta decay of Ga-62 

    E-Print Network [OSTI]

    Hyman, BC; Iacob, VE; Azhari, A.; Gagliardi, Carl A.; Hardy, John C.; Mayes, VE; Neilson, RG; Sanchez-Vega, M.; Tang, X.; Trache, L.; Tribble, Robert E.

    2003-01-01T23:59:59.000Z

    We report a study of the beta decay of Ga-62, whose dominant branch is a superallowed 0(+)-->0(+) transition to the ground state of Zn-62. We find the total half-life to be 115.84+/-0.25 ms. This is the first time that the Ga-62 half-life has been...

  6. Influence of GaAs surface termination on GaSb/GaAs quantum dot structure and band offsets

    SciTech Connect (OSTI)

    Zech, E. S.; Chang, A. S.; Martin, A. J.; Canniff, J. C.; Millunchick, J. M. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Lin, Y. H. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)

    2013-08-19T23:59:59.000Z

    We have investigated the influence of GaAs surface termination on the nanoscale structure and band offsets of GaSb/GaAs quantum dots (QDs) grown by molecular-beam epitaxy. Transmission electron microscopy reveals both coherent and semi-coherent clusters, as well as misfit dislocations, independent of surface termination. Cross-sectional scanning tunneling microscopy and spectroscopy reveal clustered GaSb QDs with type I band offsets at the GaSb/GaAs interfaces. We discuss the relative influences of strain and QD clustering on the band offsets at GaSb/GaAs interfaces.

  7. cnEiFrnr,:-BR,1;q*tsE ns John Franks

    E-Print Network [OSTI]

    Short, Daniel

    cnEiFrnr,:- BR,1;q*tsE ns Acid rain John Franks The liDk betwccn sulphur at|d dtrogen odde5 sofe.i,rc fro; th..f..ts torhesethe6xh6ustsofmiilionsol porlol of acid rain, little has been don. Acid rain was mntioned by Bdish chemistRobenAngus Smirhas a factor in lhe air a.ound Manchesterand 'cor

  8. Distribution of the surface potential of epitaxial HgCdTe

    SciTech Connect (OSTI)

    Novikov, V. A., E-mail: novikovvadim@mail.ru; Grigoryev, D. V.; Bezrodnyy, D. A. [Tomsk State University, 634050, 36, Lenina Avenue, Tomsk (Russian Federation); Dvoretsky, S. A. [Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, 630090, 13, pr. Lavrentieva, Novosibirsk (Russian Federation)

    2014-09-08T23:59:59.000Z

    We studied the distribution of surface potential of the Hg{sub 1?x}Cd{sub x}Te epitaxial films grown by molecular beam epitaxy. The studies showed that the variation of the spatial distribution of surface potential in the region of the V-defect can be related to the variation of the material composition of epitaxial film. The V-defect is characterized by increased of Hg content with respect to the composition of the solid solution of Hg{sub 1?x}Cd{sub x}Te epitaxial film. In this paper, it was demonstrated that the unformed V-defects can be observed together with the macroscopic V-defects on the epitaxial film surface. These unformed V-defects can allow the creation of a complex surface potential distribution profile due to the redistribution of the solid solution composition.

  9. Manifold and method of batch measurement of Hg-196 concentration using a mass spectrometer

    DOE Patents [OSTI]

    Grossman, M.W.; Evans, R.

    1991-11-26T23:59:59.000Z

    A sample manifold and method of its use has been developed so that milligram quantities of mercury can be analyzed mass spectroscopically to determine the [sup 196]Hg concentration to less than 0.02 atomic percent. Using natural mercury as a standard, accuracy of [+-]0.002 atomic percent can be obtained. The mass spectrometer preferably used is a commercially available GC/MS manufactured by Hewlett Packard. A novel sample manifold is contained within an oven allowing flow rate control of Hg into the MS. Another part of the manifold connects to an auxiliary pumping system which facilitates rapid clean up of residual Hg in the manifold. Sample cycle time is about 1 hour. 8 figures.

  10. Manifold and method of batch measurement of Hg-196 concentration using a mass spectrometer

    DOE Patents [OSTI]

    Grossman, Mark W. (Belmont, MA); Evans, Roger (N. Hampton, NH)

    1991-01-01T23:59:59.000Z

    A sample manifold and method of its use has been developed so that milligram quantities of mercury can be analyzed mass spectroscopically to determine the .sup.196 Hg concentration to less than 0.02 atomic percent. Using natural mercury as a standard, accuracy of .+-.0.002 atomic percent can be obtained. The mass spectrometer preferably used is a commercially available GC/MS manufactured by Hewlett Packard. A novel sample manifold is contained within an oven allowing flow rate control of Hg into the MS. Another part of the manifold connects to an auxiliary pumping system which facilitates rapid clean up of residual Hg in the manifold. Sample cycle time is about 1 hour.

  11. Size-, shape-, and composition-dependent polarizabilities of SimCn (m, n = 1 - 4) clusters

    E-Print Network [OSTI]

    Lan, You-Zhao

    2011-01-01T23:59:59.000Z

    We theoretically investigate the size-, shape-, and composition-dependent polarizabilities of the SimCn (m, n = 1 - 4) clusters by using the density functional based coupled perturbed Hartree-Fock method. The size-dependence of the polarizabilities of the SimCn (m, n = 1 - 4) clusters is more complicated than that of pure Sim and Cn (m, n = 1 - 8) clusters because for a given cluster size the heteroatomic clusters have more isomers than the homoatomic ones. For the shape-dependence, we consider three kinds of shape, linear (chain), prolate, and compact. For most clusters, we can clearly observe orders of {\\alpha}(linear) > {\\alpha}(prolate) and {\\alpha}(prolate) > {\\alpha}(compact) for a given composition. The composition-dependence of polarizabilities reveals that the linear clusters have an obvious larger polarizability than both the prolate and the compact clusters especially for a given m/n value. The shape effect makes a main contribution to determine the size of the polarizability. To understand the siz...

  12. Study of asymmetric fission yield behavior from neutron-deficient Hg isotope

    SciTech Connect (OSTI)

    Perkasa, Y. S. [Department of Physics, Sunan Gunung Djati State Islamic University Bandung, Jl. A.H Nasution No. 105 Cibiru, Bandung (Indonesia); Waris, A., E-mail: awaris@fi.itb.ac.id; Kurniadi, R., E-mail: awaris@fi.itb.ac.id; Su'ud, Z., E-mail: awaris@fi.itb.ac.id [Nuclear Physics and Biophysics Research Division, Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesa No. 10 Bandung 40132 (Indonesia)

    2014-09-30T23:59:59.000Z

    A study of asymmetric fission yield behavior from a neutron-deficient Hg isotope has been conducted. The fission yield calculation of the neutron-deficient Hg isotope using Brownian Metropolis shape had showed unusual result at decreasing energy. In this paper, this interesting feature will be validated by using nine degree of scission shapes parameterization from Brosa model that had been implemented in TALYS nuclear reaction code. This validation is intended to show agreement between both model and the experiment result. The expected result from these models considered to be different due to dynamical properties that implemented in both models.

  13. Multiple-band-edge quantum-well intermixing in the InGaAs/InGaAsP/InGaP material system

    E-Print Network [OSTI]

    Coldren, Larry A.

    Multiple-band-edge quantum-well intermixing in the InGaAs/InGaAsP/InGaP material system Erik J InGaAs/InGaAsP/InGaP material system. © 2005 American Institute of Physics. DOI: 10 of achieving QWI in such active regions.3,4 However, InGaAs/InGaAsP/InGaP-based de- vices offer numerous

  14. Protonation Studies of the New Iron Carbonyl Cyanide trans-[Fe(CO)3(CN)2]2-: Implications with Respect to Hydrogenases

    E-Print Network [OSTI]

    Rauchfuss, Thomas B.

    , Fe-CO-CN-H species may be considered as minimalist biomimetic models of Fe-only and possibly the [NiFe] hydro- genase features two CN- ligands.8 This logic suggested that the replacement of a further CO by CN indicate extensive -back-bonding in the Fe-CO bond and the predominantly -bond character * Author to whom

  15. GaInNAs laser gain

    SciTech Connect (OSTI)

    CHOW,WENG W.; JONES,ERIC D.; MODINE,NORMAND A.; KURTZ,STEVEN R.; ALLERMAN,ANDREW A.

    2000-05-23T23:59:59.000Z

    The optical gain spectra for GaInNAs/GaAs quantum wells are computed using a microscopic laser theory. From these spectra, the peak gain and carrier radiative decay rate as functions of carrier density are determined. These dependences allow the study of the lasing threshold current density of GaInNAs/GaAs quantum well structures.

  16. Red emitting photonic devices using InGaP/InGaAlP material system

    E-Print Network [OSTI]

    Kangude, Yamini

    2005-01-01T23:59:59.000Z

    In this thesis, two red emitting photonic devices are presented using the InGaP/InGaAlP material system. InGaP/InGaAlP material system provides large flexibility in the band gap energy while being lattice matched to GaAs ...

  17. Electronic structure of the molecule-based magnet MnN,,CN...22 from theory and experiment

    E-Print Network [OSTI]

    Liu, Amy Y.

    of SmCo5 and Nd2Fe14B2.2 For Mn N(CN)2 2, Kurmoo et al.2 report that the structure be- haves as a canted

  18. AlGaAs/InGaAs/AlGaAs Double Barrier

    E-Print Network [OSTI]

    Perera, A. G. Unil

    -state Er. Tunneling Quantum Dot Sensors for Multi-band Infrared and Terahertz Radiation Detection G radiation detection are demonstrated. In T-QDIP structures, photoabsorption takes place in InGaAs QDs (due

  19. Modelling Glass Parisons R.M.M. Mattheij, K. Wang & H.G. ter Morsche

    E-Print Network [OSTI]

    Eindhoven, Technische Universiteit

    Modelling Glass Parisons R.M.M. Mattheij, K. Wang & H.G. ter Morsche EMail: mattheij@win.tue.nl Abstract In order to design better glass products, numerical modelling is essential. In this paper we focus, more specifically, on pressing forms, so called parison, appearing in the produc­ tion of packing glass

  20. 6035 Hg(Ar) Lamp in 6058 Fiber Optic Accessory. Pencil Style Calibration Lamps

    E-Print Network [OSTI]

    Woodall, Jerry M.

    to that of the Hg(Ar) Lamp, which is the characteristic mercury line spectrum. Forced air-cooling (i.e. from of the handle for connection to the power supply. Table 1 Usable Wavelengths of Spectral Calibration Lamps (in.2 1079.8 1084.5 1114.3 Power Supplies; AC versus DC We offer different power supplies for different needs

  1. Composition and Interface Analysis of InGaN/GaN Multiquantum...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Composition and Interface Analysis of InGaNGaN Multiquantum-Wells on GaN Substrates Using Atom Probe Tomography. Composition and Interface Analysis of InGaNGaN Multiquantum-Wells...

  2. Quantum Critical Transition Amplifies Magnetoelastic Coupling in Mn[N(CN)2]2

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Brinzari, T. V.; Chen, P.; Sun, Q.-C.; Liu, J.; Tung, L.-C.; Wang, Y.; Schlueter, J. A.; Singleton, J.; Manson, J. L.; Whangbo, M.-H.; Litvinchuk, A. P.; Musfeldt, J. L.

    2013-06-01T23:59:59.000Z

    We report the discovery of a magnetic quantum critical transition in Mn[N(CN)2]2 that drives the system from a canted antiferromagnetic state to the fully polarized state with amplified magnetoelastic coupling as an intrinsic part of the process. The local lattice distortions, revealed through systematic phonon frequency shifts, suggest a combined MnN6 octahedra distortion+counterrotation mechanism that reduces antiferromagnetic interactions and acts to accommodate the field-induced state. These findings deepen our understanding of magnetoelastic coupling near a magnetic quantum critical point and away from the static limit.

  3. Sub-Doppler Stark Spectroscopy in the A?X (1,0) Band of CN

    SciTech Connect (OSTI)

    Hall, G.E.; Hause, M.L.; Sears, T.J.

    2009-11-26T23:59:59.000Z

    The effect of external electric fields has been measured in hyperfine-resolved sub-Doppler transitions in the A {sup 2}{Pi}-X {sup 2}{Sigma} (1,0) band of the CN radical near 10900 cm{sup -1}. Static electric fields less than 1 kV/cm are sufficient to mix the most closely spaced {Lambda}-dpublets in the A state, leading to Stark spectra with both new and shifted resonances. Simulations of the saturation-dip Stark spectral line profiles allow extraction of the A-state permanent electric dipole moment with a magnitude of 0.06 {+-} 0.02 D.

  4. GaAs, AlGaAs and InGaP Tunnel Junctions for Multi-Junction Solar Cells Under Concentration: Resistance Study

    SciTech Connect (OSTI)

    Wheeldon, Jeffrey F.; Valdivia, Christopher E.; Walker, Alex; Kolhatkar, Gitanja; Hall, Trevor J.; Hinzer, Karin [Centre for Research in Photonics, University of Ottawa, Ottawa, ON (Canada); Masson, Denis; Riel, Bruno; Fafard, Simon [Cyrium Technologies Inc., Ottawa, ON (Canada); Jaouad, Abdelatif; Turala, Artur; Ares, Richard; Aimez, Vincent [Centre de Recherche en Nanofabrication et en Nanocaracterisation CRN2, Universite de Sherbrooke, Sherbrooke, QC (Canada)

    2010-10-14T23:59:59.000Z

    The following four TJ designs, AlGaAs/AlGaAs, GaAs/GaAs, AlGaAs/InGaP and AlGaAs/GaAs are studied to determine minimum doping concentration to achieve a resistance of <10{sup -4} {omega}{center_dot}cm{sup 2} and a peak tunneling current suitable for MJ solar cells up to 1500-suns concentration (operating current of 21 A/cm{sup 2}). Experimentally calibrated numerical models are used to determine how the resistance changes as a function of doping concentration. The AlGaAs/GaAs TJ design is determined to require the least doping concentration to achieve the specified resistance and peak tunneling current, followed by the GaAs/GaAs, and AlGaAs/AlGaAs TJ designs. The AlGaAs/InGaP TJ design can only achieve resistances >5x10{sup -4} {omega}cm{sup 2}.

  5. PRESSURE DEPENDENCE OF OPTICAL TRANSITIONS IN InGaN/GaN MULTIPLE QUANTUM WELLS

    E-Print Network [OSTI]

    McCluskey, Matthew

    -µm thick GaN layer deposited on a sapphire substrate, and it is capped by a 0.2-µm GaN:Mg pPRESSURE DEPENDENCE OF OPTICAL TRANSITIONS IN InGaN/GaN MULTIPLE QUANTUM WELLS W. Shan,* J.W. Ager pressure on optical transitions in InGaN/GaN multiple quantum wells (MQWs) has been studied

  6. Free carrier accumulation at cubic AlGaN/GaN heterojunctions Q. Y. Wei,1

    E-Print Network [OSTI]

    As, Donat Josef

    ) substrate,7 with GaN and AlGaN layer thickness of 600 nm and 30 nm, respectively. The layer thicknessFree carrier accumulation at cubic AlGaN/GaN heterojunctions Q. Y. Wei,1 T. Li,1 J. Y. Huang,1 F. A (Received 24 February 2012; accepted 19 March 2012; published online 3 April 2012) Cubic Al0.3Ga0.7N/GaN

  7. InGaP/GaAs/InGaP double-heterojunction bipolar transistors grown by solid-source molecular-beam epitaxy with a valved phosphorus cracker

    E-Print Network [OSTI]

    Woodall, Jerry M.

    InGaP/GaAs/InGaP double-heterojunction bipolar transistors grown by solid-source molecular; accepted 17 November 1995 The growth and device characterization of an InGaP/GaAs double-quality phosphorus-containing compounds.1­4 The growth of high-performance InGaP/ GaAs and InGaAs/InP single

  8. InGaP/InGaAsN/GaAs NpN double-heterojunction bipolar transistor

    SciTech Connect (OSTI)

    Chang, P. C. [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States); Baca, A. G. [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States); Li, N. Y. [Emcore Photovoltaics, Emcore Corporation, Albuquerque, New Mexico 87123 (United States)] [Emcore Photovoltaics, Emcore Corporation, Albuquerque, New Mexico 87123 (United States); Xie, X. M. [Emcore Photovoltaics, Emcore Corporation, Albuquerque, New Mexico 87123 (United States)] [Emcore Photovoltaics, Emcore Corporation, Albuquerque, New Mexico 87123 (United States); Hou, H. Q. [Emcore Photovoltaics, Emcore Corporation, Albuquerque, New Mexico 87123 (United States)] [Emcore Photovoltaics, Emcore Corporation, Albuquerque, New Mexico 87123 (United States); Armour, E. [Emcore Corporation, Somerset, New Jersey 08873 (United States)] [Emcore Corporation, Somerset, New Jersey 08873 (United States)

    2000-04-17T23:59:59.000Z

    We have demonstrated a functional NpN double-heterojunction bipolar transistor (DHBT) using InGaAsN for the base layer. The InGaP/In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01}/GaAs DHBT has a low V{sub ON} of 0.81 V, which is 0.13 V lower than in a InGaP/GaAs heterojunction bipolar transistor (HBT). The lower turn-on voltage is attributed to the smaller band gap (1.20 eV) of metalorganic chemical vapor deposition-grown In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} base layer. GaAs is used for the collector; thus the breakdown voltage (BV{sub CEO}) is 10 V, consistent with the BV{sub CEO} of InGaP/GaAs HBTs of comparable collector thickness and doping level. To alleviate the current blocking phenomenon caused by the larger conduction band discontinuity between InGaAsN and GaAs, a graded InGaAs layer with {delta} doping is inserted at the base-collector junction. The improved device has a peak current gain of seven with ideal current-voltage characteristics. (c) 2000 American Institute of Physics.

  9. InGaP/InGaAsN/GaAs NpN double heterojunction bipolar transistor

    SciTech Connect (OSTI)

    Chang, P.C.; Baca, A.G.; Li, N.Y.; Xie, X.M.; Sharps, P.R.; Hou, H.Q.

    2000-01-10T23:59:59.000Z

    The authors have demonstrated a functional NpN double heterojunction bipolar transistor (DHBT) using InGaAsN for base layer. The InGaP/In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01}/GaAs DHBT has a low V{sub ON} of 0.81 V, which is 0.13 V lower than in a InGaP/GaAs HBT. The lower V{sub ON} is attributed to the smaller bandgap (E{sub g}=1.20eV) of MOCVD grown In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} base layer. GaAs is used for the collector; thus the BV{sub CEO} is 10 V, consistent with the BV{sub CEO} of InGaP/GaAs Hbts of comparable collector thickness and doping level. To alleviate the current blocking phenomenon caused by the larger {triangle}E{sub C} between InGaAsN and GaAs, a graded InGaAs layer with {delta}-doping is inserted at the base-collector junction. The improved device has a peak current gain of 7 with ideal IV characteristics.

  10. Intrafacet migration effects in InGaN/GaN structures grown on triangular GaN ridges studied by submicron beam x-ray diffraction

    E-Print Network [OSTI]

    Sirenko, Andrei

    Intrafacet migration effects in InGaN/GaN structures grown on triangular GaN ridges studied for x-ray diffraction and reciprocal space mapping of InGaN/GaN multiple-quantum-well MQW structures grown on the sidewalls of 10- m-wide triangular GaN ridges with 1-1.1 facets. Samples were produced

  11. GaN0.011P0.989–GaP Double-Heterostructure Red Light-Emitting Diodes Directly Grown on GaP Substrates

    E-Print Network [OSTI]

    Tu, Charles W

    2000-01-01T23:59:59.000Z

    and C. W. Tu, GaN diodes on GaP substrates, 2000. [7] J. W.on a GaN directly grown on a GaP substrate was successfullyDH) directly a GaN grown on a (100) GaP substrate. Fig. 1(a)

  12. The first direct measurement of 12C(12C,n)23Mg at stellar energies

    E-Print Network [OSTI]

    Bucher, B; Fang, X; Heger, A; Almaraz-Calderon, S; Alongi, A; Ayangeakaa, A D; Beard, M; Best, A; Browne, J; Cahillane, C; Couder, M; deBoer, R J; Kontos, A; Lamm, L; Li, Y J; Long, A; Lu, W; Lyons, S; Notani, M; Patel, D; Paul, N; Pignatari, M; Roberts, A; Robertson, D; Smith, K; Stech, E; Talwar, R; Tan, W P; Wiescher, M; Woosley, S E

    2015-01-01T23:59:59.000Z

    Neutrons produced by the carbon fusion reaction 12C(12C,n)23Mg play an important role in stellar nucleosynthesis. However, past studies have shown large discrepancies between experimental data and theory, leading to an uncertain cross section extrapolation at astrophysical energies. We present the first direct measurement that extends deep into the astrophysical energy range along with a new and improved extrapolation technique based on experimental data from the mirror reaction 12C(12C,p)23Na. The new reaction rate has been determined with a well-defined uncertainty that exceeds the precision required by astrophysics models. Using our constrained rate, we find that 12C(12C,n)23Mg is crucial to the production of Na and Al in Pop-III Pair Instability Supernovae. It also plays a non-negligible role in the production of weak s-process elements as well as in the production of the important galactic gamma-ray emitter 60Fe.

  13. AlGaAs/InGaAsN/GaAs PnP double heterojunction bipolar transistor

    SciTech Connect (OSTI)

    Chang, P.C.; Baca, A.G.; Li, N.Y.; Sharps, P.R.; Hou, H.Q.; Laroche, J.R.; Ren, F.

    2000-01-11T23:59:59.000Z

    The authors have demonstrated a functional MOCVD-grown AlGaAs/InGaAsN/GaAsPnP DHBT that is lattice matched to GaAs and has a peak current gain ({beta}) of 25. Because of the smaller bandgap (E{sub g}=1.20eV)of In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} used for the base layer, this device has a low V{sub ON} of 0.79 V, 0.25 V lower than in a comparable Pnp AlGaAs/GaAs HBT. The BV{sub CEO} is 12 V, consistent with its GaAs collector thickness and doping level.

  14. Asymmetric interfacial abruptness in N-polar and Ga-polar GaN/AlN/GaN heterostructures

    SciTech Connect (OSTI)

    Mazumder, B.; Hurni, C. A.; Zhang, J. Y.; Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Wong, M. H.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

    2012-08-27T23:59:59.000Z

    In this letter, we report on the interfacial abruptness of GaN/AlN/GaN heterostructures with pulsed laser atom probe tomography (APT). The samples were grown by plasma-assisted molecular beam epitaxy (MBE) under both metal-rich and N-rich conditions on both Ga-polar (0001) GaN templates and N-polar (0001) GaN substrates. An NH{sub 3} assisted MBE technique was involved to grow similar Ga-polar and N-polar structures on GaN:Fe substrates and GaN/Al{sub 2}O{sub 3} templates, respectively, for a comparison study. We find in all cases the interface with net positive polarization charge was chemically abrupt, whereas the interface with net negative polarization charge was diffuse. We discuss the implications on device design and performance. These data validate the efficiency of APT in studying interfaces for better performance in devices.

  15. Superior radiation-resistant properties of InGaP/GaAs tandem solar cells

    SciTech Connect (OSTI)

    Yamaguchi, M.; Okuda, T.; Taylor, S.J.; Takamoto, T. [Toyota Technological Institute 2-12-1 Hisakata, Tempaku, Nagoya 468 (Japan)] [Toyota Technological Institute 2-12-1 Hisakata, Tempaku, Nagoya 468 (Japan); Ikeda, E.; Kurita, H. [Central Resource Laboratory, Japan Energy Company, Niizo-Minami, Toda, Saitama 335 (Japan)] [Central Resource Laboratory, Japan Energy Company, Niizo-Minami, Toda, Saitama 335 (Japan)

    1997-03-01T23:59:59.000Z

    The observation of minority-carrier injection-enhanced annealing of radiation damage to InGa{sub 0.5}P{sub 0.5}/GaAs tandem solar cells is reported. Radiation resistance of InGaP/GaAs tandem solar cells as is similar with GaAs-on-Ge cells have been confirmed with 1 MeV electron irradiations. Moreover, minority-carrier injection under light illumination and forward bias conditions is shown to enhance defect annealing in InGaP and to result in the recovery of InGaP/GaAs tandem solar cell properties. These results suggest that the InGaP/GaAs(/Ge) multijunction solar cells and InGaP-based devices have great potential for space applications. {copyright} {ital 1997 American Institute of Physics.}

  16. Three very young HgMn stars in the Orion OB1 Association

    E-Print Network [OSTI]

    Vincent M. Woolf; David L. Lambert

    1999-05-18T23:59:59.000Z

    We report the detection of three mercury-manganese stars in the Orion OB1 association. HD 37886 and BD-0 984 are in the approximately 1.7 million year old Orion OB1b. HD 37492 is in the approximately 4.6 million year old Orion OB1c. Orion OB1b is now the youngest cluster with known HgMn star members. This places an observational upper limit on the time scale needed to produce the chemical peculiarities seen in mercury-manganese stars, which should help in the search for the cause or causes of the peculiar abundances in HgMn and other chemically peculiar upper main sequence stars.

  17. Axi-symmetrical flow reactor for .sup.196 Hg photochemical enrichment

    DOE Patents [OSTI]

    Grossman, Mark W. (Belmont, MA)

    1991-01-01T23:59:59.000Z

    The present invention is directed to an improved photochemical reactor useful for the isotopic enrichment of a predetermined isotope of mercury, especially, .sup.196 Hg. Specifically, two axi-symmetrical flow reactors were constructed according to the teachings of the present invention. These reactors improve the mixing of the reactants during the photochemical enrichment process, affording higher yields of the desired .sup.196 Hg product. Measurements of the variation of yield (Y) and enrichment factor (E) along the flow axis of these reactors indicates very substantial improvement in process uniformity compared to previously used photochemical reactor systems. In one preferred embodiment of the present invention, the photoreactor system was built such that the reactor chamber was removable from the system without disturbing the location of either the photochemical lamp or the filter employed therewith.

  18. Axi-symmetrical flow reactor for [sup 196]Hg photochemical enrichment

    DOE Patents [OSTI]

    Grossman, M.W.

    1991-04-30T23:59:59.000Z

    The present invention is directed to an improved photochemical reactor useful for the isotopic enrichment of a predetermined isotope of mercury, especially, [sup 196]Hg. Specifically, two axi-symmetrical flow reactors were constructed according to the teachings of the present invention. These reactors improve the mixing of the reactants during the photochemical enrichment process, affording higher yields of the desired [sup 196]Hg product. Measurements of the variation of yield (Y) and enrichment factor (E) along the flow axis of these reactors indicates very substantial improvement in process uniformity compared to previously used photochemical reactor systems. In one preferred embodiment of the present invention, the photoreactor system was built such that the reactor chamber was removable from the system without disturbing the location of either the photochemical lamp or the filter employed therewith. 10 figures.

  19. Comparison of Self-Consistent Skyrme and Gogny Calculations for Light Hg Isotopes

    E-Print Network [OSTI]

    M. Warda; A. Staszczak; L. Próchniak

    2011-07-05T23:59:59.000Z

    The ground-state properties of neutron-deficient Hg isotopes have been investigated by the constrained self-consistent Hartree-Fock-Bogoliubov approach with the Skyrme and Gogny effective forces. In the case of the Skyrme interaction we h ave also applied the Hartree-Fock+BCS model with the state-dependent $\\delta$-pairing interaction. Potential energy surfaces and pairing properties have been compared for the both types of forces.

  20. Automated product recovery in a Hg-196 photochemical isotope separation process

    DOE Patents [OSTI]

    Grossman, M.W.; Speer, R.

    1992-07-21T23:59:59.000Z

    A method of removing deposited product from a photochemical reactor used in the enrichment of [sup 196]Hg has been developed and shown to be effective for rapid re-cycling of the reactor system. Unlike previous methods relatively low temperatures are used in a gas and vapor phase process of removal. Importantly, the recovery process is understood in a quantitative manner so that scaling design to larger capacity systems can be easily carried out. 2 figs.

  1. Automated product recovery in a HG-196 photochemical isotope separation process

    DOE Patents [OSTI]

    Grossman, Mark W. (Belmont, MA); Speer, Richard (Reading, MA)

    1992-01-01T23:59:59.000Z

    A method of removing deposited product from a photochemical reactor used in the enrichment of .sup.196 Hg has been developed and shown to be effective for rapid re-cycling of the reactor system. Unlike previous methods relatively low temperatures are used in a gas and vapor phase process of removal. Importantly, the recovery process is understood in a quantitative manner so that scaling design to larger capacity systems can be easily carried out.

  2. Beta decay of Ga-62

    E-Print Network [OSTI]

    Hyman, BC; Iacob, VE; Azhari, A.; Gagliardi, Carl A.; Hardy, John C.; Mayes, VE; Neilson, RG; Sanchez-Vega, M.; Tang, X.; Trache, L.; Tribble, Robert E.

    2003-01-01T23:59:59.000Z

    from the ex- perimental ft value for a 01?01 b decay between analog states with the relation @3# 0556-2813/2003/68~1!/015501~6!/$20.00 68 015501- of 62Ga . Hardy, V. E. Mayes, R. G. Neilson, M. Sanchez-Vega, and R. E. Tribble y, College Station...

  3. Determination of Zn, Pb, Cu, and Hg in soils of Ekpan, Nigeria

    SciTech Connect (OSTI)

    Omgbu, J.A.; Kokogho, M.A. (College of Education, Warri (Nigeria))

    1993-01-01T23:59:59.000Z

    The concentrations of zinc, lead, copper, and mercury in solids in Ekpan were determined in order to assess the impact of petroleum-refining activities. Twenty soil samples were collected 100 m apart (10 topsoils 0 to 15 cm and 10 bottom soils 15 to 30 cm). Sample solutions prepared were analyzed using the atomic absorption spectrophotometry technique. Results show that top-soil samples contain as much as 7.13 to 13.10 [mu]g/g Zn, 55.13 to 65.50 [mu]g/g Pb, 3.47 to 5.27 [mu]g/g Cu, and 4.00 to 6.50 [mu]g.g Hg. Bottom soil samples contain as much as 7.17 to 13.77 [mu]g/g Zn, 54.97 to 63.23 [mu]g/g Pb, 3.57 to 6.50 [mu]/g Cu, and 4.57 to 6.63 [mu]g/g Hg. The levels reported had an abundance ratio in the order Pb > Zn > Hg > Cu in the soil samples. It is recommended that appropriate measures be put in place by the companies to treat waste effluent before discharging them to the immediate environment. 8 refs., 2 tabs.

  4. Homogeneous and Heterogeneous Reaction and Transformation of Hg and Trace Metals in Combustion Systems

    SciTech Connect (OSTI)

    J. Helble; Clara Smith; David Miller

    2009-08-31T23:59:59.000Z

    The overall goal of this project was to produce a working dynamic model to predict the transformation and partitioning of trace metals resulting from combustion of a broad range of fuels. The information provided from this model will be instrumental in efforts to identify fuels and conditions that can be varied to reduce metal emissions. Through the course of this project, it was determined that mercury (Hg) and arsenic (As) would be the focus of the experimental investigation. Experiments were therefore conducted to examine homogeneous and heterogeneous mercury oxidation pathways, and to assess potential interactions between arsenic and calcium. As described in this report, results indicated that the role of SO{sub 2} on Hg oxidation was complex and depended upon overall gas phase chemistry, that iron oxide (hematite) particles contributed directly to heterogeneous Hg oxidation, and that As-Ca interactions occurred through both gas-solid and within-char reaction pathways. Modeling based on this study indicated that, depending upon coal type and fly ash particle size, vaporization-condensation, vaporization-surface reaction, and As-CaO in-char reaction all play a role in arsenic transformations under combustion conditions.

  5. GaN nanowires show more 3D piezoelectricity than bulk GaN

    E-Print Network [OSTI]

    Espinosa, Horacio D.

    Logo GaN nanowires show more 3D piezoelectricity than bulk GaN admin / January 11, 2012 individual gallium nitride (GaN) nanowires showing strong piezoelectric effect in 3D. This is in spite of the fact that each nanowire only measures 100nm in diameter. While GaN is ubiquitous in optoelectronic

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

    E-Print Network [OSTI]

    Saadat, Omair I

    2010-01-01T23:59:59.000Z

    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 ...

  7. Invited Paper GaN HEMT reliability

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    Invited Paper GaN HEMT reliability J.A. del Alamo *, J. Joh Microsystems Technology Laboratories mechanism recently identified in GaN high-electron mobility transistors subject to electrical stress. Under high voltage, it has been found that electrically active defects are generated in the AlGaN barrier

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

    SciTech Connect (OSTI)

    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

    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.

  9. Concurrent Collections (CnC): A new approach to parallel programming

    ScienceCinema (OSTI)

    None

    2011-10-06T23:59:59.000Z

    A common approach in designing parallel languages is to provide some high level handles to manipulate the use of the parallel platform. This exposes some aspects of the target platform, for example, shared vs. distributed memory. It may expose some but not all types of parallelism, for example, data parallelism but not task parallelism. This approach must find a balance between the desire to provide a simple view for the domain expert and provide sufficient power for tuning. This is hard for any given architecture and harder if the language is to apply to a range of architectures. Either simplicity or power is lost. Instead of viewing the language design problem as one of providing the programmer with high level handles, we view the problem as one of designing an interface. On one side of this interface is the programmer (domain expert) who knows the application but needs no knowledge of any aspects of the platform. On the other side of the interface is the performance expert (programmer or program) who demands maximal flexibility for optimizing the mapping to a wide range of target platforms (parallel / serial, shared / distributed, homogeneous / heterogeneous, etc.) but needs no knowledge of the domain. Concurrent Collections (CnC) is based on this separation of concerns. The talk will present CnC and its benefits. About the speaker Kathleen Knobe has focused throughout her career on parallelism especially compiler technology, runtime system design and language design. She worked at Compass (aka Massachusetts Computer Associates) from 1980 to 1991 designing compilers for a wide range of parallel platforms for Thinking Machines, MasPar, Alliant, Numerix, and several government projects. In 1991 she decided to finish her education. After graduating from MIT in 1997, she joined Digital Equipment?s Cambridge Research Lab (CRL). She stayed through the DEC/Compaq/HP mergers and when CRL was acquired and absorbed by Intel. She currently works in the Software and Services Group / Technology Pathfinding and Innovation.

  10. InAs=InGaP=GaAs heterojunction power Schottky rectifiers

    E-Print Network [OSTI]

    Woodall, Jerry M.

    InAs=InGaP=GaAs heterojunction power Schottky rectifiers A. Chen, M. Young and J.M. Woodall A low-matched InGaP on GaAs, to make a high-temperature power rectifier. The LT molecular beam epitaxy technique enables the formation of an abrupt interface between InAs and InGaP. This heterojunction rectifier

  11. Monolithic Millimeter-wave Distributed Amplifiers using AlGaN/GaN HEMTs

    E-Print Network [OSTI]

    York, Robert A.

    Monolithic Millimeter-wave Distributed Amplifiers using AlGaN/GaN HEMTs Rajkumar Santhakumar, Yi have been designed and fabricated using AlGaN/GaN HEMTs. One of them uses a standard HEMT for the unit-gate distributed amplifier achieves a CW peak output power of 1W and a PAE of about 16% at 4GHz. Index Terms -- GaN

  12. Role of strain in polarization switching in semipolar InGaN/GaN quantum wells

    E-Print Network [OSTI]

    Role of strain in polarization switching in semipolar InGaN/GaN quantum wells Qimin Yan,1,a Patrick November 2010 The effect of strain on the valence-band structure of 112¯2 semipolar InGaN grown on GaN D6 is calculated for GaN and InN using density functional theory with the Heyd­Scuseria­ Ernzerhof

  13. GaN/AlGaN heterojunction infrared detector responding in 814 and 2070 m ranges

    E-Print Network [OSTI]

    Perera, A. G. Unil

    GaN/AlGaN heterojunction infrared detector responding in 8­14 and 20­70 m ranges G. Ariyawansa, M October 2006 A GaN/AlGaN heterojunction interfacial work function internal photoemission infrared detector, the work demonstrates 54 m 5.5 THz operation of the detector based on 1s­2p± transition of Si donors in GaN

  14. High-pressure dissociation of silver mercury iodide, Ag{sub 2}HgI{sub 4}

    SciTech Connect (OSTI)

    Parfitt, D.C. [Department of Physics, Oxford University, Parks Road, Oxford OX1 3PU (United Kingdom); Hull, S. [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX (United Kingdom)]. E-mail: s.hull@rl.ac.uk; Keen, D.A. [Department of Physics, Oxford University, Parks Road, Oxford OX1 3PU (United Kingdom); ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX (United Kingdom); Crichton, W. [ESRF, 6 Rue Jules Horowitz, BP 220, 38043 Grenoble CEDEX 9 (France)

    2004-10-01T23:59:59.000Z

    High-pressure X-ray diffraction has been used to probe the behavior of the superionic conductor silver mercury iodide (Ag{sub 2}HgI{sub 4}) at pressures up to 5GPa and at temperatures from 295 to 370K. Significant changes in the diffraction spectra, indicative of structural transitions, are observed around 0.7 and 1.3GPa across the range of temperatures studied. The change at 0.7GPa is shown to correspond to the dissociation of silver mercury iodide into silver iodide and mercury iodide, i.e., Ag{sub 2}HgI{sub 4}->2AgI+HgI{sub 2}. The second transition, at 1.3GPa, is due to a structural phase transition within HgI{sub 2}. Rietveld analysis of the diffraction data is used to confirm and refine all the known crystal structures.

  15. Total and organic Hg concentrations in cephalopods from the North Eastern Atlantic waters: influence of geographical origin and feeding

    E-Print Network [OSTI]

    Boyer, Edmond

    %). With the exception of oceanic squids, the digestive gland globally displayed higher T-Hg concentrations than its toxicity as a result of its enhanced penetration through lipid membranes (Boudou et al. 1983

  16. Biokinetics of Hg and Pb accumulation in the encapsulated egg of the1 common cuttlefish Sepia officinalis: radiotracer experiments2

    E-Print Network [OSTI]

    Boyer, Edmond

    with the32 eggshell indicating that the latter acted as an efficient shield against metal penetration. From the Ocean (Cossa et al., 2002). Hg and Pb are also discharged in coastal waters due to the50 contaminated

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

    SciTech Connect (OSTI)

    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

    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.

  18. Phases of underpotentially deposited Hg on Au(111): An in situ surface X-ray diffraction study

    SciTech Connect (OSTI)

    Li, J.; Abruna, H.D. [Cornell Univ., Ithaca, NY (United States)] [Cornell Univ., Ithaca, NY (United States)

    1997-04-10T23:59:59.000Z

    We report on an in situ surface X-ray diffraction study of the underpotential deposition (UPD) of mercury on Au(111). We have observed three UPD phases present at potentials prior to bulk mercury deposition. These phases consist of two well-ordered intermediate states and what appears to be either a fully discharged two-dimensional liquid Hg layer or a monolayer of an amorphous Hg-Au alloy. Both ordered intermediate phases have hexagonal structures with lattice vectors that are rotated 30{degree} from those of the Au(111) substrate. The first phase (phase I), present at a potential of +0.68 V, was only observed on fresh flame-annealed Au(111) electrodes and appears to be an open incommensurate structure with a lattice constant of 3.86 {+-} 0.03 A. This phase appears to be metastable since it changes to a second ordered phase (phase II) after a certain time. The second phase has a more compact lattice with a = 3.34 {+-} 0.01 A and appears to be a commensurate 2x2 structure with 2/3 of the Hg atoms at threefold hollow sites and 1/3 on atop sites. Similar to the first one, this phase is also metastable and can be transformed to a final, fully discharged, state of a two-dimensional liquid Hg layer or an amorphous Hg-Au alloy. The entire Hg UPD process, from Hg{sup 2+} to the fully discharged metallic Hg layer, agrees well with a multistep mechanism based on previous electrochemical kinetic studies on polycrystalline Au electrodes. 31 refs., 10 figs., 2 tabs.

  19. Growth of AlGaN/GaN heterojunction field effect transistors on semi-insulating GaN using an AlGaN interlayer

    SciTech Connect (OSTI)

    Chen, Z.; Denbaars, S. P. [Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Materials Department, University of California, Santa Barbara, California 93106 (United States); Pei, Y.; Newman, S.; Chu, R.; Brown, D.; Keller, S.; Mishra, U. K. [Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Chung, R.; Nakamura, S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2009-03-16T23:59:59.000Z

    Semi-insulating (SI) GaN layers were grown on 4H-SiC substrates by inserting an AlGaN layer between the AlN buffer and the GaN layer. Secondary ion mass spectroscopy measurements showed that the AlGaN layer prevented Si from diffusing from the substrate into the GaN layer. X-ray diffraction and atomic force microscopy analyses showed that an optimized AlGaN interlayer does not degrade the crystal quality or surface morphology of the SI GaN. The room temperature mobility of an AlGaN/GaN heterostructure using this SI GaN was 2200 cm{sup 2}/V s. High electron mobility transistors (HEMTs) with 0.65 {mu}m long gates were also fabricated on these SI GaN buffers. A power density of 19.0 W/mm with a power added efficiency of 48% was demonstrated at 10 GHz at a drain bias of 78 V. These HEMTs also exhibited sharp pinch off, low leakage, and negligible dispersion.

  20. Strain variations in InGaAsP/InGaP superlattices studied by scanning probe microscopy

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Strain variations in InGaAsP/InGaP superlattices studied by scanning probe microscopy Huajie Chen, Kista, Sweden Abstract Strain-compensated InGaAsP/InGaP superlattices are studied in cross- section. The strain compensated InGaAsP/InGaP/InP superlattices studied here have application for light sources

  1. AlGaN/GaN Metal Oxide Semiconductor Field Effect Transistors using Titanium Dioxide P. J. HANSEN

    E-Print Network [OSTI]

    York, Robert A.

    AlGaN/GaN Metal Oxide Semiconductor Field Effect Transistors using Titanium Dioxide P. J. HANSEN 1 epitaxially on AlGaN/GaN HFET structures by molecular beam epitaxy (MBE). Growth was first performed on GaN templates to establish epitaxial growth conditions. X-ray diffraction showed [001] TiO2 || [1010]GaN

  2. AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors using barium strontium titanate

    E-Print Network [OSTI]

    York, Robert A.

    AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors using barium strontium; published 13 October 2004) Use of high-k gate dielectrics in AlGaN/GaN heterostructure field transconductance and pinchoff voltage. To achieve this, AlGaN/GaN metal-oxide-semiconductor heterostructure field

  3. In this paper, an AlGaN/GaN high electron mobility transistor (HEMT) device based on a

    E-Print Network [OSTI]

    Yang, Kyounghoon

    205 Abstract In this paper, an AlGaN/GaN high electron mobility transistor (HEMT) device basedBm at 2 GHz have been demonstrated from the fabricated device. 1. Introduction In recent years, AlGaN/GaN noise amplifier and switch. Superior results have been reported in microwave power performance of AlGaN/GaN

  4. A New Architecture for AlGaN/GaN HEMT Frequency Doubler Using Active Integrated Antenna Design Approach

    E-Print Network [OSTI]

    Itoh, Tatsuo

    A New Architecture for AlGaN/GaN HEMT Frequency Doubler Using Active Integrated Antenna Design presents a new architecture for an AlGaN/GaN HEMT frequency doubler using the active integrated antenna. The antenna operates as a fundamental frequency reflector in this circuit. Using AlGaN/GaN with 1mm gate

  5. Generation-Recombination Defects In AlGaN/GaN HEMT On SiC Substrate,

    E-Print Network [OSTI]

    Boyer, Edmond

    Generation-Recombination Defects In AlGaN/GaN HEMT On SiC Substrate, Evidenced By Low Frequency Aristide Briand, 92.195 Meudon, France Abstract. Wide bandgap devices such as AlGaN/GaN High Electron of GR- bulges related respectively to AlGaN/GaN interface and quantum well are identified. Each GR

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

    SciTech Connect (OSTI)

    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

    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.

  7. High efficiency InGaP solar cells for InGaP/GaAs tandem cell application

    SciTech Connect (OSTI)

    Takamoto, T.; Ikeda, E.; Kurita, H.; Ohmori, M. [Japan Energy Corp., Toda, Saitama (Japan). Central Research Lab.

    1994-12-31T23:59:59.000Z

    In this paper, high conversion efficiency single junction InGaP solar cells with n-p-p{sup +} structure are presented and their application to InGaP/GaAs monolithic tandem cells is discussed. In the InGaP cells, a best conversion efficiency of 18.48% was achieved by introducing the p{sup +} peak back surface field (BSF) layer with a high carrier concentration of 2 {times} 10{sup 18} cm{sup {minus}3}, which improved both short circuit current (Isc) and open circuit voltage (Voc). However, in the case of InGaP/GaAs tandem cells, a decrease in carrier concentration of the InGaP BSF layer, which was caused by the diffusion of Zn, was found to reduce the Isc and Voc of the tandem cell. The reduction in the carrier concentration was suppressed by using a thicker BSF layer of 0.5 {micro}m, which reduced the current density in the GaAs bottom cell. An InGaP/GaAs tandem cell with 27.3% efficiency and a high Voc of 2.418 V was obtained.

  8. Relaxed, high-quality InP on GaAs by using InGaAs and InGaP graded buffers to avoid phase separation

    E-Print Network [OSTI]

    Relaxed, high-quality InP on GaAs by using InGaAs and InGaP graded buffers to avoid phaseAs was 70% of that on bulk InP at both temperatures. To achieve this, graded buffers in the InGaAs, InGaP

  9. AlGaN/GaN HEMTs grown by Molecular Beam Epitaxy on sapphire, Sic, and HVPE GaN templates

    E-Print Network [OSTI]

    Manfra, Michael J.

    PS-4 AlGaN/GaN HEMTs grown by Molecular Beam Epitaxy on sapphire, Sic, and HVPE GaN templates Nils ABSTRACT Molecular Beam Epitaxy of GaN and related alloys is becoming a rival to the more established, and HVPE SI-GaN templates on sapphire. While sapphire and SI-Sic are established substrates for the growth

  10. ZrO2 gate dielectrics produced by ultraviolet ozone oxidation for GaN and AlGaN/GaN transistors

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    MOSCAP process ?ow: n-GaN substrate; Ohmic metallization andtion for a AlGaN/ GaN HEMT on a substrate which has a poorsapphire substrate, a well-passivated AlGaN/ GaN HEMT grown

  11. Green light emission by InGaN/GaN multiple-quantum-well microdisks

    SciTech Connect (OSTI)

    Hsu, Yu-Chi; Lo, Ikai, E-mail: ikailo@mail.phys.nsysu.edu.tw; Shih, Cheng-Hung; Pang, Wen-Yuan; Hu, Chia-Hsuan; Wang, Ying-Chieh; Tsai, Cheng-Da; Chou, Mitch M. C. [Department of Physics, Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China)] [Department of Physics, Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China); Hsu, Gary Z. L. [United Crystal Corporation, No. 243-3, Wenshan 36061, Miaoli, Taiwan (China)] [United Crystal Corporation, No. 243-3, Wenshan 36061, Miaoli, Taiwan (China)

    2014-03-10T23:59:59.000Z

    The high-quality In{sub x}Ga{sub 1?x}N/GaN multiple quantum wells were grown on GaN microdisks with ?-LiAlO{sub 2} substrate by using low-temperature two-step technique of plasma-assisted molecular beam epitaxy. We demonstrated that the hexagonal GaN microdisk can be used as a strain-free substrate to grow the advanced In{sub x}Ga{sub 1?x}N/GaN quantum wells for the optoelectronic applications. We showed that the green light of 566-nm wavelength (2.192?eV) emitted from the In{sub x}Ga{sub 1?x}N/GaN quantum wells was tremendously enhanced in an order of amplitude higher than the UV light of 367-nm wavelength (3.383?eV) from GaN.

  12. InGaAsN/GaAs heterojunction for multi-junction solar cells

    DOE Patents [OSTI]

    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

    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%.

  13. Resolving Two Closely Overlapping -CN Vibrations and Structure in the Langmuir Monolayer of the Long-Chain Nonadecanenitrile by Polarization Sum Frequency Generation Vibrational Spectroscopy

    SciTech Connect (OSTI)

    Zhang, Zhen; Guo, Yuan; Lu, Zhou; Velarde Ruiz Esparza, Luis A.; Wang, Hongfei

    2012-01-10T23:59:59.000Z

    Polarization sum frequency generation vibrational spectra (SFG-VS) reveals that there are two distinctively different but closely overlapping -CN vibrations at 2244.5 cm{sup -1} and 2251.1 cm{sup -1}, respectively, in the Langmuir monolayer of the long-chain nonadecanenitrile (C18CN, CH{sub 3}(CH{sub 2}){sub 17}CN, or C18CN)at the air/water interface. The blue shifted -CN groups at 2251.1 cm{sup -1} peak is about 1.8 times broader than that of the 2244.5 cm{sup -1}. Both the spectral shift and spectral width are consistent with the picture that this blue shifted peak corresponds to the solvated -CN group; while the 2244.5 cm{sup -1} peak is the signature of the less solvated -CN group. Polarization dependence of these two peaks further suggest that the -CN group corresponding to the 2251.1 cm{sup -1} peak is tilted with an average angle of 50{sup o} from interface normal, where that to the 2244.5 cm{sup -1} peak is tilted with an angle around 67{sup o}. The relative population for the -CN groups corresponding to the 2251.1 cm{sup -1} peak is about three times of that of the 2244.5 cm{sup -1} peak. These results suggest that the -CN head groups in the C18CN Langmuir monolayer are not aligned uniformly at slightly different depth, in order to avoid the strong repulsive forces between the strong -CN dipoles. The SFG-VS spectra of the O-H stretches at C18CN Langmuir monolayer is similar to those of the 4''-n-pentyl-4-cyano-p-terphenyl (5CT) monolayer, indicating complete exclusion of the water molecules from the C18CN Langmuir monolayer, but significantly different from those of the 4''-n-octyl-4-p-cyanobiphenyl (8CB) monolayer, as well as those of the air/acetonitrile aqueous solution interface. Different from previous held understandings, these results suggest that the structure of the insoluble long-chain C18CN Langmuir monolayer is significantly different from that of the Gibbs adsorption layer of the short chain soluble acetonitrile or propanenitrile aqueous solution surfaces. These observations not only shed new light on understanding the detailed structure and interactions in the molecular monolayer and films, but also suggest the importance of the polarization and spectral resolution in the SFG studies.

  14. Preprint version 2011 IEEE International Conference on Robotics and Automation, Shanghai, CN Haptic Teleoperation of Multiple Unmanned Aerial Vehicles

    E-Print Network [OSTI]

    Preprint version 2011 IEEE International Conference on Robotics and Automation, Shanghai, CN Haptic Teleoperation of Multiple Unmanned Aerial Vehicles over the Internet Dongjun Lee, Antonio Franchi, Paolo Robuffo control framework for multiple unmanned aerial vehicles (UAVs) over the Internet, consisting of the three

  15. You will arrive at International Terminal of Haneda Airport. http://www.tokyo-airport-bldg.co.jp/cn/

    E-Print Network [OSTI]

    Hasegawa, Shuji

    You will arrive at International Terminal of Haneda Airport. http://www.tokyo-airport-bldg.co.jp/cn/ http://www.tokyo-airport-bldg.co.jp/kr/ Move to Terminal 1 or 2 (domestic terminal) by free terminal shuttle bus in Airport. Buy a ticket for Monorail and take Monorail to Hamamatsu-Cho Station () (Terminal

  16. PDF versions of previous colloquia and more information can be found in "events" at http://gcosmo.bao.ac.cn/

    E-Print Network [OSTI]

    Tian, Weidong

    -materials and devices, and less well known microwave related research efforts for energy related applications. All://gcosmo.bao.ac.cn/ 2012 37 / Number 37,2012 TIME: Wednesday, 3:00 PM, June 27, 2012 LOCATION: A601 NAOC Microwave are in the area of microwave / millimeter wave / THz devices, circuits, antennas and their applications

  17. IAEA-CN-69/EXP2/12 Highly Radiative Plasmas for Local Transport Studies and Power and Particle

    E-Print Network [OSTI]

    energy production (7.6ÊMJ) in a TFTR pulse. Comparisons of the measured radiated power profiles the severe problem of concentrated power loading of the divertor.Ê[2] Experiments have shown that a large1 IAEA-CN-69/EXP2/12 Highly Radiative Plasmas for Local Transport Studies and Power and Particle

  18. Experimental and Theoretical Examination of C-CN and C-H Bond Activations of Acetonitrile Using Zerovalent Nickel

    E-Print Network [OSTI]

    Jones, William D.

    Experimental and Theoretical Examination of C-CN and C-H Bond Activations of Acetonitrile Using and density functional theory show that the reaction of acetonitrile with a zerovalent nickel bis -nitrile complex and the activation products. The lowest energy transition state is an 3 -acetonitrile

  19. InGaP/GaAs and InGaAs mechanically-stacked triple-junction solar cells

    SciTech Connect (OSTI)

    Takamoto, T.; Ikeda, E.; Agui, T. [Japan Energy Corp., Toda, Saitama (Japan)] [and others

    1997-12-31T23:59:59.000Z

    Triple-junction cells with AM1.5 efficiencies of over 33% have been demonstrated. A planar type InGaP/GaAs monolithic dual-junction cell was fabricated on a semi-insulating FaAs substrate, which has high infra-red transparency. Then a dual-junction cell, with efficiency of 27--28%, was mechanically stacked on an InGaAs cell fabricated on an InP substrate. The bottom InGaAs cell showed an efficiency of 6.2% under the InGaP/GaAs cell, and a total efficiency of 33--34% was achieved for the four-terminal triple-junction cell.

  20. Intrinsic Spin Hall Effect Induced by Quantum Phase Transition in HgCdTe Quantum Wells

    SciTech Connect (OSTI)

    Yang, Wen; Chang, Kai; /Beijing, Inst. Semiconductors; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19T23:59:59.000Z

    Spin Hall effect can be induced both by the extrinsic impurity scattering and by the intrinsic spin-orbit coupling in the electronic structure. The HgTe/CdTe quantum well has a quantum phase transition where the electronic structure changes from normal to inverted. We show that the intrinsic spin Hall effect of the conduction band vanishes on the normal side, while it is finite on the inverted side. This difference gives a direct mechanism to experimentally distinguish the intrinsic spin Hall effect from the extrinsic one.

  1. Quantum Anomalous Hall Effect in Hg_1-yMn_yTe Quantum Wells

    SciTech Connect (OSTI)

    Liu, Chao-Xing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Qi, Xiao-Liang; /Stanford U., Phys. Dept.; Dai, Xi; Fang, Zhong; /Beijing, Inst. Phys.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19T23:59:59.000Z

    The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg{sub 1-y}Mn{sub y}Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the Mn atoms, and the quantized Hall conductance is predicted for a range of quantum well thickness and the concentration of the Mn atoms. This effect enables dissipationless charge current in spintronics devices.

  2. Graphene induced remote surface scattering in graphene/AlGaN/GaN heterostructures

    SciTech Connect (OSTI)

    Liu, Xiwen; Li, Dan; Wang, Bobo; Liu, Bin; Chen, Famin; Jin, Guangri; Lu, Yanwu, E-mail: ywlu@bjtu.edu.cn [Department of Physics, Beijing Jiaotong University, Beijing 100044 (China)

    2014-10-20T23:59:59.000Z

    The mobilities of single-layer graphene combined with AlGaN/GaN heterostructures on two-dimensional electron gases in graphene/AlGaN/GaN double heterojunction are calculated. The impact of electron density in single-layer graphene is also studied. Remote surface roughness (RSR) and remote interfacial charge (RIC) scatterings are introduced into this heterostructure. The mobilities limited by RSR and RIC are an order of magnitude higher than that of interface roughness and misfit dislocation. This study contributes to designing structures for generation of higher electron mobility in graphene/AlGaN/GaN double heterojunction.

  3. Experimental evidence of Ga-vacancy induced room temperature ferromagnetic behavior in GaN films

    SciTech Connect (OSTI)

    Roul, Basanta; Kumar, Mahesh [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India); Central Research Laboratory, Bharat Electronics, Bangalore 560013 (India); Rajpalke, Mohana K.; Bhat, Thirumaleshwara N.; Krupanidhi, S. B. [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India); Kalghatgi, A. T. [Central Research Laboratory, Bharat Electronics, Bangalore 560013 (India); Kumar, Nitesh; Sundaresan, A. [Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P. O., Bangalore 560064 (India)

    2011-10-17T23:59:59.000Z

    We have grown Ga deficient GaN epitaxial films on (0001) sapphire substrate by plasma-assisted molecular beam epitaxy and report the experimental evidence of room temperature ferromagnetic behavior. The observed yellow emission peak in room temperature photoluminescence spectra and the peak positioning at 300 cm{sup -1} in Raman spectra confirms the existence of Ga vacancies. The x-ray photoelectron spectroscopic measurements further confirmed the formation of Ga vacancies; since the N/Ga is found to be >1. The ferromagnetism is believed to originate from the polarization of the unpaired 2p electrons of N surrounding the Ga vacancy.

  4. Ultra-Thin, Triple-Bandgap GaInP/GaAs/GaInAs Monolithic Tandem Solar Cells

    SciTech Connect (OSTI)

    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.

    2007-02-01T23:59:59.000Z

    The performance of state-of-the-art, series-connected, lattice-matched (LM), triple-junction (TJ), III-V tandem solar cells could be improved substantially (10-12%) by replacing the Ge bottom subcell with a subcell having a bandgap of {approx}1 eV. For the last several years, research has been conducted by a number of organizations to develop {approx}1-eV, LM GaInAsN to provide such a subcell, but, so far, the approach has proven unsuccessful. Thus, the need for a high-performance, monolithically integrable, 1-eV subcell for TJ tandems has remained. In this paper, we present a new TJ tandem cell design that addresses the above-mentioned problem. Our approach involves inverted epitaxial growth to allow the monolithic integration of a lattice-mismatched (LMM) {approx}1-eV GaInAs/GaInP double-heterostructure (DH) bottom subcell with LM GaAs (middle) and GaInP (top) upper subcells. A transparent GaInP compositionally graded layer facilitates the integration of the LM and LMM components. Handle-mounted, ultra-thin device fabrication is a natural consequence of the inverted-structure approach, which results in a number of advantages, including robustness, potential low cost, improved thermal management, incorporation of back-surface reflectors, and possible reclamation/reuse of the parent crystalline substrate for further cost reduction. Our initial work has concerned GaInP/GaAs/GaInAs tandem cells grown on GaAs substrates. In this case, the 1-eV GaInAs experiences 2.2% compressive LMM with respect to the substrate. Specially designed GaInP graded layers are used to produce 1-eV subcells with performance parameters nearly equaling those of LM devices with the same bandgap (e.g., LM, 1-eV GaInAsP grown on InP). Previously, we reported preliminary ultra-thin tandem devices (0.237 cm{sup 2}) with NREL-confirmed efficiencies of 31.3% (global spectrum, one sun) (1), 29.7% (AM0 spectrum, one sun) (2), and 37.9% (low-AOD direct spectrum, 10.1 suns) (3), all at 25 C. Here, we include recent results of testing similar devices under the concentrated AMO spectrum, and also present the first demonstration of a high-efficiency, ultra-thin GaInP/GaAs/GaInAs tandem cell processed on a flexible kapton handle.

  5. September 16-21, 2007 Las Vegas, Nevada Gate recess technology on AlGaN/GaN HFET with InGaN as etch-stop layer

    E-Print Network [OSTI]

    Pala, Nezih

    0 2 V(V) C(pF) Before etching (material) After etching (device) G AlGaN substrate i-GaN DS AlN AlGaN substrate AlN i-GaN AlGaN S G DAlGaNAlGaN InGaNInGaN Standard gate recess InGaN stop layer gate recess InGaNICNS 7 September 16-21, 2007 ­ Las Vegas, Nevada Gate recess technology on AlGaN/GaN HFET with InGaN

  6. Rutile films grown by molecular beam epitaxy on GaN and AlGaN/GaN P. J. Hansen

    E-Print Network [OSTI]

    York, Robert A.

    Rutile films grown by molecular beam epitaxy on GaN and AlGaN/GaN P. J. Hansen Materials Department March 2005 Titanium dioxide TiO2, with the rutile structure was grown on 0001 oriented GaN and 0001 Al0.33Ga0.67N/GaN heterostructure field effect transistor HFET structures by molecular beam epitaxy. X

  7. Single-Wire Light-Emitting Diodes Based on GaN Wires Containing Both Polar and Nonpolar InGaN/GaN Quantum Wells

    E-Print Network [OSTI]

    Single-Wire Light-Emitting Diodes Based on GaN Wires Containing Both Polar and Nonpolar InGaN/GaN based on radial p­i­n multi quantum well (QW) junctions have been realized from GaN wires grown by catalyst- free metal organic vapor phase epitaxy. The Inx Ga1Àx N/GaN undoped QW system is coated over both

  8. High density plasma damage in InGaP/GaAs as AlGaAs/GaAs high electron mobility transistors

    SciTech Connect (OSTI)

    Lee, J.W.; Pearton, S.J. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Ren, F.; Kopf, R.F.; Kuo, J.M. [Bell Labs., Murray Hill, NJ (United States). Lucent Technologies; Shul, R.J. [Sandia National Labs., Albuquerque, NM (United States); Constantine, C.; Johnson, D. [Plasma-Therm Inc., St. Petersburg, FL (United States)

    1998-11-01T23:59:59.000Z

    The introduction of plasma damage in InGaP/GaAs and AlGaAs/GaAs high electron mobility transistors (HEMTs) has been investigated using both inductively coupled plasma and electron cyclotron resonance Ar discharges. The saturated drain-source current is found to be decreased through introduction of compensating deep levels into the InGaP or AlGaAs donor layer. The degradation of device performance is a strong function of ion energy and ion flux, and an advantage of both high density plasma tools is that ion energy can be reduced by increasing the plasma density. Increasing process pressure and source power, and decreasing radio-frequency chuck power produce the lowest amounts of plasma damage in HEMTs.

  9. Total eclipse of the heart: The AM CVn Gaia14aae / ASSASN-14cn

    E-Print Network [OSTI]

    Campbell, H C; Fraser, M; Hodgkin, S T; de Miguel, E; Gänsicke, B T; Steeghs, D; Hourihane, A; Breedt, E; Littlefair, S P; Koposov, S E; Wyrzykowski, L; Altavilla, G; Blagorodnova, N; Clementini, G; Damljanovic, G; Delgado, A; Dennefeld, M; Drake, A J; Fernández-Hernández, J; Gilmore, G; Gualandi, R; Hamanowicz, A; Handzlik, B; Hardy, L K; Harrison, D L; Ilkiewicz, K; Jonker, P G; Kochanek, C S; Kolaczkowski, Z; Kostrzewa-Rutkowska, Z; Kotak, R; van Leeuwen, G; Leto, G; Ochner, P; Pawlak, M; Palaversa, L; Rixon, G; Rybicki, K; Shappee, B J; Smartt, S J; Torres, M A P; Tomasella, L; Turatto, M; Ulaczyk, K; van Velzen, S; Vince, O; Walton, N A; Wielgórski, P; Wevers, T; Whitelock, P; Yoldas, A; De Angeli, F; Burgess, P; Busso, G; Busuttil, R; Butterley, T; Chambers, K C; Copperwheat, C; Danilet, A B; Dhillon, V S; Evans, D W; Eyer, L; Froebrich, D; Gomboc, A; Holland, G; Holoien, T W -S; Jarvis, J F; Kaiser, N; Kann, D A; Koester, D; Kolb, U; Komossa, S; Magnier, E A; Mahabal, A; Polshaw, J; Prieto, J L; Prusti, T; Riello, M; Scholz, A; Simonian, G; Stanek, K Z; Szabados, L; Waters, C; Wilson, R W

    2015-01-01T23:59:59.000Z

    We report the discovery and characterisation of a deeply eclipsing AM CVn-system, Gaia14aae (= ASSASN-14cn). Gaia14aae was identified independently by the All-Sky Automated Survey for Supernovae (ASAS-SN; Shappee et al. 2014) and by the Gaia Science Alerts project, during two separate outbursts. A third outburst is seen in archival Pan-STARRS-1 (PS1; Schlafly et al. 2012; Tonry et al. 2012; Magnier et al. 2013) and ASAS-SN data. Spectroscopy reveals a hot, hydrogen-deficient spectrum with clear double-peaked emission lines, consistent with an accreting double degenerate classification. We use follow-up photometry to constrain the orbital parameters of the system. We find an orbital period of 49.71 min, which places Gaia14aae at the long period extremum of the outbursting AM CVn period distribution. Gaia14aae is dominated by the light from its accreting white dwarf. Assuming an orbital inclination of 90 degrees for the binary system, the contact phases of the white dwarf lead to lower limits of 0.78 M solar an...

  10. Pressure-Induced Enhanced Magnetic Anisotropy in Mn(N(CN)2)2

    SciTech Connect (OSTI)

    Quintero, P. A. [University of Florida, Gainesville; Rajan, D. [University of Florida, Gainesville; Peprah, M. K. [University of Florida, Gainesville; Brinzari, T. V. [University of Florida, Gainesville; Fishman, Randy Scott [ORNL; Talham, Daniel R. [University of Florida, Gainesville; Meisel, Mark W. [University of Florida, Gainesville

    2015-01-01T23:59:59.000Z

    Using DC and AC magnetometry, the pressure dependence of the magnetization of the threedimensional antiferromagnetic coordination polymer Mn(N(CN)2)2 was studied up to 12 kbar and down to 8 K. The magnetic transition temperature, Tc, increases dramatically with applied pressure (P), where a change from Tc(P = ambient) = 16:0 K to Tc(P = 12:1 kbar) = 23:5 K was observed. In addition, a marked difference in the magnetic behavior is observed above and below 7.1 kbar. Specifically, for P < 7:1 kbar, the differences between the field-cooled and zero-field-cooled (fc-zfc) magnetizations, the coercive field, and the remanent magnetization decrease with increasing pressure. However, for P > 7:1 kbar, the behavior is inverted. Additionally, for P > 8:6 kbar, minor hysteresis loops are observed. All of these effects are evidence of the increase of the superexchange interaction and the appearance of an enhanced exchange anisotropy with applied pressure.

  11. Comparison of compressive and tensile relaxed composition-graded GaAsP and ,,Al...InGaP substrates

    E-Print Network [OSTI]

    Comparison of compressive and tensile relaxed composition-graded GaAsP and ,,Al...InGaP substrates, around 104 cm-2 . The structures, grown on GaP or GaAs, consist of graded In-fraction InGaP and AlInGaP. High surface roughness and branch defects in Al InGaP lead to the lowest quality virtual substrates we

  12. Carrier Dynamics in InGaN/GaN SQW Structure Probed by the Transient Grating Method

    E-Print Network [OSTI]

    Okamoto, Koichi

    Carrier Dynamics in InGaN/GaN SQW Structure Probed by the Transient Grating Method; 78.55.Cr; 78.67.De; S7.14 Carrier dynamics in GaN and InGaN/GaN SQW structures were observed by using inhomogeneity of In composition. Recently, InGaN/GaN-based light emitting diodes (LEDs) have been commercialized

  13. N-Face GaN/AlGaN HEMTs Fabricated Through Layer Transfer Technology

    E-Print Network [OSTI]

    Chung, Jinwook

    We present a new method to fabricate N-face GaN/AlGaN high electron mobility transistors (HEMTs). These devices are extremely promising for ultrahigh frequency applications where low contact resistances and excellent carrier ...

  14. Development and Industrialization of InGaN/GaN LEDs on Patterned...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    of InGaNGaN LEDs on Patterned Sapphire Substrates for Low Cost Emitter Architecture Development and Industrialization of InGaNGaN LEDs on Patterned Sapphire...

  15. Breakdown mechanism in AlGaN/GaN HEMTs on Si substrate

    E-Print Network [OSTI]

    Lu, Bin

    AlGaN/GaN high electron mobility transistors (HEMTs) grown on Si substrates have attracted a great interest for power electronics applications. Despite the low cost of the Si substrate, the breakdown voltage (V[subscript ...

  16. Report on International Collaboration Involving the FE Heater and HG-A Tests at Mont Terri

    SciTech Connect (OSTI)

    Houseworth, Jim; Rutqvist, Jonny; Asahina, Daisuke; Chen, Fei; Vilarrasa, Victor; Liu, Hui-Hai; Birkholzer, Jens

    2013-11-06T23:59:59.000Z

    Nuclear waste programs outside of the US have focused on different host rock types for geological disposal of high-level radioactive waste. Several countries, including France, Switzerland, Belgium, and Japan are exploring the possibility of waste disposal in shale and other clay-rich rock that fall within the general classification of argillaceous rock. This rock type is also of interest for the US program because the US has extensive sedimentary basins containing large deposits of argillaceous rock. LBNL, as part of the DOE-NE Used Fuel Disposition Campaign, is collaborating on some of the underground research laboratory (URL) activities at the Mont Terri URL near Saint-Ursanne, Switzerland. The Mont Terri project, which began in 1995, has developed a URL at a depth of about 300 m in a stiff clay formation called the Opalinus Clay. Our current collaboration efforts include two test modeling activities for the FE heater test and the HG-A leak-off test. This report documents results concerning our current modeling of these field tests. The overall objectives of these activities include an improved understanding of and advanced relevant modeling capabilities for EDZ evolution in clay repositories and the associated coupled processes, and to develop a technical basis for the maximum allowable temperature for a clay repository. The R&D activities documented in this report are part of the work package of natural system evaluation and tool development that directly supports the following Used Fuel Disposition Campaign (UFDC) objectives: ? Develop a fundamental understanding of disposal-system performance in a range of environments for potential wastes that could arise from future nuclear-fuel-cycle alternatives through theory, simulation, testing, and experimentation. ? Develop a computational modeling capability for the performance of storage and disposal options for a range of fuel-cycle alternatives, evolving from generic models to more robust models of performance assessment. For the purpose of validating modeling capabilities for thermal-hydro-mechanical (THM) processes, we developed a suite of simulation models for the planned full-scale FE Experiment to be conducted in the Mont Terri URL, including a full three-dimensional model that will be used for direct comparison to experimental data once available. We performed for the first time a THM analysis involving the Barcelona Basic Model (BBM) in a full three-dimensional field setting for modeling the geomechanical behavior of the buffer material and its interaction with the argillaceous host rock. We have simulated a well defined benchmark that will be used for codeto- code verification against modeling results from other international modeling teams. The analysis highlights the complex coupled geomechanical behavior in the buffer and its interaction with the surrounding rock and the importance of a well characterized buffer material in terms of THM properties. A new geomechanical fracture-damage model, TOUGH-RBSN, was applied to investigate damage behavior in the ongoing HG-A test at Mont Terri URL. Two model modifications have been implemented so that the Rigid-Body-Spring-Network (RBSN) model can be used for analysis of fracturing around the HG-A microtunnel. These modifications are (1) a methodology to compute fracture generation under compressive stress conditions and (2) a method to represent anisotropic elastic and strength properties. The method for computing fracture generation under compressive load produces results that roughly follow trends expected for homogeneous and layered systems. Anisotropic properties for the bulk rock were represented in the RBSN model using layered heterogeneity and gave bulk material responses in line with expectations. These model improvements were implemented for an initial model of fracture damage at the HG-A test. While the HG-A test model results show some similarities with the test observations, differences between the model results and observations remain.

  17. Siemens Pittsburgh, PA Novelis Corporation Atlanta, GA

    E-Print Network [OSTI]

    McGaughey, Alan

    Industrial Design ­ Shanghai, China Eaton Corporation ­ Pittsburgh, PA CMU, CTTEC ­ PittsburghSiemens ­ Pittsburgh, PA Novelis Corporation ­ Atlanta, GA Expense

  18. Strain-balanced InGaN/GaN multiple quantum wells

    SciTech Connect (OSTI)

    Van Den Broeck, D. M.; Hosalli, A. M.; Bedair, S. M. [Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Bharrat, D.; El-Masry, N. A. [Department of Material Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2014-07-21T23:59:59.000Z

    InGaN/GaN multiple quantum well (MQW) structures suffer from a high amount of compressive strain in the InGaN wells and the accompanied piezoelectric field resulting in both a blue shift in emission and a reduction of emission intensity. We report the growth of In{sub x}Ga{sub 1?x}N/GaN “strain-balanced” multiple quantum wells (SBMQWs) grown on thick In{sub y}Ga{sub 1?y}N templates for x?>?y by metal organic chemical vapor deposition. SBMQWs consist of alternating layers of In{sub x}Ga{sub 1?x}N wells and GaN barriers under compressive and tensile stress, respectively, which have been lattice matched to a thick In{sub y}Ga{sub 1?y}N template. Growth of the In{sub y}Ga{sub 1?y}N template is also detailed in order to achieve thick, relaxed In{sub y}Ga{sub 1?y}N grown on GaN without the presence of V-grooves. When compared to conventional In{sub x}Ga{sub 1?x}N/GaN MQWs grown on GaN, the SBMQW structures exhibit longer wavelength emission and higher emission intensity for the same InN mole fraction due to a reduction in the well strain and piezoelectric field. By matching the average lattice constant of the MQW active region to the lattice constant of the In{sub y}Ga{sub 1?y}N template, essentially an infinite number of periods can be grown using the SBMQW growth method without relaxation-related effects. SBMQWs can be utilized to achieve longer wavelength emission in light emitting diodes without the use of excess indium and can be advantageous in addressing the “green gap.”.

  19. High current gain InGaN=GaN HBTs with C operating temperature

    E-Print Network [OSTI]

    Asbeck, Peter M.

    with an $20 nm low-temperature (Tg ¼ 550 C) GaN buffer layer on a (0001) sapphire substrate. The layer 1018 cmÀ3 Buffer GaN 2.5 mm ­ Substrate Sapphire ­ ­ HBT device processing began by depositing a 100 nmHigh current gain InGaN=GaN HBTs with 300 C operating temperature D.M. Keogh, P.M. Asbeck, T. Chung

  20. Switchable piezoelectric transduction in AlGaN/GaN MEMS resonators

    E-Print Network [OSTI]

    Weinstein, Dana

    This work presents a new switching mechanism in piezoelectric transduction of AlGaN/GaN bulk acoustic resonators. A piezoelectric transducer is formed in the AlGaN, between a top Schottky electrode and a 2D electron gas ...

  1. Spontaneous emission in GaN/InGaN photonic crystal nanopillars

    E-Print Network [OSTI]

    Boyer, Edmond

    . 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

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

    SciTech Connect (OSTI)

    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

    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%.

  3. Fine structure of Fe-Co-Ga and Fe-Cr-Ga alloys with low Ga content

    SciTech Connect (OSTI)

    Kleinerman, Nadezhda M., E-mail: kleinerman@imp.uran.ru; Serikov, Vadim V., E-mail: kleinerman@imp.uran.ru; Vershinin, Aleksandr V., E-mail: kleinerman@imp.uran.ru; Mushnikov, Nikolai V., E-mail: kleinerman@imp.uran.ru; Stashkova, Liudmila A., E-mail: kleinerman@imp.uran.ru [Institute of Metal Physics UB RAS, S. Kovalevskaya str. 18, 620990 Ekaterinburg (Russian Federation)

    2014-10-27T23:59:59.000Z

    Investigation of Ga influence on the structure of Fe-Cr and Fe-Co alloys was performed with the use of {sup 57}Fe Mössbauer spectroscopy and X-ray diffraction methods. In the alloys of the Fe-Cr system, doping with Ga handicaps the decomposition of solid solutions, observed in the binary alloys, and increases its stability. In the alloys with Co, Ga also favors the uniformity of solid solutions. The analysis of Mössbauer experiments gives some grounds to conclude that if, owing to liquation, clusterization, or initial stages of phase separation, there exist regions enriched in iron, some amount of Ga atoms prefer to enter the nearest surroundings of iron atoms, thus forming binary Fe-Ga regions (or phases)

  4. TEM Characterization of InAs/GaAs Quantum Dots Capped by a GaSb/GaAs Layer

    SciTech Connect (OSTI)

    Beltran, AM [Universidad de Cadiz, Spain; Ben, Teresa [Universidad de Cadiz, Spain; Sanchez, AM [Universidad de Cadiz, Spain; Sales Lerida, David [ORNL; Chisholm, Matthew F [ORNL; Varela del Arco, Maria [ORNL; Pennycook, Stephen J [ORNL; Galindo, Pedro [Universidad de Cadiz, Spain; Ripalda, JM [Instituto de Microelectronica de Madrid (CNM, CSIC); Molina Rubio, Sergio I [ORNL

    2008-01-01T23:59:59.000Z

    It is well known that there is intense interest in expanding the usable wavelength for electronic devices. This is one of the reasons to study new self-assembled semiconductor nanostructures. Telecommunication applications use InGaAsP/InP emitting at 1.3 and 1.55 m. Research efforts are dedicated to develop GaAs technology in order to achieve emission at the same range as InP, so GaAs could be used for optical fibre communications. Ga(As)Sb on InAs/GaAs quantum dots (QDs) is a promising nanostructure to be used in telecommunications. The introduction of antimony during or after the QDs growth is an effective solution to obtain a red shift in the emission wavelength, even at room temperature.

  5. Excitonic properties of strained wurtzite and zinc-blende GaNAlxGa1xN quantum dots

    E-Print Network [OSTI]

    Fonoberov, Vladimir

    Excitonic properties of strained wurtzite and zinc-blende GaNÕAlxGa1ÀxN quantum dots Vladimir A 2003 We investigate exciton states theoretically in strained GaN/AlN quantum dots with wurtzite WZ of GaN QDs.1­8 Molecu- lar beam epitaxial growth in the Stranski­Krastanov mode of wurtzite WZ Ga

  6. Morphological and compositional variations in strain-compensated InGaAsP/InGaP superlattices

    E-Print Network [OSTI]

    Feenstra, Randall

    Morphological and compositional variations in strain- compensated InGaAsP/InGaP superlattices R of Technology, Kista, Sweden Abstract We have investigated the properties of strain-compensated InGaAsP/In- GaP superlattices, grown by metalorganic vapor phase epitaxy, with and without InP interlayers inserted in the InGaP

  7. Operating Characteristics of GaAs/InGaP Self Aligned Stripe Lasers Benjamin J. Stevens1

    E-Print Network [OSTI]

    Operating Characteristics of GaAs/InGaP Self Aligned Stripe Lasers Benjamin J. Stevens1 , Kristian of GaAs based self-aligned lasers based upon a single overgrowth. A lattice matched n-doped InGaP layer were exposed to oxygen. True buried heterostructures devices utilising InGaP clad- ding layers have

  8. Microstructure and luminescent properties of novel InGaP alloys on relaxed GaAsP substrates

    E-Print Network [OSTI]

    Microstructure and luminescent properties of novel InGaP alloys on relaxed GaAsP substrates M. J of unconventional alloys of InGaP with In fraction of 0.2­0.4 grown on fully relaxed GaAsP virtual substrates demonstrate growth of extremely high quality InGaP heterostructures which hold promise for fabrication

  9. Band Offsets of InGaP/GaAs Heterojunctions by Scanning Tunneling Spectroscopy Y. Dong and R. M. Feenstra

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Band Offsets of InGaP/GaAs Heterojunctions by Scanning Tunneling Spectroscopy Y. Dong and R. M Abstract Scanning tunneling microscopy and spectroscopy are used to study InGaP/GaAs heterojunctions computation of the tunnel current. Curve fitting of theory to experiment is performed. Using an InGaP band gap

  10. Negative capacitance in GaN/AlGaN heterojunction dual-band detectors L. E. Byrum,1

    E-Print Network [OSTI]

    Dietz, Nikolaus

    Negative capacitance in GaN/AlGaN heterojunction dual-band detectors L. E. Byrum,1 G. Ariyawansa,1 online 2 September 2009 A study of trap states in n+ -GaN/AlGaN heterostructures using electrical related absorption centers attributed to shallow Si-donor pinned to the AlGaN barrier , N-vacancy/ C

  11. High Power Wideband AlGaN/GaN HEMT Feedback Amplifier Module with Drain and Feedback Loop

    E-Print Network [OSTI]

    Itoh, Tatsuo

    High Power Wideband AlGaN/GaN HEMT Feedback Amplifier Module with Drain and Feedback Loop amplifier module using AlGaN/GaN high electron mobility transistor (HEMT) has been developed that covers radars and communications systems. GaN-based HEMT's for high power applications at microwave frequencies

  12. On Maximum Norm of Exterior Product and A Conjecture of C.N. Yang

    E-Print Network [OSTI]

    Zhilin Luo

    2015-01-08T23:59:59.000Z

    Let $V$ be a finite dimensional inner product space over $\\mathbb{R}$ with dimension $n$, where $n\\in \\mathbb{N}$, $\\wedge^{r}V$ be the exterior algebra of $V$, the problem is to find $\\max_{\\| \\xi \\| = 1, \\| \\eta \\| = 1}\\| \\xi \\wedge \\eta \\|$ where $k,l$ $\\in \\mathbb{N},$ $\\forall \\xi \\in \\wedge^{k}V, \\eta \\in \\wedge^{l}V.$ This is a problem suggested by the famous Nobel Prize Winner C.N. Yang. He solved this problem for $k\\leq 2$ in [1], and made the following \\textbf{conjecture} in [2] : If $n=2m$, $k=2r$, $l=2s$, then the maximum is achieved when $\\xi_{max} = \\frac{\\omega^{k}}{\\| \\omega^{k}\\|}, \\eta_{max} = \\frac{\\omega^{l}}{\\| \\omega^{l}\\|}$, where $ \\omega = \\Sigma_{i=1}^m e_{2i-1}\\wedge e_{2i}, $ and $\\{e_{k}\\}_{k=1}^{2m}$ is an orthonormal basis of V. From a physicist's point of view, this problem is just the dual version of the easier part of the well-known Beauzamy-Bombieri inequality for product of polynomials in many variables, which is discussed in [4]. Here the duality is referred as the well known Bose-Fermi correspondence, where we consider the skew-symmetric algebra(alternative forms) instead of the familiar symmetric algebra(polynomials in many variables) In this paper, for two cases we give estimations of the maximum of exterior products, and the Yang's conjecture is answered partially under some special cases.

  13. Impact ionization in N-polar AlGaN/GaN high electron mobility transistors

    SciTech Connect (OSTI)

    Killat, N., E-mail: Nicole.Killat@bristol.ac.uk, E-mail: Martin.Kuball@bristol.ac.uk; Uren, M. J.; Kuball, M., E-mail: Nicole.Killat@bristol.ac.uk, E-mail: Martin.Kuball@bristol.ac.uk [Center for Device Thermography and Reliability (CDTR), H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Keller, S.; Kolluri, S.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of Santa Barbara California, Santa Barbara, California 93106 (United States)

    2014-08-11T23:59:59.000Z

    The existence of impact ionization as one of the open questions for GaN device reliability was studied in N-polar AlGaN/GaN high electron mobility transistors. Electroluminescence (EL) imaging and spectroscopy from underneath the device gate contact revealed the presence of hot electrons in excess of the GaN bandgap energy even at moderate on-state bias conditions, enabling impact ionization with hole currents up to several hundreds of pA/mm. The detection of high energy luminescence from hot electrons demonstrates that EL analysis is a highly sensitive tool to study degradation mechanisms in GaN devices.

  14. Michael J. Poston Atlanta, GA 30307

    E-Print Network [OSTI]

    Orlando, Thomas

    Page | 1 Michael J. Poston Atlanta, GA 30307 Michael.Poston@gatech.edu Cell: 770.561.4756 U.S. Citizen Education PhD Candidate in Chemistry Georgia Institute of Technology, Atlanta, GA August 2007 with Application to Lunar Observations," JGR ­ Planets, 118, 105, doi: 10.1002/jgre.20025. Poston, M. J

  15. Tunable two-dimensional plasmon resonances in an InGaAs/InP high electron mobility transistor

    E-Print Network [OSTI]

    Peale, Robert E.

    of materials systems such as GaAs/AlGaAs,3 InGaP/InGaAs/GaAs,4 GaN/AlGaN,2,5 and Si Ref. 1 have been explored

  16. Pedosphere 16(5): 566-571, 2006 ISSN 1002-0160/CN 32-1315/P

    E-Print Network [OSTI]

    Sparks, Donald L.

