Search Results - (Author, Cooperation:W. Goetz)

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  1. 1
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    Publication Date:
    2013-06-01
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
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  2. 2
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    Publication Date:
    2013-09-28
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
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  3. 3
    P. Y. Meslin ; O. Gasnault ; O. Forni ; S. Schroder ; A. Cousin ; G. Berger ; S. M. Clegg ; J. Lasue ; S. Maurice ; V. Sautter ; S. Le Mouelic ; R. C. Wiens ; C. Fabre ; W. Goetz ; D. Bish ; N. Mangold ; B. Ehlmann ; N. Lanza ; A. M. Harri ; R. Anderson ; E. Rampe ; T. H. McConnochie ; P. Pinet ; D. Blaney ; R. Leveille ; D. Archer ; B. Barraclough ; S. Bender ; D. Blake ; J. G. Blank ; N. Bridges ; B. C. Clark ; L. DeFlores ; D. Delapp ; G. Dromart ; M. D. Dyar ; M. Fisk ; B. Gondet ; J. Grotzinger ; K. Herkenhoff ; J. Johnson ; J. L. Lacour ; Y. Langevin ; L. Leshin ; E. Lewin ; M. B. Madsen ; N. Melikechi ; A. Mezzacappa ; M. A. Mischna ; J. E. Moores ; H. Newsom ; A. Ollila ; R. Perez ; N. Renno ; J. B. Sirven ; R. Tokar ; M. de la Torre ; L. d'Uston ; D. Vaniman ; A. Yingst
    American Association for the Advancement of Science (AAAS)
    Published 2013
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    Publication Date:
    2013-09-28
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
    Published by:
    http://www.aaas.org/