    Pedosphere 16(5): 566-571, 2006 ISSN 1002-0160/CN 32-1315/P @ 2006 Soil Science Society of China The remaining phosphorus (Prem),P concentration that remains in solution after shaking soil with 0.01 mol L-' CaCl2 containing 60 pg mL-l P, is a very useful index for studies related to the chemistry of variable

  17. FUPWG Meeting Agenda - Atlanta, GA | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Atlanta, GA FUPWG Meeting Agenda - Atlanta, GA 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,...

  18. AlGaN/GaN heterostructure prepared on a Si (110) substrate via pulsed sputtering

    SciTech Connect (OSTI)

    Watanabe, T.; Ohta, J.; Kondo, T.; Ohashi, M.; Ueno, K.; Kobayashi, A. [Institute of Industrial Science (IIS), The University of Tokyo, 4-6-1 Komaba, Tokyo 153-8505 (Japan); Fujioka, H., E-mail: hfujioka@iis.u-tokyo.ac.jp [Institute of Industrial Science (IIS), The University of Tokyo, 4-6-1 Komaba, Tokyo 153-8505 (Japan); CREST, Japan Science and Technology Corporation (JST), 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075 (Japan)

    2014-05-05T23:59:59.000Z

    GaN films were grown on Si (110) substrates using a low-temperature growth technique based on pulsed sputtering. Reduction of the growth temperature suppressed the strain in the GaN films, leading to an increase in the critical thickness for crack formation. In addition, an AlGaN/GaN heterostructure with a flat heterointerface was prepared using this technique. Furthermore, the existence of a two dimensional electron gas at the heterointerface with a mobility of 1360 cm{sup 2}/Vs and a sheet carrier density of 1.3?×?10{sup 13}?cm{sup ?2} was confirmed. Finally, the use of the AlGaN/GaN heterostructure in a high electron mobility transistor was demonstrated. These results indicate that low-temperature growth via pulsed sputtering is quite promising for the fabrication of GaN-based electronic devices.

  19. 56 IEEE JOURNAL OF PHOTOVOLTAICS, VOL. 2, NO. 1, JANUARY 2012 Metamorphic GaAsP and InGaP Solar Cells on GaAs

    E-Print Network [OSTI]

    Haller, Gary L.

    56 IEEE JOURNAL OF PHOTOVOLTAICS, VOL. 2, NO. 1, JANUARY 2012 Metamorphic GaAsP and InGaP Solar bandgap range. Index Terms--Epitaxy, GaAsP, InGaP, metamorphic. I. INTRODUCTION TODAY'S highest efficiency

  20. Defect structures in rapidly degraded InGaAsP/InGaP double-heterostructure lasers

    SciTech Connect (OSTI)

    Ueda, O.; Wakao, K.; Yamaguchi, A.; Isozumi, S.; Komiya, S.

    1985-03-01T23:59:59.000Z

    Rapidly degraded InGaAsP/InGaP double-heterostructure lasers grown on (001)-oriented GaAs substrates by liquid phase epitaxy have been investigated by photolumi

  1. Emission properties of heterostructures with a (GaAsSb-InGaAs)/GaAs bilayer quantum well

    SciTech Connect (OSTI)

    Zvonkov, B. N.; Nekorkin, S. M.; Vikhrova, O. V.; Dikareva, N. V., E-mail: dikareva@nifti.unn.ru [Nizhni Novgorod State University, Physical-Technical Research Institute (Russian Federation)

    2013-09-15T23:59:59.000Z

    The specific features of the emission characteristics of GaAs-based heterostructures with a GaAs{sub 1-x}Sb{sub x}-In{sub y}Ga{sub 1-y}As bilayer quantum well are studied. The heterostructures are grown by metal-organic chemical vapor deposition (MOCVD). With an analysis of previously reported data on the MOCVD growth process taken into account, the temperature range (560-580 Degree-Sign C), the relation between the fluxes emitted by the sources of Group-V and -III elements ( Less-Than-Or-Equivalent-To 1), and the order of layer growth for the production of the active region of a GaAs/InGaP laser heterostructure are determined experimentally. The active region is a GaAs{sub 0.75}Sb{sub 0.25}-In{sub 0.2}Ga{sub 0.8}As bilayer quantum well. For the structure, a 1075-nm electroluminescence signal attributed to indirect transitions between the valence band of the GaAs{sub 0.75}Sb{sub 0.25} layer and the conduction band of the In{sub 0.2}Ga{sub 0.8}As layer is observed. An increase in the continuous-wave pump current yields a decrease in the 1075-nm emission intensity and initiates stable lasing at a wavelength of 1022 nm at a threshold current density of 1.4 kA cm{sup -2} at room temperature. Lasing occurs at transitions direct in coordinate space.

  2. AlGaN/GaN HFET Single-Ended Frequency Doubler Younkyu Chung and Tatsuo Itoh

    E-Print Network [OSTI]

    Itoh, Tatsuo

    AlGaN/GaN HFET Single-Ended Frequency Doubler Younkyu Chung and Tatsuo Itoh Department-mail: ykchung@ee.ucla.edu Abstract - This paper presents the first single-ended AlGaN/GaN heterojunction field, respectively. For the frequency doubler with 1mm gate periphery AlGaN/GaN HFET, conversion gain of 0.17 d

  3. Materials Science and Engineering B59 (1999) 319322 Microcalorimetric absorption spectroscopy in GaNAlGaN

    E-Print Network [OSTI]

    Nabben, Reinhard

    1999-01-01T23:59:59.000Z

    Microcalorimetric measurements of small absorption coefficients have been performed on thin GaN­AlGaN quantum wells in GaN­AlGaN quantum wells Axel Go¨ldner a, *, Axel Hoffmann a , Bernard Gil b , Pierre Lefebvre b at the energy of the GaN buffer and at the energy of the thick AlGaN barrier layers, we could also readily

  4. Al fraction induced effects on the capacitance characteristics -GaN/AlxGa1-xN IR detectors

    E-Print Network [OSTI]

    Dietz, Nikolaus

    substrate. As shown in Fig. 1(a), the device structures consist of a 0.2 m n+ -GaN top contact (emitter.1117/12.828156 Proc. of SPIE Vol. 7467 74670W-1 #12;(a) Sapphire Substrate n GaN Bottom Contact AlxGa1-xN Barrier n GaNAl fraction induced effects on the capacitance characteristics of n+ -GaN/AlxGa1-xN IR detectors

  5. Improvement of breakdown voltage in InGaP/InGaAs/GaAs heterostructure MESFETs for MMICs

    SciTech Connect (OSTI)

    Koh, Inoue; Yamane, Yasuro; Shiojima, Kenji [NTT LSI Lab., Kanagawa (Japan)] [and others

    1995-12-31T23:59:59.000Z

    This paper describes the trade-off between breakdown voltage and RF performance of InGaP/InGaAs/GaAs heterostructure MESFETs for power amplifiers and oscillators in multi-function MMICs in the millimeter-wave range. The authors successfully improved both gate-drain and drain-source breakdown voltages while maintaining excellent high-frequency performance by using a double-layered gate consisting of WSiN with different nitrogen contents, and by varying epitaxial layer thickness and implantation dose.

  6. Structural and optical properties of InGaN–GaN nanowire heterostructures grown by molecular beam epitaxy

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Limbach, F. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Gotschke, T. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Stoica, T. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Calarco, R. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Sutter, E. [Brookhaven National Lab., Upton, NY (United States); Ciston, J. [Brookhaven National Lab., Upton, NY (United States); Cusco, R. [Consell Superior d'Investigacions Cientifiques (CSIC), Barcelona (Spain); Artus, L. [Consell Superior d'Investigacions Cientifiques (CSIC), Barcelona (Spain); Kremling, S. [Univ. Wurzburg, Wilhelm Conrad Rontgen Research Centre Complex Matter Systems, Wurzburg (Germany); Hofling, S. [Univ. Wurzburg, Wilhelm Conrad Rontgen Research Centre Complex Matter Systems, Wurzburg (Germany); Worschech, L. [Univ. Wurzburg, Wilhelm Conrad Rontgen Research Centre Complex Matter Systems, Wurzburg (Germany); Grutzmacher, D. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany)

    2011-01-07T23:59:59.000Z

    InGaN/GaN nanowire (NW) heterostructures grown by plasma assisted molecular beam epitaxy were studied in comparison to their GaN and InGaN counterparts. The InGaN/GaN heterostructure NWs are composed of a GaN NW, a thin InGaN shell, and a multifaceted InGaN cap wrapping the top part of the GaN NW. High-resolution transmission electron microscopy (HRTEM) images taken from different parts of a InGaN/GaN NW show a wurtzite structure of the GaN core and the epitaxial InGaN shell around it, while additional crystallographic domains are observed whithin the InGaN cap region. Large changes in the lattice parameter along the wire, from pure GaN to higher In concentration demonstrate the successful growth of a complex InGaN/GaN NW heterostructure. Photoluminescence (PL) spectra of these heterostructure NW ensembles show rather broad and intense emission peak at 2.1 eV. However, ?-PL spectra measured on single NWs reveal a reduced broadening of the visible luminescence. The analysis of the longitudinal optical phonon Raman peak position and its shape reveal a variation in the In content between 20% and 30%, in agreement with the values estimated by PL and HRTEM investigations. The reported studies are important for understanding of the growth and properties of NW heterostructures suitable for applications in optoelectronics and photovoltaics.

  7. Necessity of Ga prelayers in GaAs/Ge growth using gas-source molecular beam epitaxy

    E-Print Network [OSTI]

    in a highly defective GaAs layer.as5 Recently, InGaP light-emitting diodes have been fabricated on Si using

  8. Demonstrating the Model Nature of the High-Temperature Superconductor HgBa2CuO4+d

    SciTech Connect (OSTI)

    Barisic, Neven; Li, Yuan; Zhao, Xudong; Cho, Yong-Chan; Chabot-Couture, Guillaume; Yu, Guichuan; Greven, Martin; /SLAC, SSRL /Boskovic Inst., Zagreb /Stanford U., Phys. Dept. /Jilin U. /Stanford U., Appl. Phys. Dept.

    2008-09-30T23:59:59.000Z

    The compound HgBa{sub 2}CuO{sub 4+{delta}} (Hg1201) exhibits a simple tetragonal crystal structure and the highest superconducting transition temperature (T{sub c}) among all single Cu-O layer cuprates, with T{sub c} = 97 K (onset) at optimal doping. Due to a lack of sizable single crystals, experimental work on this very attractive system has been significantly limited. Thanks to a recent breakthrough in crystal growth, such crystals have now become available. Here, we demonstrate that it is possible to identify suitable heat treatment conditions to systematically and uniformly tune the hole concentration of Hg1201 crystals over a wide range, from very underdoped (T{sub c} = 47 K, hole concentration p {approx} 0.08) to overdoped (T{sub c} = 64 K, p {approx} 0.22). We then present quantitative magnetic susceptibility and DC charge transport results that reveal the very high-quality nature of the studied crystals. Using XPS on cleaved samples, we furthermore demonstrate that it is possible to obtain large surfaces of good quality. These characterization measurements demonstrate that Hg1201 should be viewed as a model high-temperature superconductor, and they provide the foundation for extensive future experimental work.

  9. Le gisement Ag Hg de Zgounder (Jebel Siroua, Anti-Atlas, Maroc) : un pithermal noprotrozoque de type

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    Le gisement Ag Hg de Zgounder (Jebel Siroua, Anti- Atlas, Maroc) : un épithermal néoprotérozoïque Compagnie minière de Touissit (CMT), 279, bd Zerktouni, Casablanca, Maroc Abstract The Zgounder ore deposit and more as a silver metallogenic province Résumé Le gisement argentifère de Zgounder (Anti-Atlas, Maroc

  10. Trace Metals (Cd, Cu, Hg, and Pb) Accumulation Recorded in the Intertidal Mudflat Sediments of Three Coastal

    E-Print Network [OSTI]

    Long, Bernard

    Trace Metals (Cd, Cu, Hg, and Pb) Accumulation Recorded in the Intertidal Mudflat Sediments the intertidal mudflat sedi- ments of the coastal lagoons Chiricahueto, Estero de Urías, and Ohuira surrounding these lagoons. Keywords 210 Pb geochronology. Coastal lagoons . Metal pollution . Mudflat

  11. High-efficiency radiation-resistant InGaP/GaAs tandem solar cells

    SciTech Connect (OSTI)

    Takamoto, T. [Toyota Technological Inst., Tempaku, Nagoya (Japan); [Japan Energy Corp., Toda, Saitama (Japan); Yamaguchi, M.; Taylor, S.J. [Toyota Technological Inst., Tempaku, Nagoya (Japan); Ikeda, E.; Agui, T.; Kurita, H. [Japan Energy Corp., Toda, Saitama (Japan)

    1997-12-31T23:59:59.000Z

    A world-record efficiency of 26.9% (AM0, 28 C) has been obtained for InGaP/GaAs tandem solar cells fabricated by the MOCVD method. The radiation resistance of the InGaP/GaAs tandem solar cells has also been evaluated following 1 MeV electron irradiation. Degradation in the tandem cell performance has been confirmed to be mainly attributed to large degradation in the GaAs bottom cell, which features a highly doped base layer. Similar radiation-resistance with GaAs-on-Ge cells has been observed for the InGaP/GaAs tandem cell. However, some recovery of the tandem cell performance has been found due to minority-carrier injection under light illumination of forward bias, which causes defect annealing in InGaP cells. The optimal design of the InGaP base layer thickness for current matching at end of life (EOL) (after irradiation with 10{sup 15} electrons cm{sup {minus}2}) has been examined.

  12. A versatile source to produce high-intensity, pulsed supersonic radical beams for crossed-beam experiments: The cyanogen radical CN,,X2

    E-Print Network [OSTI]

    Kaiser, Ralf I.

    CN radicals in a low- pressure fast-flow chemical reactor. Although valuable ki- netic data of the ablated species with molecular nitrogen, which acts also as a seeding gas. A chopper wheel located after

  13. 1994-2010 China Academic Journal Electronic Publishing House. All rights reserved. http://www.cnki.net 38 (2009~OE) 6 http: www. wuli. ac. cn

    E-Print Network [OSTI]

    Gao, Hongjun

    § --° · ¢ /»,,> ·¤ ¨ ,¢¶ , ··¤ ~ ª ,--¿ · ... ^ l----`¸ ° . ,, ...·° ¡¡ ¡¡ Graphene,~ ¶ ¿ , ­, ··¤ ,Æ,,,, -- Preparation been exploited to prepare high quality Graphene. Three main methods are reviewed, including the thermal://www.cnki.net ¡¡Îï Àí ¡¤38 (2009~OE) 6 ¡¡ ¡¡ ¡¡ ¡¡ ¡¡ ¡¡ ¡¡ ¡¡ ¡¡ ¡¡ ¡¡ ¡¡ ¡¡ http: www. wuli. ac. cn Graphene¿ § º

  14. Highly uniform, multi-stacked InGaAs/GaAs quantum dots embedded in a GaAs nanowire

    SciTech Connect (OSTI)

    Tatebayashi, J., E-mail: tatebaya@iis.u-tokyo.ac.jp; Ota, Y. [NanoQUINE, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Ishida, S.; Nishioka, M.; Iwamoto, S.; Arakawa, Y. [NanoQUINE, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2014-09-08T23:59:59.000Z

    We demonstrate a highly uniform, dense stack of In{sub 0.22}Ga{sub 0.78}As/GaAs quantum dot (QD) structures in a single GaAs nanowire (NW). The size (and hence emission energy) of individual QD is tuned by careful control of the growth conditions based on a diffusion model of morphological evolution of NWs and optical characterization. By carefully tailoring the emission energies of individual QD, dot-to-dot inhomogeneous broadening of QD stacks in a single NW can be as narrow as 9.3?meV. This method provides huge advantages over traditional QD stack using a strain-induced Stranski-Krastanow growth scheme. We show that it is possible to fabricate up to 200 uniform QDs in single GaAs NWs using this growth technique without degradation of the photoluminescence intensity.

  15. Strain induced variations in band offsets and built-in electric fields in InGaN/GaN multiple quantum wells

    E-Print Network [OSTI]

    Alpay, S. Pamir

    Strain induced variations in band offsets and built-in electric fields in InGaN/GaN multiple InxGa1-xN(InGaN)/GaN multilayers on the In composition and misfit strain. The results indicate that for non-polar m-plane configurations with ½1210InGaN//½1210GaN and ½0001InGaN//½0001GaN epitaxial

  16. Multi-bands photoconductive response in AlGaN/GaN multiple quantum wells

    SciTech Connect (OSTI)

    Chen, G.; Rong, X.; Xu, F. J.; Tang, N. [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Wang, X. Q., E-mail: wangshi@pku.edu.cn; Shen, B., E-mail: bshen@pku.edu.cn [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China); Fu, K.; Zhang, B. S. [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Ruoshui Road 398, 215123 Suzhou (China); Hashimoto, H.; Yoshikawa, A. [Center for SMART Green Innovation Research, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Ge, W. K. [Department of Physics, Tsinghua University, Beijing 100871 (China)

    2014-04-28T23:59:59.000Z

    Based on the optical transitions among the quantum-confined electronic states in the conduction band, we have fabricated multi-bands AlGaN/GaN quantum well infrared photodetectors. Crack-free AlGaN/GaN multiple quantum wells (MQWs) with atomically sharp interfaces have been achieved by inserting an AlN interlayer, which releases most of the tensile strain in the MQWs grown on the GaN underlayer. With significant reduction of dark current by using thick AlGaN barriers, photoconductive responses are demonstrated due to intersubband transition in multiple regions with center wavelengths of 1.3, 2.3, and 4??m, which shows potential applications on near infrared detection.

  17. High-performance InGaP/GaAs pnp {delta}-doped heterojunction bipolar transistor

    SciTech Connect (OSTI)

    Tsai, J.-H. [National Kaohsiung Normal University, Department of Electronic Engineering (China)], E-mail: jhtsai@nknucc.nknu.edu.tw; Chiu, S.-Y.; Lour, W.-S. [National Taiwan Ocean University, Department of Electrical Engineering (China); Guo, D.-F. [Air Force Academy, Department of Electronic Engineering (China)

    2009-07-15T23:59:59.000Z

    In this article, a novel InGaP/GaAs pnp {delta}-doped heterojunction bipolar transistor is first demonstrated. Though the valence band discontinuity at InGaP/GaAs heterojunction is relatively large, the addition of a {delta}-doped sheet between two spacer layers at the emitter-base (E-B) junction effectively eliminates the potential spike and increases the confined barrier for electrons, simultaneously. Experimentally, a high current gain of 25 and a relatively low E-B offset voltage of 60 mV are achieved. The offset voltage is much smaller than the conventional InGaP/GaAs pnp HBT. The proposed device could be used for linear amplifiers and low-power complementary integrated circuit applications.

  18. Synthesis, morphology and optical properties of GaN and AlGaN semiconductor nanostructures

    SciTech Connect (OSTI)

    Kuppulingam, B., E-mail: drbaskar2009@gmail.com; Singh, Shubra, E-mail: drbaskar2009@gmail.com; Baskar, K., E-mail: drbaskar2009@gmail.com [Crystal Growth Centre, Anna University, Chennai-600025 (India)

    2014-04-24T23:59:59.000Z

    Hexagonal Gallium Nitride (GaN) and Aluminum Gallium Nitride (AlGaN) nanoparticles were synthesized by sol-gel method using Ethylene Diamine Tetra Acetic acid (EDTA) complex route. Powder X-ray diffraction (PXRD) analysis confirms the hexagonal wurtzite structure of GaN and Al{sub 0.25}Ga{sub 0.75}N nanoparticles. Surface morphology and elemental analysis were carried out by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray spectroscopy (EDX). The room temperature Photoluminescence (PL) study shows the near band edge emission for GaN at 3.35 eV and at 3.59 eV for AlGaN nanoparticles. The Aluminum (Al) composition of 20% has been obtained from PL emission around 345 nm.

  19. Effect of polarization on intersubband transition in AlGaN/GaN multiple quantum wells

    SciTech Connect (OSTI)

    Chen, G.; Li, Z. L.; Wang, X. Q.; Huang, C. C.; Rong, X.; Xu, F. J.; Tang, N.; Qin, Z. X.; Shen, B. [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China)] [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Sang, L. W.; Sumiya, M. [Optical and Electronic Materials Unit, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)] [Optical and Electronic Materials Unit, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Chen, Y. H. [Laboratory of Semiconductor Material Science, Institute of Semiconductors, CAS, Beijing 100083 (China)] [Laboratory of Semiconductor Material Science, Institute of Semiconductors, CAS, Beijing 100083 (China); Ge, W. K. [Department of Physics, Tsinghua University, Beijing 100871 (China)] [Department of Physics, Tsinghua University, Beijing 100871 (China)

    2013-05-13T23:59:59.000Z

    Intersubband transitions (ISBT) of AlGaN/GaN multiple quantum wells (MQWs) with wavelength towards atmospheric window (3-5 {mu}m) have been investigated. A Ga-excess epitaxial method is used in the molecular beam epitaxy leading to ultra-sharp interface and negligible elements inter-diffusion. The absorption peak wavelength of the ISBT was successfully tuned in the range of 3-4 {mu}m by modifying the GaN well thickness from 2.8 to 5.5 nm. It was further found that the polarization charge density of the AlGaN/GaN MQWs was about -0.034 C/m{sup 2} which gave rise to blueshift of the ISBT wavelength and thus partially compensated its redshift with increasing well thickness.

  20. InGaN/GaN single-quantum-well microdisks

    SciTech Connect (OSTI)

    Hsu, Yu-Chi; Lo, Ikai; Shih, Cheng-Hung; Pang, Wen-Yuan; Hu, Chia-Hsuan; Wang, Ying-Chieh; Chou, Mitch M. C. [Department of Physics, Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China)

    2012-06-11T23:59:59.000Z

    We have grown In{sub x}Ga{sub 1-x}N/GaN quantum wells atop GaN microdisk with {gamma}-LiAlO{sub 2} substrate by using plasma-assisted molecular beam epitaxy. The structural and optical properties of the samples were analyzed by transmission electron microscopy, x-ray diffraction, cathodoluminescence, and photoluminescence measurements. Based on the measured results, we obtained the indium concentration of the In{sub x}Ga{sub 1-x}N/GaN single quantum well to be x = 0.25 with a band-gap energy of 2.31 eV, which is consistent with the bowing effect of bulk In{sub x}Ga{sub 1-x}N: E{sub g}(x) = [3.42 - x * 2.65 - x * (1 - x) * 2.4] eV.

  1. Atomic layer deposition of GaN using GaCl3 and NH3 Oh Hyun Kim, Dojun Kim, and Tim Andersona

    E-Print Network [OSTI]

    Anderson, Timothy J.

    be grown at lower temperature than by CVD. As example, ALD growth of device quality GaAs, GaP, and InGaP

  2. Dependence of the ground-state transition energy versus optical pumping in GaAsSb/InGaAs/GaAs heterostructures

    SciTech Connect (OSTI)

    Morozov, S. V.; Kryzhkov, D. I., E-mail: krizh@ipmras.ru; Aleshkin, V. Ya. [Institute for Physics of Microstructures, RAS, 603950 Nizhny Novgorod (Russian Federation); Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation); Yablonsky, A. N.; Krasilnik, Z. F. [Institute for Physics of Microstructures, RAS, 603950 Nizhny Novgorod (Russian Federation); Zvonkov, B. N.; Vikhrova, O. V. [Physical-Technical Research Institute, Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation)

    2014-01-13T23:59:59.000Z

    In this work, we report on the time-resolved photoluminescence studies of a double quantum well In{sub 0.2}Ga{sub 0.8}As/GaAs{sub 0.8}Sb{sub 0.2}/GaAs heterostructure which, in contrast to the GaAsSb/GaAs structures, is expected to provide effective confinement of electrons due to additional InGaAs layer. The studies at 4.2?K have revealed a complicated nonmonotonic dependence of the ground-state transition energy on the concentration of nonequilibrium charge carriers in the quantum well. The effect observed in this work is important in terms of creating sources of radiation, including stimulated emission, on the basis of InGaAs/GaAsSb/GaAs structures.

  3. AlGaN/GaN field effect transistors for power electronics—Effect of finite GaN layer thickness on thermal characteristics

    SciTech Connect (OSTI)

    Hodges, C., E-mail: chris.hodges@bristol.ac.uk; Anaya Calvo, J.; Kuball, M. [H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL (United Kingdom)] [H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL (United Kingdom); Stoffels, S.; Marcon, D. [IMEC, Kapeldreef 75, B3001 Leuven (Belgium)] [IMEC, Kapeldreef 75, B3001 Leuven (Belgium)

    2013-11-11T23:59:59.000Z

    AlGaN/GaN heterostructure field effect transistors with a 150?nm thick GaN channel within stacked Al{sub x}Ga{sub 1?x}N layers were investigated using Raman thermography. By fitting a thermal simulation to the measured temperatures, the thermal conductivity of the GaN channel was determined to be 60?W m{sup ?1} K{sup ?1}, over 50% less than typical GaN epilayers, causing an increased peak channel temperature. This agrees with a nanoscale model. A low thermal conductivity AlGaN buffer means the GaN spreads heat; its properties are important for device thermal characteristics. When designing power devices with thin GaN layers, as well as electrical considerations, the reduced channel thermal conductivity must be considered.

  4. InGaAsP/InGaP buried heterostructure lasers at 810 nm

    SciTech Connect (OSTI)

    Wakao, K.; Isozumi, S.; Nishi, H.; Ohsaka, S.

    1984-12-01T23:59:59.000Z

    InGaAsP/InGaP buried heterostructure lasers emitting at 810 nm have been grown on GaAs substrates using two-step liquid-phase epitaxy. A threshold current of 79 mA and an external differential quantum efficiency of 26% are obtained. Fundamental transverse mode operation up to 3 mW is achieved in the laser with the active region of 3.5 ..mu..m wide.

  5. Simplified 2DEG carrier concentration model for composite barrier AlGaN/GaN HEMT

    SciTech Connect (OSTI)

    Das, Palash, E-mail: d.palash@gmail.com; Biswas, Dhrubes, E-mail: d.palash@gmail.com [Indian Institute of Technology Kharagpur, Kharagpur - 721302, West Bengal (India)

    2014-04-24T23:59:59.000Z

    The self consistent solution of Schrodinger and Poisson equations is used along with the total charge depletion model and applied with a novel approach of composite AlGaN barrier based HEMT heterostructure. The solution leaded to a completely new analytical model for Fermi energy level vs. 2DEG carrier concentration. This was eventually used to demonstrate a new analytical model for the temperature dependent 2DEG carrier concentration in AlGaN/GaN HEMT.

  6. Ohmic contacts to n-GaSb

    E-Print Network [OSTI]

    Yang, Zhengchong

    1997-01-01T23:59:59.000Z

    In recent years, the Ill-V semiconductor GaSb and its ternary alloys containing antimony have exhibited interesting electrical and optical properties for device applications which include negative resistance tunnel devices, lasers, detectors and FET...

  7. The structure of GaAs/Si(211) heteroepitaxial layers

    SciTech Connect (OSTI)

    Liliental-Weber, Z.; Weber, E.R.; Washburn, J.; Liu, T.Y.; Kroemer, H.

    1985-05-01T23:59:59.000Z

    Gallium arsenide films grown on (211)Si by molecular-beam epitaxy have been investigated using transmission electron microscopy. The main defects observed in the alloy were of misfit dislocations, stacking faults, and microtwin lamellas. Silicon surface preparation was found to play an important role on the density of defects formed at the Si/GaAs interface. Two different types of strained-layer superlattices, InGaAs/InGaP and InGaAs/GaAs, were applied either directly to the Si substrate, to a graded layer (GaP-InGaP), or to a GaAs buffer layer to stop the defect propagation into the GaAs films. Applying InGaAs/GaAs instead of InGaAs/InGaP was found to be more effective in blocking defect propagation. In all cases of strained-layer superlattices investigated, dislocation propagation was stopped primarily at the top interface between the superlattice package and GaAs. Graded layers and unstrained AlGaAs/GaAs superlattices did not significantly block dislocations propagating from the interface with Si. Growing of a 50 nm GaAs buffer layer at 505/sup 0/C followed by 10 strained-layer superlattices of InGaAs/GaAs (5 nm each) resulted in the lowest dislocation density in the GaAs layer (approx.5 x 10/sup 7//cm/sup 2/) among the structures investigated. This value is comparable to the recently reported density of dislocations in the GaAs layers grown on (100)Si substrates. Applying three sets of the same strained layers decreased the density of dislocations an additional approx.2 to 3 times.

  8. Over 30{percent} efficient InGaP/GaAs tandem solar cells

    SciTech Connect (OSTI)

    Takamoto, T.; Ikeda, E.; Kurita, H. [Central Research Laboratory, Japan Energy Corporation, 3-17-35 Niizo-Minami, Toda, Saitama 335 (Japan)] [Central Research Laboratory, Japan Energy Corporation, 3-17-35 Niizo-Minami, Toda, Saitama 335 (Japan); Ohmori, M. [Japan Energy Research Center Company, Ltd., 1-11-9 Azabudai, Minato-ku, Tokyo 106 (Japan)] [Japan Energy Research Center Company, Ltd., 1-11-9 Azabudai, Minato-ku, Tokyo 106 (Japan)

    1997-01-01T23:59:59.000Z

    A two-terminal monolithic InGaP/GaAs tandem solar cell with a new efficiency record of 30.28{percent} is realized with a practical large area of 4 cm{sup 2} under one-sun air-mass 1.5 global illumination. We report improvements of the tandem cell performance by introducing a double-hetero (hereafter DH) structure InGaP tunnel junction, in which the InGaP layers are surrounded by high band gap AlInP barriers. The DH structure by AlInP barriers increase the peak current of InGaP tunnel junction. The AlInP barrier directly below the InGaP top cell, which takes the part of a back surface field (hereafter BSF) layer, is found to be considerably effective in reflecting minority carriers in the top cell. The AlInP BSF layer does not only form a high potential barrier but also prevents the diffusion of zinc from a high doped tunnel junction toward the top cell during epitaxial growth. Furthermore, an InGaP tunnel junction reduces the absorption loss, which exists in a GaAs tunnel junction, and increases the photogenerated current in the GaAs bottom cell. {copyright} {ital 1997 American Institute of Physics.}

  9. GaTe semiconductor for radiation detection

    DOE Patents [OSTI]

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

    2009-06-23T23:59:59.000Z

    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.

  10. Probing temperature gradients within the GaN buffer layer of AlGaN/GaN high electron mobility transistors with Raman thermography

    SciTech Connect (OSTI)

    Hodges, C., E-mail: chris.hodges@bristol.ac.uk; Pomeroy, J.; Kuball, M. [H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL (United Kingdom)

    2014-02-14T23:59:59.000Z

    We demonstrate the ability of confocal Raman thermography using a spatial filter and azimuthal polarization to probe vertical temperature gradients within the GaN buffer layer of operating AlGaN/GaN high electron mobility transistors. Temperature gradients in the GaN layer are measured by using offset focal planes to minimize the contribution from different regions of the GaN buffer. The measured temperature gradient is in good agreement with a thermal simulation treating the GaN thermal conductivity as homogeneous throughout the layer and including a low thermal conductivity nucleation layer to model the heat flow between the buffer and substrate.

  11. Quantum Critical Transition Amplifies Magnetoelastic Coupling in Mn[N(CN)2]2

    SciTech Connect (OSTI)

    Brinzari, T. V.; Chen, P.; Sun, Q.-C.; Liu, J.; Tung, L.-C.; Wang, Y.; Schlueter, J. A.; Singleton, J.; Manson, J. L.; Whangbo, M.-H.; Litvinchuk, A. P.; Musfeldt, J. L.

    2013-06-01T23:59:59.000Z

    We report the discovery of a magnetic quantum critical transition in Mn[N(CN)2]2 that drives the system from a canted antiferromagnetic state to the fully polarized state with amplified magnetoelastic coupling as an intrinsic part of the process. The local lattice distortions, revealed through systematic phonon frequency shifts, suggest a combined MnN6 octahedra distortion+counterrotation mechanism that reduces antiferromagnetic interactions and acts to accommodate the field-induced state. These findings deepen our understanding of magnetoelastic coupling near a magnetic quantum critical point and away from the static limit.

  12. Disentangling the Mn moments on different sublattices in the half-metallic ferrimagnet Mn3?xCoxGa

    SciTech Connect (OSTI)

    Klaer, P.; Jenkins, C.A.; Alijani, V.; Winterlik, J.; Balke, B.; Felser, C.; Elmers, H.J.

    2011-05-03T23:59:59.000Z

    Ferrimagnetic Mn{sub 3-x}Co{sub x}Ga compounds have been investigated by magnetic circular dichroism in x-ray absorption (XMCD). Compounds with x > 0.5 crystallize in the CuHg{sub 2}Ti structure. A tetragonal distortion of the cubic structure occurs for x {le} 0.5. For the cubic phase, magnetometry reveals a linearly increasing magnetization of 2x Bohr magnetons per formula unit obeying the generalized Slater-Pauling rule. XMCD confirms the ferrimagnetic character with Mn atoms occupying two different sublattices with antiparallel spin orientation and different degrees of spin localization and identifies the region 0.6 < x {le} 0.8 as most promising for a high spin polarization at the Fermi level. Individual Mn moments on inequivalent sites are compared to theoretical predictions.

  13. Thermoelectric effects in wurtzite GaN and AlxGa1-xN alloys and Alexander A. Balandin

    E-Print Network [OSTI]

    with the active thermoelectric cooling implemented on the same material system can improve the device performance, for the pro- posed cooling system should also be based on GaN. To real- ize this, the high-efficiency Ga,6 Great progress has been achieved in GaN-based microwave technology. GaN transistors with very high

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

    E-Print Network [OSTI]

    Wetzel, Christian M.

    2007-01-01T23:59:59.000Z

    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

  15. The Effect of the Thermal Boundary Resistance on Self-Heating of AlGaN/GaN HFETs

    E-Print Network [OSTI]

    The Effect of the Thermal Boundary Resistance on Self-Heating of AlGaN/GaN HFETs 1. Introduction, performance of these devices has been limited by self-heating [1] [6]. Thus, accurate modeling of heat diffusion and self-heating effects in AlGaN/GaN heterostructures and device optimization based

  16. InAsGaPInGaP high-temperature power Schottky rectifier and J. M. Woodall

    E-Print Network [OSTI]

    Woodall, Jerry M.

    °C. Further improvement of the thermal stability is expected to be achieved by reducing the diffusion is thought to be due to strong covalent bonding at the InAs/GaP interface. The InAs/GaP heterointerface effectively blocks impurity diffusion. Since InGaP is superior to GaP for high-power applica- tions, as shown

  17. GaAs-based self-aligned laser incorporating InGaP opto-electronic confinement layer

    E-Print Network [OSTI]

    GaAs-based self-aligned laser incorporating InGaP opto-electronic confinement layer K.M. Groom, B fabrication, is demonstrated. An n-doped InGaP layer is utilised for both electrical and optical confinement-doped InGaP current blocking layer that also provides optical confinement. This tech- nology relies

  18. GaN/ZnO and AlGaN/ZnO heterostructure LEDs: growth, fabrication, optical and electrical characterization

    E-Print Network [OSTI]

    Wetzel, Christian M.

    GaN/ZnO and AlGaN/ZnO heterostructure LEDs: growth, fabrication, optical and electrical 12180-3590, U.S.A. ABSTRACT The wide bandgap polar semiconductors GaN and ZnO and their related alloys fields, and surface terminations. With a small lattice mismatch of ~1.8 % between GaN and Zn

  19. Direct Evidence of Nanoscale Carrier Localization in InGaN/GaN Structures Grown on Si Substrates

    E-Print Network [OSTI]

    Nabben, Reinhard

    Direct Evidence of Nanoscale Carrier Localization in InGaN/GaN Structures Grown on Si Substrates: time-resolved photoluminescence, quantum dots, InGaN, Si substrate There exists a strong continuous expensive and are limited in size. Thus, heteroepitaxial growth of GaN on silicon substrates seems

  20. Inclined dislocation-pair relaxation mechanism in homoepitaxial green GaInN/GaN light-emitting diodes

    E-Print Network [OSTI]

    Wetzel, Christian M.

    -emitting diodes LEDs on low-defect density bulk GaN substrate, but not in green LEDs on sapphire substrate an ideal substrate for homoepitaxial growth. Here we study the microstructural properties of green GaInN/GaN-Koehler force10 resulting from a macroscopic relaxation of strain. II. CRYSTAL GROWTH c plane bulk GaN substrate

  1. Junction Temperature Measurements and Thermal Modeling of GaInN/GaN Quantum Well Light-Emitting Diodes

    E-Print Network [OSTI]

    Wetzel, Christian M.

    quantum well (QW) light-emitting diodes (LEDs) grown on sapphire and bulk GaN substrate by micro efficiency in dies grown on GaN substrates with a thermal resistance of 75 K/W. For dies on sapphire of GaN-based blue and green LEDs grown on sapphire and GaN substrates using micro-Raman spectroscopy

  2. Correlation between structural properties and optical amplification in InGaN/GaN heterostructures grown by molecular beam epitaxy

    E-Print Network [OSTI]

    Nabben, Reinhard

    . The lateral homogeneity can be drastically improved using a template of GaN grown on the sapphire substrate-grown heterostructures can drastically be reduced by using a template of MOVPE-GaN on the sapphire substrate, which leadsCorrelation between structural properties and optical amplification in InGaN/GaN heterostructures

  3. Ultra-high frequency photoconductivity decay in GaAs/Ge/GaAs double heterostructure grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y. [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Johnston, S. W. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)] [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Maurya, D.; Priya, S. [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Umbel, R. [Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2013-03-04T23:59:59.000Z

    GaAs/Ge/GaAs double heterostructures (DHs) were grown in-situ using two separate molecular beam epitaxy chambers. High-resolution x-ray rocking curve demonstrates a high-quality GaAs/Ge/GaAs heterostructure by observing Pendelloesung oscillations. The kinetics of the carrier recombination in Ge/GaAs DHs were investigated using photoconductivity decay measurements by the incidence excitation from the front and back side of 15 nm GaAs/100 nm Ge/0.5 {mu}m GaAs/(100)GaAs substrate structure. High-minority carrier lifetimes of 1.06-1.17 {mu}s were measured when excited from the front or from the back of the Ge epitaxial layer, suggests equivalent interface quality of GaAs/Ge and Ge/GaAs. Wavelength-dependent minority carrier recombination properties are explained by the wavelength-dependent absorption coefficient of Ge.

  4. Metastable states in InGaN/GaN MQW structures doped with Sm, Eu, and Eu + Sm

    SciTech Connect (OSTI)

    Mezdrogina, M. M., E-mail: Margaret.M@mail.ioffe.ru [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Kozhanova, Yu. V. [St. Petersburg State Polytechnical University (Russian Federation)

    2013-04-15T23:59:59.000Z

    Measurements of the microphotoluminescence (microPL) spectra of InGaN/GaN:Sm and InGaN/GaN:Eu quantum well (QW) structures show that the action of a magnetic field gives rise to Van Vleck paramagnetism for Eu{sup 3+} and Sm{sup 3+}. The macrophotoluminescence (macroPL) spectra recorded after measuring the microPL spectra of InGaN/GaN QW structures doped with Sm or Eu + Sm at a high excitation level (>10{sup 23} photons cm{sup -2} s{sup -1}) in magnetic fields contain no QW emission lines which are present in the macroPL spectra recorded before these microPL measurements. This is indicative of the presence of photoinduced defects. Annealing of the InGaN/GaN:Sm and InGaN/GaN:(Eu + Sm) structures reduces the concentration of photoinduced defects.

  5. Gas-source molecular beam epitaxial growth and characterization of the (Al,In,Ga)NP/GaP material system and Its applications to light-emitting diodes

    E-Print Network [OSTI]

    Odnoblyudov, Vladimir

    2006-01-01T23:59:59.000Z

    on metamorphic growth of InGaP layers on GaP substrates, astemperature amber photoluminescence from InGaP QWs, grownon a metamorphic InGaP layer. References: Fred Shubert E. ,

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

    SciTech Connect (OSTI)

    Krishnamoorthy, Sriram, E-mail: krishnamoorthy.13@osu.edu, E-mail: rajan@ece.osu.edu; Akyol, Fatih [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Rajan, Siddharth, E-mail: krishnamoorthy.13@osu.edu, E-mail: rajan@ece.osu.edu [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2014-10-06T23:59:59.000Z

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

  7. Unique determination of the -CN group tilt angle in Langmuir monolayers using sum-frequency polarization null angle and phase

    SciTech Connect (OSTI)

    Velarde Ruiz Esparza, Luis A.; Wang, Hongfei

    2013-10-14T23:59:59.000Z

    The relative phase and amplitude ratio between the ssp and ppp polarization combinations of the vibrational sum-frequency generation (SFG) response can be uniquely and accurately determined by the polarization null angle (PNA) method. In this report we show that PNA measurements of the -CN vibration in the 4-n pentyl-4'-cyanoterphenyl (5CT) Langmuir monolayer at the air/water interface yields ssp and ppp response of the same phase, while those in the 4-n-octyl-4'cyanobiphenyl (8CB) Langmuir monolayer have the opposite phase. Accordingly, the -CN group in the 5CT monolayer is tilted around 25+/-2 from the interface normal, while that in the 8CB is tilted around 57+/-2, consistent with the significant differences in the phase diagrams and hydrogen bonding SFG spectra of the two Langmuir monolayers as reported in the literature. These results also demonstrate that in SFG studies the relative phase information of the different polarization combinations, especially for the ssp and ppp, is important in the unique determination of the tilt angle and conformation of a molecular group at the interface.

  8. ccsd-00000821(version1):6Nov2003 Alloy effects in Ga1-xInxN/GaN heterostructures

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    ccsd-00000821(version1):6Nov2003 Alloy effects in Ga1-xInxN/GaN heterostructures Duc-Phuong Nguyen, France We show that the large band offsets between GaN and InN and the heavy carrier effec- tive masses preclude the use of the Virtual Crystal Approximation to describe the electronic structure of Ga1-xInxN/GaN

  9. DESIGN, GROWTH, FABRICATION AND CHARACTERIZATION OF HIGH-BAND GAP InGaN/GaN SOLAR CELLS

    E-Print Network [OSTI]

    Honsberg, Christiana

    DESIGN, GROWTH, FABRICATION AND CHARACTERIZATION OF HIGH-BAND GAP InGaN/GaN SOLAR CELLS Omkar Jani1 with a band gap of 2.4 eV or greater. InxGa1-xN is one of a few alloys that can meet this key requirement. InGaN.4 eV. InGaN has the appropriate optical properties and has been well demonstrated for light

  10. AlGaN/GaN MIS-HEMT Gate Structure Improvement Using Al2O3 Deposited by PEALD

    E-Print Network [OSTI]

    Boyer, Edmond

    AlGaN/GaN MIS-HEMT Gate Structure Improvement Using Al2O3 Deposited by PEALD R. Meunier1 , A, 38054 Grenoble Cedex 9, France 2 LAAS-CNRS, 7 Avenue du Colonel Roche, 31400 Toulouse, France AlGaN /GaN behavior. Those trapped charges can be associated to the carbon contamination of the AlGaN surface

  11. Emission mechanisms of bulk GaN and InGaN quantum wells prepared by lateral epitaxial overgrowth

    E-Print Network [OSTI]

    Bowers, John

    Emission mechanisms of bulk GaN and InGaN quantum wells prepared by lateral epitaxial overgrowth S for publication 5 January 1999 The emission mechanisms of bulk GaN and InGaN quantum wells QWs were studied suggest that TDs simply reduce the net volume of light-emitting area. This effect is less pronounced in InGaN

  12. Comparison of strong coupling regimes in bulk GaAs, GaN and ZnO semiconductor microcavities

    E-Print Network [OSTI]

    Boyer, Edmond

    , transmission and absorption spectra of bulk GaAs, GaN and ZnO microcavities, in order to compareComparison of strong coupling regimes in bulk GaAs, GaN and ZnO semiconductor microcavities SAs and GaN microcavities. PACS numbers: 78.67.-n, 71.36.+c, 78.20.Ci, 78.55.Cr, 78.55.Et Keywords: polariton

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

    E-Print Network [OSTI]

    As, Donat Josef

    molecular beam epitaxy on free standing 3C-SiC 001 substrates. During growth of Al0.15Ga0.85N/GaN quantum growth of the quantum structures an 800 nm thick GaN buffer layer was deposited on the 3C-SiC substrate. The buffer and the c-AlGaN/GaN quantum wells were grown at a substrate temperature of 720 °C. The layers were

  14. Nanoair-bridged lateral overgrowth of GaN on ordered nanoporous GaN template

    SciTech Connect (OSTI)

    Wang, Y.D.; Zang, K.Y.; Chua, S.J.; Tripathy, S.; Chen, P.; Fonstad, C.G. [Singapore-MIT Alliance, E4-04-10, 4 Engineering Drive 3, Singapore 117576 (Singapore) and Centre for Optoelectronics, Department of Electrical and Computer Engineering, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore); Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602 (Singapore); Department of Electrical and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2005-12-19T23:59:59.000Z

    We report the growth of high-quality GaN epilayers on an ordered nanoporous GaN template by metalorganic chemical vapor deposition. The nanopores in GaN template were created by inductively coupled plasma etching using anodic aluminum oxide film as an etch mask. The average pore diameter and interpore distance is about 65 and 110 nm, respectively. Subsequent overgrowth of GaN first begins at the GaN crystallite surface between the pores, and then air-bridge-mediated lateral overgrowth leads to the formation of the continuous layer. Microphotoluminescence and micro-Raman measurements show improved optical properties and significant strain relaxation in the overgrown layer when compared to GaN layer of same thickness simultaneously grown on sapphire without any template. Similar to conventional epitaxial lateral overgrown GaN, such overgrown GaN on a nanopatterned surface would also serve as a template for the growth of ultraviolet-visible light-emitting III-nitride devices.

  15. AlGaN/GaN HEMT With 300-GHz fmax

    E-Print Network [OSTI]

    Chung, Jinwook W.

    We report on a gate-recessed AlGaN/GaN high-electron mobility transistor (HEMT) on a SiC substrate with a record power-gain cutoff frequency (f[subscript max]). To achieve this high f[subscript max], we combined a low-damage ...

  16. Gate-First AlGaN/GaN HEMT Technology for High-Frequency Applications

    E-Print Network [OSTI]

    Piner, Edwin L.

    This letter describes a gate-first AlGaN/GaN high-electron mobility transistor (HEMT) with a W/high-k dielectric gate stack. In this new fabrication technology, the gate stack is deposited before the ohmic contacts, and ...

  17. High Indium Concentration InGaN/GaN Grown on Sapphire Substrate by MOCVD

    E-Print Network [OSTI]

    Hartono, Haryono

    The InGaN system provides the opportunity to fabricate light emitting devices over the whole visible and ultraviolet spectrum due to band-gap energies E[subscript g] varying between 3.42 eV for GaN and 1.89 eV for InN. ...

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

    E-Print Network [OSTI]

    Lu, Bin

    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 ...

  19. Investigation of Strain in AlGaN/GaN Multi Quantum Wells by Complementary Techniques

    SciTech Connect (OSTI)

    Devaraju, G.; Sathish, N.; Pathak, A. P. [School of Physics, University of Hyderabad, Central University (P.0), Hyderabad 500 046 (India); Dhamodaran, S. [Department of Physics, Indian Institute of Technology, IIT P O, Kanpur UP 208016 (India); Gaca, J.; Wojcik, M. [Institute of Electronic Materials Technology, 01-919 Warsaw, ul. Wolczynska 133 (Poland); Turos, A. [Institute of Electronic Materials Technology, 01-919 Warsaw, ul. Wolczynska 133 (Poland); Soltan Institute for Nuclear Studies, Swierk/Otwock, Warsaw (Poland); Arora, B. M. [Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400 005 (India)

    2009-03-10T23:59:59.000Z

    Al{sub 0.49}Ga{sub 0.51}N(12 nm)/GaN (13 nm) Multi Quantum Wells of 15 periods are grown on sapphire by MOCVD technique. GaN/AlN, each of thickness 200 nm and 20 nm respectively, are used as buffer layers between substrate and epilayer to incorporate the strain in epilayers. It is a well established technique to engineer the band gap in Al{sub x}Ga{sub 1-x}N by adjusting alloy composition. These samples are used in visible and UV light emitters. In the present study, we employ a photoluminescence technique to estimate the composition and luminescence peak positions of AlGaN and GaN. Crystallinity and quality of interfaces have been studied by Rocking curve scan. The Threading Dislocations formed at the GaN buffer layer travel across the entire layers to the surface to form good quality films. Photo-luminescence results show a very sharp GaN peak at 3.4 eV, as observed and reported by others, which shows that samples are free from point defects.

  20. Trap Activation Energy and Transport Parameters of HgI$_2$ Crystals for Bubble-Plasma Diagnostics

    E-Print Network [OSTI]

    M. B. Miller; V. F. Kushniruk; A. V. Sermyagin

    2003-01-13T23:59:59.000Z

    In recent data on neutron induced acoustic cavitation in deuterium--containing liquids obtained by neutron measurements it was shown that very high temperatures could arise in some special cases. To study temperature of so--called bubble plasma it is desirable to have micro--detectors of X-rays, which can be prepared on the basis of room--temperature semiconductor detectors, in particular on mercuric iodide ($\\alpha$--HgI$_2$) crystals. Having in view this aim, the properties of gel--grown ($\\alpha$--HgI$_2$) crystals was studied by means of isothermal currents, and trap parameters was estimated. Results are promising for special aim of preparing X-ray detectors with moderate energy resolution needed in bubble--plasma diagnostic, though improving of crystal growing technology is necessary. {\\it PACS:} 29.40.Wk; 52.70.La {\\it Keywords:} X-ray and gamma--ray measurements; semiconductor detectors; mercuric iodide; plasma diagnostics; cavitation

  1. Gallium surface diffusion on GaAs (001) surfaces measured by crystallization dynamics of Ga droplets

    SciTech Connect (OSTI)

    Bietti, Sergio, E-mail: sergio.bietti@mater.unimib.it; Somaschini, Claudio; Esposito, Luca; Sanguinetti, Stefano [L–NESS and Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 55, I–20125 Milano (Italy); Fedorov, Alexey [L–NESS and CNR–IFN, via Anzani 42, I-22100 Como (Italy)

    2014-09-21T23:59:59.000Z

    We present accurate measurements of Ga cation surface diffusion on GaAs surfaces. The measurement method relies on atomic force microscopy measurement of the morphology of nano–disks that evolve, under group V supply, from nanoscale group III droplets, earlier deposited on the substrate surface. The dependence of the radius of such nano-droplets on crystallization conditions gives direct access to Ga diffusion length. We found an activation energy for Ga on GaAs(001) diffusion E{sub A}=1.31±0.15 eV, a diffusivity prefactor of D{sub 0}?=?0.53(×2.1±1) cm{sup 2} s{sup ?1} that we compare with the values present in literature. The obtained results permit to better understand the fundamental physics governing the motion of group III ad–atoms on III–V crystal surfaces and the fabrication of designable nanostructures.

  2. Lattice-matched epitaxial GaInAsSb/GaSb thermophotovoltaic devices

    SciTech Connect (OSTI)

    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

    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.

  3. Green cubic GaInN/GaN light-emitting diode on microstructured silicon (100)

    SciTech Connect (OSTI)

    Stark, Christoph J. M.; Detchprohm, Theeradetch; Wetzel, Christian, E-mail: wetzel@ieee.org [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States) [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Future Chips Constellation, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180 (United States); Lee, S. C.; Brueck, S. R. J. [Department of Electrical and Computer Engineering and Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico 87106 (United States)] [Department of Electrical and Computer Engineering and Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico 87106 (United States); Jiang, Y.-B. [Department of Earth and Planetary Science, University of New Mexico, Albuquerque, New Mexico 87131 (United States)] [Department of Earth and Planetary Science, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2013-12-02T23:59:59.000Z

    GaInN/GaN light-emitting diodes free of piezoelectric polarization were prepared on standard electronic-grade Si(100) substrates. Micro-stripes of GaN and GaInN/GaN quantum wells in the cubic crystal structure were grown on intersecting (111) planes of microscale V-grooved Si in metal-organic vapor phase epitaxy, covering over 50% of the wafer surface area. Crystal phases were identified in electron back-scattering diffraction. A cross-sectional analysis reveals a cubic structure virtually free of line defects. Electroluminescence over 20 to 100??A is found fixed at 487?nm (peak), 516?nm (dominant). Such structures therefore should allow higher efficiency, wavelength-stable light emitters throughout the visible spectrum.

  4. Structural and optical properties of core–shell Ag{sub 2}S/HgS nanostructures

    SciTech Connect (OSTI)

    Basyach, Priyanka; Choudhury, Amarjyoti, E-mail: ajc@tezu.ernet.in

    2013-07-15T23:59:59.000Z

    Graphical abstract: - Highlights: • Core–shell Ag{sub 2}S/HgS nanostructures are successfully synthesized. • The particle size and the structure were confirmed through TEM images. • The absorbance analysis reveals red shift with increasing shell concentration. • A transition from TYPE 1 to TYPE 2 core–shell nanostructure is observed. - Abstract: Here we report on a two-step synthesis route for fabrication of core–shell Ag{sub 2}S/HgS nanostructures. Nanoscale Ag{sub 2}S semiconductors are prepared by a standard redox reaction using AgNO{sub 3} and CS{sub 2} as the reactants in PVP. HgS layers are developed on Ag{sub 2}S cores through S-S bonding at the interface separating the two systems. The properties of these core–shell nanostructures are studied via various spectroscopic and microscopic tools like UV–Vis absorption spectra, photoluminescence spectra, X-ray diffraction pattern and transmission electron microscopic images. Change in optical properties is observed while varying the shell thickness in the sample. A detailed study on the luminescence properties reveal transition from TYPE 1 to TYPE 2 core–shell nanostructures is observed with increasing shell thickness.

  5. Perfect electrical switching of edge channel transport in HgTe quantum wells controlled by gate voltage

    SciTech Connect (OSTI)

    Fu, Hua-Hua, E-mail: hhfu@mail.hust.edu.cn; Wu, Dan-Dan; Gu, Lei [College of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2014-08-14T23:59:59.000Z

    We present a proposal to realize a perfect electrical switching of topological edge-state transport in a HgTe quantum well (QW). In our device design, we place a strip-like top gate voltage in a conventional quantum-point-contact (QPC) region in the HgTe QW. The numerical calculations show that upon increasing the gate voltage, two new conductance channels are developed in the transport direction and just neighbouring the boundaries of the top gate. The quantum states in the new channels can couple with the edge states to open a gap in energy spectrum, and in turn the gap width can be adjusted by the gate voltage, indicating that switch-on/off of the edge channels can be manipulated in a controllable way. Our device can not only be considered as a development of the conventional QPC structure based on the HgTe QW but also provides a new route to realize topological electrical switchers.

  6. Large internal dipole moment in InGaN/GaN quantum dots Irina A. Ostapenko, Gerald Hnig, Christian Kindel, Sven Rodt, Andr Strittmatter et al.

    E-Print Network [OSTI]

    Nabben, Reinhard

    Large internal dipole moment in InGaN/GaN quantum dots Irina A. Ostapenko, Gerald Hönig, Christian transitions in wurtzite InGaN/GaN coupled quantum dot nanowire heterostructures with polarization internal dipole moment in InGaN/GaN quantum dots Irina A. Ostapenko,a Gerald Hönig, Christian Kindel, Sven

  7. Investigation of large Stark shifts in InGaN/GaN multiple quantum wells Guibao Xu, Guan Sun, Yujie J. Ding, Hongping Zhao, Guangyu Liu et al.

    E-Print Network [OSTI]

    Gilchrist, James F.

    Investigation of large Stark shifts in InGaN/GaN multiple quantum wells Guibao Xu, Guan Sun, Yujie overgrowth on residual strain and In incorporation in a-plane InGaN/GaN quantum wells on r- sapphire substrates J. Appl. Phys. 113, 023506 (2013) Anisotropic lattice relaxation in non-c-plane InGaN/GaN multiple

  8. Quantum confinement in GaP nanoclusters

    SciTech Connect (OSTI)

    Laurich, B.K.; Smith, D.C.; Healy, M.D.

    1994-06-01T23:59:59.000Z

    We have prepared GaP and GaAs nanoclusters from organometallic condensation reactions of E[Si(ChH{sub 3})3]3 (E = P, As) and GaCl{sub 3}. The size of the as synthesized clusters is 10 {Angstrom} to 15 {Angstrom}. Larger clusters of 20 {Angstrom} to 30 {Angstrom} size were obtained by thermal annealing of the as grown material. X-ray diffraction and transmission electron microscopy confirm the high crystalline quality. A lattice contraction of 6.7% could be seen for 10 {Angstrom} sized GaAs clusters. The clusters are nearly spherical in shape. Optical absorption spectra show a distinct line which can be assigned to the fundamental transition of the quantum confined electronic state. The measured blue shift, with respect to the GaP bulk absorption edge is 0.53 eV. As the cluster is smaller than the exciton radius, we can calculate the cluster size from this blue shift and obtain 20.2 {Angstrom}, consistent with the results from X-ray diffraction of 19.5 {Angstrom} for the same sample.

  9. UID-GaN doping1016 cm-3 2 m 5 m2 m

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    2 µm Drain Silicon UID-GaN ­ doping1016 cm-3 1.1 µm 2 µm GateSource 2 µm 5 µm2 µm AirAir Al0.25GaN ­ doping1015 cm-3 30 nm Drain Silicon UID-GaN P-GaNSource AirAir AlxGaN Drain Silicon UID-GaN GateSource AirAir AlxGaN Gate (a) (b) (c) Drain Silicon UID-GaN P-GaNSource AirAir AlxGaN Gate (d) P-GaN P-GaN 30

  10. 1-D and 2-D homoleptic dicyanamide structures, [Ph{sub 4}P]{sub 2}{Co{sup II}[N(CN){sub 2}]{sub 4}} and [Ph{sub 4}P]{M[N(CN){sub 2}]{sub 3}} (M = Mn, Co).

    SciTech Connect (OSTI)

    Raebiger, J. W.; Manson, J. L.; Sommer, R. D.; Geiser, U.; Rheingold, A. L.; Miller, J. S.; Materials Science Division; Univ. of Utah; Univ. of Delaware

    2001-05-21T23:59:59.000Z

    The homoleptic complexes [Ph{sub 4}P]{sub 2}{l_brace}Co[N(CN){sub 2}]{sub 4}{r_brace} and [Ph{sub 4}P]{l_brace}M[N(CN){sub 2}]{sub 3}{r_brace} [ M = Co, Mn] have been structurally as well as magnetically characterized. The complexes containing {l_brace}M[N(CN){sub 2}]{sub 4}{r_brace}{sup 2-} form 1-D chains, which are bridged via a common dicyanamide ligand in {l_brace}M[N(CN){sub 2}]{sub 3}{r_brace}{sup -} to form a 2-D structure. The five-atom [NCNCN]{sup -} ligands lead to a {sup 4}T{sub 1g} ground state for Co(II) which has an unquenched spin-orbit coupling that is reflected in the magnetic properties. Long-range magnetic ordering was not observed in any of these materials.

  11. In-situ spectroscopic ellipsometry for real time composition control of Hg{sub 1{minus}x}Cd{sub x}Te grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Dat, R.; Aqariden, F.; Chandra, D.; Shih, H.D. [Raytheon TI Systems, Sensors and Infrared Lab., Dallas, TX (United States); Duncan, W.M. [Texas Instruments Inc., Dallas, TX (United States). Components and Materials Research Center

    1998-12-31T23:59:59.000Z

    Spectral ellipsometry (SE) was applied to in situ composition control of Hg{sub 1{minus}x}Cd{sub x}Te grown by molecular beam epitaxy (MBE), and the impact of surface topography of the Hg{sub 1{minus}x}Cd{sub x}Te layers on the accuracy of SE was investigated. Of particular importance is the presence of surface defects, such as voids in MBE-Hg{sub 1{minus}x}Cd{sub x}Te layers. While dislocations do not have any significant impact on the dielectric functions, the experimental data in this work show that MBE-Hg{sub 1{minus}x}Cd{sub x}Te samples having the same composition, but different void densities, have different effective dielectric functions.

  12. Carrier capture dynamics of single InGaAs/GaAs quantum-dot layers

    SciTech Connect (OSTI)

    Chauhan, K. N.; Riffe, D. M.; Everett, E. A.; Kim, D. J.; Yang, H. [Physics Department, Utah State University, Logan, Utah 84322-4415 (United States)] [Physics Department, Utah State University, Logan, Utah 84322-4415 (United States); Shen, F. K. [Center for Surface Analysis and Applications, Utah State University, Logan, Utah 84322-4415 (United States)] [Center for Surface Analysis and Applications, Utah State University, Logan, Utah 84322-4415 (United States)

    2013-05-28T23:59:59.000Z

    Using 800 nm, 25-fs pulses from a mode locked Ti:Al{sub 2}O{sub 3} laser, we have measured the ultrafast optical reflectivity of MBE-grown, single-layer In{sub 0.4}Ga{sub 0.6}As/GaAs quantum-dot (QD) samples. The QDs are formed via two-stage Stranski-Krastanov growth: following initial InGaAs deposition at a relatively low temperature, self assembly of the QDs occurs during a subsequent higher temperature anneal. The capture times for free carriers excited in the surrounding GaAs (barrier layer) are as short as 140 fs, indicating capture efficiencies for the InGaAs quantum layer approaching 1. The capture rates are positively correlated with initial InGaAs thickness and annealing temperature. With increasing excited carrier density, the capture rate decreases; this slowing of the dynamics is attributed to Pauli state blocking within the InGaAs quantum layer.

  13. Epitaxial GaN films by hyperthermal ion-beam nitridation of Ga droplets

    SciTech Connect (OSTI)

    Gerlach, J. W.; Ivanov, T.; Neumann, L.; Hoeche, Th.; Hirsch, D.; Rauschenbach, B. [Leibniz-Institut fuer Oberflaechenmodifizierung (IOM), D-04318 Leipzig (Germany)

    2012-06-01T23:59:59.000Z

    Epitaxial GaN film formation on bare 6H-SiC(0001) substrates via the process of transformation of Ga droplets into a thin GaN film by applying hyperthermal nitrogen ions is investigated. Pre-deposited Ga atoms in well defined amounts form large droplets on the substrate surface which are subsequently nitridated at a substrate temperature of 630 Degree-Sign C by a low-energy nitrogen ion beam from a constricted glow-discharge ion source. The Ga deposition and ion-beam nitridation process steps are monitored in situ by reflection high-energy electron diffraction. Ex situ characterization by x-ray diffraction and reflectivity techniques, Rutherford backscattering spectrometry, and electron microscopy shows that the thickness of the resulting GaN films depends on the various amounts of pre-deposited gallium. The films are epitaxial to the substrate, exhibit a mosaic like, smooth surface topography and consist of coalesced large domains of low defect density. Possible transport mechanisms of reactive nitrogen species during hyperthermal nitridation are discussed and the formation of GaN films by an ion-beam assisted process is explained.

  14. GaAs photoconductive semiconductor switch

    DOE Patents [OSTI]

    Loubriel, G.M.; Baca, A.G.; Zutavern, F.J.

    1998-09-08T23:59:59.000Z

    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 is disclosed. 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. 5 figs.

  15. GaAs photoconductive semiconductor switch

    DOE Patents [OSTI]

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

    1998-01-01T23:59:59.000Z

    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.

  16. GaN: Defect and Device Issues

    SciTech Connect (OSTI)

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

    1998-11-09T23:59:59.000Z

    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.

  17. High-temperature molecular beam epitaxial growth of AlGaN/GaN on GaN templates with reduced interface impurity levels

    SciTech Connect (OSTI)

    Koblmueller, G. [Department of Materials, University of California, Santa Barbara, California 93106 (United States); Walter Schottky Institut, Technische Universitaet Muenchen, D-85748 Garching (Germany); Chu, R. M.; Raman, A.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Speck, J. S. [Department of Materials, University of California, Santa Barbara, California 93106 (United States)

    2010-02-15T23:59:59.000Z

    We present combined in situ thermal cleaning and intentional doping strategies near the substrate regrowth interface to produce high-quality AlGaN/GaN high electron mobility transistors on semi-insulating (0001) GaN templates with low interfacial impurity concentrations and low buffer leakage. By exposing the GaN templates to an optimized thermal dissociation step in the plasma-assisted molecular beam epitaxy environment, oxygen, carbon, and, to lesser extent, Si impurities were effectively removed from the regrowth interface under preservation of good interface quality. Residual Si was further compensated by C-doped GaN via CBr{sub 4} to yield highly resistive GaN buffer layers. Improved N-rich growth conditions at high growth temperatures were then utilized for subsequent growth of the AlGaN/GaN device structure, yielding smooth surface morphologies and low residual oxygen concentration with large insensitivity to the (Al+Ga)N flux ratio. Room temperature electron mobilities of the two-dimensional electron gas at the AlGaN/GaN interface exceeded >1750 cm{sup 2}/V s and the dc drain current reached {approx}1.1 A/mm at a +1 V bias, demonstrating the effectiveness of the applied methods.

  18. 1 Managed by UT-Battelle for the U.S. Department of Energy NF/IDS Hg Vessel Layout 30 Jun 09

    E-Print Network [OSTI]

    McDonald, Kirk

    1 Managed by UT-Battelle for the U.S. Department of Energy NF/IDS Hg Vessel Layout 30 Jun 09 Cryostat 2 Front Drain Mercury Vessel Concept Matthew F. Glisson Van Graves #12;2 Managed by UT-Battelle;3 Managed by UT-Battelle for the U.S. Department of Energy NF/IDS Hg Vessel Layout 30 Jun 09 Cross Section

  19. Defect studies in low-temperature-grown GaAs

    SciTech Connect (OSTI)

    Bliss, D.E.

    1992-11-01T23:59:59.000Z

    High content of excess As is incorporated in GaAs grown by low-temperature molecular-beam-epitaxy (LTMBE). The excess As exists primarily as As antisite defects AsGa and a lesser extent of gallium vacancies V[sub Ga]. The neutral AsGa-related defects were measured by infrared absorption at 1[mu]m. Gallium vacancies, V[sub Ga], was investigated by slow positron annihilation. Dependence of defect contents on doping was studied by Si and Be dopants. No free carriers are generated by n-type or p-type doping up to 10[sup 19] cm[sup [minus]3] Si or Be. Raman data indicate Be occupies Ga substitutional sites but Si atom is not substitutional. Si induces more As[sub Ga] in the layer. As As[sub Ga] increases, photoquenchable As[sub Ga] decreases. Fraction of photoquenchable defects correlates to defects within 3 nearest neighbor separations disrupting the metastability. Annealing reduces neutral As[sub Ga] content around 500C, similar to irradiation damaged and plastically deformed Ga[sub As], as opposed to bulk grown GaAs in which As[sub Ga]-related defects are stable up to 1100C. The lower temperature defect removal is due to V[sub Ga] enhanced diffusion of As[sub Ga] to As precipitates. The supersaturated V[sub GA] and also decreases during annealing. Annealing kinetics for As[sub Ga]-related defects gives 2.0 [plus minus] 0.3 eV and 1.5 [plus minus] 0.3 eV migration enthalpies for the As[sub Ga] and V[sub Ga]. This represents the difference between Ga and As atoms hopping into the vacancy. The non-photoquenchable As[sub Ga]-related defects anneal with an activation energy of 1.1 [plus minus] 0.3eV. Be acceptors can be activated by 800C annealing. Temperature difference between defect annealing and Be activation formation of As[sub Ga]-Be[sub Ga] pairs. Si donors can only be partially activated.

  20. PHYSICAL REVIEW B 85, 045319 (2012) Photoluminescence from In0.5Ga0.5As/GaP quantum dots coupled to photonic crystal cavities

    E-Print Network [OSTI]

    Vuckovic, Jelena

    2012-01-01T23:59:59.000Z

    in materials systems, including InP/InGaP,6­9 InP/GaP,10,11 InP/AlGaInP,12,13 GaInP/GaP,14 InAs/GaP,15 and Al have been observed only in the InP/InGaP and InP/AlGaInP systems. GaP-based materials, by contrastP compared to InGaP is preferable for on-chip frequency downconversion to telecom wavelengths. Recently,17

  1. Optical spectroscopy of quantum confined states in GaAs/AlGaAs quantum well tubes

    SciTech Connect (OSTI)

    Shi, Teng; Fickenscher, Melodie; Smith, Leigh; Jackson, Howard [Department of Physics, University of Cincinnati, Cincinnati, OH 45221 (United States); Yarrison-Rice, Jan [Department of Physics, Miami University, Oxford, OH 45056 (United States); Gao, Qiang; Tan, Hoe; Jagadish, Chennupati [Department of Electronic Materials and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Etheridge, Joanne [Monash Centre for Electron Microscopy, Monash University, Victoria, 3800 (Australia); Wong, Bryan M. [Materials Chemistry Department, Sandia National Laboratories, Livermore, CA 94551 (United States)

    2013-12-04T23:59:59.000Z

    We have investigated the quantum confinement of electronic states in GaAs/Al{sub x}Ga{sub 1?x}As nanowire heterostructures which contain radial GaAs quantum wells of either 4nm or 8nm. Photoluminescence and photoluminescence excitation spectroscopy are performed on single nanowires. We observed emission and excitation of electron and hole confined states. Numerical calculations of the quantum confined states using the detailed structural information on the quantum well tubes show excellent agreement with these optical results.

  2. Strain-induced fundamental optical transition in (In,Ga)As/GaP quantum dots

    SciTech Connect (OSTI)

    Robert, C., E-mail: cedric.robert@insa-rennes.fr, E-mail: cedric.robert@tyndall.ie; Pedesseau, L.; Cornet, C.; Jancu, J.-M.; Even, J.; Durand, O. [Université Européenne de Bretagne, INSA Rennes, France and CNRS, UMR 6082 Foton, 20 Avenue des Buttes de Coësmes, 35708 Rennes (France)] [Université Européenne de Bretagne, INSA Rennes, France and CNRS, UMR 6082 Foton, 20 Avenue des Buttes de Coësmes, 35708 Rennes (France); Nestoklon, M. O. [Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation)] [Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Pereira da Silva, K. [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain) [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain); Departamento de Física, Universidade Federal do Ceará, P.O. Box 6030, Fortaleza–CE, 60455-970 (Brazil); Alonso, M. I. [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain)] [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain); Goñi, A. R. [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain) [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain); ICREA, Passeig Lluís Companys 23, 08010 Barcelona (Spain); Turban, P. [Equipe de Physique des Surfaces et Interfaces, Institut de Physique de Rennes UMR UR1-CNRS 6251, Université de Rennes 1, F-35042 Rennes Cedex (France)] [Equipe de Physique des Surfaces et Interfaces, Institut de Physique de Rennes UMR UR1-CNRS 6251, Université de Rennes 1, F-35042 Rennes Cedex (France)

    2014-01-06T23:59:59.000Z

    The nature of the ground optical transition in an (In,Ga)As/GaP quantum dot is thoroughly investigated through a million atoms supercell tight-binding simulation. Precise quantum dot morphology is deduced from previously reported scanning-tunneling-microscopy images. The strain field is calculated with the valence force field method and has a strong influence on the confinement potentials, principally, for the conduction band states. Indeed, the wavefunction of the ground electron state is spatially confined in the GaP matrix, close to the dot apex, in a large tensile strain region, having mainly Xz character. Photoluminescence experiments under hydrostatic pressure strongly support the theoretical conclusions.

  3. Midinfrared intersubband absorption in GaN/AlGaN superlattices on Si(111) templates

    SciTech Connect (OSTI)

    Kandaswamy, P. K.; Monroy, E. [CEA/CNRS group 'Nanophysique et semiconducteurs', INAC/SP2M/NPSC, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Machhadani, H.; Sakr, S.; Tchernycheva, M.; Julien, F. H. [Photis, Institut d'Electronique Fondamentale, Universite Paris-Sud, 91405 Orsay Cedex (France); Bougerol, C. [CEA/CNRS group 'Nanophysique et semiconducteurs', Institut Neel, 25 rue des Martyrs, 38042 Grenoble Cedex 9 (France)

    2009-10-05T23:59:59.000Z

    We report on the observation of midinfrared intersubband absorption in Si-doped GaN/AlGaN superlattices grown by plasma-assisted molecular-beam epitaxy on semi-insulating GaN-on-Si(111) templates. TM-polarized absorption attributed to transition between the first two electronic levels in the quantum wells peaked in the range from 2 to 9 {mu}m. The relative spectral width remains around 20% in the whole midinfrared spectral range. Doping is predicted to have a large influence on the intersubband absorption energy due to screening of polarization-induced internal electric field.

  4. Energy absorption in Ni-Mn-Ga/ polymer composites

    E-Print Network [OSTI]

    Feuchtwanger, Jorge

    2006-01-01T23:59:59.000Z

    In recent years Ni-Mn-Ga has attracted considerable attention as a new kind of actuator material. Off-stoichiometric single crystals of Ni2MnGa can regularly exhibit 6% strain in tetragonal martensites and orthorhombic ...

  5. Degradation mechanisms of GaN high electron mobility transistors

    E-Print Network [OSTI]

    Joh, Jungwoo

    2007-01-01T23:59:59.000Z

    In spite of their extraordinary performance, GaN high electron mobility transistors (HEMT) have still limited reliability. In RF power applications, GaN HEMTs operate at high voltage where good reliability is essential. ...

  6. On strongly GA-convex functions and stochastic processes

    SciTech Connect (OSTI)

    Bekar, Nurgül Okur [Department of Statistics, Giresun University, Giresun (Turkey); Akdemir, Hande Günay; ??can, ?mdat [Department of Mathematics, Giresun University, Giresun (Turkey)

    2014-08-20T23:59:59.000Z

    In this study, we introduce strongly GA-convex functions and stochastic processes. We provide related well-known Kuhn type results and Hermite-Hadamard type inequality for strongly GA-convex functions and stochastic processes.

  7. TEM-Untersuchungen an GaN basierten Halbleiterheterostrukturen fur

    E-Print Network [OSTI]

    Schubart, Christoph

    TEM-Untersuchungen an GaN basierten Halbleiterheterostrukturen f¨ur optoelektronische Anwendungen . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 5.1.2 Versetzungen bei Homoapitaxie auf GaN-Substraten . . . . 79 5.2 Versetzungsreduktion durch

  8. GaN Nanopore Arrays: Fabrication and Characterization

    E-Print Network [OSTI]

    Wang, Yadong

    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 ...

  9. Height stabilization of GaSb/GaAs quantum dots by Al-rich capping

    SciTech Connect (OSTI)

    Smakman, E. P., E-mail: e.p.smakman@tue.nl; Koenraad, P. M. [Department of Applied Physics, Eindhoven University of Technology, Den Dolech 2, 5612 AZ Eindhoven (Netherlands); DeJarld, M.; Martin, A. J.; Millunchick, J. [Department of Material Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Luengo-Kovac, M.; Sih, V. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

    2014-09-01T23:59:59.000Z

    GaSb quantum dots (QDs) in a GaAs matrix are investigated with cross-sectional scanning tunneling microscopy (X-STM) and photoluminescence (PL). We observe that Al-rich capping materials prevent destabilization of the nanostructures during the capping stage of the molecular beam epitaxy (MBE) growth process and thus preserves the QD height. However, the strain induced by the absence of destabilization causes many structural defects to appear around the preserved QDs. These defects originate from misfit dislocations near the GaSb/GaAs interface and extend into the capping layer as stacking faults. The lack of a red shift in the QD PL suggests that the preserved dots do not contribute to the emission spectra. We suggest that a better control over the emission wavelength and an increase of the PL intensity is attainable by growing smaller QDs with an Al-rich overgrowth.

  10. 2DEG electrodes for piezoelectric transduction of AlGaN/GaN MEMS resonators

    E-Print Network [OSTI]

    Weinstein, Dana

    A 2D electron gas (2DEG) interdigitated transducer (IDT) in Gallium Nitride (GaN) resonators is introduced and demonstrated. This metal-free transduction does not suffer from the loss mechanisms associated with more commonly ...

  11. High-field quasi-ballistic transport in AlGaN/GaN heterostructures

    SciTech Connect (OSTI)

    Danilchenko, B. A.; Tripachko, N. A. [Institute of Physics, NASU, Pr. Nauki 46, Kiev 03028 (Ukraine); Belyaev, A. E. [Institute of Semiconductor Physics, NASU, Pr. Nauki 45, Kiev 03028 (Ukraine); Vitusevich, S. A., E-mail: s.vitusevich@fz-juelich.de; Hardtdegen, H.; Lüth, H. [Peter Grünberg Institute (PGI-8,PGI-9), Forschungszentrum Jülich, Jülich D-52425 (Germany)

    2014-02-17T23:59:59.000Z

    Mechanisms of electron transport formation in 2D conducting channels of AlGaN/GaN heterostructures in extremely high electric fields at 4.2?K have been studied. Devices with a narrow constriction for the current flow demonstrate high-speed electron transport with an electron velocity of 6.8?×?10{sup 7}?cm/s. Such a velocity is more than two times higher than values reported for conventional semiconductors and about 15% smaller than the limit value predicted for GaN. Superior velocity is attained in the channel with considerable carrier reduction. The effect is related to a carrier runaway phenomenon. The results are in good agreement with theoretical predictions for GaN-based materials.

  12. AlGaN/GaN High-Electron-Mobility Transistor Employing an Additional Gate for High-Voltage Switching Applications

    E-Print Network [OSTI]

    Seo, Kwang Seok

    AlGaN/GaN High-Electron-Mobility Transistor Employing an Additional Gate for High-Voltage Switching 16, 2004; accepted May 10, 2005; published September 8, 2005) We have proposed and fabricated an AlGaN/GaN: GaN, AlGaN, HEMT, switch 1. Introduction GaN has attracted attention for high-power and high

  13. Cubic AlGaN/GaN Hetero-Junction Field-Effect Transistors with Normally-on and Normally-off

    E-Print Network [OSTI]

    As, Donat Josef

    Cubic AlGaN/GaN Hetero-Junction Field-Effect Transistors with Normally-on and Normally-effect transistors (HFETs) in GaN technology. HFET structures were fabricated of non-polar cubic AlGaN/GaN hetero insulation of 3C-SiC was realized by Ar+ implantation before c-AlGaN/GaN growth. HFETs with normally

  14. A 3-10 GHZLCR-matched Power Amplifier using Flip-Chip Mounted AlGaN/GaN HEMTs

    E-Print Network [OSTI]

    York, Robert A.

    WE4A-5 A 3-10 GHZLCR-matched Power Amplifier using Flip-Chip Mounted AlGaN/GaN HEMTs Jane J a GaN-based broadband power amplifier using AlGaN/GaN-HEMTs, grown on sapphire substrates amplifier using GaN- HEMTs-on-Sapphire. I INTRODUCTION GaN HEMTs have enormous potential for realizing high

  15. IPAP Conference Series 1: IWN2000, Nov., 2000 1 Morphology Dependent Growth Kinetics of Ga-polar GaN(0001)

    E-Print Network [OSTI]

    Cohen, Philip I.

    IPAP Conference Series 1: IWN2000, Nov., 2000 1 Morphology Dependent Growth Kinetics of Ga-polar GaN, cohen@ece.umn.edu GaN grown on Ga polar GaN templates prepared by metal-organic vapor deposition shows to equilibrium models of the growth. The results indicate that Ga-polar GaN(0001) has a step energy of the order

  16. Engineering of AlGaN-Delta-GaN Quantum-Well Gain Media for Mid-and Deep-Ultraviolet Lasers

    E-Print Network [OSTI]

    Gilchrist, James F.

    Engineering of AlGaN-Delta-GaN Quantum-Well Gain Media for Mid- and Deep-Ultraviolet Lasers Volume.1109/JPHOT.2013.2248705 1943-0655/$31.00 Ó2013 IEEE #12;Engineering of AlGaN-Delta-GaN Quantum-Well Gain@Lehigh.Edu). Abstract: The gain characteristics of AlGaN-delta-GaN quantum wells (QWs) with varying delta-GaN positions

  17. Recent progress in InGaAsSb/GaSb TPV devices

    SciTech Connect (OSTI)

    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

    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.

  18. AlGaAs/GaAs photovoltaic converters for high power narrowband radiation

    SciTech Connect (OSTI)

    Khvostikov, Vladimir; Kalyuzhnyy, Nikolay; Mintairov, Sergey; Potapovich, Nataliia; Shvarts, Maxim; Sorokina, Svetlana; Andreev, Viacheslav [Ioffe Physical-Technical Institute, 26 Polytechnicheskaya, St. Petersburg, 194021 (Russian Federation); Luque, Antonio [Ioffe Physical-Technical Institute, 26 Polytechnicheskaya, St. Petersburg, 194021, Russia and Instituto de Energia Solar, Universidad Politecnica de Madrid, Madrid (Spain)

    2014-09-26T23:59:59.000Z

    AlGaAs/GaAs-based laser power PV converters intended for operation with high-power (up to 100 W/cm{sup 2}) radiation were fabricated by LPE and MOCVD techniques. Monochromatic (? = 809 nm) conversion efficiency up to 60% was measured at cells with back surface field and low (x = 0.2) Al concentration 'window'. Modules with a voltage of 4 V and the efficiency of 56% were designed and fabricated.

  19. Sheet resistance under Ohmic contacts to AlGaN/GaN heterostructures

    SciTech Connect (OSTI)

    Haj?asz, M., E-mail: m.hajlasz@m2i.nl [Materials innovation institute (M2i), Mekelweg 2, 2628 CD, Delft (Netherlands); MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); Donkers, J. J. T. M.; Sque, S. J.; Heil, S. B. S. [NXP Semiconductors Research, High Tech Campus 46, 5656 AE, Eindhoven (Netherlands); Gravesteijn, D. J. [NXP Semiconductors Research, High Tech Campus 46, 5656 AE, Eindhoven (Netherlands); MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); Rietveld, F. J. R. [NXP Semiconductors, Gerstweg 2, 6534 AE, Nijmegen (Netherlands); Schmitz, J. [MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands)

    2014-06-16T23:59:59.000Z

    For the determination of specific contact resistance in semiconductor devices, it is usually assumed that the sheet resistance under the contact is identical to that between the contacts. This generally does not hold for contacts to AlGaN/GaN structures, where an effective doping under the contact is thought to come from reactions between the contact metals and the AlGaN/GaN. As a consequence, conventional extraction of the specific contact resistance and transfer length leads to erroneous results. In this Letter, the sheet resistance under gold-free Ti/Al-based Ohmic contacts to AlGaN/GaN heterostructures on Si substrates has been investigated by means of electrical measurements, transmission electron microscopy, and technology computer-aided design simulations. It was found to be significantly lower than that outside of the contact area; temperature-dependent electrical characterization showed that it exhibits semiconductor-like behavior. The increase in conduction is attributed to n-type activity of nitrogen vacancies in the AlGaN. They are thought to form during rapid thermal annealing of the metal stack when Ti extracts nitrogen from the underlying semiconductor. The high n-type doping in the region between the metal and the 2-dimensional electron gas pulls the conduction band towards the Fermi level and enhances horizontal electron transport in the AlGaN. Using this improved understanding of the properties of the material underneath the contact, accurate values of transfer length and specific contact resistance have been extracted.