    Latest Papers from Table of Contents or Articles in Press
  4. 4
    C. R. Webster ; P. R. Mahaffy ; G. J. Flesch ; P. B. Niles ; J. H. Jones ; L. A. Leshin ; S. K. Atreya ; J. C. Stern ; L. E. Christensen ; T. Owen ; H. Franz ; R. O. Pepin ; A. Steele ; C. Achilles ; C. Agard ; J. A. Alves Verdasca ; R. Anderson ; D. Archer ; C. Armiens-Aparicio ; R. Arvidson ; E. Atlaskin ; A. Aubrey ; B. Baker ; M. Baker ; T. Balic-Zunic ; D. Baratoux ; J. Baroukh ; B. Barraclough ; K. Bean ; L. Beegle ; A. Behar ; J. Bell ; S. Bender ; M. Benna ; J. Bentz ; G. Berger ; J. Berger ; D. Berman ; D. Bish ; D. F. Blake ; J. J. Blanco Avalos ; D. Blaney ; J. Blank ; H. Blau ; L. Bleacher ; E. Boehm ; O. Botta ; S. Bottcher ; T. Boucher ; H. Bower ; N. Boyd ; B. Boynton ; E. Breves ; J. Bridges ; N. Bridges ; W. Brinckerhoff ; D. Brinza ; T. Bristow ; C. Brunet ; A. Brunner ; W. Brunner ; A. Buch ; M. Bullock ; S. Burmeister ; M. Cabane ; F. Calef ; J. Cameron ; J. Campbell ; B. Cantor ; M. Caplinger ; J. Caride Rodriguez ; M. Carmosino ; I. Carrasco Blazquez ; A. Charpentier ; S. Chipera ; D. Choi ; B. Clark ; S. Clegg ; T. Cleghorn ; E. Cloutis ; G. Cody ; P. Coll ; P. Conrad ; D. Coscia ; A. Cousin ; D. Cremers ; J. Crisp ; A. Cros ; F. Cucinotta ; C. d'Uston ; S. Davis ; M. Day ; M. de la Torre Juarez ; L. DeFlores ; D. DeLapp ; J. DeMarines ; D. DesMarais ; W. Dietrich ; R. Dingler ; C. Donny ; B. Downs ; D. Drake ; G. Dromart ; A. Dupont ; B. Duston ; J. Dworkin ; M. D. Dyar ; L. Edgar ; K. Edgett ; C. Edwards ; L. Edwards ; B. Ehlmann ; B. Ehresmann ; J. Eigenbrode ; B. Elliott ; H. Elliott ; R. Ewing ; C. Fabre ; A. Fairen ; K. Farley ; J. Farmer ; C. Fassett ; L. Favot ; D. Fay ; F. Fedosov ; J. Feldman ; S. Feldman ; M. Fisk ; M. Fitzgibbon ; M. Floyd ; L. Fluckiger ; O. Forni ; A. Fraeman ; R. Francis ; P. Francois ; C. Freissinet ; K. L. French ; J. Frydenvang ; A. Gaboriaud ; M. Gailhanou ; J. Garvin ; O. Gasnault ; C. Geffroy ; R. Gellert ; M. Genzer ; D. Glavin ; A. Godber ; F. Goesmann ; W. Goetz ; D. Golovin ; F. Gomez Gomez ; J. Gomez-Elvira ; B. Gondet ; S. Gordon ; S. Gorevan ; J. Grant ; J. Griffes ; D. Grinspoon ; J. Grotzinger ; P. Guillemot ; J. Guo ; S. Gupta ; S. Guzewich ; R. Haberle ; D. Halleaux ; B. Hallet ; V. Hamilton ; C. Hardgrove ; D. Harker ; D. Harpold ; A. M. Harri ; K. Harshman ; D. Hassler ; H. Haukka ; A. Hayes ; K. Herkenhoff ; P. Herrera ; S. Hettrich ; E. Heydari ; V. Hipkin ; T. Hoehler ; J. Hollingsworth ; J. Hudgins ; W. Huntress ; J. Hurowitz ; S. Hviid ; K. Iagnemma ; S. Indyk ; G. Israel ; R. Jackson ; S. Jacob ; B. Jakosky ; E. Jensen ; J. K. Jensen ; J. Johnson ; M. Johnson ; S. Johnstone ; A. Jones ; J. Joseph ; I. Jun ; L. Kah ; H. Kahanpaa ; M. Kahre ; N. Karpushkina ; W. Kasprzak ; J. Kauhanen ; L. Keely ; O. Kemppinen ; D. Keymeulen ; M. H. Kim ; K. Kinch ; P. King ; L. Kirkland ; G. Kocurek ; A. Koefoed ; J. Kohler ; O. Kortmann ; A. Kozyrev ; J. Krezoski ; D. Krysak ; R. Kuzmin ; J. L. Lacour ; V. Lafaille ; Y. Langevin ; N. Lanza ; J. Lasue ; S. Le Mouelic ; E. M. Lee ; Q. M. Lee ; D. Lees ; M. Lefavor ; M. Lemmon ; A. Lepinette Malvitte ; R. Leveille ; E. Lewin-Carpintier ; K. Lewis ; S. Li ; L. Lipkaman ; C. Little ; M. Litvak ; E. Lorigny ; G. Lugmair ; A. Lundberg ; E. Lyness ; M. Madsen ; J. Maki ; A. Malakhov ; C. Malespin ; M. Malin ; N. Mangold ; G. Manhes ; H. Manning ; G. Marchand ; M. Marin Jimenez ; C. Martin Garcia ; D. Martin ; M. Martin ; J. Martinez-Frias ; J. Martin-Soler ; F. J. Martin-Torres ; P. Mauchien ; S. Maurice ; A. McAdam ; E. McCartney ; T. McConnochie ; E. McCullough ; I. McEwan ; C. McKay ; S. McLennan ; S. McNair ; N. Melikechi ; P. Y. Meslin ; M. Meyer ; A. Mezzacappa ; H. Miller ; K. Miller ; R. Milliken ; D. Ming ; M. Minitti ; M. Mischna ; I. Mitrofanov ; J. Moersch ; M. Mokrousov ; A. Molina Jurado ; J. Moores ; L. Mora-Sotomayor ; J. M. Morookian ; R. Morris ; S. Morrison ; R. Mueller-Mellin ; J. P. Muller ; G. Munoz Caro ; M. Nachon ; S. Navarro Lopez ; R. Navarro-Gonzalez ; K. Nealson ; A. Nefian ; T. Nelson ; M. Newcombe ; C. Newman ; H. Newsom ; S. Nikiforov ; B. Nixon ; E. Noe Dobrea ; T. Nolan ; D. Oehler ; A. Ollila ; T. Olson ; M. A. de Pablo Hernandez ; A. Paillet ; E. Pallier ; M. Palucis ; T. Parker ; Y. Parot ; K. Patel ; M. Paton ; G. Paulsen ; A. Pavlov ; B. Pavri ; V. Peinado-Gonzalez ; L. Peret ; R. Perez ; G. Perrett ; J. Peterson ; C. Pilorget ; P. Pinet ; J. Pla-Garcia ; I. Plante ; F. Poitrasson ; J. Polkko ; R. Popa ; L. Posiolova ; A. Posner ; I. Pradler ; B. Prats ; V. Prokhorov ; S. W. Purdy ; E. Raaen ; L. Radziemski ; S. Rafkin ; M. Ramos ; E. Rampe ; F. Raulin ; M. Ravine ; G. Reitz ; N. Renno ; M. Rice ; M. Richardson ; F. Robert ; K. Robertson ; J. A. Rodriguez Manfredi ; J. J. Romeral-Planello ; S. Rowland ; D. Rubin ; M. Saccoccio ; A. Salamon ; J. Sandoval ; A. Sanin ; S. A. Sans Fuentes ; L. Saper ; P. Sarrazin ; V. Sautter ; H. Savijarvi ; J. Schieber ; M. Schmidt ; W. Schmidt ; D. Scholes ; M. Schoppers ; S. Schroder ; S. Schwenzer ; E. Sebastian Martinez ; A. Sengstacken ; R. Shterts ; K. Siebach ; T. Siili ; J. Simmonds ; J. B. Sirven ; S. Slavney ; R. Sletten ; M. Smith ; P. Sobron Sanchez ; N. Spanovich ; J. Spray ; S. Squyres ; K. Stack ; F. Stalport ; T. Stein ; N. Stewart ; S. L. Stipp ; K. Stoiber ; E. Stolper ; B. Sucharski ; R. Sullivan ; R. Summons ; D. Sumner ; V. Sun ; K. Supulver ; B. Sutter ; C. Szopa ; F. Tan ; C. Tate ; S. Teinturier ; I. ten Kate ; P. Thomas ; L. Thompson ; R. Tokar ; M. Toplis ; J. Torres Redondo ; M. Trainer ; A. Treiman ; V. Tretyakov ; R. Urqui-O'Callaghan ; J. Van Beek ; T. Van Beek ; S. VanBommel ; D. Vaniman ; A. Varenikov ; A. Vasavada ; P. Vasconcelos ; E. Vicenzi ; A. Vostrukhin ; M. Voytek ; M. Wadhwa ; J. Ward ; E. Weigle ; D. Wellington ; F. Westall ; R. C. Wiens ; M. B. Wilhelm ; A. Williams ; J. Williams ; R. Williams ; R. B. Williams ; M. Wilson ; R. Wimmer-Schweingruber ; M. Wolff ; M. Wong ; J. Wray ; M. Wu ; C. Yana ; A. Yen ; A. Yingst ; C. Zeitlin ; R. Zimdar ; M. P. Zorzano Mier
    American Association for the Advancement of Science (AAAS)
    Published 2013
    Staff View
    Publication Date:
    2013-07-23
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
    Published by:
    http://www.aaas.org/

    Latest Papers from Table of Contents or Articles in Press
  5. 5
    Götz, W. ; Schöner, A. ; Pensl, G. ; Suttrop, W. ; Choyke, W. J. ; Stein, R. ; Leibenzeder, S.

    [S.l.] : American Institute of Physics (AIP)
    Published 1993
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Hall-effect and infrared-absorption measurements are performed on n-type 4H-SiC samples to investigate the energy positions of the ground state and the excited states of the nitrogen donor in the 4H polytype of silicon carbide. Two electrically active levels (Hall effect) and three series of absorption lines (infrared spectra) are assigned to two nitrogen donor species which substitute on the two inequivalent lattice sites (h,k) in 4H-SiC. Valley-orbit splitting of the ground-state level of the nitrogen donors on hexagonal sites (h) is found to be equal to ΔEvo(h)=7.6 meV. It is shown that the energy position of excited states of both nitrogen donors can be calculated by the effective-mass approximation by assuming anisotropic effective masses m⊥=0.18m0 and m(parallel)=0.22m0. The influence of the two inequivalent lattice sites on the values of ionization energy and valley orbit splitting of the nitrogen donor ground-state levels is discussed.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.352983

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  6. 6
    Götz, W.

    [S.l.] : American Institute of Physics (AIP)
    Published 1998
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    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Thermal donors (TDs) are generated in Czochralski (CZ)-grown silicon by heat treatments around 450 °C. They form several individual effective-mass-like donors with slightly different ionization energies and act as double donors (TDx0,TDx+). Heat treatments at elevated temperatures (e.g., 〉500 °C) lead to a competition of the formation and the annihilation of TDs. We studied the formation and the annihilation of TDs in the temperature range between 520 and 700 °C. CZ-grown Si samples with an initial total TD concentration of ∼5×1015 cm−3 were employed to study the annihilation of TDs. The number of interstitial oxygen atoms generated per annihilated TD center depends on the temperature and ranges from 4 to 24. For the temperature range investigated the activation energy for thermal annihilation of TDs was determined to be 2.5±0.4 eV. The same CZ-Si material but with an initial TD concentration of ∼2×1013 cm−3 was used to study the formation of TDs. During annealing, the concentrations of individual TDs reach equilibrium concentrations, which depend on the temperature of the final annealing step and the total oxygen concentration. We demonstrate that a model in which the individual TDx centers are represented by oxygen clusters of different sizes consistently explains our experimental data. © 1998 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.368586