  20. TEM and HRXRD Analysis of LP MOVPE Grown InGaP/GaAs epilayers

    SciTech Connect (OSTI)

    Pelosi, Claudio; Bosi, Matteo; Attolini, Giovanni; Germini, Fabrizio; Frigeri, Cesare [CNR-IMEM Institute, Parco Area delle Scienze 37a, Loc Fontanini 43010 Parma (Italy); Prutskij, Tatiana [Instituto de Ciencias, BUAP, Privada 17 Norte, no. 3417, colSanMiguel Hueyotlipan, 72050 Puebla, Pue. (Mexico)

    2007-04-10T23:59:59.000Z

    The diffusion phenomena at interfaces between GaAs/InGaP layers grown by low pressure MOVPE have been studied by dark field (DF) transmission Electron Microscopy (TEM) and High resolution X-ray Diffractometry (HRXRD). By comparing the results of the two techniques a mismatched layer containing P or P and In has been evidenced. The causes of this behavior are briefly discussed.

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

    E-Print Network [OSTI]

    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

    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.

  2. InGaN/GaN quantum wells for polariton laser diodes: Role of inhomogeneous broadening

    SciTech Connect (OSTI)

    Glauser, Marlene; Mounir, Christian; Rossbach, Georg; Feltin, Eric; Carlin, Jean-François; Butté, Raphaël; Grandjean, Nicolas [École Polytechnique Fédérale de Lausanne (EPFL), Institute of Condensed Matter Physics, CH-1015 Lausanne (Switzerland)

    2014-06-21T23:59:59.000Z

    Contrary to the case of III-nitride based visible light-emitting diodes for which the inhomogeneous linewidth broadening characteristic of InGaN-based multiple quantum well (MQW) heterostructures does not appear as a detrimental parameter, such a broadening issue can prevent a microcavity (MC) system entering into the strong light-matter coupling regime (SCR). The impact of excitonic disorder in low indium content (x???0.1) In{sub x}Ga{sub 1–x}N/GaN MQW active regions is therefore investigated for the subsequent realization of polariton laser diodes by considering both simulations and optical characterizations. It allows deriving the requirements for such MQWs in terms of absorption, emission linewidth, and Stokes shift. Systematic absorption-like and photoluminescence (PL) spectroscopy experiments are performed on single and multiple In{sub 0.1}Ga{sub 0.9}N/GaN quantum wells (QWs). Micro-PL mappings reveal a low temperature PL linewidth of ?30?meV, compatible with SCR requirements, for single QWs for which the microscopic origin responsible for this broadening is qualitatively discussed. When stacking several InGaN/GaN QWs, a departure from such a narrow linewidth value and an increase in the Stokes shift are observed. Various possible reasons for this degradation such as inhomogeneous built-in field distribution among the QWs are then identified. An alternative solution for the MC design to achieve the SCR with the InGaN alloy is briefly discussed.

  3. Rapid Communications Strong piezoelectricity in individual GaN nanowires

    E-Print Network [OSTI]

    Espinosa, Horacio D.

    Rapid Communications Strong piezoelectricity in individual GaN nanowires Majid Minary@northwestern.edu (Received 12 July 2011; accepted 15 September 2011) Abstract GaN nanowires are promising building blocks piezoelectricity in individual single-crystal GaN nanowires revealed by direct measurement of the piezoelectric

  4. GaN Radiation Detectors for Particle Physics and

    E-Print Network [OSTI]

    Glasgow, University of

    GaN Radiation Detectors for Particle Physics and Synchrotron Applications James Paul Grant and monitoring applications. Gallium nitride (GaN) was investigated as a radiation hard particle detector diameter on three epitaxial GaN wafers grown on a sapphire sub- strate. Two of the wafers were obtained

  5. New Faces of GaN: Growth, Doping and Devices

    E-Print Network [OSTI]

    California at Santa Barbara, University of

    New Faces of GaN: Growth, Doping and Devices James S. Speck Materials Department University of California Santa Barbara, CA LEO of a-GaN from circular opening Engineering Insights 2006 #12;#12;Personnel. Wraback (ARL) $$$ JST ­ ERATO UCSB SSLDC AFOSR ONR #12;Reversed direction of polarization Bulk GaN

  6. Analysis of the AlGaN/GaN vertical bulk current on Si, sapphire, and free-standing GaN substrates

    SciTech Connect (OSTI)

    Perez-Tomas, A.; Fontsere, A.; Llobet, J. [IMB-CNM-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, CAT (Spain); Placidi, M. [IREC, Jardins Dones de Negre 1, 08930 Sant Adria de Besos, Barcelona (Spain); Rennesson, S.; Chenot, S.; Moreno, J. C.; Cordier, Y. [CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Baron, N. [CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); PICOGIGA International, Pl M. Rebuffat, Courtaboeuf 7, 91140 Villejust (France)

    2013-05-07T23:59:59.000Z

    The vertical bulk (drain-bulk) current (I{sub db}) properties of analogous AlGaN/GaN hetero-structures molecular beam epitaxially grown on silicon, sapphire, and free-standing GaN (FS-GaN) have been evaluated in this paper. The experimental I{sub db} (25-300 Degree-Sign C) have been well reproduced with physical models based on a combination of Poole-Frenkel (trap assisted) and hopping (resistive) conduction mechanisms. The thermal activation energies (E{sub a}), the (soft or destructive) vertical breakdown voltage (V{sub B}), and the effect of inverting the drain-bulk polarity have also been comparatively investigated. GaN-on-FS-GaN appears to adhere to the resistive mechanism (E{sub a} = 0.35 eV at T = 25-300 Degree-Sign C; V{sub B} = 840 V), GaN-on-sapphire follows the trap assisted mechanism (E{sub a} = 2.5 eV at T > 265 Degree-Sign C; V{sub B} > 1100 V), and the GaN-on-Si is well reproduced with a combination of the two mechanisms (E{sub a} = 0.35 eV at T > 150 Degree-Sign C; V{sub B} = 420 V). Finally, the relationship between the vertical bulk current and the lateral AlGaN/GaN transistor leakage current is explored.

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

    E-Print Network [OSTI]

    McKittrick, Joanna

    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

  8. Electron mobility enhancement in AlN/GaN/AlN heterostructures with InGaN nanogrooves

    E-Print Network [OSTI]

    improve the room-temperature carrier mobility in wurtzite AlN/GaN/AlN heterostructures, which is limited consider a narrow groove made of InxGa1-xN with small In content x inside a wurtzite AlN/GaN/AlN heteroN 2 nm /GaN 3 nm /AlN 3 nm . A well-known feature of wurtzite heterostructures is a strong buit

  9. Growth of GaN on porous SiC and GaN substrates C. K. Inoki1

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Growth of GaN on porous SiC and GaN substrates C. K. Inoki1 , T. S. Kuan1 , Ashutosh Sagar2 , C, Albuquerque, NM 87185 4 Beckman Institute, University of Illinois, Urbana, IL 61801 GaN films were grown on porous SiC and GaN templates using both plasma-assisted molecular beam epitaxy (PAMBE) and metal

  10. Structural, morphological, and optical properties of AlGaN/GaN heterostructures with AlN buffer and interlayer

    E-Print Network [OSTI]

    Ozbay, Ekmel

    N buffer layer BL grown on an Al2O3 substrate and an AlN IL grown under the AlGaN ternary layer TL. In the present study, we investigate the effects of an AlN BL on an Al2O3 substrate and an AlN IL between an AlGaNStructural, morphological, and optical properties of AlGaN/GaN heterostructures with AlN buffer

  11. Vapor-liquid equilibria of coal-derived liquids; 3: Binary systems with tetralin at 200 mmHg

    SciTech Connect (OSTI)

    Blanco, B.; Beltran, S.; Cabezas, J.L. (University Coll., Burgos (Spain). Dept. of Chemical Engineering); Coca, J. (Univ. of Oviedo (Spain). Dept. of Chemical Engineering)

    1994-01-01T23:59:59.000Z

    Isobaric vapor-liquid equilibrium data are reported for binary systems of tetralin with p-xylene, [gamma]-picoline, piperidine, and pyridine; all systems were measured at 26.66 kPa (200 mmHg) with a recirculation still. Liquid-phase activity coefficients were correlated using the Van Laar, Wilson, NRTL, and UNIQUAC equations. Vapor-phase nonidealities were found negligible under the experimental conditions of this work, and deviations of the liquid phase from the ideal behavior, as described by Raoult's law, were found to be slightly positive for all the systems.

  12. From Schottky to Ohmic graphene contacts to AlGaN/GaN heterostructures: Role of the AlGaN layer microstructure

    SciTech Connect (OSTI)

    Fisichella, G. [CNR-IMM, Strada VIII, 5, 95121 Catania (Italy); Department of Electronic Engineering, University of Catania, 95124 Catania (Italy); Greco, G.; Roccaforte, F.; Giannazzo, F. [CNR-IMM, Strada VIII, 5, 95121 Catania (Italy)

    2014-08-11T23:59:59.000Z

    The electrical behaviour of graphene (Gr) contacts to Al{sub x}Ga{sub 1?x}N/GaN heterostructures has been investigated, focusing, in particular, on the impact of the AlGaN microstructure on the current transport at Gr/AlGaN interface. Two Al{sub 0.25}Ga{sub 0.75}N/GaN heterostructures with very different quality in terms of surface roughness and defectivity, as evaluated by atomic force microscopy (AFM) and transmission electron microscopy, were compared in this study, i.e., a uniform and defect-free sample and a sample with a high density of typical V-defects, which locally cause a reduction of the AlGaN thickness. Nanoscale resolution current voltage (I-V) measurements by an Au coated conductive AFM tip were carried out at several positions both on the bare and Gr-coated AlGaN surfaces. Rectifying contacts were found onto both bare AlGaN surfaces, but with a more inhomogeneous and lower Schottky barrier height (?{sub B}???0.6?eV) for AlGaN with V-defects, with respect to the case of the uniform AlGaN (?{sub B}???0.9?eV). Instead, very different electrical behaviours were observed in the presence of the Gr interlayer between the Au tip and AlGaN, i.e., a Schottky contact with reduced barrier height (?{sub B} ? 0.4?eV) for the uniform AlGaN and an Ohmic contact for the AlGaN with V-defects. Interestingly, excellent lateral uniformity of the local I-V characteristics was found in both cases and can be ascribed to an averaging effect of the Gr electrode over the AlGaN interfacial inhomogeneities. Due to the locally reduced AlGaN layer thickness, V defect act as preferential current paths from Gr to the 2DEG and can account for the peculiar Ohmic behaviour of Gr contacts on defective AlGaN.

  13. Lattice-Mismatched GaAs/InGaAs Two-Junction Solar Cells by Direct Wafer Bonding

    SciTech Connect (OSTI)

    Tanabe, K.; Aiken, D. J.; Wanlass, M. W.; Morral, A. F.; Atwater, H. A.

    2006-01-01T23:59:59.000Z

    Direct bonded interconnect between subcells of a lattice-mismatched III-V compound multijunction cell would enable dislocation-free active regions by confining the defect network needed for lattice mismatch accommodation to tunnel junction interfaces, while metamorphic growth inevitably results in less design flexibility and lower material quality than is desirable. The first direct-bond interconnected multijunction solar cell, a two-terminal monolithic GaAs/InGaAs two-junction solar cell, is reported and demonstrates viability of direct wafer bonding for solar cell applications. The tandem cell open-circuit voltage was approximately the sum of the subcell open-circuit voltages. This achievement shows direct bonding enables us to construct lattice-mismatched III-V multijunction solar cells and is extensible to an ultrahigh efficiency InGaP/GaAs/InGaAsP/InGaAs four-junction cell by bonding a GaAs-based lattice-matched InGaP/GaAs subcell and an InP-based lattice-matched InGaAsP/InGaAs subcell. The interfacial resistance experimentally obtained for bonded GaAs/InP smaller than 0.10 Ohm-cm{sup 2} would result in a negligible decrease in overall cell efficiency of {approx}0.02%, under 1-sun illumination.

  14. X-ray diffraction analysis of InGaP/GaAs heterointerfaces grown by metalorganic chemical vapor deposition

    SciTech Connect (OSTI)

    Nittono, T.; Hyuga, F. [NTT System Electronics Laboratories 3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa, 243-01 (Japan)] [NTT System Electronics Laboratories 3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa, 243-01 (Japan)

    1997-03-01T23:59:59.000Z

    InGaP/GaAs heterointerfaces grown by metalorganic chemical vapor deposition have been characterized by a high-resolution x-ray diffraction analysis of multiple quantum well structures. The flow of AsH{sub 3} to InGaP surface produces an InGaAs-like interfacial layer at the GaAs-on-InGaP interface, indicating P atoms of the InGaP surface are easily replaced by As atoms. The flow of PH{sub 3} to GaAs surface, on the other hand, does not make any detectable interfacial layer, indicating that almost no As atoms of the GaAs surface are replaced by P atoms. It is also found that the flow of trimethylgallium (TMG) to the InGaP surface produces a GaP-like interfacial layer. This interfacial layer is probably formed by the reaction between TMG and excessive P atoms on the InGaP surface or residual PH{sub 3} in the growth chamber. {copyright} {ital 1997 American Institute of Physics.}

  15. Physica B 376377 (2006) 486490 Preferential substitution of Fe on physically equivalent Ga sites in GaN

    E-Print Network [OSTI]

    Nabben, Reinhard

    2006-01-01T23:59:59.000Z

    in GaN W. GehlhoffÃ, D. Azamat1 , U. Haboeck, A. Hoffmann Institute for Solid State Physics, Technical freestanding hydride vapor phase grown GaN have been studied in the X- and Q-band. A complex resonance pattern with C3v symmetry in the wurtzite structure of GaN. Aside from the displacement of their magnetic axis

  16. Superluminescence in Green Emission GaInN/GaN Quantum Well Structures under Pulsed Laser Excitation

    E-Print Network [OSTI]

    Wetzel, Christian M.

    and bulk GaN substrates, respectively. Under intense pulsed photo excitation, we observed strong the same excitation conditions, the blue shift for the m-axis grown structure on bulk GaN substrate is less-plane sapphire substrate and along the non-polar m-axis on m-plane bulk GaN substrate. The frequently used

  17. Transferring oxygen isotopes to 1,2,4-benzotriazine 1-oxides forming the corresponding 1,4-dioxides by using the HOF$CH3CN complex

    E-Print Network [OSTI]

    Gates, Kent. S.

    Transferring oxygen isotopes to 1,2,4-benzotriazine 1-oxides forming the corresponding 1,4-dioxides Available online 14 August 2012 Keywords: Oxygen transfer 18 O isotope Tirapazamine HOF$CH3CN F2/N2 N is their ability to capitalize on the low oxygen (hypoxic) environment found in many solid tumors. The lead

  18. Draft Genome sequence of Frankia sp. strains CN3 , an atypical, non-infective (Nod-) ineffective (Fix-) isolate from Coriaria nepalensis

    SciTech Connect (OSTI)

    Ghodhbane-Gtari, Faten [University of New Hampshire; Beauchemin, Nicholas [University of New Hampshire; Bruce, David [Los Alamos National Laboratory (LANL); Chain, Patrick S. G. [Lawrence Livermore National Laboratory (LLNL); Chen, Amy [U.S. Department of Energy, Joint Genome Institute; Davenport, Karen W. [Los Alamos National Laboratory (LANL); Deshpande, Shweta [U.S. Department of Energy, Joint Genome Institute; Detter, J. Chris [U.S. Department of Energy, Joint Genome Institute; Furnholm, Teal [University of New Hampshire; Goodwin, Lynne A. [Los Alamos National Laboratory (LANL); Gtari, Maher [University of New Hampshire; Han, Cliff [Los Alamos National Laboratory (LANL); Han, James [U.S. Department of Energy, Joint Genome Institute; Huntemann, Marcel [U.S. Department of Energy, Joint Genome Institute; Ivanova, N [U.S. Department of Energy, Joint Genome Institute; Kyrpides, Nikos C [U.S. Department of Energy, Joint Genome Institute; Land, Miriam L [ORNL; Markowitz, Victor [U.S. Department of Energy, Joint Genome Institute; Mavromatis, K [U.S. Department of Energy, Joint Genome Institute; Nolan, Matt [U.S. Department of Energy, Joint Genome Institute; Nouioui, Imen [University of Tunis-El Manar, Tunisia; Pagani, Ioanna [U.S. Department of Energy, Joint Genome Institute; Pati, Amrita [U.S. Department of Energy, Joint Genome Institute; Pitluck, Sam [U.S. Department of Energy, Joint Genome Institute; Santos, Catarina [Instiuto Celular e Aplicada, Portugal; Sen, Arnab [University of North Bengal, Siliguri, India; Sur, Saubashya [University of North Bengal, Siliguri, India; Szeto, Ernest [U.S. Department of Energy, Joint Genome Institute; Tavares, Fernando [Instiuto Celular e Aplicada, Portugal; Hazuki, Teshima [Los Alamos National Laboratory (LANL); Thakur, Subarna [University of North Bengal, Siliguri, India; Wall, Luis [University of Quilmes, Argentina; Woyke, Tanja [U.S. Department of Energy, Joint Genome Institute; Tisa, Louis S. [University of New Hampshire

    2013-01-01T23:59:59.000Z

    We report here the genome sequence of Frankia sp. strain CN3, which was isolated from Coriaria nepalensis. This genome sequence is the first from the fourth lineage of Frankia, that are unable to re-infect actinorhizal plants. At 10 Mb, it represents the largest Frankia genome sequenced to date.

  19. 80 K anomaly and its effect on the superconducting and magnetic transition in deuterated -,,BEDT-TTF...2CuN,,CN...2Br

    E-Print Network [OSTI]

    Zuo, Fulin

    careful transport and magnetic measurements on single crystals of deuterated - ET 2Cu N CN 2 Br cooling through 80 K will freeze the high temperature magnetic phase to low temperatures and the presence ordering of the chains. In this paper, we report careful transport and magnetic measurements on several

  20. Composition and Interface Analysis of InGaN/GaN Multiquantum-Wells on GaN Substrates Using Atom Probe Tomography

    SciTech Connect (OSTI)

    Liu, Fang; Huang, Li; Davis, Robert F.; Porter, Lisa M.; Schreiber, Daniel K.; Kuchibhatla, S. V. N. T.; Shutthanandan, V.; Thevuthasan, Suntharampillai; Preble, Edward; Paskova, Tanya; Evans, K. R.

    2014-09-04T23:59:59.000Z

    In0.20Ga0.80N/GaN multi-quantum wells grown on [0001]-oriented GaN substrates with and without an InGaN buffer layer were characterized using three-dimensional atom probe tomography. In all samples, the upper interfaces of the QWs were slightly more diffuse than the lower interfaces. The buffer layers did not affect the roughness of the interfaces within the quantum well structure, a result attributed to planarization of the surface of the 1st GaN barrier layer which had an average root-mean-square roughness of 0.177 nm. The In and Ga distributions within the MQWs followed the expected distributions for a random alloy with no indications of In clustering.

  1. Point defect balance in epitaxial GaSb

    SciTech Connect (OSTI)

    Segercrantz, N., E-mail: natalie.segercrantz@aalto.fi; Slotte, J.; Makkonen, I.; Kujala, J.; Tuomisto, F. [Department of Applied Physics, Aalto University, P.O. Box 14100, FIN-00076 Aalto Espoo (Finland); Song, Y.; Wang, S. [Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Göteborg (Sweden); State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences 865 Changning Road, Shanghai 200050 (China)

    2014-08-25T23:59:59.000Z

    Positron annihilation spectroscopy in both conventional and coincidence Doppler broadening mode is used for studying the effect of growth conditions on the point defect balance in GaSb:Bi epitaxial layers grown by molecular beam epitaxy. Positron annihilation characteristics in GaSb are also calculated using density functional theory and compared to experimental results. We conclude that while the main positron trapping defect in bulk samples is the Ga antisite, the Ga vacancy is the most prominent trap in the samples grown by molecular beam epitaxy. The results suggest that the p–type conductivity is caused by different defects in GaSb grown with different methods.

  2. Room-temperature cw operation of InGaAsP/InGaP lasers at 727 nm grown on GaAs substrates by liquid phase epitaxy

    SciTech Connect (OSTI)

    Wakao, K.; Nishi, H.; Kusunoki, T.; Isozumi, S.; Ohsaka, S.

    1984-06-01T23:59:59.000Z

    InGaAsP/InGaP lasers emitting at 724--727 nm have been fabricated on GaAs substrates using liquid phase epitaxy. The threshold current is reduced to 8 kA/cm/sup 2/ by thinning the active layer. Room-temperature cw operation is achieved for the first time in the lasing wavelength range below 760 nm in this quaternary system.

  3. Self-assembled In0.5Ga0.5As quantum dots on GaP Yuncheng Song,a

    E-Print Network [OSTI]

    Haller, Gary L.

    SAQDs . Several groups have investigated the growth of both InP and In-rich InGaP SAQDs on GaP.7­12 Most temperature operation of vis- ible light emitting diodes LEDs using InP/GaP and InGaP/ GaP SAQDs, respectively

  4. Current crowding in GaInN / GaN LEDs grown on insulating substrates X. Guo, E. F. Schubert and J. Jahns

    E-Print Network [OSTI]

    Jahns, Jürgen

    Current crowding in GaInN / GaN LEDs grown on insulating substrates X. Guo, E. F. Schubert and J spreading in a mesa-structure GaN-based LED grown on an insulating or semi-insulating substrate. (b. Jahns Current crowding in mesa-structure GaInN/GaN light-emitting diodes (LEDs) grown on insulating

  5. Gas-source molecular beam epitaxial growth and characterization of the (Al,In,Ga)NP/GaP material system and Its applications to light-emitting diodes

    E-Print Network [OSTI]

    Odnoblyudov, Vladimir

    2006-01-01T23:59:59.000Z

    ? G, Kcal/mol GaP GaN AlN o Substrate temperature, C Figurenm-thick GaN 0.006 P 0.994 layer on substrate temperature.substrate temperature for Reactions formation of AlP, GaP, GaN and

  6. IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 51, NO. 2, FEBRUARY 2003 653 AlGaN/GaN HFET Power Amplifier Integrated With

    E-Print Network [OSTI]

    Itoh, Tatsuo

    the first demonstration of a GaN-based HFET was done on a sapphire substrate in 1993 [1]­[3]. This is due crystal quality compared to that of the sapphire substrate. Thanks to steadfast progress in AlGaN/GaN HFETIEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 51, NO. 2, FEBRUARY 2003 653 AlGaN/GaN

  7. Tunable THz plasmon resonances in InGaAs/InP HEMT R. E. Peale*a

    E-Print Network [OSTI]

    Peale, Robert E.

    , high ns, and small m*. A variety of materials systems such as GaAs/AlGaAs [3], InGaP/InGaAs/GaAs [4

  8. Prospective emission efficiency and in-plane light polarization of nonpolar m-plane InxGa1-xN/GaN blue light emitting diodes fabricated on freestanding GaN substrates

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    fabricated on freestanding GaN substrates T. Koyama and T.on freestanding m-plane GaN substrates. Although the ? inton the freestanding GaN substrate. cause the current was

  9. Reactive codoping of GaAlInP compound semiconductors

    DOE Patents [OSTI]

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

    2008-02-12T23:59:59.000Z

    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.

  10. Influence of Ga content on the structure and anomalous Hall effect of Fe{sub 1?x}Ga{sub x} thin films on GaSb(100)

    SciTech Connect (OSTI)

    Anh Tuan, Duong; Shin, Yooleemi; Viet Cuong, Tran; Cho, Sunglae, E-mail: slcho@ulsan.ac.kr [Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Phan, The-Long [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of)

    2014-05-07T23:59:59.000Z

    The Fe{sub 1?x}Ga{sub x} thin films (x?=?0.4, 0.5) have been grown on GaSb(100) substrate using molecular beam epitaxy. An epitaxial film with bcc ?-Fe crystal structure (A2) is observed in Fe{sub 0.6}Ga{sub 0.4} film, while an impure Fe{sub 3}Ga phase with DO{sub 3} structure is appeared in Fe{sub 0.5}Ga{sub 0.5} film. The saturated magnetizations at room temperature are observed to be 570?emu/cm{sup 3} and 180?emu/cm{sup 3} and the coercivities to be 170 and 364?Oe for Fe{sub 0.6}Ga{sub 0.4} and Fe{sub 0.5}Ga{sub 0.5}, respectively. A hysteresis trend in Hall resistance vs. magnetic field is observed for Fe{sub 0.5}Ga{sub 0.5} film. However, there is a weak hysteresis noticed in Fe{sub 0.4}Ga{sub 0.6} thin film.

  11. Catastrophic degradation of InGaAsP/InGaP double-heterostructure lasers grown on (001) GaAs substrates by liquid-phase epitaxy

    SciTech Connect (OSTI)

    Ueda, O.; Wakao, K.; Komiya, S.; Yamaguchi, A.; Isozumi, S.; Umebu, I.

    1985-12-01T23:59:59.000Z

    Catastrophically degraded InGaAsP/InGaP double-heterostructure lasers grown on (001) GaAs substrates by liquid-phase epitaxy, emitting at 727 and 810 nm are investigated by photoluminescence topography, scanning electron microscopy, transmission electron microscopy, and energy dispersive x-ray spectroscopy. The degradation is mainly due to catastrophic optical damage at the facet, i.e., development of <110> dark-line defects from the facet, and rarely due to catastrophic optical damage at some defects, i.e., development of <110> dark-line defects from the defects inside the stripe region. These <110> dark-line defects correspond to complicated dislocation networks connected with dark knots, and are quite similar to those observed in catastrophically degraded GaAlAs/GaAs double-heterostructure lasers. The degradation characteristics of the InGaAsP/InGaP double-heterostructure lasers are rather similar to those in GaAlAs/GaAs double-heterostructure lasers concerning the catastrophic degradation.

  12. Crystallographic analysis of the structure of livingstonite HgSb{sub 4}S{sub 8} from refined data

    SciTech Connect (OSTI)

    Borisov, S. V., E-mail: borisov@che.nsk.su; Pervukhina, N. V.; Magarill, S. A.; Kuratieva, N. V. [Russian Academy of Sciences, Nikolaev Institute of Inorganic Chemistry, Siberian Branch (Russian Federation); Vasil'ev, V. I., E-mail: itret@uiggm.nsc.ru [Russian Academy of Sciences, Institute of Geology and Mineralogy, Siberian Branch (Russian Federation)

    2010-03-15T23:59:59.000Z

    An X-ray diffraction study of mineral livingstonite (HgSb{sub 4}S{sub 8}) from Khaydarkan (Kyrgyzstan) has been performed on a Bruker Nonius X8Apex diffractometer with a 4K CCD detector (R = 0.031). The unit-cell parameters were found to be a = 30.1543(10) A, b = 3.9953(2) A, c = 21.4262(13) A, {beta} = 104.265(1){sup o}, V = 2501.7(2) A{sup 3}, Z = 8, d{sub calcd} = 5.013 g/cm{sup 3}, and sp. gr. A2/a. It was confirmed that livingstonite belongs to rod-layers structures. In one type of layer, two double Sb{sub 2}S{sub 4} chains are bound by disulfide groups [S{sub 2}]{sup 2-} (S-S 2.078(2) A); in the other type, these chains are bound via Hg{sup 2+} cations. A crystallographic analysis confirmed the existence of independent pseudotranslational ordering in the cation and anion matrices, which is characteristic of the lozenge-like structures of sulfides and sulfosalts.

  13. Dynamics of thermalization in GaInN/GaN quantum wells grown on ammonothermal GaN

    SciTech Connect (OSTI)

    Binder, J.; Korona, K. P.; Wysmo?ek, A.; Kami?ska, M. [Faculty of Physics, University of Warsaw, ul. Hoza 69, 00-681 Warsaw (Poland); Köhler, K.; Kirste, L.; Ambacher, O. [Fraunhofer Institute for Applied Solid State Physics, Tullastr. 72, 79108 Freiburg (Germany); Zaj?c, M.; Dwili?ski, R. [AMMONO SA, Czerwonego Krzy?a 2/31, 00-377 Warsaw (Poland)

    2013-12-14T23:59:59.000Z

    In this work, we present measurements of the dynamics of photoexcited carriers in GaInN/GaN quantum wells (QWs) grown on ammonothermal GaN, especially thermalization and recombination rates. Emission properties were measured by time-resolved photoluminescence (PL) and electroluminescence spectroscopy. Due to the use of high quality homoepitaxial material, we were able to obtain very valuable data on carrier thermalization. The temperature dependence of the QW energy observed in PL shows characteristic S-shape with a step of about 10?meV. Such a behavior (related to thermalization and localization at potential fluctuations) is often reported for QWs; but in our samples, the effect is smaller than in heteroepitaxial InGaN/GaN QWs due to lower potential fluctuation in our material. Absorption properties were studied by photocurrent spectroscopy measurements. A comparison of emission and absorption spectra revealed a shift in energy of about 60?meV. Contrary to PL, the QW energy observed in absorption decreases monotonically with temperature, which can be described by a Bose-like dependence E(T)?=?E(0) ? ?/(exp(?/T) ? 1), with parameters ??=?(0.11?±?0.01) eV, ??=?(355?±?20)?K, or by a Varshni dependence with coefficients ??=?(10?±?3) × 10{sup ?4}?eV/K and ??=?(1500?±?500) K. Taking into account absorption and emission, the fluctuation amplitude (according to Eliseev theory) was ??=?14?meV. The time resolved PL revealed that in a short period (<1?ns) after excitation, the PL peaks were broadened because of the thermal distribution of carriers. We interpreted this distribution in terms of quasi-temperature (T{sub q}) of the carriers. The initial T{sub q} was of the order of 500?K. The thermalization led to a fast decrease of T{sub q}. The obtained cooling time in the QW was ?{sub C}?=?0.3?ns, which was faster than the observed recombination time ?{sub R}?=?2.2?ns (at 4?K)

  14. Hall, Seebeck, and Nernst Coefficients of Underdoped HgBa2CuO4+?: Fermi-Surface Reconstruction in an Archetypal Cuprate Superconductor

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Doiron-Leyraud, Nicolas; Lepault, S.; Cyr-Choinière, O.; Vignolle, B.; Grissonnanche, G.; Laliberté, F.; Chang, J.; Bariši?, N.; Chan, M. K.; Ji, L.; Zhao, X.; Li, Y.; Greven, M.; Proust, C.; Taillefer, Louis

    2013-06-01T23:59:59.000Z

    Charge-density-wave order has been observed in cuprate superconductors whose crystal structure breaks the square symmetry of the CuO2 planes, such as orthorhombic YBa2Cu3Oy (YBCO), but not so far in cuprates that preserve that symmetry, such as tetragonal HgBa2CuO4+? (Hg1201). We have measured the Hall (RH), Seebeck (S), and Nernst (?) coefficients of underdoped Hg1201 in magnetic fields large enough to suppress superconductivity. The high-field RH(T) and S(T) are found to drop with decreasing temperature and become negative, as also observed in YBCO at comparable doping. In YBCO, the negative RH and S are signatures of a small electron pocket caused by Fermi-surface reconstruction, attributed to charge-density-wave modulations observed in the same range of doping and temperature. We deduce that a similar Fermi-surface reconstruction takes place in Hg1201, evidence that density-wave order exists in this material. A striking similarity is also found in the normal-state Nernst coefficient ?(T), further supporting this interpretation. Given the model nature of Hg1201, Fermi-surface reconstruction appears to be common to all hole-doped cuprates, suggesting that density-wave order is a fundamental property of these materials.

  15. Manipulation of emission energy in GaAs/AlGaAs core-shell nanowires with radial heterostructure

    SciTech Connect (OSTI)

    Barbosa, B. G.; Arakaki, H.; Souza, C. A. de; Pusep, Yu. A. [Instituto de Fisica de São Carlos, Universidade de São Paulo, 13560-970 Sao Carlos, SP (Brazil)

    2014-03-21T23:59:59.000Z

    Photoluminescence was studied in GaAs/AlGaAs nanowires (NWs) with different radial heterostructures. We demonstrated that manipulation of the emission energy may be achieved by appropriate choice of the shell structure. The emission at highest energy is generated in the NWs with tunneling thin AlGaAs inner shell and thin GaAs outer shell due to recombination of the photoexcited electrons confined in the outer shell with the holes in the core. Lower energy emission was shown to occur in the NWs with thick outer shell grown in the form of a short-period GaAs/AlGaAs multiple quantum well structure. In this case, the tunneling probability through the multiple quantum wells controls the energy emitted by the NWs. The doping of core results in dominated low energy emission from the GaAs core.

  16. Structural and Morphological Difference Between Ti/TiN/TiCN Coatings Grown in Multilayer and Graded Form

    SciTech Connect (OSTI)

    Restrepo, E.; Baena, A.; Agudelo, C.; Castillo, H.; Devia, A. [Laboratorio de Fisica del Plasma, Universidad Nacional de Colombia Sede Manizales, Campus La Nubia, Manizales (Colombia); Marino, A. [Departamento de Fisica, Universidad Nacional de Colombia Sede Bogota, Av. Cra. 30 No. 45-03, Bogota (Colombia)

    2006-12-04T23:59:59.000Z

    Thin films can be grown in super-lattice, multilayers and graded form, having each one advantages and disadvantages. The difference between multilayer and graded coatings is the interface. In multilayers the interface is abrupt and in graded coatings it is diffuse. The interface influences many chemical and physical properties of the materials, and its choice depends on the application. Graded coatings have the advantage of having gradual properties such as thermal expansion coefficient and lattice parameter, avoiding adherence problems due to good match between their component materials. In this work the comparison between some properties of coatings grown as multilayer and graded is performed. The materials are produced using the sputtering DC technique because of its facility to control the deposition parameters and generate a slow growth. The target is a disc of titanium and the samples are made of stainless steel 304. The working gases are argon, nitrogen and methane, which are mixed according to the material to be produced, i.e. Ti layer is grown with argon, the TiN film is produced with a mixture of argon and nitrogen, and the TiCN material is obtained mixing argon, nitrogen and methane. These materials are characterized with AFM in order to determine grain size and with XPS studying the chemical composition and performing depth profiles.

  17. 0.7-eV GaInAs Junction for a GaInP/GaAs/GaInAs(1eV)/GaInAs(0.7eV) Four-Junction Solar Cell

    SciTech Connect (OSTI)

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

    2006-01-01T23:59:59.000Z

    We discuss recent developments in III-V multijunction solar cells, focusing on adding a fourth junction to the Ga{sub 0.5}In{sub 0.5} P/GaAs/Ga{sub 0.75}In{sub 0.25}As inverted three-junction cell. This cell, grown inverted on GaAs so that the lattice-mismatched Ga{sub 0.75}In{sub 0.25}As 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 Ga{sub x}In{sub 1-x}As 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 Ga{sub x}In{sub 1-x}As 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.

  18. Ga adsorbate on (0001) GaN: In situ characterization with quadrupole mass spectrometry and reflection high-energy electron diffraction

    E-Print Network [OSTI]

    Brown, J S; Koblmuller, G; Wu, F; Averbeck, R; Riechert, H; Speck, J S

    2006-01-01T23:59:59.000Z

    PA-MBE GaN growth conditions, with substrate temperatures ofthe GaN surface roughness evolution, substrate vicinality,vapor and substrate temperature could form the basis for GaN

  19. Refractive index of erbium doped GaN thin films

    SciTech Connect (OSTI)

    Alajlouni, S.; Sun, Z. Y.; Li, J.; Lin, J. Y.; Jiang, H. X., E-mail: hx.jiang@ttu.edu [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States); Zavada, J. M. [Department of Electrical and Computer Engineering, Polytechnic Institute of New York University, Brooklyn, New York 11201 (United States)

    2014-08-25T23:59:59.000Z

    GaN is an excellent host for erbium (Er) to provide optical emission in the technologically important as well as eye-safe 1540?nm wavelength window. Er doped GaN (GaN:Er) epilayers were synthesized on c-plane sapphire substrates using metal organic chemical vapor deposition. By employing a pulsed growth scheme, the crystalline quality of GaN:Er epilayers was significantly improved over those obtained by conventional growth method of continuous flow of reaction precursors. X-ray diffraction rocking curve linewidths of less than 300?arc sec were achieved for the GaN (0002) diffraction peak, which is comparable to the typical results of undoped high quality GaN epilayers and represents a major improvement over previously reported results for GaN:Er. Spectroscopic ellipsometry was used to determine the refractive index of the GaN:Er epilayers in the 1540?nm wavelength window and a linear dependence on Er concentration was found. The observed refractive index increase with Er incorporation and the improved crystalline quality of the GaN:Er epilayers indicate that low loss GaN:Er optical waveguiding structures are feasible.

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

    SciTech Connect (OSTI)

    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

    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.

  1. Graphene in ohmic contact for both n-GaN and p-GaN

    SciTech Connect (OSTI)

    Zhong, Haijian; Liu, Zhenghui; Shi, Lin; Xu, Gengzhao; Fan, Yingmin; Huang, Zengli [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Wang, Jianfeng; Ren, Guoqiang; Xu, Ke, E-mail: kxu2006@sinano.ac.cn [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Suzhou Nanowin Science and Technology Co., Ltd., Suzhou 215123 (China)

    2014-05-26T23:59:59.000Z

    The wrinkles of single layer graphene contacted with either n-GaN or p-GaN were found both forming ohmic contacts investigated by conductive atomic force microscopy. The local I–V results show that some of the graphene wrinkles act as high-conductive channels and exhibiting ohmic behaviors compared with the flat regions with Schottky characteristics. We have studied the effects of the graphene wrinkles using density-functional-theory calculations. It is found that the standing and folded wrinkles with zigzag or armchair directions have a tendency to decrease or increase the local work function, respectively, pushing the local Fermi level towards n- or p-type GaN and thus improving the transport properties. These results can benefit recent topical researches and applications for graphene as electrode material integrated in various semiconductor devices.

  2. Photocapacitance study of type-II GaSb/GaAs quantum ring solar cells

    SciTech Connect (OSTI)

    Wagener, M. C.; Botha, J. R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Carrington, P. J.; Krier, A. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)

    2014-01-07T23:59:59.000Z

    In this study, the density of states associated with the localization of holes in GaSb/GaAs quantum rings are determined by the energy selective charging of the quantum ring distribution. The authors show, using conventional photocapacitance measurements, that the excess charge accumulated within the type-II nanostructures increases with increasing excitation energies for photon energies above 0.9?eV. Optical excitation between the localized hole states and the conduction band is therefore not limited to the ?(k?=?0) point, with pseudo-monochromatic light charging all states lying within the photon energy selected. The energy distribution of the quantum ring states could consequently be accurately related from the excitation dependence of the integrated photocapacitance. The resulting band of localized hole states is shown to be well described by a narrow distribution centered 407?meV above the GaAs valence band maximum.

  3. Efficiency enhancement of InGaN/GaN solar cells with nanostructures

    SciTech Connect (OSTI)

    Bai, J.; Yang, C. C.; Athanasiou, M.; Wang, T. [Department of Electronics and Electrical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)

    2014-02-03T23:59:59.000Z

    We demonstrate InGaN/GaN multi-quantum-well solar cells with nanostructures operating at a wavelength of 520?nm. Nanostructures with a periodic nanorod or nanohole array are fabricated by means of modified nanosphere lithography. Under 1 sun air-mass 1.5 global spectrum illumination, a fill factor of 50 and an open circuit voltage of 1.9?V are achieved in spite of very high indium content in InGaN alloys usually causing degradation of crystal quality. Both the nanorod array and the nanohole array significantly improve the performance of solar cells, while a larger enhancement is observed for the nanohole array, where the conversion efficiency is enhanced by 51%.

  4. Intersubband absorption in AlN/GaN/AlGaN coupled quantum wells

    SciTech Connect (OSTI)

    Driscoll, Kristina; Bhattacharyya, Anirban; Moustakas, Theodore D.; Paiella, Roberto; Zhou, Lin; Smith, David J. [Department of Electrical and Computer Engineering and Photonics Center, Boston University, 8 Saint Mary's Street, Boston, Massachusetts 02215 (United States); Department of Physics and School of Materials, Arizona State University, Tempe, Arizona 85287 (United States)

    2007-10-01T23:59:59.000Z

    AlN/GaN/AlGaN coupled quantum wells grown by molecular beam epitaxy have been developed and characterized via intersubband absorption spectroscopy. In these structures, an AlGaN layer of sufficiently low Al content is used to achieve strong interwell coupling without the need for ultrathin inner barriers. At the same time, AlN is used in the outer barriers to provide the large quantum confinement required for near-infrared intersubband transitions. The composition of the inner barriers also provides a continuously tunable parameter to control the coupling strength. Double intersubband absorption peaks are measured in each sample, at photon energies in good agreement with theoretical expectations.

  5. GaN based nanorods for solid state lighting

    SciTech Connect (OSTI)

    Li Shunfeng; Waag, Andreas [Institute of Semiconductor Technology, Braunschweig University of Technology, 38106 Braunschweig (Germany)

    2012-04-01T23:59:59.000Z

    In recent years, GaN nanorods are emerging as a very promising novel route toward devices for nano-optoelectronics and nano-photonics. In particular, core-shell light emitting devices are thought to be a breakthrough development in solid state lighting, nanorod based LEDs have many potential advantages as compared to their 2 D thin film counterparts. In this paper, we review the recent developments of GaN nanorod growth, characterization, and related device applications based on GaN nanorods. The initial work on GaN nanorod growth focused on catalyst-assisted and catalyst-free statistical growth. The growth condition and growth mechanisms were extensively investigated and discussed. Doping of GaN nanorods, especially p-doping, was found to significantly influence the morphology of GaN nanorods. The large surface of 3 D GaN nanorods induces new optical and electrical properties, which normally can be neglected in layered structures. Recently, more controlled selective area growth of GaN nanorods was realized using patterned substrates both by metalorganic chemical vapor deposition (MOCVD) and by molecular beam epitaxy (MBE). Advanced structures, for example, photonic crystals and DBRs are meanwhile integrated in GaN nanorod structures. Based on the work of growth and characterization of GaN nanorods, GaN nanoLEDs were reported by several groups with different growth and processing methods. Core/shell nanoLED structures were also demonstrated, which could be potentially useful for future high efficient LED structures. In this paper, we will discuss recent developments in GaN nanorod technology, focusing on the potential advantages, but also discussing problems and open questions, which may impose obstacles during the future development of a GaN nanorod based LED technology.

  6. Improved performance of HgCdTe infrared detector focal plane arrays by modulating light field based on photonic crystal structure

    SciTech Connect (OSTI)

    Liang, Jian; Hu, Weida, E-mail: wdhu@mail.sitp.ac.cn; Ye, Zhenhua; Li, Zhifeng; Chen, Xiaoshuang, E-mail: xschen@mail.sitp.ac.cn; Lu, Wei [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai 200083 (China); Liao, Lei [Department of Physics and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072 (China)

    2014-05-14T23:59:59.000Z

    An HgCdTe long-wavelength infrared focal plane array photodetector is proposed by modulating light distributions based on the photonic crystal. It is shown that a promising prospect of improving performance is better light harvest and dark current limitation. To optimize the photon field distributions of the HgCdTe-based photonic crystal structure, a numerical method is built by combining the finite-element modeling and the finite-difference time-domain simulation. The optical and electrical characteristics of designed HgCdTe mid-wavelength and long-wavelength photon-trapping infrared detector focal plane arrays are obtained numerically. The results indicate that the photon crystal structure, which is entirely compatible with the large infrared focal plane arrays, can significantly reduce the dark current without degrading the quantum efficiency compared to the regular mesa or planar structure.

  7. Novel signal inversion of laser beam induced current for femtosecond-laser-drilling-induced junction on vacancy-doped p-type HgCdTe

    SciTech Connect (OSTI)

    Qiu, W. C.; Wang, R.; Xu, Z. J.; Jiang, T. [College of Photoelectric Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073 (China); Cheng, X. A., E-mail: xiang-ai-cheng@126.com [College of Photoelectric Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073 (China); State Key Laboratory of High Performance Computing, National University of Defense Technology, Changsha, Hunan 410073 (China); Science and Technology on Electro-Optical Information Security Control Laboratory, Hebei 065201 (China)

    2014-05-28T23:59:59.000Z

    In this paper, experimental results of temperature-dependent signal inversion of laser beam induced current (LBIC) for femtosecond-laser-drilling-induced junction on vacancy-doped p-type HgCdTe are reported. LBIC characterization shows that the traps induced by femtosecond laser drilling are sensitive to temperature. Theoretical models for trap-related p-n junction transformation are proposed and demonstrated using numerical simulations. The simulations are in good agreement with the experimental results. The effects of traps and mixed conduction are possibly the main reasons that result in the novel signal inversion of LBIC microscope at room temperature. The research results provide a theoretical guide for practical applications of large-scale array HgCdTe infrared photovoltaic detectors formed by femtosecond laser drilling, which may act as a potential new method for fabricating HgCdTe photodiodes.

  8. Reduction of gap states of ternary IIIV semiconductor surfaces by sulfur passivation: Comparative studies of AlGaAs and InGaP

    E-Print Network [OSTI]

    Kim, Sehun

    studies of AlGaAs and InGaP J. M. Seo School of Physics and Technology, Jeonbuk National University on liquid-phase-epitaxy-grown n-type InGaP and AlGaAs surfaces have been studied using x-ray photoelectron treatment in air. For InGaP, sulfur atoms initially reacted with both surface In and Ga atoms and reacted

  9. In0.6Ga0.4AsGaAs quantum-dot infrared photodetector with operating temperature up to 260 K

    E-Print Network [OSTI]

    Florida, University of

    the large band gap material such as AlGaAs or InGaP as blocking barrier to reduce the device dark current 100 K by us- ing a large band gap material such as AlGaAs or InGaP as the blocking barrier to reduce temperature up to 260 K without using the wide band gap AlGaAs or InGaP current blocking bar- rier. The sample

  10. Phase-locking of an InP/InGaP/InGaAs resonant tunneling diode relaxation oscillator by direct optical injection

    E-Print Network [OSTI]

    Eisenstein, Gadi

    Phase-locking of an InP/InGaP/InGaAs resonant tunneling diode relaxation oscillator by direct relaxation oscillator is demonstrated. The diode is an Al-free InP/InGaP/InGaAs structure in the InP/InGaAs/InGaP aluminum-free material system, following the work of Cohen and Ritter [6

  11. Simultaneous enhancement of electron overflow reduction and hole injection promotion by tailoring the last quantum barrier in InGaN/GaN light-emitting diodes

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    the last quantum barrier in InGaN/GaN light-emitting diodes Zabu Kyaw, Zi-Hui Zhang, Wei Liu, Swee Tiam Tan injection and efficiency droop in InGaN/GaN light-emitting diodes with step-stage multiple- quantum distribution in InGaN/GaN light-emitting diodes with graded thickness quantum barriers Appl. Phys. Lett. 102

  12. IEEE ELECTRON DEVICE LETTERS, VOL. 21, NO. 12, DECEMBER 2000 549 Dual-Gate AlGaN/GaN Modulation-Doped

    E-Print Network [OSTI]

    Rodwell, Mark J. W.

    IEEE ELECTRON DEVICE LETTERS, VOL. 21, NO. 12, DECEMBER 2000 549 Dual-Gate AlGaN/GaN Modulation--We demonstrate dual-gate AlGaN/GaN modula- tion-doped field-effect transistors (MODFETs) with gate-lengths of 0 power amplifiers. Index Terms--AlGaN/GaN, broadband power amplifiers, dual-gate FETs. I. INTRODUCTION

  13. Graded-base InGaN/GaN heterojunction bipolar light-emitting transistors B. F. Chu-Kung,a

    E-Print Network [OSTI]

    Asbeck, Peter M.

    Graded-base InGaN/GaN heterojunction bipolar light-emitting transistors B. F. Chu-Kung,a M. Feng, G; published online 25 August 2006 The authors report radiative recombination from a graded-base InGaN/GaN microwave power has been obtained from GaN field-effect transistors, very few operational GaN-based HBTs

  14. InGaN/GaN multiple-quantum-well light-emitting diodes with a grading InN composition suppressing the Auger recombination

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    InGaN/GaN multiple-quantum-well light-emitting diodes with a grading InN composition suppressing://scitation.aip.org/content/aip/journal/apl/105/3?ver=pdfcov Published by the AIP Publishing Articles you may be interested in High efficiency InGaN/GaN (2014); 10.1063/1.4867023 Effect of V-defects on the performance deterioration of InGaN/GaN multiple

  15. Polarized emission lines from A-and B-type excitonic complexes in single InGaN/GaN quantum dots

    E-Print Network [OSTI]

    Nabben, Reinhard

    Polarized emission lines from A- and B-type excitonic complexes in single InGaN/GaN quantum dots M Cathodoluminescence measurements on single InGaN/GaN quantum dots QDs are reported. Complex spectra with up to five spectral region have been realized based on InGaN structures.1 Single-photon emission from GaN/AlN quantum

  16. Fabry-Perot effects in InGaN/GaN heterostructures on Si-substrate C. Hums, T. Finger, T. Hempel, J. Christen, and A. Dadgara

    E-Print Network [OSTI]

    Nabben, Reinhard

    Fabry-Perot effects in InGaN/GaN heterostructures on Si-substrate C. Hums, T. Finger, T. Hempel, J spectra of InGaN/GaN heterostructures and quantum wells epitaxially grown on Si 111 substrates. This Fabry-Perot effect results from the high refractive index contrasts at the GaN/Si and the Air/InGaN interfaces

  17. Determination of two-dimensional electron and hole gas carriers in AlGaN/GaN/AlN heterostructures grown by Metal

    E-Print Network [OSTI]

    Ozbay, Ekmel

    on nominally undoped Al0.25Ga0.75N/GaN/AlN heterostructures grown on sapphire substrates prepared by metal undoped Al0.25Ga0.75N/GaN/ AlN heterostructures grown on sapphire substrate. © 2007 Elsevier B.V. All of AlGaN on a thick GaN epilayer on a semi- insulating substrate. Spontaneous and strain induced

  18. Nonpolar cubic AlGaN/GaN heterojunction field-effect transistor on Ar+ implanted 3CSiC ,,001...

    E-Print Network [OSTI]

    As, Donat Josef

    through the substrate. Cubic AlGaN/GaN heterostructures were grown in a RibeNonpolar cubic AlGaN/GaN heterojunction field-effect transistor on Ar+ implanted 3C­SiC ,,001... E HFET was fabricated of nonpolar cubic AlGaN/GaN grown on Ar+ implanted 3C­SiC 001 by molecular beam

  19. On the mechanisms of InGaN electron cooler in InGaN/GaN light-emitting diodes

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    . Schubert, Q. Dai, J. K. Kim, E. F. Schubert, J. Piprek, and Y. Park, "Origin of efficiency droop in Ga. Tansu, "Current injection efficiency induced efficiency-droop in InGaN quantum well light. Van de Walle, "Indirect Auger recombination as a cause of efficiency droop in nitride light

  20. Generation and transportation mechanisms for two-dimensional hole gases in GaN/AlGaN/GaN double heterostructures

    SciTech Connect (OSTI)

    Nakajima, Akira, E-mail: a-nakajima@aist.go.jp; Ogura, Masahiko; Makino, Toshiharu; Nishizawa, Shin-ichi; Ohashi, Hiromichi; Yamasaki, Satoshi [Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Central 2, 1-1-1 Umezono, Tsukuba 305-8568 (Japan); Liu, Pucheng; Kakushima, Kuniyuki; Iwai, Hiroshi [Frontier Collaborative Research Center, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori, Yokohama, Kanagawa 226-8503 (Japan)

    2014-04-21T23:59:59.000Z

    The electrical properties of two-dimensional hole gases (2DHGs) in GaN/AlGaN/GaN double heterostructures were investigated. The layers were grown on sapphire substrates and a high-quality bulk GaN substrate. The coexistence of 2DHG and 2D electron gases on both sides of the AlGaN layer was confirmed by Hall effect measurements at 80–460?K. It was also verified that the 2DHGs were generated by negative polarization at the undoped GaN/AlGaN interface, which did not have a doped Mg acceptor. It was also demonstrated that the 2DHG density could be controlled by varying the AlGaN layer thickness and was inversely related to the 2DHG mobility. The measured relation indicated that the 2DHG mobility is mainly limited by phonon scatterings at around room temperature. As a result, the maximum 2DHG mobility of 16 cm{sup 2}/Vs at 300?K was achieved with a density of 1?×?10{sup 13}?cm{sup ?2}.

  1. Temperature dependency of the emission properties from positioned In(Ga)As/GaAs quantum dots

    SciTech Connect (OSTI)

    Braun, T.; Schneider, C.; Maier, S.; Forchel, A.; Höfling, S.; Kamp, M. [Technische Physik, Physikalisches Institut and Wilhelm Conrad Röntgen-Research Center for Complex Material Systems, Universität Würzburg, Am Hubland, D-97074, Würzburg (Germany); Igusa, R.; Iwamoto, S.; Arakawa, Y. [University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2014-09-15T23:59:59.000Z

    In this letter we study the influence of temperature and excitation power on the emission linewidth from site-controlled InGaAs/GaAs quantum dots grown on nanoholes defined by electron beam lithography and wet chemical etching. We identify thermal electron activation as well as direct exciton loss as the dominant intensity quenching channels. Additionally, we carefully analyze the effects of optical and acoustic phonons as well as close-by defects on the emission linewidth by means of temperature and power dependent micro-photoluminescence on single quantum dots with large pitches.

  2. Origins of ion irradiation-induced Ga nanoparticle motion on GaAs surfaces

    SciTech Connect (OSTI)

    Kang, M.; Wu, J. H.; Chen, H. Y.; Thornton, K.; Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Sofferman, D. L. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, Adelphi University, Garden City, New York 11530-0701 (United States); Beskin, I. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)] [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)

    2013-08-12T23:59:59.000Z

    We have examined the origins of ion irradiation-induced nanoparticle (NP) motion. Focused-ion-beam irradiation of GaAs surfaces induces random walks of Ga NPs, which are biased in the direction opposite to that of ion beam scanning. Although the instantaneous NP velocities are constant, the NP drift velocities are dependent on the off-normal irradiation angle, likely due to a difference in surface non-stoichiometry induced by the irradiation angle dependence of the sputtering yield. It is hypothesized that the random walks are initiated by ion irradiation-induced thermal fluctuations, with biasing driven by anisotropic mass transport.

  3. Wavelength limits for InGaN quantum wells on GaN

    SciTech Connect (OSTI)

    Pristovsek, Markus, E-mail: markus@pristovsek.de [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)] [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)

    2013-06-17T23:59:59.000Z

    The emission wavelength of coherently strained InGaN quantum wells (QW) is limited by the maximum thickness before relaxation starts. For high indium contents x>40% the resulting wavelength decreases because quantum confinement dominates. For low indium content x<40% the electron hole wave function overlap (and hence radiative emission) is strongly reduced with increasing QW thickness due to the quantum confined Stark effect and imposes another limit. This results in a maximum usable emission wavelength at around 600?nm for QWs with 40%-50% indium content. Relaxed InGaN buffer layers could help to push this further, especially on non- and semi-polar orientations.

  4. Application of the ASME code in the design of the GA-4 and GA-9 casks

    SciTech Connect (OSTI)

    Mings, W.J. (USDOE Idaho Field Office, Idaho Falls, ID (United States)); Koploy, M.A. (General Atomics, San Diego, CA (United States))

    1992-01-01T23:59:59.000Z

    General Atomics (GA) is developing two spent fuel shipping casks for transport by legal weight truck (LWT). The casks are designed to the loading, environmental conditions and safety requirements defined in Title 10 of the Code of Federal Regulations, Part 71 (10CFR71). To ensure that all components of the cask meet the 10CFR71 rules, GA established structural design criteria for each component based on NRC Regulatory Guides and the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code). This paper discusses the criteria used for different cask components, how they were applied and the conservatism and safety margins built into the criteria and assumption.

  5. Application of the ASME code in the design of the GA-4 and GA-9 casks

    SciTech Connect (OSTI)

    Mings, W.J. [USDOE Idaho Field Office, Idaho Falls, ID (United States); Koploy, M.A. [General Atomics, San Diego, CA (United States)

    1992-08-01T23:59:59.000Z

    General Atomics (GA) is developing two spent fuel shipping casks for transport by legal weight truck (LWT). The casks are designed to the loading, environmental conditions and safety requirements defined in Title 10 of the Code of Federal Regulations, Part 71 (10CFR71). To ensure that all components of the cask meet the 10CFR71 rules, GA established structural design criteria for each component based on NRC Regulatory Guides and the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code). This paper discusses the criteria used for different cask components, how they were applied and the conservatism and safety margins built into the criteria and assumption.

  6. Two-color picosecond and continuous-wave experiments on anti-Stokes and Stokes carrier-transfer phenomena in GaAs/AlxGa1 xAs and InGaP2 /AlxGa1 xAs heterostructures

    E-Print Network [OSTI]

    Hohng, Sung Chul

    -transfer phenomena in GaAs/AlxGa1 xAs and InGaP2 /AlxGa1 xAs heterostructures S. C. Hohng, D. W. Khang, Y. H. Ahn, J evidence of the two-step absorption process in anti-Stokes photoluminescence in both GaAs/AlxGa1 xAs and InGaP

  7. Demonstration of a semipolar (10(1)over-bar(3)over-bar) InGaN/GaN green light emitting diode

    E-Print Network [OSTI]

    2005-01-01T23:59:59.000Z

    InGaN / GaN green light emitting diode R. Sharma, a? P. M.green ??525 nm? light emitting diode ?LED?. The fabricated

  8. Spatialpatternsofhomeoboxgene expressioninthedevelopingmammalianCN$

    E-Print Network [OSTI]

    Stern, Claudio

    Antennapedia and the human gene HHo. c10 c~rf- fer by only three of the terminal 53 amino acids4. An editorial

  9. SF6432-CN

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of Scienceand Requirements RecentlyElectronicResourcesjobs RunningSEABRV 148002/01/12 Page 1 of

  10. SF6432-CN Construction

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of Scienceand Requirements RecentlyElectronicResourcesjobs RunningSEABRV 148002/01/12 Page 1

  11. CnLrJGD

    Office of Legacy Management (LM)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOn AprilA group currentBradleyTableSelling Corp -KWatertowni5W 95.5x-L* d! CT NC0I

  12. Distributed bragg reflector using AIGaN/GaN

    DOE Patents [OSTI]

    Waldrip, Karen E.; Lee, Stephen R.; Han, Jung

    2004-08-10T23:59:59.000Z

    A supported distributed Bragg reflector or superlattice structure formed from a substrate, a nucleation layer deposited on the substrate, and an interlayer deposited on the nucleation layer, followed by deposition of (Al,Ga,B)N layers or multiple pairs of (Al,Ga,B)N/(Al,Ga,B)N layers, where the interlayer is a material selected from AlN, Al.sub.x Ga.sub.1-x N, and AlBN with a thickness of approximately 20 to 1000 angstroms. The interlayer functions to reduce or eliminate the initial tensile growth stress, thereby reducing cracking in the structure. Multiple interlayers utilized in an AlGaN/GaN DBR structure can eliminate cracking and produce a structure with a reflectivity value greater than 0.99.

  13. Ion-beam-induced chemical disorder in GaN

    SciTech Connect (OSTI)

    Ishimaru, Manabu; Zhang, Yanwen; Weber, William J.

    2009-09-08T23:59:59.000Z

    Atomistic structures of high-energy ion irradiated GaN have been examined using transmission electron microscopy (TEM). Single crystalline GaN substrates were irradiated at cryogenic temperature with 2 MeV Au2+ ions to a fluence of 7.35x1015 Au/cm2. Cross-sectional TEM observations revealed that damaged layers consisting of amorphous and nanocrystalline phases are formed at the surface and buried depth of the as-irradiated GaN substrate. Atomic radial distribution functions of the amorphous/poly-nanocrystalline regions showed that not only heteronuclear Ga-N bonds but also homonuclear Ga-Ga bonds exist within the first coordination shell. It was found that the ratio of heteronuclear-to-homonuclear bonds, i.e., the degree of chemical disorder is different between the surface and buried damaged layers. The alternation of chemical disorder was attributed to the difference in the defect formation processes between these layers.

  14. Radiation Hard AlGaN Detectors and Imager

    SciTech Connect (OSTI)

    None

    2012-05-01T23:59:59.000Z

    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.

  15. Scientific uncertainties in atmospheric mercury models III: Boundary and initial conditions, model grid resolution, and Hg(II) reduction mechanism

    SciTech Connect (OSTI)

    Lin, Che-Jen [ORNL; Pongprueksa, Pruek [Lamar University; Lindberg, Steven Eric [ORNL; Jang, Carey [U.S. Environmental Protection Agency, Raleigh, North Carolina; Braverman, Thomas [U.S. Environmental Protection Agency, Raleigh, North Carolina; Bullock, Russell O [NOAA; Ho, Thomas [ORNL; Chu, Hsing-Wei [Lamar University

    2008-03-01T23:59:59.000Z

    In this study, the model response in terms of simulated mercury concentration and deposition to boundary condition (BC), initial condition (IC), model grid resolution (12 km versus 36 km), and two alternative Hg(II) reduction mechanisms, was investigated. The model response to the change of gaseous elemental mercury (GEM) concentration from 0 to 2 ngm3 in IC/BC is found to be very linear (r240.99) based on the results of sensitivity simulations in July 2001. An increase of 1 ngm3 of GEM in BC resulted in an increase of 0.81 ngm3 in the monthly average of total mercury concentration, and 1270 ngm2 in the monthly total deposition. IC has similar but weaker effects compared to those of BC. An increase of 1 ngm3 of GEM in IC resulted in an increase of 0.14 ngm3 in the monthly average of total mercury concentration, and 250 ngm2 in the monthly total deposition. Varying reactive gaseous mercury (RGM) or particulate mercury (PHg) in BC/IC has much less significant impact. Simulation results at different grid resolutions show good agreement (slope 0.950 1.026, r 0.816 0.973) in mercury concentration, dry deposition, and total deposition. The agreement in wet deposition is somewhat weaker (slope 0.770 0.794, r 0.685 0.892) due to the difference in emission dilution and simulated precipitation that subsequently change reaction rates in the aqueous phase. Replacing the aqueous Hg(II)-HO2 reduction by either RGM reduction by CO (51018cm3 molecule1 s1) or photoreduction of RGM (1105 s1) gives significantly better model agreement with the wet deposition measured by Mercury Deposition Network (MDN). Possible ranges of the reduction rates are estimated based on model sensitivity results. The kinetic estimate requires further verification by laboratory studies.

  16. O?[]O? nuclear ?-decay of ?²Ga

    E-Print Network [OSTI]

    Hyman, Bruce Carl

    1999-01-01T23:59:59.000Z

    information, MARS was focused such that only fully stripped N=Z ions were passed, with the vast majority of them being Ga. The second phase of the experiment was a I3-y coincidence experiment. At the back-end of MARS, a 1" x 1 '!4" x 3" four..., using the Weinberg-Salam model of electroweak interactions, to be [23]: A& ? d, ?= ? [41n(mz/m )+ln(m /m?)+2K+A +" ]. (16) Here mz is the mass of the Z boson, me the proton mass, mx is the low energy cutoff for the second and third terms that arise...

  17. ¹?C(n,?) ¹?C as a Test Case in the Evaluation of a New Method to Determine Spectroscopic Factors Using Asymptotic Normalization Coefficients

    E-Print Network [OSTI]

    McCleskey, Matthew Edgar

    2012-02-14T23:59:59.000Z

    14C(n,?)15C AS A TEST CASE IN THE EVALUATION OF A NEW METHOD TO DETERMINE SPECTROSCOPIC FACTORS USING ASYMPTOTIC NORMALIZATION COEFFICIENTS A Dissertation by MATTHEW EDGAR MCCLESKEY Submitted to the Office of Graduate Studies... FACTORS USING ASYMPTOTIC NORMALIZATION COEFFICIENTS A Dissertation by MATTHEW EDGAR MCCLESKEY Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR...

  18. Thng tin pht t my ghi m v khon chi tr phc li Bo Him Tht Nghip gn nht c th tip cn 24 ting

    E-Print Network [OSTI]

    Thông tin phát t máy ghi âm v khon chi tr phúc li Bo Him Tht Nghip gn nht có th tip cn 24 ting mt chiu, Th Hai n Th Sáu, hoc vào nhng ngày cui tun. Thông tin chi tr phúc li UI c cp nht hng ngày, và phn ánh sinh hot h s vào ngày làm vic trc ó. nhn c thông tin v khon chi tr ca mình, xin làm nhng s la chn

  19. March an t Pereira 954, Providen cia, San tiago. fon os: (56-2) 2690223 -2690224 -2690225. web: www.cn ach ile.cl

    E-Print Network [OSTI]

    Pérez, Carlos E.

    -XQLR #12;Norm as y Procedim ien tos para la Acreditación , Com isión Nacion al de Acreditación . CNA: www.cn ach ile.cl 2 ,QWURGXFFLyQ El presen te docu m en to describe las Norm as y Procedim ien tos orm as y procedim ien tos propu estos por su s Com ités Con su ltivos, aplicará tran sitoriam en te

  20. P-type doping of GaN

    SciTech Connect (OSTI)

    Wong, R.K.

    2000-04-10T23:59:59.000Z

    After implantation of As, As + Be, and As + Ga into GaN and annealing for short durations at temperatures as high as 1500 C, the GaN films remained highly resistive. It was apparent from c-RBS studies that although implantation damage did not create an amorphous layer in the GaN film, annealing at 1500 C did not provide enough energy to completely recover the radiation damage. Disorder recovered significantly after annealing at temperatures up to 1500 C, but not completely. From SIMS analysis, oxygen contamination in the AIN capping layer causes oxygen diffusion into the GaN film above 1400 C. The sapphire substrate (A1203) also decomposed and oxygen penetrated into the backside of the GaN layer above 1400 C. To prevent donor-like oxygen impurities from the capping layer and the substrate from contaminating the GaN film and compensating acceptors, post-implantation annealing should be done at temperatures below 1500 C. Oxygen in the cap could be reduced by growing the AIN cap on the GaN layer after the GaN growth run or by depositing the AIN layer in a ultra high vacuum (UHV) system post-growth to minimize residual oxygen and water contamination. With longer annealing times at 1400 C or at higher temperatures with a higher quality AIN, the implantation drainage may fully recover.

  1. Segregation of In to dislocations in InGaN

    E-Print Network [OSTI]

    Horton, Matthew K.; Rhode, Sneha; Sahonta, Suman-Lata; Kappers, Menno J.; Haigh, Sarah J.; Pennycook, Timothy J.; Humphreys, Colin J.; Dusane, Rajiv O.; Moram, Michelle A.

    2015-01-16T23:59:59.000Z

    .; Fischer, A. J.; Thaler, G.; Banas, M. A. Effect of dislocation density on efficiency droop in GaInN?GaN light-emitting diodes. Applied Physics Letters 2007, 91, 231114 DOI: 10.1063/1.2822442. (3) Schubert, M. F.; Xu, J.; Kim, J. K.; Schubert, E. F.; Kim... , M. H.; Yoon, S.; Lee, S. M.; Sone, C.; Sakong, T.; Park, Y. Polarization-matched GaInN?AlGaInN multi-quantum-well light-emitting diodes with reduced efficiency droop. Applied Physics Letters 2008, 93, 041102 DOI: 10.1063/1.2963029. (4) Hsu, J. W. P...

  2. Surface Science Analysis of GaAs Photocathodes Following Sustained...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Analysis of GaAs Photocathodes Following Sustained Electron Beam Delivery. Abstract: Degradation of the photocathode materials employed in photoinjectors represents a challenge for...

  3. Self-aligned InGaP/GaAs heterojunction bipolar transistors for microwave power application

    SciTech Connect (OSTI)

    Ren, F.; Abernathy, C.R.; Pearton, S.J.; Lothian, J.R.; Wisk, P.W.; Fullowan, T.R.; Youngkai Chen (AT and T Bell Labs., Murray Hill, NJ (United States)); Yang, L.W.; Fu, S.T.; Brozovich, R.S. (General Electric Co., Syracuse, NY (USSR))

    1993-07-01T23:59:59.000Z

    As an alternative to AlGaAs/GaAs heterojunction bipolar transistors (HBT's) for microwave applications, InGaP/ GaAs HBT's with carbon-doped base layers grown by metal organic molecular beam epitaxy (MOMBE) are demonstrated with excellent dc, RF, and microwave performance. As previously reported, with a 700-[angstrom]-thick base layer (135-[Omega]/[open square] sheet resistance), a dc current gain of 25, and cutoff frequency and maximum frequency of oscillation above 70 GHz were measured for a 2 [times] 5-[mu]m[sup 2] emitter area device. A device with 12 cells, each consisting of a 2 [times] 15-[mu] m[sup 2] emitter area device for a total emitter area of 360 [mu] m[sup 2], was power tested at 4 GHz under continuous-wave (CW) bias condition. The device delivered 0.6-W output power with 13-dB linear gain and a power-added efficiency of 50%.

  4. High efficiency InGaN/GaN light emitting diodes with asymmetric triangular multiple quantum wells

    SciTech Connect (OSTI)

    Chang, Chiao-Yun; Li, Hen; Lu, Tien-Chang, E-mail: timtclu@mail.nctu.edu.tw [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, 1001 University Road, Hsinchu, Taiwan 300 (China)

    2014-03-03T23:59:59.000Z

    In this study, we demonstrated high efficiency InGaN/GaN light emitting diodes (LEDs) with asymmetric triangular multiple quantum wells (MQWs). Asymmetric triangular MQWs not only contribute to uniform carrier distribution in InGaN/GaN MQWs but also yield a low Auger recombination rate. In addition, asymmetric triangular MQWs with gallium face-oriented inclination band profiles can be immune from the polarization charge originating from typical c-plane InGaN/GaN quantum well structures. In the experiment, LEDs incorporated with asymmetric triangular MQWs with gallium face-oriented inclination band profiles exhibited a 60.0% external quantum efficiency at 20?mA and a 27.0% efficiency droop at 100?mA (corresponding to a current density of 69?A/cm{sup 2}), which accounted for an 11.7% efficiency improvement and a 31.1% droop reduction compared with symmetric square quantum well structure LEDs.

  5. Influence of substrate quality on structural properties of AlGaN/GaN superlattices grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Schubert, F. [NaMLab gGmbH, Nöthnitzer Straße 64, 01187 Dresden (Germany); Merkel, U.; Schmult, S. [TU Dresden, Institute of Semiconductors and Microsystems, Nöthnitzer Straße 64, 01187 Dresden (Germany); Mikolajick, T. [NaMLab gGmbH, Nöthnitzer Straße 64, 01187 Dresden (Germany); TU Dresden, Institute of Semiconductors and Microsystems, Nöthnitzer Straße 64, 01187 Dresden (Germany)

    2014-02-28T23:59:59.000Z

    Short-period AlGaN/GaN superlattices were established as versatile test structures to investigate the structural properties of molecular beam epitaxy (MBE)-grown GaN and AlGaN layers and their dependence on the GaN substrate quality. X-ray diffractometry data of the investigated superlattices allow access to relevant structural parameters such as aluminum mole fraction and layer thicknesses. The occurrence of theoretically predicted intense high-order satellite peaks and pronounced interface fringes in the diffraction pattern reflects abrupt interfaces and perfect 2-dimensional growth resulting in smooth surfaces. The data unambiguously demonstrate that the structural quality of the MBE grown layers is limited by the structural properties of the GaN substrate.

  6. First principles calculation of a large variation in dielectric tensor through the spin crossover in the CsFe[Cr(CN){sub 6}] Prussian blue analogue

    SciTech Connect (OSTI)

    Middlemiss, Derek S., E-mail: derekmiddlemiss@gmail.com, E-mail: R.J.Deeth@warwick.ac.uk; Deeth, Robert J., E-mail: derekmiddlemiss@gmail.com, E-mail: R.J.Deeth@warwick.ac.uk [Inorganic Computational Chemistry Group, Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2014-04-14T23:59:59.000Z

    The dielectric response of spin-crossover (SCO) materials is a key property facilitating their use in next-generation information processing technologies. Solid state hybrid density functional theory calculations show that the temperature-induced and strongly hysteretic SCO transition in the Cs{sup +}Fe{sup 2+}[Cr{sup 3+}(CN{sup ?}){sub 6}] Prussian blue analogue (PBA) is associated with a large change (?) in both the static, ??{sup 0}(HS ? LS), and high frequency, ??{sup ?}(HS ? LS) dielectric constants. The SCO-induced variation in CsFe[Cr(CN){sub 6}] is significantly greater than the experimental ?? values observed previously in other SCO materials. The phonon contribution, ??{sup phon}(HS ? LS), determined within a lattice dynamics approach, dominates over the clamped nuclei term, ??{sup ?}(HS ? LS), and is in turn dominated by the low-frequency translational motions of Cs{sup +} cations within the cubic voids of the Fe[Cr(CN){sub 6}]{sup ?} framework. The Cs{sup +} translational modes couple strongly to the large unit cell volume change occurring through the SCO transition. PBAs and associated metal-organic frameworks emerge as a potentially fruitful class of materials in which to search for SCO transitions associated with large changes in dielectric response and other macroscopic properties.

  7. Ferromagnetic semiconductors based upon AlGaP M. E. Overberg,a)

    E-Print Network [OSTI]

    Hebard, Arthur F.

    band-gap ternary InGaP, which is lattice matched to GaAs. An immediate application of the DMS, with its wide band-gap binary GaP, AlP and ternary InGaP, AlGaP, AlInP components, is used for devices

  8. Radiation response of single and dual junction p{sup +}n InGaP/GaAs space solar cells

    SciTech Connect (OSTI)

    Walters, R.J.; Xapsos, M.A.; Summers, G.P. [Naval Research Lab., Washington, DC (United States); Cotal, H.L.; Messenger, S.R. [SFA, Inc., Largo, MD (United States)

    1997-12-31T23:59:59.000Z

    The radiation response of single and dual-junction p{sup +}n InGaP/GaAs solar cells is studied. The degradation mechanisms of single-junction InGaP cells are identified, and characteristic degradation curves in terms of displacement damage dose are calculated. The response of dual-junction cells is presented, and the response of each sub-cell is discussed. The cell response is compared with those of other technologies. The effect of current injection on irradiated InGaP cell is presented.

  9. DC characteristics of OMVPE-grown N-p-n InGaP/InGaAsN DHBTs

    SciTech Connect (OSTI)

    Li, N.Y.; Chang, P.C.; Baca, A.G.; Xie, X.M.; Sharps, P.R.; Hou, H.Q.

    2000-01-04T23:59:59.000Z

    The authors demonstrate, for the first time, a functional N-p-n heterojunction bipolar transistor using a novel material, InGaAsN, with a bandgap energy of 1.2eV as the p-type base layer. A 300{angstrom}-thick In{sub x}Ga{sub 1-x}As graded layer was introduced to reduce the conduction band offset at the p-type InGaAsN base and n-type GaAs collector junction. For an emitter size of 500 {mu}m{sup 2}, a peak current gain of 5.3 has been achieved.

  10. Surface donor states distribution post SiN passivation of AlGaN/GaN heterostructures

    SciTech Connect (OSTI)

    Goyal, Nitin, E-mail: nitin@unik.no [Carinthian Tech Research CTR AG, Europastraße 4/1, Technologiepark Villach, A- 9524 Villach/St. Magdalen (Austria); Department of Electronics and Telecommunication, Norwegian University of Science and Technology, Trondheim NO7034 (Norway); Fjeldly, Tor A. [Department of Electronics and Telecommunication, Norwegian University of Science and Technology, Trondheim NO7034 (Norway)

    2014-07-21T23:59:59.000Z

    In this paper, we present a physics based analytical model to describe the effect of SiN passivation on two-dimensional electron gas density and surface barrier height in AlGaN/GaN heterostructures. The model is based on an extraction technique to calculate surface donor density and surface donor level at the SiN/AlGaN interface. The model is in good agreement with the experimental results and promises to become a useful tool in advanced design and characterization of GaN based heterostructures.

  11. Free-standing AlxGa1-xAs heterostructures by gas-phase etching of germanium

    E-Print Network [OSTI]

    As compounds encompassing low aluminum content AlGaAs, InGaAs, InGaP, etc. , typi- cally, a sacrificial Al

  12. SNS Target Test Facility: Prototype Hg Operations and Remote Handling Tests P. T. Spampinato, T. W. Burgess, J. B. Chesser, V. B. Graves, and S.L. Schrock

    E-Print Network [OSTI]

    McDonald, Kirk

    SNS Target Test Facility: Prototype Hg Operations and Remote Handling Tests P. T. Spampinato, T. W remote handling techniques and tools for replacing target system components. During the past year and analytical data. These included a welded-tube heat exchanger, an electromagnetic flow meter, a hydraulically

  13. Reliability of AlGaN/GaN high electron mobility transistors on low dislocation density bulk GaN substrate: Implications of surface step edges

    SciTech Connect (OSTI)

    Killat, N., E-mail: Nicole.Killat@bristol.ac.uk, E-mail: Martin.Kuball@bristol.ac.uk; Montes Bajo, M.; Kuball, M., E-mail: Nicole.Killat@bristol.ac.uk, E-mail: Martin.Kuball@bristol.ac.uk [Center for Device Thermography and Reliability (CDTR), H.H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Paskova, T. [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States) [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States); Materials Science and Engineering Department, North Carolina State University, Raleigh, North Carolina 27695 (United States); Evans, K. R. [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States)] [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States); Leach, J. [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States) [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States); Electrical and Computer Engineering Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Li, X.; Özgür, Ü.; Morkoç, H. [Electrical and Computer Engineering Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)] [Electrical and Computer Engineering Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Chabak, K. D.; Crespo, A.; Gillespie, J. K.; Fitch, R.; Kossler, M.; Walker, D. E.; Trejo, M.; Via, G. D.; Blevins, J. D. [Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States)] [Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States)

    2013-11-04T23:59:59.000Z

    To enable gaining insight into degradation mechanisms of AlGaN/GaN high electron mobility transistors, devices grown on a low-dislocation-density bulk-GaN substrate were studied. Gate leakage current and electroluminescence (EL) monitoring revealed a progressive appearance of EL spots during off-state stress which signify the generation of gate current leakage paths. Atomic force microscopy evidenced the formation of semiconductor surface pits at the failure location, which corresponds to the interaction region of the gate contact edge and the edges of surface steps.

  14. Mesoscopic photovoltaic effect in GaAs/Ga1-xAlxAs Aharonov-Bohm rings L. Angers, A. Chepelianskii, R. Deblock, B. Reulet, and H. Bouchiat

    E-Print Network [OSTI]

    Shepelyansky, Dima

    Mesoscopic photovoltaic effect in GaAs/Ga1-xAlxAs Aharonov-Bohm rings L. Angers, A. Chepelianskii specific dc voltage. We have investigated this photovoltaic PV effect on GaAs/Ga1-xAlxAs Aharonov is generally done by measuring the dc induced signal sometimes called photovoltaic effect which has also given

  15. GROWTH OF GaN ON POROUS SiC AND GaN SUBSTRATES C. K. Inoki and T. S. Kuan

    E-Print Network [OSTI]

    Feenstra, Randall

    1 GROWTH OF GaN ON POROUS SiC AND GaN SUBSTRATES C. K. Inoki and T. S. Kuan Department of Physics Institute, University of Illinois, Urbana, IL 61801 ABSTRACT We have studied the growth of GaN on porous SiC and GaN substrates, employing both plasma-assisted molecular beam epitaxy (PAMBE) and metalorganic

  16. GaN-based two-dimensional surface-emitting photonic crystal lasers with AlN/GaN distributed Bragg reflector

    E-Print Network [OSTI]

    Fan, Shanhui

    GaN-based two-dimensional surface-emitting photonic crystal lasers with AlN/GaN distributed Bragg 14 December 2007; published online 11 January 2008 GaN-based two-dimensional 2D surface-emitting photonic crystal PC lasers with AlN/GaN distributed Bragg reflectors are fabricated and demonstrated

  17. Dislocation and morphology control during molecular-beam epitaxy of AlGaN/GaN heterostructures directly on sapphire substrates

    E-Print Network [OSTI]

    Manfra, Michael J.

    Dislocation and morphology control during molecular-beam epitaxy of AlGaN/GaN heterostructures-dimensional arrays Appl. Phys. Lett. 100, 203117 (2012) Partially filled intermediate band of Cr-doped GaN films Appl at telecommunication wavelengths J. Appl. Phys. 111, 093721 (2012) GaN epitaxy on Cu(110) by metal organic chemical

  18. Collector-up light-emitting charge injection transistors in n-lnGaAs/lnAIAs/ plllnGaAs and n-lnGaAs/lnP/p-InGaAs heterostructures

    E-Print Network [OSTI]

    Luryi, Serge

    Collector-up light-emitting charge injection transistors in n-lnGaAs/lnAIAs/ plllnGaAs and n (Received 23 November 1992; accepted for publication 4 March 1993) The realization of collector-up light for the collector stripe definition. Electrons, injected over the wide-gap heterostructure barrier (InAlAs or In

  19. Free excitons in wurtzite GaN A. V. Rodina*

    E-Print Network [OSTI]

    Nabben, Reinhard

    Free excitons in wurtzite GaN A. V. Rodina* I. Physics Institute, Justus Liebig University in wurtzite GaN. Using polarization-dependent measurements we were able to resolve the fine-structure energy these data a theory is developed for the exciton energy structure in hexagonal semiconductors with wurtzite

  20. Ohmic contacts to p-type GaP

    E-Print Network [OSTI]

    Jorge Estevez, Humberto Angel

    1996-01-01T23:59:59.000Z

    was measured by the Cox-Strack method. Ohmic contacts based on the Zn/Pd system were developed. The Zn(350A)/Pd(IOOA)/p-GaP and Zn(350A)/Pd(IOOA)/p-GaP gave rather high values of the contact resistivity, 3-8xl 0-4 f2CM2. An improvement in the contact...

  1. The development of integrated chemical microsensors in GaAs

    SciTech Connect (OSTI)

    CASALNUOVO,STEPHEN A.; ASON,GREGORY CHARLES; HELLER,EDWIN J.; HIETALA,VINCENT M.; BACA,ALBERT G.; HIETALA,S.L.

    1999-11-01T23:59:59.000Z

    Monolithic, integrated acoustic wave chemical microsensors are being developed on gallium arsenide (GaAs) substrates. With this approach, arrays of microsensors and the high frequency electronic components needed to operate them reside on a single substrate, increasing the range of detectable analytes, reducing overall system size, minimizing systematic errors, and simplifying assembly and packaging. GaAs is employed because it is both piezoelectric, a property required to produce the acoustic wave devices, and a semiconductor with a mature microelectronics fabrication technology. Many aspects of integrated GaAs chemical sensors have been investigated, including: surface acoustic wave (SAW) sensors; monolithic SAW delay line oscillators; GaAs application specific integrated circuits (ASIC) for sensor operation; a hybrid sensor array utilizing these ASICS; and the fully monolithic, integrated SAW array. Details of the design, fabrication, and performance of these devices are discussed. In addition, the ability to produce heteroepitaxial layers of GaAs and aluminum gallium arsenide (AlGaAs) makes possible micromachined membrane sensors with improved sensitivity compared to conventional SAW sensors. Micromachining techniques for fabricating flexural plate wave (FPW) and thickness shear mode (TSM) microsensors on thin GaAs membranes are presented and GaAs FPW delay line and TSM resonator performance is described.

  2. Ohmic contacts to p-type Ga

    E-Print Network [OSTI]

    Jorge Estevez, Humberto Angel

    1996-01-01T23:59:59.000Z

    was measured by the Cox-Strack method. Ohmic contacts based on the Zn/Pd system were developed. The Zn(350A)/Pd(IOOA)/p-GaP and Zn(350A)/Pd(IOOA)/p-GaP gave rather high values of the contact resistivity, 3-8xl 0-4 f2CM2. An improvement in the contact...

  3. Polarized x-ray spectroscopy of quaternary ferromagnetic semiconductor (Ga,Mn)(As,P)

    E-Print Network [OSTI]

    Wadley, P.

    2011-01-01T23:59:59.000Z

    quaternary diluted magnetic semiconductor (Ga,Mn)(As,P) as aIn diluted magnetic semiconductors such as (Ga,Mn)As, whichquaternary diluted magnetic semiconductors such as (Ga,Mn)(

  4. Amorphization Processes in Au Ion Irradiated GaN at 150 - 300...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Processes in Au Ion Irradiated GaN at 150 - 300 K. Amorphization Processes in Au Ion Irradiated GaN at 150 - 300 K. Abstract: Epitaxial single-crystal gallium nitride (GaN) films...

  5. Damage Evolution in GaN Under MeV Heavy Ion Implantation. | EMSL

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Evolution in GaN Under MeV Heavy Ion Implantation. Damage Evolution in GaN Under MeV Heavy Ion Implantation. Abstract: Damage evaluation processes in patterned GaN implanted by 3...

  6. Structural Defects in Laterally Overgrown GaN Layers Grown on Non-polar Substrates

    E-Print Network [OSTI]

    Liliental-Weber, Z.; Ni, X.; Morkoc, H.

    2007-01-01T23:59:59.000Z

    Overgrown GaN Layers Grown on Non-polar Substrates Z.in GaN layers grown on polar and non-polar substrates areGaN-based layers, since they are grown heteroepitaxially on foreign substrates (

  7. Imaging of InGaN inhomogeneities using visible apertureless near-field scanning optical microscope

    E-Print Network [OSTI]

    Stebounova, Larissa V.; Romanyuk, Yaroslav E.; Chen, Dongxue; Leone, Stephen R.

    2007-01-01T23:59:59.000Z

    InGaN dots deposited on a GaN substrate. 44 In that work, itGaN buffer layer is grown after the nitridation of the substrate.

  8. Mapping misorientation and crystallographic tilt in GaN layers via polychromatic microdiffraction

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    coefficients between GaN and the substrate. Understandingpenetrate both the GaN layer and the substrate. Two samplespattern from the GaN layer and the substrate on a charge-

  9. Selective epitaxial growth of monolithically integrated GaN-based light emitting diodes with AlGaN/GaN driving transistors

    SciTech Connect (OSTI)

    Liu, Zhaojun; Ma, Jun; Huang, Tongde; Liu, Chao; May Lau, Kei, E-mail: eekmlau@ust.hk [Photonics Technology Center, Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

    2014-03-03T23:59:59.000Z

    In this Letter, we report selective epitaxial growth of monolithically integrated GaN-based light emitting diodes (LEDs) with AlGaN/GaN high-electron-mobility transistor (HEMT) drivers. A comparison of two integration schemes, selective epitaxial removal (SER), and selective epitaxial growth (SEG) was made. We found the SER resulted in serious degradation of the underlying LEDs in a HEMT-on-LED structure due to damage of the p-GaN surface. The problem was circumvented using the SEG that avoided plasma etching and minimized device degradation. The integrated HEMT-LEDs by SEG exhibited comparable characteristics as unintegrated devices and emitted modulated blue light by gate biasing.

  10. Elastic properties of Pu metal and Pu-Ga alloys

    SciTech Connect (OSTI)

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

    2010-01-05T23:59:59.000Z

    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.

  11. Nucleation of GaN/AlN quantum dots

    SciTech Connect (OSTI)

    Adelmann, C; Daudin, B; Oliver, R; Briggs, G; Rudd, R

    2003-10-13T23:59:59.000Z

    We study the nucleation of GaN islands grown by plasma-assisted molecular-beam epitaxy on AlN in a Stranski-Krastanov mode. In particular, we assess the variation of their height and density as a function of GaN coverage. We show that the GaN growth passes four stages: initially, the growth is layer-by-layer; subsequently, bidimensional precursor islands form, which transform into genuine three-dimensional islands. During the latter stage, the height and the density of the islands increase with GaN coverage until the density saturates. During further GaN growth, the density remains constant and a bimodal height distribution appears. The variation of island height and density as a function of substrate temperature is discussed in the framework of an equilibrium model for Stranski-Krastanov growth [R. E. Rudd et al., Phys. Rev. Lett. 90, 146101 (2003)].

  12. Impact of GaN cap on charges in Al?O?/(GaN/)AlGaN/GaN metal-oxide-semiconductor heterostructures analyzed by means of capacitance measurements and simulations

    SciTech Connect (OSTI)

    ?apajna, M., E-mail: milan.tapajna@savba.sk; Jurkovi?, M.; Válik, L.; Haš?ík, Š.; Gregušová, D.; Kuzmík, J. [Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava (Slovakia); Brunner, F.; Cho, E.-M. [Ferdinand-Braun-Institut, Leibniz Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Strasse 4, 12489 Berlin (Germany); Hashizume, T. [Research Center for Integrated Quantum Electronics (RCIQE), Hokkaido University, 060-0814 Sapporo, Japan and JST-CREST, 102-0075 Tokyo (Japan)

    2014-09-14T23:59:59.000Z

    Oxide/semiconductor interface trap density (D{sub it}) and net charge of Al?O?/(GaN)/AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor (MOS-HEMT) structures with and without GaN cap were comparatively analyzed using comprehensive capacitance measurements and simulations. D{sub it} distribution was determined in full band gap of the barrier using combination of three complementary capacitance techniques. A remarkably higher D{sub it} (?5–8?×?10¹²eV?¹?cm?²) was found at trap energies ranging from EC-0.5 to 1?eV for structure with GaN cap compared to that (D{sub it}???2–3?×?10¹²eV?¹?cm?²) where the GaN cap was selectively etched away. D{sub it} distributions were then used for simulation of capacitance-voltage characteristics. A good agreement between experimental and simulated capacitance-voltage characteristics affected by interface traps suggests (i) that very high D{sub it} (>10¹³eV?¹?cm?²) close to the barrier conduction band edge hampers accumulation of free electron in the barrier layer and (ii) the higher D{sub it} centered about EC-0.6?eV can solely account for the increased C-V hysteresis observed for MOS-HEMT structure with GaN cap. Analysis of the threshold voltage dependence on Al?O? thickness for both MOS-HEMT structures suggests that (i) positive charge, which compensates the surface polarization, is not necessarily formed during the growth of III-N heterostructure, and (ii) its density is similar to the total surface polarization charge of the GaN/AlGaN barrier, rather than surface polarization of the top GaN layer only. Some constraints for the positive surface compensating charge are discussed.

  13. First principles phase diagram calculations for the wurtzitestructure systems AlN--GaN, GaN--InN, and AlN--InN

    E-Print Network [OSTI]

    Burton, Benjamin P.

    First principles phase diagram calculations for the wurtzite­structure systems AlN--GaN, GaN for the wurtzite­structure quasibinary systems AlN--GaN, GaN--InN, and AlN--InN. Cluster expansion Hamiltonians. Miscibility gaps are predicted for all three quasibinaries, with consolute points, #X C , T C #, for AlN--GaN

  14. AlGaN/GaN/AlN quantum-well field-effect transistors with highly resistive AlN epilayers

    E-Print Network [OSTI]

    Jiang, Hongxing

    AlGaN/GaN/AlN quantum-well field-effect transistors with highly resistive AlN epilayers Z. Y. Fana 66506-2601 Received 23 November 2005; accepted 5 January 2006; published online 16 February 2006 AlGaN/GaN/AlN quantum-well field-effect transistors have been demonstrated. By replacing a semi-insulating GaN epilayer

  15. AlGaN/GaN MIS-HEMT Gate Structure Improvement Using Al2O3 Deposited by Plasma-Enhanced ALD

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    AlGaN/GaN MIS-HEMT Gate Structure Improvement Using Al2O3 Deposited by Plasma-Enhanced ALD R(0)438782894 Abstract - In this work we evaluate the influence of the Al2O3 ALD deposition technique on AlGaN/GaN MIS drastically reduced with a measured average of 1e-11 A/mm for a drain-source bias of 5V. 1. Introduction AlGaN

  16. Low Phase-Noise 5 GHz AlGaN/GaN HEMT Oscillator Integrated with BaxSr1-xTiO3 Thin Films

    E-Print Network [OSTI]

    York, Robert A.

    Low Phase-Noise 5 GHz AlGaN/GaN HEMT Oscillator Integrated with BaxSr1-xTiO3 Thin Films Hongtao Xu -- A C-band MMIC oscillator in GaN HEMT technology with BaxSr1-xTiO3 (BST) film capacitors integrated with the common gate HEMT to generate negative resistance. The oscillator, based on AlGaN/GaN HEMT with 0.7um gate

  17. Large linear magnetoresistance in a GaAs/AlGaAs heterostructure

    SciTech Connect (OSTI)

    Aamir, Mohammed Ali, E-mail: aamir@physics.iisc.ernet.in; Goswami, Srijit, E-mail: aamir@physics.iisc.ernet.in; Ghosh, Arindam [Department of Physics, Indian Institute of Science, Bangalore 560 012 (India); Baenninger, Matthias; Farrer, Ian; Ritchie, David A. [Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Tripathi, Vikram [Department of Theoretical Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Pepper, Michael [Department of Electrical and Electronic Engineering, University College, London WC1E 7JE (United Kingdom)

    2013-12-04T23:59:59.000Z

    We report non-saturating linear magnetoresistance (MR) in a two-dimensional electron system (2DES) at a GaAs/AlGaAs heterointerface in the strongly insulating regime. We achieve this by driving the gate voltage below the pinch-off point of the device and operating it in the non-equilibrium regime with high source-drain bias. Remarkably, the magnitude of MR is as large as 500% per Tesla with respect to resistance at zero magnetic field, thus dwarfing most non-magnetic materials which exhibit this linearity. Its primary advantage over most other materials is that both linearity and the enormous magnitude are retained over a broad temperature range (0.3 K to 10 K), thus making it an attractive candidate for cryogenic sensor applications.

  18. Sidewall passivation for InGaN/GaN nanopillar light emitting diodes

    SciTech Connect (OSTI)

    Choi, Won Hyuck; Abraham, Michael; Yu, Shih-Ying [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); You, Guanjun; Liu, Jie; Wang, Li; Xu, Jian, E-mail: jianxu@engr.psu.edu [Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Mohney, Suzanne E., E-mail: mohney@ems.psu.edu [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2014-07-07T23:59:59.000Z

    We studied the effect of sidewall passivation on InGaN/GaN multiquantum well-based nanopillar light emitting diode (LED) performance. In this research, the effects of varying etch rate, KOH treatment, and sulfur passivation were studied for reducing nanopillar sidewall damage and improving device efficiency. Nanopillars prepared under optimal etching conditions showed higher photoluminescence intensity compared with starting planar epilayers. Furthermore, nanopillar LEDs with and without sulfur passivation were compared through electrical and optical characterization. Suppressed leakage current under reverse bias and four times higher electroluminescence (EL) intensity were observed for passivated nanopillar LEDs compared with unpassivated nanopillar LEDs. The suppressed leakage current and EL intensity enhancement reflect the reduction of non-radiative recombination at the nanopillar sidewalls. In addition, the effect of sulfur passivation was found to be very stable, and further insight into its mechanism was gained through transmission electron microscopy.

  19. Evaluation of the two-photon absorption characteristics of GaSb/GaAs quantum rings

    SciTech Connect (OSTI)

    Wagener, M. C.; Botha, J. R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Carrington, P. J. [Department of Electronic and Electrical Engineering, University College London, London (United Kingdom); Krier, A. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)

    2014-07-28T23:59:59.000Z

    The optical parameters describing the sub-bandgap response of GaSb/GaAs quantum rings solar cells have been obtained from photocurrent measurements using a modulated pseudo-monochromatic light source in combination with a second, continuous photo-filling source. By controlling the charge state of the quantum rings, the photoemission cross-sections describing the two-photon sub-bandgap transitions could be determined independently. Temperature dependent photo-response measurements also revealed that the barrier for thermal hole emission from the quantum rings is significantly below the quantum ring localisation energy. The temperature dependence of the sub-bandgap photo-response of the solar cell is also described in terms of the photo- and thermal-emission characteristics of the quantum rings.

  20. Single photon emission from site-controlled InGaN/GaN quantum dots

    SciTech Connect (OSTI)

    Zhang, Lei; Hill, Tyler A.; Deng, Hui, E-mail: dengh@umich.edu [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109 (United States)] [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109 (United States); Teng, Chu-Hsiang; Lee, Leung-Kway; Ku, Pei-Cheng, E-mail: peicheng@umich.edu [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109 (United States)] [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109 (United States)

    2013-11-04T23:59:59.000Z

    Single photon emission was observed from site-controlled InGaN/GaN quantum dots. The single-photon nature of the emission was verified by the second-order correlation function up to 90?K, the highest temperature to date for site-controlled quantum dots. Micro-photoluminescence study on individual quantum dots showed linearly polarized single exciton emission with a lifetime of a few nanoseconds. The dimensions of these quantum dots were well controlled to the precision of state-of-the-art fabrication technologies, as reflected in the uniformity of their optical properties. The yield of optically active quantum dots was greater than 90%, among which 13%–25% exhibited single photon emission at 10?K.

  1. High internal and external quantum efficiency InGaN/GaN solar cells

    SciTech Connect (OSTI)

    Matioli, Elison; Neufeld, C. J.; Iza, Michael; Cruz, S. C.; Al-Heji, Ali A.; Chen, Xu; Farrell, Rober M.; Keller, Stacia; DenBaars, Steven; Mishra, U. K.; Nakamura, Shuji; Speck, J. S.; Weisbuch, Claude

    2011-01-01T23:59:59.000Z

    High internal and external quantum efficiency GaN/InGaN solar cells are demonstrated. The internal quantum efficiency was assessed through the combination of absorption and external quantum efficiency measurements. The measured internal quantum efficiency, as high as 97%, revealed an efficient conversion of absorbed photons into electrons and holes and an efficient transport of these carriers outside the device. Improved light incoupling into the solar cells was achieved by texturing the surface. A peak external quantum efficiency of 72%, a fill factor of 79%, a short-circuit current density of 1.06?mA/cm{sup 2} , and an open circuit voltage of 1.89 V were achieved under 1 sun air-mass 1.5 global spectrumillumination conditions.

  2. Infrared reflection of GaN and AlGaN thin film heterostructures with AlN buffer layers

    E-Print Network [OSTI]

    Wetzel, Christian M.

    Infrared reflection of GaN and AlGaN thin film heterostructures with AlN buffer layers C. Wetzel, Nagoya, Japan Received 11 December 1995; accepted for publication 21 February 1996 Infrared reflection, their alloys and potential substrates need to be investigated as well. Here we present a study of the infrared

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

    E-Print Network [OSTI]

    Wetzel, Christian M.

    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

  4. Pulsed Current-Voltage-Temperature Characteristics of AlGaN/GaN High Electron Mobility Transistor under Isothermal Conditions

    E-Print Network [OSTI]

    Seo, Kwang Seok

    , such as current collapse (power slump), the self-heating effect and the power scaling problem. In this paper, we have studied the self-heating effect using pulsed current-voltage (IV) and current- voltage self-heating affects the AlGaN/GaN HEMT's operation. It can be thought that a reason for the power

  5. Self-Heating Effects in GaN/AlGaN Heterostructure Field-Effect Transistors and Device Structure Optimization

    E-Print Network [OSTI]

    Self-Heating Effects in GaN/AlGaN Heterostructure Field-Effect Transistors and Device Structure time, performance of these devices has been limited by self-heating and other problems associated-3]. At the same time, performance of these devices has been limited by self-heating and other problems associated

  6. Fabrication of quantum point contacts by engraving GaAsAlGaAs heterostructures with a diamond tip

    E-Print Network [OSTI]

    Hohls, Frank

    by hot-filament chemical vapor deposition of polycrystalline diamond onto a prepat- terned siliconFabrication of quantum point contacts by engraving GaAsÕAlGaAs heterostructures with a diamond tip for publication 17 July 2002 We use the all-diamond tip of an atomic force microscope for the direct engraving

  7. Reconstructions of GaN,,0001... and ,,0001... surfaces: Ga-rich metallic A. R. Smith and R. M. Feenstraa)

    E-Print Network [OSTI]

    wurtzite material.1­9 A common theme regarding the growth of these surfaces in the absence of hydrogen and elec- tronic properties of two reconstructions for wurtzite GaN: the 1 1 structure of the GaN 0001

  8. Electronic band-structure engineering of GaAs/AlxGa1(xAs quantum well superlattices with substructures

    E-Print Network [OSTI]

    Cao, Wenwu

    Electronic band-structure engineering of GaAs/AlxGa1(xAs quantum well superlattices investigation on the band structures of electrons in both infinite and finite semiconductor quantum well of these two materials, narrower passbands and/or broad stopbands can be obtained for electrons with energy

  9. OPTIMIZATION OF GaN WINDOW LAYER FOR InGaN SOLAR CELLS USING POLARIZATION EFFECT

    E-Print Network [OSTI]

    Honsberg, Christiana

    on the design of wide-band gap GaN window layers for InGaN solar cells. Window layers serve to passivate the top into account during design of the solar cell to improve its collection efficiency. Previously, we have. The present work is a subset of the design optimization process for such solar cells, where we focus

  10. Si-CMOS-Like Integration of AlGaN/GaN Dielectric-Gated High-Electron-Mobility Transistors

    E-Print Network [OSTI]

    Johnson, Derek Wade

    2014-07-31T23:59:59.000Z

    the engineering of high mobility, high carrier density channels at III-Nitride heterointerfaces. In order to seize market share from silicon, the cost of manufacturing GaN-based devices must be further reduced. With the successful realization of 200mm Ga...

  11. Output Harmonic Termination Techniques for AlGaN/GaN HEMT Power Amplifiers Using Active Integrated Antenna Approach

    E-Print Network [OSTI]

    Itoh, Tatsuo

    Output Harmonic Termination Techniques for AlGaN/GaN HEMT Power Amplifiers Using Active Integrated 1200, Los Angeles, CA 90045 Abstract -- In this paper, effects of output harmonic terminations on PAE termination, we observe a substantial increase in PAE and output power. Further, we demonstrate the high

  12. Diffusion of a Ga adatom on the GaAs(001)c(44)heterodimer surface: A first principles study

    E-Print Network [OSTI]

    Khare, Sanjay V.

    Diffusion of a Ga adatom on the GaAs(001)c(4×4)heterodimer surface: A first principles study J Diffusion barriers Reconstruction Density functional calculations The adsorption and diffusion behavior functional theory (DFT) computations in the local density approxima- tion. Structural and bonding features

  13. Electric field dependent radiative decay kinetics of polar InGaN/GaN quantum heterostructures at low fields

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Electric field dependent radiative decay kinetics of polar InGaN/GaN quantum heterostructures with increasing external electric field, with the radiative component exhibiting weaker field dependence. © 2009 applied electric field in Ref. 12, the electric field dependent radiative recombination in particular has

  14. Wavelength dependence of the threshold in an InGaP-InAlGaP vertical cavity surface emitting laser

    SciTech Connect (OSTI)

    Chow, W.W.; Schneider, R.P. Jr.; Lott, J.A.; Choquette, K.D. (Sandia National Laboratories, Albuquerque, New Mexico 87185-0350 (United States))

    1994-07-11T23:59:59.000Z

    The wavelength dependence of the threshold in an InGaP-InAlGaP vertical cavity surface emitting laser is investigated using a microscopic theory of the semiconductor gain medium. Good agreement is found between experiment and theory for the minimum threshold lasing wavelength for a range of laser structures.

  15. Si-CMOS-Like Integration of AlGaN/GaN Dielectric-Gated High-Electron-Mobility Transistors 

    E-Print Network [OSTI]

    Johnson, Derek Wade

    2014-07-31T23:59:59.000Z

    the engineering of high mobility, high carrier density channels at III-Nitride heterointerfaces. In order to seize market share from silicon, the cost of manufacturing GaN-based devices must be further reduced. With the successful realization of 200mm Ga...

  16. Ga induced superstructures as templates for lattice matched hetroepitaxial growth of GaN on Si(111) substrate

    SciTech Connect (OSTI)

    Kumar, Praveen; Kuyyalil, Jithesh; Shivaprasad, S. M. [Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, 560 064 Bangalore (India)

    2010-11-29T23:59:59.000Z

    High quality GaN is grown by plasma assisted molecular beam epitaxy on Ga induced superstructural phases of Si(111)7x7. Three stable surface phases induced by Ga adsorption, viz., (1x1), (6.3x6.3), and ({radical}3x{radical}3)R30 deg., are employed as templates to grow epitaxial (0001) GaN thin films. GaN grown on Si({radical}3x{radical}3)R30 deg. -Ga is found to be highly crystalline with intense (0002) x-ray diffraction and photoluminescence peaks with low full width at half maximum, low surface roughness, and stoichiometric surface composition. The high quality of these GaN films formed at a low temperature of 400 deg. C is explained by the integral (x2) lattice matching between the unit cell of GaN and the ({radical}3x{radical}3) phase. The experiments demonstrate a plausible approach of adsorbate induced surface modifications as templates for III-V hetroepitaxy on Si surfaces.

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

    E-Print Network [OSTI]

    Lu, Bin

    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 ...

  18. Sputtering of Si, SiC, InAs, InP, Ge, GaAs, GaSb, and GaN by electrosprayed nanodroplets

    SciTech Connect (OSTI)

    Borrajo-Pelaez, Rafael; Grustan-Gutierrez, Enric; Gamero-Castaño, Manuel, E-mail: mgameroc@uci.edu [Department of Mechanical and Aerospace Engineering, University of California, Irvine, California 92697 (United States)

    2013-11-14T23:59:59.000Z

    This article presents a characterization of the damage caused by energetic beams of electrosprayed nanodroplets striking the surfaces of single-crystal semiconductors including Si, SiC, InAs, InP, Ge, GaAs, GaSb, and GaN. The sputtering yield (number of atoms ejected per projectile's molecule), sputtering rate, and surface roughness are measured as functions of the beam acceleration potential. The maximum values of the sputtering yields range between 1.9 and 2.2 for the technological important but difficult to etch SiC and GaN respectively, and 4.5 for Ge. The maximum sputtering rates for the non-optimized beam flux conditions used in our experiments vary between 409?nm/min for SiC and 2381?nm/min for GaSb. The maximum sputtering rate for GaN is 630?nm/min. Surface roughness increases modestly with acceleration voltage, staying within 2?nm and 20?nm for all beamlet acceleration potentials and materials except Si. At intermediate acceleration potentials, the surface of Si is formed by craters orders of magnitude larger than the projectiles, yielding surface roughness in excess of 60?nm. The effect of projectile dose is studied in the case of Si. This parameter is correlated with the formation of the large craters typical of Si, which suggests that the accumulation of damage following consecutive impacts plays an important role in the interaction between beamlet and target.

  19. Strain relaxation effect by nanotexturing InGaN/GaN multiple quantum well

    SciTech Connect (OSTI)

    Ramesh, V.; Kikuchi, A.; Kishino, K. [Department of Electrical and Electronics Engineering, Sophia University, Tokyo 102-8554, Japan and Nano-technology Research Center, Sophia University, Tokyo 102-8554 (Japan); CREST, JST, Saitama 332-0012 (Japan); Funato, M.; Kawakami, Y. [CREST, JST, Saitama 332-0012 (Japan); Department of Electronics Science and Engineering, Kyoto University, Kyoto 615-8510 (Japan)

    2010-06-15T23:59:59.000Z

    The relaxation of lattice-mismatched strain by deep postetching was systematically investigated for InGaN/GaN multiple quantum wells (MQWs). A planar heterojunction wafer, which included an In{sub 0.21}Ga{sub 0.79}N (3.2 nm)/GaN (14.8 nm) MQW, was etched by inductively coupled plasma dry etching, to fabricate high-density nanopillar, nanostripe, and nanohole arrays. The etching depth was 570 nm for all nanostructures. The diameter of the nanopillars was varied from 50 to 300 nm, then the mesa stripe width of the nanostripes and the diameter of the nanoholes were varied from 100 nm to 440 nm and 50 nm to 310 nm, respectively. The effect of strain relaxation on various optical properties was investigated. For example, in an array of nanopillars with diameter 130 nm and interval 250 nm, a large blueshift in the photoluminescence (PL) emission peak from 510 nm (as-grown) to 459 nm occurred at room temperature (RT). PL internal quantum efficiency (defined by the ratio of PL integral intensity at 300 K to that at 4.2 K) was enhanced from 34% (as-grown) to 60%, and the PL decay time at 4.2 K was reduced from 22 ns (as-grown) to 4.2 ns. These results clearly indicate the reduction of lattice-mismatched strain by postetching, which enhanced strain reduction with decreasing nanopillar diameter down to a diameter of 130 nm, where the strain reduction became saturated. The dependence of RT-PL decay time on nanopillar diameter was measured, and the surface nonradiative recombination velocity was estimated to be 5.8x10{sup 2} cm/s. This relatively slow rate indicates a little etching damage.

  20. Infrared emission from the substrate of GaAs-based semiconductor lasers Mathias Ziegler,1,a

    E-Print Network [OSTI]

    Peinke, Joachim

    by metal- organic vapor phase epitaxy on a n-type GaAs substrate. The red-emitting laser employs an InGaP

  1. Partially filled intermediate band of Cr-doped GaN films

    SciTech Connect (OSTI)

    Sonoda, S. [Department of Electronics, Kyoto Institute of Technology, Kyoto 606-8585 (Japan)

    2012-05-14T23:59:59.000Z

    We investigated the band structure of sputtered Cr-doped GaN (GaCrN) films using optical absorption, photoelectron yield spectroscopy, and charge transport measurements. It was found that an additional energy band is formed in the intrinsic band gap of GaN upon Cr doping, and that charge carriers in the material move in the inserted band. Prototype solar cells showed enhanced short circuit current and open circuit voltage in the n-GaN/GaCrN/p-GaN structure compared to the GaCrN/p-GaN structure, which validates the proposed concept of an intermediate-band solar cell.

  2. Improved synthesis and crystal structure of the flexible pillared layer porous coordination polymer: Ni(1,2-bis(4-pyridyl)ethylene)[Ni(CN)(4)

    SciTech Connect (OSTI)

    Wong-Ng, W.; Culp, J. T.; Chen, Y. S.; Zavalij, P.; Espinal, L.; Siderius, D. W.; Allen, A. J.; Scheins, S Matranga, C

    2013-04-04T23:59:59.000Z

    This paper reports our synthesis of flexible coordination polymer, Ni(L)[Ni(CN){sub 4}], (L = 1,2-bis(4- pyridyl)ethylene (nicknamed bpene)), and its structural characterization using synchrotron single crystal X-ray diffraction. The structure of the purplish crystals has been determined to be monoclinic, space group P2{sub 1}/m, a = 13.5941(12) Å, b = 14.3621(12) Å, c = 14.2561(12) Å, {beta} = 96.141(2){degrees|, V = 2767.4(4) Å{sup 3}, Z = 4, D{sub c} = 1.46 g cm{sup -1}. Ni(bpene)[Ni(CN){sub 4}] assumes a pillared layer structure with layers defined by Ni[Ni(CN){sub 4}]{sub n} nets and bpene ligands acting as pillars. With the present crystallization technique which involves the use of concentrated ammonium hydroxide solution and dimethyl sulfoxide (DMSO), disordered free bpene ligands and solvents of crystallization (DMSO and water molecules) occupy the pores, resulting in a formula of Ni(bpene)[Ni(CN){sub 4}](1/2)bpene.DMSO.2H{sub 2}O, or Ni{sub 2}N{sub 7}C{sub 24}H{sub 2}.5SO{sub 3}. Without the inclusion of free bpene ligands and solvent molecules, the free volume is approximately 61% of the total volume; this free volume fraction is reduced to 50% with the free ligands present. Pores without the free ligands were found to have a local diameter of 5.7 Å and a main aperture of 3.5 Å. Based on the successful crystal synthesis, we also devised a new bulk synthetic technique which yielded a polycrystalline material with a significantly improved CO{sub 2} uptake as compared to the originally reported powder material. The improved synthetic technique yielded a polycrystalline material with 40% higher CO{sub 2} uptake compared to the previously reported powder material. An estimated 14.4 molecules of CO{sub 2} per unit cell was obtained.

  3. Field dependent emission rates in radiation damaged GaAs

    SciTech Connect (OSTI)

    Fleming, R. M.; Myers, S. M.; Wampler, W. R.; Lang, D. V.; Seager, C. H.; Campbell, J. M. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1415 (United States)

    2014-07-07T23:59:59.000Z

    We have measured the temperature and field dependence of emission rates from five traps in electron damaged GaAs. Four of the traps have previously been identified as radiation defects. One of the traps, seen in higher doped diodes, has not been previously identified. We have fit the data to a multiphonon emission theory that allows recombination in GaAs to be characterized over a broad range of temperature and electric field. These results demonstrate an efficient method to calculate field-dependent emission rates in GaAs.

  4. Evidence of N substitution by Mn in GaN

    E-Print Network [OSTI]

    Pereira, LMC; Decoster, S; Correia, JG; da Silva, MR; Vantomme, A; Araújo, JP

    2012-01-01T23:59:59.000Z

    We report on the lattice location of Mn in wurtzite GaN using beta? emission channeling. In addition to the majority substituting for Ga, we locate up to 20% of the Mn atoms in N sites. We propose that the incorporation of Mn in N sites is enabled under sufficiently high concentrations of N vacancies, and stabilized by a highly charged state of the Mn cations. Since N substitution by Mn impurities in wurtzite GaN has never been observed experimentally or even considered theoretically before, it challenges the current paradigm of transition metal incorporation in wide-gap dilute magnetic semiconductors.

  5. Ferromagnetism in undoped One-dimensional GaN Nanowires

    SciTech Connect (OSTI)

    Jeganathan, K., E-mail: kjeganathan@yahoo.com, E-mail: jagan@physics.bdu.ac.in; Purushothaman, V. [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli - 620 024 (India)] [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli - 620 024 (India); Debnath, R. [Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4 (Canada)] [Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4 (Canada); Arumugam, S. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli – 620 024 (India)] [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli – 620 024 (India)

    2014-05-15T23:59:59.000Z

    We report an intrinsic ferromagnetism in vertical aligned GaN nanowires (NW) fabricated by molecular beam epitaxy without any external catalyst. The magnetization saturates at ?0.75 × emu/gm with the applied field of 3000 Oe for the NWs grown under the low-Gallium flux of 2.4 × 10{sup ?8} mbar. Despite a drop in saturation magnetization, narrow hysteresis loop remains intact regardless of Gallium flux. Magnetization in vertical standing GaN NWs is consistent with the spectral analysis of low-temperature photoluminescence pertaining to Ga-vacancies associated structural defects at the nanoscale.

  6. Optical spectroscopy of cubic GaN in nanowires

    SciTech Connect (OSTI)

    Renard, J. [CEA-CNRS Group 'Nanophysique et semiconducteurs', CEA-Grenoble INAC-SP2M, Institut Neel, CNRS, Universite Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France); Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z4 (Canada); Tourbot, G. [CEA-CNRS Group 'Nanophysique et semiconducteurs', CEA-Grenoble INAC-SP2M, Institut Neel, CNRS, Universite Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France); CEA-LETI, MINATEC, 17 rue des Martyrs 38054 Grenoble Cedex 9 (France); Sam-Giao, D.; Bougerol, C.; Daudin, B.; Gayral, B. [CEA-CNRS Group 'Nanophysique et semiconducteurs', CEA-Grenoble INAC-SP2M, Institut Neel, CNRS, Universite Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France)

    2010-08-23T23:59:59.000Z

    We show that highly homogeneous cubic GaN can be grown by plasma-assisted molecular beam epitaxy on wurtzite GaN nanowires. The line width of the donor bound exciton is below 3 meV and can reach 1.6 meV in the best parts of the studied sample. This allows to perform a detailed spectroscopy of cubic GaN, and, in particular, to determine the precise spectral positions of the donor bound exciton, the fundamental free exciton and the split-off exciton in a photoluminescence experiment.

  7. Yrast structure of the two-proton- and three-neutron-hole nucleus {sup 203}Hg from the decay of a 53/2{sup +} isomer

    SciTech Connect (OSTI)

    Szpak, B.; Maier, K. H.; Fornal, B.; Broda, R.; Cieplicka, N.; Krolas, W.; Pawlat, T.; Wrzesinski, J. [Niewodniczanski Institute of Nuclear Physics PAN, Krakow (Poland); Smolkowska, A. S. [Niewodniczanski Institute of Nuclear Physics PAN, Krakow (Poland); Gdansk University of Technology, Gdansk (Poland); Carpenter, M. P.; Janssens, R. V. F.; Zhu, S. [Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2011-06-15T23:59:59.000Z

    The decay of a new, 53/2{sup +}, isomer at 8281 keV in {sup 203}Hg has been studied by {gamma} coincidence spectroscopy. A half-life of 146(30) ns was measured. In addition, another isomeric, 39/2{sup +}, level with a half-life of 7.8(1.5) ns was observed. Some elements of the Rydstroem shell-model interaction have been adjusted to reproduce level energies in nuclei with two to four holes in the {sup 208}Pb core. With this interaction, the new states in the five-hole nucleus {sup 203}Hg are reproduced with an rms error of 105 keV.

  8. Electrical spin injection using GaCrN in a GaN based spin light emitting diode

    SciTech Connect (OSTI)

    Banerjee, D.; Ganguly, S.; Saha, D., E-mail: dipankarsaha@iitb.ac.in [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India); IITB-Monash Research Academy, Indian Institute of Technology Bombay, Mumbai 400076 (India); Adari, R.; Sankaranarayan, S.; Kumar, A. [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India)] [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India); Aldhaheri, R. W.; Hussain, M. A.; Balamesh, A. S. [Department of Electrical and Computer Engineering, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)] [Department of Electrical and Computer Engineering, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

    2013-12-09T23:59:59.000Z

    We have demonstrated electrical spin-injection from GaCrN dilute magnetic semiconductor (DMS) in a GaN-based spin light emitting diode (spin-LED). The remanent in-plane magnetization of the thin-film semiconducting ferromagnet has been used for introducing the spin polarized electrons into the non-magnetic InGaN quantum well. The output circular polarization obtained from the spin-LED closely follows the normalized in-plane magnetization curve of the DMS. A saturation circular polarization of ?2.5% is obtained at 200?K.

  9. Structural and optical properties of GaAs-based heterostructures with Ge and Ge/InGaAs quantum wells

    SciTech Connect (OSTI)

    Aleshkin, V. Ya.; Dubinov, A. A., E-mail: sanya@ipm.sci-nnov.ru; Drozdov, M. N. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Zvonkov, B. N. [Nizhni Novgorod State University, Research Physical Technical Institute (Russian Federation); Kudryavtsev, K. E.; Tonkikh, A. A.; Yablonskiy, A. N. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Werner, P. [Max Planck Institute of Microstructure Physics (Germany)

    2013-05-15T23:59:59.000Z

    GaAs-based heterostructures with Ge and Ge/InGaAs quantum wells are grown by laser-assisted sputtering. Structural and optical studies of the heterostructures are carried out. A broad photoluminescence line is observed in the wavelength range from 1300 to 1650 nm. The line corresponds to indirect transitions in the momentum space of the Ge quantum wells and to transitions between the In{sub 0.28}Ga{sub 0.72}As and Ge layers, indirect in coordinate space, but direct in momentum space.

  10. Microscopic, electrical and optical studies on InGaN/GaN quantum wells based LED devices

    SciTech Connect (OSTI)

    Mutta, Geeta Rani; Venturi, Giulia; Castaldini, Antonio; Cavallini, Anna [Department of Physics and Astronomy, University of Bologna, Viale Carlo Berti Pichat 6/II, 40127 Bologna (Italy); Meneghini, Matteo; Zanoni, Enrico; Meneghesso, Gaudenzio [University of Padova, Department of Information Engineering, via Gradenigo 6/B, Padova 35131 (Italy); Zhu, Dandan; Humphreys, Colin [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom)

    2014-02-21T23:59:59.000Z

    We report here on the micro structural, electronic and optical properties of a GaN-based InGaN/GaN MQW LED grown by the MOVPE method. The present study shows that the threading dislocations present in these LED structures are terminated as V pits at the surface and have an impact on the electrical and optical activity of these devices. It has been pointed that these dislocations were of edge, screw and mixed types. EBIC maps suggest that the electrically active defects are screw and mixed dislocations and behave as nonradiative recombinant centres.

  11. Waveguide effect of GaAsSb quantum wells in a laser structure based on GaAs

    SciTech Connect (OSTI)

    Aleshkin, V. Ya. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)] [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Afonenko, A. A. [Belarussian State University (Belarus)] [Belarussian State University (Belarus); Dikareva, N. V. [Research Physical-Technical Institute of Nizhni Novgorod State University (Russian Federation)] [Research Physical-Technical Institute of Nizhni Novgorod State University (Russian Federation); Dubinov, A. A., E-mail: sanya@ipm.sci-nnov.ru; Kudryavtsev, K. E.; Morozov, S. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)] [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Nekorkin, S. M. [Research Physical-Technical Institute of Nizhni Novgorod State University (Russian Federation)] [Research Physical-Technical Institute of Nizhni Novgorod State University (Russian Federation)

    2013-11-15T23:59:59.000Z

    The waveguide effect of GaAsSb quantum wells in a semiconductor-laser structure based on GaAs is studied theoretically and experimentally. It is shown that quantum wells themselves can be used as waveguide layers in the laser structure. As the excitation-power density attains a value of 2 kW/cm{sup 2} at liquid-nitrogen temperature, superluminescence at the wavelength corresponding to the optical transition in bulk GaAs (at 835 nm) is observed.

  12. High temperature stable W and WSi{sub x} ohmic contacts on GaN and InGaN

    SciTech Connect (OSTI)

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

    1996-06-01T23:59:59.000Z

    Conventional III-V metallizations chemes such as Au/Ge/Ni, Ti/Pt/Au, and Au/Be were found to display poor thermal stability on both GaN and InGaN, with extensive reaction and contact degradation at {le}500 C. By contrast, W was found to produce low contact resistance ({rho}{sub c}{similar_to}8x10{sup -5}{Omega}cm{sup 2}) to n-GaN. Ga outdiffusion to the surface of thin (500 A) W films was found after annealing at 1,100 C, but not at 1000 C. Interfacial abruptness increased by 300A after 1,100 C annealing. In the case of WSi{sub X} (X=0.45), Ga outdiffusion was absent even at 1,100 C, but again there was interfacial broadening and some phase changes in the WSi{sub X}. On In{sub 0.5}Ga{sub 0.5}N, a minimum specific contact resistivity of 1.5 x10{sup -5}{Omega}cm{sup 2} was obtained for WSi{sub X} annealed at 700 C. These contacts retained a smooth morphology and abrupt interfaces to 800 C. Graded In{sub X}Ga{sub 1-X}N layers have been employed on GaAs/AlGaAs HBTs (heterojunction bipolar transistors), replacing conventional In{sub X}Ga{sub 1-X}As layers. R{sub C} values of 5x10{sup -7}{Omega}cm{sup 2} were obtained for nonalloyed Ti/Pt/Au on the InGaN, and the morphologies were superior to those of InGaAs contact layers. This proves to have significant advantages for fabrication of sub-micron HBTs. Devices with emitter dimensions of 2x5{mu}m{sup 2} displayed gains of 35 for a base doping level of 7x10{sup 19}cm{sup -3} and stable long-term behavior.

  13. Analytical modeling of AlGaN/AlN/GaN heterostructures including effects of distributed surface donor states

    SciTech Connect (OSTI)

    Goyal, Nitin, E-mail: nitin@unik.no [Carinthian Tech Research CTR AG, Europastraße 4/1, Technologiepark Villach, A-9524 Villach/St. Magdalen (Austria); Department of Electronics and Telecommunication, Norwegian University of Science and Technology, Trondheim NO7034 (Norway); Fjeldly, Tor A. [Department of Electronics and Telecommunication, Norwegian University of Science and Technology, Trondheim NO7034 (Norway)

    2014-07-14T23:59:59.000Z

    In this paper, a physics based analytical model is presented for calculation of the two-dimensional electron gas density and the bare surface barrier height of AlGaN/AlN/GaN material stacks. The presented model is based on the concept of distributed surface donor states and the self-consistent solution of Poisson equation at the different material interfaces. The model shows good agreement with the reported experimental data and can be used for the design and characterization of advanced GaN devices for power and radio frequency applications.

  14. Characterization of AlGaN/GaN Heterostructure Field Effect Transistors (HFETs) with Variable Thickness Channel and Substrate Type

    SciTech Connect (OSTI)

    Hussein, A. SH.; Hassan, Z.; Hassan, H. Abu; Thahab, S. M. [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia)

    2010-07-07T23:59:59.000Z

    In this study, AlGaN/GaN-based heterostructure field effect transistor (HFET) was simulated by using ISE TCAD software. The effects of varying thickness, substrate type and doping channel levels were investigated. The device output characteristics of drain current and voltage with various gate biases were presented. A maximum drain current and extrinsic transconductance were achieved with AlGaN HFET grown on AlN/SiC substrate. The device performance can be improved by optimizing the substrate type and heavily doped channel layer which will reduce the contact resistance and enhance the transconductance. All results are comparable with the experimental results obtained by other researchers.

  15. Prospective emission efficiency and in-plane light polarization of nonpolar m-plane InxGa1-xN/GaN blue light emitting diodes fabricated on freestanding GaN substrates

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    m-plane In x Ga 1?x N / GaN blue light emitting diodesmea- surements. Since the blue MQW emission is polarized toS. Nakamura and G. Fasol, The Blue Laser Diode ?Springer,

  16. Thermodynamic Studies of [H2Rh(diphosphine)2]+ and [HRh(diphosphine)2(CH3CN)]2+ Complexes in Acetonitrile

    SciTech Connect (OSTI)

    Aaron D. Wilson; Alexander J. M. Miller; Daniel L. DuBois; Jay A. Labinger; John E. Bercaw

    2011-04-01T23:59:59.000Z

    Thermodynamic studies of a series of [H2Rh(PP)2]+ and [HRh(PP)2(CH3CN)]2+ complexes have been carried out in acetonitrile. Seven different diphosphine (PP) ligands were selected to allow variation of the electronic properties of the ligand substituents, the cone angles, and the natural bite angles (NBAs). Oxidative addition of H2 to [Rh(PP)2]+ complexes is favored by diphosphine ligands with large NBAs, small cone angles, and electron donating substituents, with the NBA being the dominant factor. Large pKa values for [HRh(PP)2(CH3CN)]2+ complexes are favored by small ligand cone angles, small NBAs, and electron donating substituents with the cone angles playing a major role. The hydride donor abilities of [H2Rh(PP)2]+ complexes increase as the NBAs decrease, the cone angles decrease, and the electron donor abilities of the substituents increase. These results indicate that if solvent coordination is involved in hydride transfer or proton transfer reactions, the observed trends can be understood in terms of a combination of two different steric effects, NBAs and cone angles, and electron-donor effects of the ligand substituents.

  17. Thermodynamic Studies of [H2Rh(diphosphine)2]+ and [HRh(diphosphine)2(CH3CN)]2+ Complexes in Acetonitrile

    SciTech Connect (OSTI)

    Wilson, Aaron D.; Miller, Alexander J.; DuBois, Daniel L.; Labinger, Jay A.; Bercaw, John E.

    2010-04-19T23:59:59.000Z

    Thermodynamic studies of a series of [H2Rh(PP)2]+ and [HRh(PP)2(CH3CN)]2+ complexes have been carried out in acetonitrile. Seven different diphosphine (PP) ligands were selected to allow variation of the electronic properties of the ligand substituents, the cone angles, and the natural bite angles (NBAs). Oxidative addition of H2 to [Rh(PP)2]+ complexes is favored by diphosphine ligands with large NBAs, small cone angles, and electron donating substituents, with the NBA being the dominant factor. Large pKa values for [HRh(PP)2(CH3CN)]2+ complexes are favored by small ligand cone angles, small NBAs, and electron donating substituents with the cone angles playing a major role. The hydride donor abilities of [H2Rh(PP)2]+ complexes increase as the NBAs decrease, the cone angles decrease, and the electron donor abilities of the substituents increase. These results indicate that if solvent coordination is involved in hydride transfer or proton transfer reactions, the observed trends can be understood in terms of a combination of two different steric effects, NBAs and cone angles, and electron-donor effects of the ligand substituents. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  18. Transverse acoustic actuation of Ni-Mn-Ga single crystals

    E-Print Network [OSTI]

    Simon, Jesse Matthew

    2007-01-01T23:59:59.000Z

    Two methods for the transverse acoustic actuation of {110}-cut Ni-Mn-Ga single crystals are discussed. In this actuation mode, crystals are used that have the {110}- type twinning planes parallel to the base of the crystal. ...

  19. Beta-decay branching ratios of 62Ga

    E-Print Network [OSTI]

    A. Bey; B. Blank; G. Canchel; C. Dossat; J. Giovinazzo; I. Matea; V. Elomaa; T. Eronen; U. Hager; M. Hakala; A. Jokinen; A. Kankainen; I. Moore; H. Penttila; S. Rinta-Antila; A. Saastamoinen; T. Sonoda; J. Aysto; N. Adimi; G. De France; J. C. Thomas; G. Voltolini; T. Chaventré

    2008-04-17T23:59:59.000Z

    Beta-decay branching ratios of 62Ga have been measured at the IGISOL facility of the Accelerator Laboratory of the University of Jyvaskyla. 62Ga is one of the heavier Tz = 0, 0+ -> 0+ beta-emitting nuclides used to determine the vector coupling constant of the weak interaction and the Vud quark-mixing matrix element. For part of the experimental studies presented here, the JYFLTRAP facility has been employed to prepare isotopically pure beams of 62Ga. The branching ratio obtained, BR= 99.893(24)%, for the super-allowed branch is in agreement with previous measurements and allows to determine the ft value and the universal Ft value for the super-allowed beta decay of 62Ga.

  20. GaBo{sub 3} crystal growth from flux

    SciTech Connect (OSTI)

    Rudenko, V.V. [Institute of Physics, Krasnoyarsk (Russian Federation)

    1995-03-01T23:59:59.000Z

    Synthesis of the chemical compound GaBO{sub 3} was first reported in paper, and the crystallographic determination of its structure and unit cell parameters was presented in paper. The chemical compound GaBO{sub 3} crystallizes in a calcite structure type with the hexagonal unit cell Parameters a{sub H} = 4.568 and c{sub H} = 14.18 {Angstrom}. GaBO{sub 3} crystals in the form of (111) hexagonal plates were grown from the solvent B{sub 2}O{sub 3}-Bi{sub 2}O{sub 3} by the method of sponvineous crystallization. That technique was hard to reproduce, however. We decided to grow a GaBO{sub 3} crystal as an object for possible studies of various physical properties. 8 refs., 2 figs.

  1. Evaporation-based Ge/.sup.68 Ga Separation

    DOE Patents [OSTI]

    Mirzadeh, Saed (Albuquerque, NM); Whipple, Richard E. (Los Alamos, NM); Grant, Patrick M. (Los Alamos, NM); O'Brien, Jr., Harold A. (Los Alamos, NM)

    1981-01-01T23:59:59.000Z

    Micro concentrations of .sup.68 Ga in secular equilibrium with .sup.68 Ge in strong aqueous HCl solution may readily be separated in ionic form from the .sup.68 Ge for biomedical use by evaporating the solution to dryness and then leaching the .sup.68 Ga from the container walls with dilute aqueous solutions of HCl or NaCl. The chloro-germanide produced during the evaporation may be quantitatively recovered to be used again as a source of .sup.68 Ga. If the solution is distilled to remove any oxidizing agents which may be present as impurities, the separation factor may easily exceed 10.sup.5. The separation is easily completed and the .sup.68 Ga made available in ionic form in 30 minutes or less.

  2. Electrical degradation mechanisms of RF power GaAs PHEMTs

    E-Print Network [OSTI]

    Villanueva, Anita A. (Anita Ariel), 1978-

    2007-01-01T23:59:59.000Z

    GaAs Pseudomorphic High-Electron Mobility Transistors (PHEMTs) are widely used in RF power applications. Since these devices typically operate at high power levels and under high voltage biasing, their electrical reliability ...

  3. Quantitative analysis of compositional changes in InGaAs/InGaAsP quantum wells on GaAs induced by intermixing with a low temperature grown InGaP cap layer

    SciTech Connect (OSTI)

    Hulko, O.; Thompson, D. A.; Czaban, J. A.; Simmons, J. G. [Centre for Emerging Devices and Technologies (CEDT), McMaster University, Hamilton, Ontario L8S 4L8 (Canada)

    2006-08-07T23:59:59.000Z

    Energy-dispersive x-ray spectroscopy was used to analyze quantum well intermixing between an InGaAs quantum well (QW) and InGaAsP barriers grown on GaAs induced by a low temperature, molecular beam epitaxy grown, InGaP cap. This cap layer produces an enhanced blueshift of the photoluminescence (PL) wavelength following postgrowth annealing, and degradation of the PL signal. Cross-sectional transmission electron microscopy reveals modification of the whole structure, with formation of arsenic precipitates, broadening, and subsequent disappearance of the QWs in the capped structure. Uncapped samples are relatively unchanged. Increased phosphorus observed in the QW for capped structures confirms the diffusion of phosphorus from the P-rich cap.

  4. Sandia National Laboratories: GaN-based nanowire laser

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    GaN-based nanowire laser BES Web Highlight: Single-mode gallium nitride nanowire lasers On January 28, 2013, in EC, Energy Efficiency, Solid-State Lighting A new top-down method...

  5. Micro Raman Spectroscopy of Annealed Erbium Implanted GaN

    E-Print Network [OSTI]

    Vajpeyi, Agam P.

    Wurtzite GaN epilayers grown by metal organic chemical vapor deposition on sapphire substrates were subsequently ion implanted with Er to a dose of 5×10¹? cm?². The implanted samples were annealed in nitrogen atmosphere ...

  6. AlGaAs/GaAs quantum well infrared detectors and modulators

    E-Print Network [OSTI]

    Dave, Digant Praful

    1990-01-01T23:59:59.000Z

    of boundary condition (1) we find that F=D=O Applying the boundary conditions (2) and (3) to the Schrodinger equation we get four ordinary equations. at x=-a -Asin(qa) + Bcos(qa) = Ce-" qAcos(qa) + qBsin(qa) = sCe ~ (4 7) (4 6) atx= a Asin... been extensively used for quantum well applications and studies is because of the excellent lattice match that exists between GaAs and AIAs. This feature is quite clear from the Fig. 2. They have less than 0. 13/o of lattice mismatch. The lattice...

  7. Characteristics of Novel InGaAsN Double Heterojunction Bipolar Transistors

    SciTech Connect (OSTI)

    LI,N.Y.; CHANG,PING-CHIH; BACA,ALBERT G.; LAROCHE,J.R.; REN,F.; ARMOUR,E.; SHARPS,P.R.; HOU,H.Q.

    2000-08-01T23:59:59.000Z

    The authors demonstrate, for the first time, both functional Pnp AlGaAs/InGaAsN/GaAs (Pnp InGaAsN) and Npn InGaP/InGaAsN/GaAs (Npn InGaAsN) double heterojunction bipolar transistors (DHBTs) using a 1.2 eV In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} as the base layer for low-power electronic applications. The Pnp InGaAsN DHBT has a peak current gain ({beta}) of 25 and a low turn-on voltage (V{sub ON}) of 0.79 V. This low V{sub ON} is {approximately} 0.25 V lower than in a comparable Pnp AlGAAs/GaAs HBT. For the Npn InGaAsN DHBT, it has a low V{sub ON} of 0.81 V, which is 0.13 V lower than in an InGaP/GaAs HBT. A peak {beta} of 7 with nearly ideal I-V characteristics has been demonstrated. Since GaAs is used as the collector of both Npn and Pnp InGaAsN DHBTs, the emitter-collector breakdown voltage (BV{sub CEO}) are 10 and 12 V, respectively, consistent with the BV{sub CEO} of Npn InGaP/GaAs and Pnp AlGaAs/GaAs HBTs of comparable collector thickness and doping level. All these results demonstrate the potential of InGaAsN DHBTs as an alternative for application in low-power electronics.

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

    SciTech Connect (OSTI)

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

    2006-05-01T23:59:59.000Z

    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%.

  9. Wurtzite GaN Surface Structures Studied by Scanning Tunneling Microscopy and Reflection High Energy

    E-Print Network [OSTI]

    Feenstra, Randall

    Wurtzite GaN Surface Structures Studied by Scanning Tunneling Microscopy and Reflection High Energy studies of the surface reconstructions for both the Ga-face and the N-face of wurtzite GaN films grown a surface phenomenon. Although numerous surface studies of wurtzite GaN have been performed, progress

  10. MBE growth and applications of cubic AlN/GaN quantum wells

    E-Print Network [OSTI]

    As, Donat Josef

    MBE growth and applications of cubic AlN/GaN quantum wells Donat J. As* and Christian Mietze Keywords cubic AlN, GaN, interband and intersubband transitions, MBE, resonant tunneling * Corresponding regions. In this contribution, the latest achievement in the MBE of phase-pure cubic GaN, AlN, and AlN/GaN

  11. Behavior of aluminum adsorption and incorporation at GaN(0001) surface: First-principles study

    SciTech Connect (OSTI)

    Qin, Zhenzhen; Xiong, Zhihua, E-mail: xiong-zhihua@126.com; Wan, Qixin [Key Laboratory for Optoelectronics and Communication of Jiangxi Province, Jiangxi Science and Technology Normal University, Nanchang 330018 (China); Qin, Guangzhao [Theoretical Condensed Matter Physics and Computational Materials Physics Laboratory, University of Chinese Academy of Sciences, Beijing 101408 (China)

    2013-11-21T23:59:59.000Z

    First-principles calculations are performed to study the energetics and atomic structures of aluminum adsorption and incorporation at clean and Ga-bilayer GaN(0001) surfaces. We find the favorable adsorption site changes from T4 to T1 as Al coverage increased to 1 monolayer on the clean GaN(0001) surface, and a two-dimensional hexagonal structure of Al overlayer appears. It is interesting the Al atoms both prefer to concentrate in one deeper Ga layer of clean and Ga-bilayer GaN(0001) surface, respectively, while different structures could be achieved in above surfaces. For the case of clean GaN(0001) surface, corresponding to N-rich and moderately Ga-rich conditions, a highly regular superlattice structure composed of wurtzite GaN and AlN becomes favorable. For the case of Ga-bilayer GaN(0001) surface, corresponding to extremely Ga-rich conditions, the Ga bilayer is found to be sustained stable in Al incorporating process, leading to an incommensurate structure directly. Furthermore, our calculations provide an explanation for the spontaneous formation of ordered structure and incommensurate structure observed in growing AlGaN films. The calculated results are attractive for further development of growth techniques and excellent AlGaN/GaN heterostructure electronic devices.

  12. Large atomic displacements associated with the nitrogen antisite in GaN T. Mattila*

    E-Print Network [OSTI]

    Large atomic displacements associated with the nitrogen antisite in GaN T. Mattila* Laboratory of an extensive theoretical study of the nitrogen antisite in GaN. The neutral antisite in c-GaN is reported the nitrogen antisite and the yellow luminescence commonly observed in GaN is discussed. S0163-1829 96 05824

  13. Vertical design of cubic GaN-based high electron mobility transistors R. Granzner,1,a)

    E-Print Network [OSTI]

    As, Donat Josef

    Vertical design of cubic GaN-based high electron mobility transistors R. Granzner,1,a) E. Tschumak 2011; accepted 24 October 2011; published online 1 December 2011) Cubic (zinc blende) AlGaN=GaN heterostructures for application in GaN-based high electron mobility transistors are investigated theoretically

  14. Watching GaN Nanowires Grow Eric A. Stach,*, Peter J. Pauzauskie, Tevye Kuykendall,

    E-Print Network [OSTI]

    Yang, Peidong

    Watching GaN Nanowires Grow Eric A. Stach,*, Peter J. Pauzauskie, Tevye Kuykendall, Joshua of the growth of GaN nanowires via a self-catalytic vapor-liquid-solid (VLS) mechanism. High temperature thermal decomposition of GaN in a vacuum yields nanoscale Ga liquid droplets and gallium/nitrogen vapor species

  15. In situ growth regime characterization of cubic GaN using reflection high energy electron diffraction

    E-Print Network [OSTI]

    As, Donat Josef

    from Knudsen cells. Cubic GaN layers were deposited at 720 °C directly on 3C-SiC substrates shutters the GaN surface was exposed to different Ga fluxes for a certain time. The substrate temperatureIn situ growth regime characterization of cubic GaN using reflection high energy electron

  16. Strain dependent facet stabilization in selective-area heteroepitaxial growth of GaN nanostructures

    E-Print Network [OSTI]

    Sharma, Pradeep

    of submicron GaN islands on GaN-sapphire, AlN-sapphire, and bare sapphire substrates. It is shown that strain due to the lattice mismatch between GaN and the underlying substrate has a significant influence- structures has received less attention. Heteroepitaxial growth of GaN is commonly carried out on substrates

  17. Quadrupole mass spectrometry desorption analysis of Ga adsorbate on AIN (0001)

    E-Print Network [OSTI]

    Brown, J S; Koblmuller, G; Averbeck, R; Riechert, H; Speck, J S

    2006-01-01T23:59:59.000Z

    substrate temperatures similar to those used during PA-MBE growth of GaN /substrate temperature of 668– 669 ° C pre- dicted by the Ga/ GaNon GaN ?0001?. 13 At the 672± 2 ° C substrate temperature in

  18. Vertical strain and doping gradients in thick GaN layers H. Siegle,a)

    E-Print Network [OSTI]

    Nabben, Reinhard

    between layer and common substrates, e.g., sapphire or GaAs.1 Consequently, most GaN layers and also from the surface of the GaN layer nearer to the substrate interface, as can be seen from the CLVertical strain and doping gradients in thick GaN layers H. Siegle,a) A. Hoffmann, L. Eckey, and C

  19. Structural and electronic properties of Fe3+ in GaN from optical and EPR experiments

    E-Print Network [OSTI]

    Nabben, Reinhard

    into GaN to compensate inherent n-type conductivity and to produce semi-insulating substrate materialStructural and electronic properties of Fe3+ and Fe2+ centers in GaN from optical and EPR, and electronic properties of Fe-doped GaN. A set of high-quality GaN crystals doped with Fe at concentrations

  20. Terahertz plasma wave resonance of two-dimensional electrons in InGaP/InGaAs/GaAs high-electron-mobility transistors

    SciTech Connect (OSTI)

    Otsuji, Taiichi; Hanabe, Mitsuhiro; Ogawara, Osamu [Kyushu Institute of Technology, Graduate School of Computer Science and Systems Engineering, 680-4 Kawazu, Iizuka, Fukuoka, 820-8502 (Japan)

    2004-09-13T23:59:59.000Z

    We have observed the frequency dependence of the plasma resonant intensity in the terahertz range for a short gate-length InGaP/InGaAs/GaAs pseudomorphic high-electron-mobility transistor. The plasma resonance excitation was performed by means of interband photoexcitation using the difference-frequency component of a photomixed laser beam. Under sufficient density of two-dimensional (2D) conduction electrons (>10{sup 12} cm{sup -2}) and a moderate modulation index (the ratio of the density of photoexcited electrons to the initial density of the 2D electrons) we clearly observed the plasma-resonant peaks at 1.9 and 5.8 THz corresponding to the fundamental and third-harmonic resonance at room temperature, which is in good agreement with theory.

  1. A one-dimensional Fickian model to predict the Ga depth profiles in three-stage Cu(In,Ga)Se{sub 2}

    SciTech Connect (OSTI)

    Rodriguez-Alvarez, H., E-mail: humberto.rodriguez@helmholtz-berlin.de [International Iberian Nanotechnology Laboratory, Avenida Mestre Jose Veiga s/n, 4715-330 Braga (Portugal); Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin (Germany); Mainz, R. [Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin (Germany); Sadewasser, S. [International Iberian Nanotechnology Laboratory, Avenida Mestre Jose Veiga s/n, 4715-330 Braga (Portugal)

    2014-05-28T23:59:59.000Z

    We present a one-dimensional Fickian model that predicts the formation of a double Ga gradient during the fabrication of Cu(In,Ga)Se{sub 2} thin films by three-stage thermal co-evaporation. The model is based on chemical reaction equations, structural data, and effective Ga diffusivities. In the model, the Cu(In,Ga)Se{sub 2} surface is depleted from Ga during the deposition of Cu-Se in the second deposition stage, leading to an accumulation of Ga near the back contact. During the third deposition stage, where In-Ga-Se is deposited at the surface, the atomic fluxes within the growing layer are inverted. This results in the formation of a double Ga gradient within the Cu(In,Ga)Se{sub 2} layer and reproduces experimentally observed Ga distributions. The final shape of the Ga depth profile strongly depends on the temperatures, times and deposition rates used. The model is used to evaluate possible paths to flatten the marked Ga depth profile that is obtained when depositing at low substrate temperatures. We conclude that inserting Ga during the second deposition stage is an effective way to achieve this.

  2. Regrowth of diluted magnetic semiconductor GaMnAs on InGaP (001) surfaces to realize freestanding micromechanical structures

    SciTech Connect (OSTI)

    Choi, Hyung Kook; Lee, Joon Sue; Cho, Sung Woon; Lee, Won Oh; Shim, Seung Bo; Park, Yun Daniel [CSCMR and FPRD Department of Physics and Astronomy, Seoul National University, NS 50, Seoul 151- 747 (Korea, Republic of)

    2007-03-15T23:59:59.000Z

    Low temperature molecular beam epitaxy regrowths of Ga{sub 1-x}Mn{sub x}As (x{approx_equal}0.04) diluted magnetic semiconductors on GaAs/In{sub 1-y}Ga{sub y}P/GaAs(001) and In{sub 1-y}Ga{sub y}P/GaAs(001) (y{approx_equal}0.51) heterostructures prepared by metal-organic chemical vapor deposition are described. The resulting Ga{sub 1-x}Mn{sub x}As properties are comparable to epitaxial films grown directly on GaAs (001) substrates from in situ reflection high-energy electron diffraction, x-ray diffraction, magnetometry, and transport measurements with magnetic ordering temperature of as-grown films to range between {approx}50 and {approx}60 K. Postgrowth low temperature annealing enhances both magnetic and transport properties. Perfect etch selectivity between Ga{sub 1-x}Mn{sub x}As/GaAs and In{sub 1-y}Ga{sub y}P is utilized to realize suspended Ga{sub 1-x}Mn{sub x}As/GaAs doubly clamped beam micromechanical freestanding structures.

  3. Anti-phase domains in cubic GaN

    SciTech Connect (OSTI)

    Maria Kemper, Ricarda; Schupp, Thorsten; Haeberlen, Maik; Lindner, Joerg; Josef As, Donat [University of Paderborn, Department of Physics, Warburger Str. 100, D-33098 Paderborn (Germany); Niendorf, Thomas; Maier, Hans-Juergen [University of Paderborn, Lehrstuhl fuer Werkstoffkunde, Pohlweg 47-49, D-33098 Paderborn (Germany); Dempewolf, Anja; Bertram, Frank; Christen, Juergen [University of Magdeburg, Institut fuer Festkoerperphysik, P.O. Box 4120, D-39016 Magdeburg (Germany); Kirste, Ronny; Hoffmann, Axel [Technische Universitaet Berlin, Institute of Solid State Physics, Hardenbergstr. 36, D-10623 Berlin (Germany)

    2011-12-15T23:59:59.000Z

    The existence of anti-phase domains in cubic GaN grown on 3C-SiC/Si (001) substrates by plasma-assisted molecular beam epitaxy is reported. The influence of the 3C-SiC/Si (001) substrate morphology is studied with emphasis on the anti-phase domains (APDs). The GaN nucleation is governed by the APDs of the substrate, resulting in equal plane orientation and the same anti-phase boundaries. The presence of the APDs is independent of the GaN layer thickness. Atomic force microscopy surface analysis indicates lateral growth anisotropy of GaN facets in dependence of the APD orientation. This anisotropy can be linked to Ga and N face types of the {l_brace}111{r_brace} planes, similar to observations of anisotropic growth in 3C-SiC. In contrast to 3C-SiC, however, a difference in GaN phase composition for the two types of APDs can be measured by electron backscatter diffraction, {mu}-Raman and cathodoluminescence spectroscopy.

  4. Green (In,Ga,Al)P-GaP light-emitting diodes grown on high-index GaAs surfaces

    SciTech Connect (OSTI)

    Ledentsov, N. N., E-mail: nikolay.ledentsov@v-i-systems.com; Shchukin, V. A. [VI Systems GmbH, Hardenbergstr. 7, Berlin D-10623 (Germany); Lyytikäinen, J.; Okhotnikov, O. [Optoelectronics Research Centre, Tampere University of Technology, Tampere FI-33720 (Finland); Shernyakov, Yu. M.; Payusov, A. S.; Gordeev, N. Yu.; Maximov, M. V. [A. F. Ioffe Physical Technical Institute of the Russian Academy of Sciences, Politekhnicheskaya 26, St. Petersburg 194021 (Russian Federation); Schlichting, S.; Nippert, F.; Hoffmann, A. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, Berlin D-10623 (Germany)

    2014-11-03T23:59:59.000Z

    We report on green (550–560?nm) electroluminescence (EL) from (Al{sub 0.5}Ga{sub 0.5}){sub 0.5}In{sub 0.5}P-(Al{sub 0.8}Ga{sub 0.2}){sub 0.5}In{sub 0.5}P double p-i-n heterostructures with monolayer-scale GaP insertions in the cladding layers and light-emitting diodes based thereupon. The structures are grown side-by-side on high-index and (100) GaAs substrates by molecular beam epitaxy. At moderate current densities (?500?A/cm{sup 2}), the EL intensity of the structures is comparable for all substrate orientations. Opposite to the (100)-grown strictures, the EL spectra of (211) and (311)-grown devices are shifted towards shorter wavelengths (?550?nm at room temperature). At high current densities (>1?kA/cm{sup 2}), a much higher EL intensity is achieved for the devices grown on high-index substrates. The integrated intensity of (311)-grown structures gradually saturates at current densities above 4?kA/cm{sup 2}, whereas no saturation is revealed for (211)-grown structures up to the current densities above 14?kA/cm{sup 2}. We attribute the effect to the surface orientation-dependent engineering of the GaP band structure, which prevents the escape of the nonequilibrium electrons into the indirect conduction band minima of the p-doped (Al{sub 0.8}Ga{sub 0.2}){sub 0.5}In{sub 0.5}P cladding layers.

  5. Crystal Growth And Characterization of the Model High-Temperature Superconductor HgBa{sub 2}CuO{sub 4+{delta}}

    SciTech Connect (OSTI)

    Zhao, Xudong; Yu, Guichuan; Cho, Yong-Chan; Chabot-Couture, Guillaume; Barisic, Neven; Bourges, Philippe; Kaneko, Nobuhisa; Li, Yuan; Lu, Li; Motoyama, Eugene M.; Vajk,; Greven, Martin; /Stanford U., Appl. Phys. Dept. /SLAC, SSRL /Jilin U. /Stanford U., Phys. Dept. /Saclay /NIST, Wash., D.C.

    2007-03-16T23:59:59.000Z

    Since the discovery of high-transition-temperature (T{sub c}) superconductivity in La{sub 2-x}Ba{sub x}CuO{sub 4} in 1986, the study of the lamellar copper oxides has remained at the forefront of condensed matter physics. Apart from their unusually high values of T{sub c}, these materials also exhibit a variety of complex phenomena and phases. This rich behavior is a consequence of the lamellar crystal structures, formed of copper-oxygen sheets separated by charge reservoir layers, and of the strong electron-electron correlations in the copper-oxygen sheets. After two decades of intensive research, which has stimulated many valuable new insights into correlated electron systems in general, there remains a lack of consensus regarding the correct theory for high-T{sub c} superconductivity. The ultimate technological goal of room-temperature superconductivity might only be attained after the development of a deeper understanding of the mercury-based compounds HgBa{sub 2}Ca{sub n-1}Cu{sub n}OI{sub 2n+2+{delta}}, which currently exhibit the highest T{sub c}values. One very important issue in this regard is the role of electronic versus chemical and structural inhomogeneities in these materials, and the associated need to separate material-specific properties from those that are essential to superconductivity. Unfortunately, there has been remarkably little scientific work on the mercury-based compounds because sizable crystals have not been available; quantitative measurements of any kind would be invaluable benchmarks for testing the theories of high-T{sub c} superconductivity. The compounds HgBa{sub 2}Ca{sub n-1}Cu{sub n}OI{sub 2n+2+{delta}} can be viewed as model systems not only because of their record high-T{sub c} values, but also because of their high-symmetry crystal structures. Of particular interest is the simplest member of this materials family, HgBa{sub 2}CuO{sub 4+{delta}} (Hg1201), which possesses only one copper-oxygen sheet per unit cell (n = 1), as shown schematically in Figure 1a. The largest crystals obtained by previous growth methods do not exceed 1 mm{sup 3}, and hence are insufficient in size for detailed studies by many experimental techniques. Here we report a novel recipe for the growth of Hg1201 crystals as well as detailed sample characterization results, including initial inelastic magnetic neutron scattering data. We note that samples grown by the method described here have already enabled recent optical conductivity, inelastic X-ray scattering, and angle-resolved photoemission studies.

  6. High intensity low temperature (HILT) performance of space concentrator GaInP/GaInAs/Ge MJ SCs

    SciTech Connect (OSTI)

    Shvarts, Maxim Z., E-mail: shvarts@scell.ioffe.ru; Kalyuzhnyy, Nikolay A.; Mintairov, Sergey A.; Soluyanov, Andrei A.; Timoshina, Nailya Kh. [Ioffe Physical-Technical Institute, 26 Polytekhnicheskaya str., St.-Petersburg, 194021 (Russian Federation); Gudovskikh, Alexander S. [Saint-Petersburg Academic University - Nanotechnology Research and Education Centre RAS, St. Petersburg, 194021 (Russian Federation); Luque, Antonio [Ioffe Physical-Technical Institute, 26 Polytekhnicheskaya str., St.-Petersburg, 194021, Russia and Instituto de Energia Solar, Universidad Politecnica de Madrid, Madrid (Spain)

    2014-09-26T23:59:59.000Z

    In the work, the results of an investigation of GaInP/GaInAs/Ge MJ SCs intended for converting concentrated solar radiation, when operating at low temperatures (down to ?190 °C) are presented. A kink of the cell I-V characteristic has been observed in the region close to V{sub oc} starting from ?20°C at operation under concentrated sunlight. The causes for its occurrence have been analyzed and the reasons for formation of a built-in potential barrier for majority charge carriers at the n-GaInP/n-Ge isotype hetero-interface are discussed. The effect of charge carrier transport in n-GaInP/n-pGe heterostructures on MJ SC output characteristics at low temperatures has been studied including EL technique.

  7. Polarization field engineering of GaN/AlN/AlGaN superlattices for enhanced thermoelectric properties

    SciTech Connect (OSTI)

    Sztein, Alexander, E-mail: asztein@umail.ucsb.edu [Materials Department, University of California, Santa Barbara, California 93106 (United States); Bowers, John E.; DenBaars, Steven P.; Nakamura, Shuji [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)

    2014-01-27T23:59:59.000Z

    A novel polarization field engineering based strategy to simultaneously achieve high electrical conductivity and low thermal conductivity in thermoelectric materials is demonstrated. Polarization based electric fields are used to confine electrons into two-dimensional electron gases in GaN/AlN/Al{sub 0.2}Ga{sub 0.8}N superlattices, resulting in improved electron mobilities as high as 1176 cm{sup 2}/Vs and in-plane thermal conductivity as low as 8.9?W/mK. The resulting room temperature ZT values reach 0.08, a factor of four higher than InGaN and twelve higher than GaN, demonstrating the potential benefits of this polarization based engineering strategy for improving the ZT and efficiencies of thermoelectric materials.

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

    E-Print Network [OSTI]

    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

    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.

  9. A new InGaP/GaAs tunneling heterostructure-emitter bipolar transistor (T-HEBT)

    SciTech Connect (OSTI)

    Tsai, Jung-Hui, E-mail: jhtsai@nknucc.nknu.edu.tw [National Kaohsiung Normal University, Department of Electronic Engineering, Taiwan (China); Lee, Ching-Sung [Feng Chia University, Department of Electronic Engineering, Taiwan (China); Lour, Wen-Shiung [National Taiwan Ocean University, Department of Electrical Engineering, Taiwan (China); Ma, Yung-Chun; Ye, Sheng-Shiun [National Kaohsiung Normal University, Department of Electronic Engineering, Taiwan (China)

    2011-05-15T23:59:59.000Z

    Excellent characteristics of an InGaP/GaAs tunneling heterostructure-emitter bipolar transistor (T-HEBT) are first demonstrated. The insertion of a thin n-GaAs emitter layer between tynneling confinement and base layers effectivelty eliminates the potential spike at base-emitter junction and reduces the collector-emitter offset voltage, while the thin InGaP tunneling confinement layer is employed to reduce the transporting time across emitter region for electrons and maintain the good confinement effect for holes. Experimentally, the studied T-HEBN exhibits a maximum current gain of 285, a relatively low offset voltage of 40 mW, and a current-gain cutoff frequency of 26.4 GHz.

  10. Reduced thermal resistance in AlGaN/GaN multi-mesa-channel high electron mobility transistors

    SciTech Connect (OSTI)

    Asubar, Joel T., E-mail: joel@rciqe.hokudai.ac.jp; Yatabe, Zenji; Hashizume, Tamotsu [Research Center for Integrated Quantum Electronics (RCIQE) and Graduate School of Information Science and Technology, Hokkaido University, Sapporo (Japan); Japan Science and Technology Agency (JST), CREST, 102-0075 Tokyo (Japan)

    2014-08-04T23:59:59.000Z

    Dramatic reduction of thermal resistance was achieved in AlGaN/GaN Multi-Mesa-Channel (MMC) high electron mobility transistors (HEMTs) on sapphire substrates. Compared with the conventional planar device, the MMC HEMT exhibits much less negative slope of the I{sub D}-V{sub DS} curves at high V{sub DS} regime, indicating less self-heating. Using a method proposed by Menozzi and co-workers, we obtained a thermal resistance of 4.8?K-mm/W at ambient temperature of ?350?K and power dissipation of ?9?W/mm. This value compares well to 4.1?K-mm/W, which is the thermal resistance of AlGaN/GaN HEMTs on expensive single crystal diamond substrates and the lowest reported value in literature.

  11. Epitaxial growth of Cu,,In,Ga...Se2 on GaAs,,110... and A. Rockett

    E-Print Network [OSTI]

    Rockett, Angus

    . INTRODUCTION The Cu(In, Ga)Se2 CIGS absorber layer in a recent record-efficiency CIGS solar cell1 has a 220.13 Commercially supplied ``epi-ready'' liquid- encapsulated Czo

  12. Influence of stress on optical transitions in GaN nanorods containing a single InGaN/GaN quantum disk

    SciTech Connect (OSTI)

    Zhuang, Y. D.; Shields, P. A.; Allsopp, D. W. E., E-mail: d.allsopp@bath.ac.uk [Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY (United Kingdom); Bruckbauer, J.; Edwards, P. R.; Martin, R. W. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

    2014-11-07T23:59:59.000Z

    Cathodoluminescence (CL) hyperspectral imaging has been performed on GaN nanorods containing a single InGaN quantum disk (SQD) with controlled variations in excitation conditions. Two different nanorod diameters (200 and 280?nm) have been considered. Systematic changes in the CL spectra from the SQD were observed as the accelerating voltage of the electron beam and its position of incidence are varied. It is shown that the dominant optical transition in the SQD varies across the nanorod as a result of interplay between the contributions of the deformation potential and the quantum-confined Stark effect to the transition energy as consequence of radial variation in the pseudomorphic strain.

  13. High Power Wideband AlGaN/GaN HEMT Feedback Amplifier Module Y. Chung, S. Cai, W. Lee, Y. Lin, C. P. Wen, K. L. Wang, and T. Itoh

    E-Print Network [OSTI]

    Itoh, Tatsuo

    High Power Wideband AlGaN/GaN HEMT Feedback Amplifier Module Y. Chung, S. Cai, W. Lee, Y. Lin, C. P wideband feedback amplifier module using AlGaN/GaN high electron mobility transistor (HEMT) has been of 12 V (Vds) and a gate voltage of -3 V (Vgs). A feedback amplifier with AlGaN/GaN HEMT GaN-based HEMT

  14. Low temperature carrier redistribution dynamics in InGaN/GaN quantum wells

    SciTech Connect (OSTI)

    Badcock, T. J., E-mail: Thomas.badcock@crl.toshiba.co.uk; Dawson, P.; Davies, M. J. [School of Physics and Astronomy, Photon Science Institute, Alan Turing Building, University of Manchester, Manchester M13 9PL (United Kingdom); Kappers, M. J.; Massabuau, F. C.-P.; Oehler, F.; Oliver, R. A.; Humphreys, C. J. [Department of Materials Science and Metallurgy, 27 Charles Babbage Road, University of Cambridge, Cambridge CB3 0FS (United Kingdom)

    2014-03-21T23:59:59.000Z

    We have studied the carrier recombination dynamics in an InGaN/GaN multiple quantum well structure as a function of emission energy and excitation density between temperatures of 10?K and 100?K. Under relatively low levels of excitation, the photoluminescence (PL) intensity and decay time of emission on the high energy side of the luminescence spectrum decrease strongly between 10?K and 50?K. In contrast, for emission detected on the low energy side of the spectrum, the PL intensity and decay time increase over the same temperature range. These results are consistent with a thermally activated carrier redistribution process in which the (temperature dependent) average timescale for carrier transfer into or out of a localised state depends on the energy of the given state. Thus, the transfer time out of shallow, weakly localised states is considerably shorter than the arrival time into more deeply localised states. This picture is consistent with carriers hopping between localisation sites in an uncorrelated disorder potential where the density of localised states decreases with increasing localisation depth, e.g., a exponential or Gaussian distribution resulting from random alloy disorder. Under significantly higher levels of excitation, the increased occupation fraction of the localised states results in a greater average separation distance between unoccupied localised states, causing a suppression of the spectral and dynamic signatures of the hopping transfer of carriers.

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

    SciTech Connect (OSTI)

    Boonstra, R.H.

    1993-08-01T23:59:59.000Z

    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.

  16. Impact of high energy particles in InGaP/InGaAs pseudomorphic HEMTs

    SciTech Connect (OSTI)

    Ohyama, H.; Hakata, T. [Kumamoto National Coll. of Technology, Nishigoshi, Kumamoto (Japan)] [Kumamoto National Coll. of Technology, Nishigoshi, Kumamoto (Japan); Simoen, E.; Claeys, C. [IMEC, Leuven (Belgium)] [IMEC, Leuven (Belgium); Kuroda, S. [Fujitsu Quantum Devices Ltd., Yamanashi (Japan)] [Fujitsu Quantum Devices Ltd., Yamanashi (Japan); Takami, Y. [Rikkyo Univ., Yokosuka, Kanagawa (Japan)] [Rikkyo Univ., Yokosuka, Kanagawa (Japan); Sunaga, H. [Takasaki JAERI, Takasaki, Gunma (Japan)] [Takasaki JAERI, Takasaki, Gunma (Japan)

    1998-12-01T23:59:59.000Z

    Irradiation damage and its recovery behavior resulting from thermal annealing in InGaP/InGaAs pseudomorphic HEMTs, subjected to a 20-MeV alpha ray and 220-MeV carbon, are studied for the first time. The drain current and effective mobility decrease after irradiation, while the threshold voltage increases in positive direction. The degradation of device performance increases with increasing fluence. The decrease of the mobility is thought to be due to the scattering of channel electrons with the induced lattice defects and also to the decrease of the electron density in the two dimensional electron gas (2DEG) region. The influence of the radiation source on the degradation and recovery is discussed by comparison with 1-MeV electron and 1-MeV fast neutron exposures with respect to the number of knock-on atoms and the nonionizing energy loss (NIEL). Isochronal thermal annealing for temperatures ranging from 75 to 300 C shows that the device performance degraded by the irradiation recovers completely.

  17. The first principle study of Ni{sub 2}ScGa and Ni{sub 2}TiGa

    SciTech Connect (OSTI)

    Özduran, Mustafa [Ahi Evran Üniversitesi Fen Edebiyat Fakültesi Fizik Bölümü, K?r?ehir (Turkey); Turgut, Kemal [Yüksek Lisans Ö?rencisi, K?r?ehir (Turkey); Arikan, Nihat [Ahi Evran Üniversitesi E?itim Fakültesi ?lkö?retim Bölümü, K?r?ehir (Turkey); ?yigör, Ahmet; Candan, Abdullah [Ahi Evran Üniversitesi Merkezi Ara?t?rma Laboratuvar?, K?r?ehir (Turkey)

    2014-10-06T23:59:59.000Z

    We computed the electronic structure, elastic moduli, vibrational properties, and Ni{sub 2}TiGa and Ni{sub 2}ScGa alloys in the cubic L2{sub 1} structure. The obtained equilibrium lattice constants of these alloys are in good agreement with available data. In cubic systems, there are three independent elastic constants, namely C{sub 11}, C{sub 12} and C{sub 44}. We calculated elastic constants in L2{sub 1} structure for Ni{sub 2}TiGa and Ni{sub 2}ScGa using the energy-strain method. The electronic band structure, total and partial density of states for these alloys were investigated within density functional theory using the plane-wave pseudopotential method implemented in Quantum-Espresso program package. From band structure, total and projected density of states, we observed metallic characters of these compounds. The electronic calculation indicate that the predominant contributions of the density of states at Fermi level come from the Ni 3d states and Sc 3d states for Ni{sub 2}TiGa, Ni 3d states and Sc 3d states for Ni{sub 2}ScGa. The computed density of states at Fermi energy are 2.22 states/eV Cell for Ni{sub 2}TiGa, 0.76 states/eV Cell for Ni{sub 2}ScGa. The vibrational properties were obtained using a linear response in the framework at the density functional perturbation theory. For the alloys, the results show that the L2{sub 1} phase is unstable since the phonon calculations have imagine modes.

  18. Reduced lattice temperature high-speed operation of pseudomorphic InGaAdGaAs field-effect transistors

    E-Print Network [OSTI]

    Kolodzey, James

    ,um GaAs buffer, 170 A Ino.zGao,sAs strained channel, 50 A undoped Ale,,,Ga,,,As undoped spacer, S dimensions of 0.25 x 200 pm and 0.5 X 200 pm with a source-drain spacing of 2 ,um. The MODFETs have gate dimensions of 0.35~ 100 pm and 0.47X 100 pm with a source-drain spacing of 1 ,um. The MISFETs have

  19. Optically Detected Extended X-Ray Absorption Fine Structure Study of InGaN/GaN Single Quantum Wells

    SciTech Connect (OSTI)

    Rigopoulos, N.; Hamilton, B.; Davies, G. J.; Towlson, B. M. [School of Electrical and Electronic Engineering, University of Manchester, Manchester M60 1QD (United Kingdom); Poolton, N. R. J. [Synchrotron Radiation Department, Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom); Dawson, P.; Graham, D. M. [School of Physics and Astronomy, University of Manchester, Manchester M60 1QD (United Kingdom); Kappers, M. J.; Humphreys, C. J. [Dept. of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Carlson, S. [MAX-lab, Lund University, P.O. Box 118, SE- 221 00 Lund (Sweden)

    2007-04-10T23:59:59.000Z

    We have investigated the local atomic environment of the Ga atoms in an InxGa1-xN single quantum well structure using Optically Detected Extended X-ray Absorption Fine Structure (OD-EXAFS). A comparison of the OD-EXAFS data with a theoretical model shows the technique to be site selective for this particular structure and reveals that the quantum well emission originates from regions with x=0.15.

  20. Europium doping of zincblende GaN by ion implantation K. Lorenz,1,2,a

    E-Print Network [OSTI]

    As, Donat Josef

    /channeling spectrometry. A low concentration 10% of wurtzite phase inclusions was observed by XRD analysis in as-lattice parameter of wurtzite GaN W-GaN . For ZB-GaN:Eu, a large fraction of Eu ions is found on a high symmetry-GaN:Eu. The implantation damage in ZB-GaN:Eu could partly be removed by thermal annealing, but an increase in the wurtzite