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  7. 7
    Götz, W.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1998
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    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Hall-effect measurements were conducted on unintentionally doped n-type GaN films grown on sapphire substrates by hydride vapor phase epitaxy. Film nucleation involved either a GaCl or ZnO pretreatment. Variable temperature Hall-effect measurements reveal a dependence of both the electron concentration and the Hall mobility on film thickness. We demonstrate that this dependence is indicative of a nonuniform distribution of electrically active defects. For GaCl-pretreated sapphire the presence of a highly conductive, 200-nm-thick near-interface layer is likely to account for the observed phenomena. For ZnO-pretreated sapphire the Hall-effect data clearly indicate a continuous reduction of the defect density with increasing film thickness. © 1998 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.121017

    Articles: DFG German National Licenses
  8. 8
    Götz, W. ; Johnson, N. M. ; Chen, C. ; Liu, H. ; Kuo, C. ; Imler, W.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1996
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    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The electronic properties of Si donors in heteroepitaxial layers of GaN were investigated. The n-type GaN layers were grown by metalorganic chemical vapor deposition and either intentionally doped with Si or unintentionally doped. The samples were evaluated by variable temperature Hall effect measurements and photoluminescence (PL) spectroscopy. For both types of samples the n-type conductivity was found to be dominated by a donor with an activation energy between 12 and 17 meV. This donor is attributed to Si atoms substituting for Ga in the GaN lattice (SiGa). The range of activation energies is due to different levels of donor concentrations and acceptor compensation in our samples. The assignment of a PL signature to a donor–acceptor pair recombination involving the Si donor level as the initial state of the radiative transition yields the position of the optical Si donor level in the GaN bandgap at ∼Ec–(22±4) meV. A deeper donor level is also present in our GaN material with an activation energy of ∼34 meV which is tentatively assigned to oxygen donors substituting for nitrogen (ON). © 1996 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.115805

    Articles: DFG German National Licenses
  9. 9
    Götz, W. ; Johnson, N. M. ; Bour, D. P.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1996
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Deep level defects in Mg-doped, p-type GaN were characterized by deep level transient spectroscopy (DLTS) and photoemission capacitance transient spectroscopy (ODLTS). The measurements were conducted on n+-p junction diodes grown by metalorganic chemical vapor deposition. DLTS revealed discrete deep levels in the lower half of the band gap with activation energies for hole emission of 0.21, 0.39, and 0.41 eV. While DLTS is able to detect deep levels only in the proximity of the valance band edge in p-type, wide band-gap semiconductors, ODLTS enables detection of deep levels throughout the band gap of GaN. The ODLTS spectrum of Mg-doped, p-type GaN is dominated by a deep level with an optical threshold energy for photoionization of ∼1.8 eV. This deep level, which appears to be energetically located near midgap is present in the highest concentration (∼2.4×1015 cm−3) among the deep levels detected in our GaN material. None of the detected deep levels is present in sufficient concentration to significantly compensate the shallow acceptor dopant in our Mg-doped, p-type GaN. © 1996 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.116075

    Articles: DFG German National Licenses
  10. 10
    Götz, W. ; Johnson, N. M. ; Street, R. A. ; Amano, H. ; Akasaki, I.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1995
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    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Electronic defects in n-type GaN were characterized by photoemission capacitance transient spectroscopy. Conventional deep level transient spectroscopy is of limited use in semiconductors with wide band gaps (e.g., 3.4 eV for GaN at 300 K) because it utilizes thermal energy for charge emission which restricts the accessible range of bandgap energies to within ∼0.9 eV of either band edge, for practical measurement conditions. For electron photoemission to the conduction band, four deep levels were detected at optical threshold energies of approximately 0.87, 0.97, 1.25, and 1.45 eV. It is suggested that the above photodetected deep levels may participate in the 2.2 eV defect luminescence transitions, which are also demonstrated for our material. © 1995 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.113235

    Articles: DFG German National Licenses
  11. 11
    Götz, W. ; Johnson, N. M. ; Amano, H. ; Akasaki, I.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    In n-type GaN grown by metalorganic chemical vapor deposition two new electronic defects were detected and characterized by deep level transient spectroscopy (DLTS). Schottky-barrier diodes with Ohmic back contacts and low series resistance were fabricated in GaN layers grown on sapphire. The diodes display well behaved current-voltage and capacitance-voltage characteristics and permit unambiguous DLTS evaluation. The new deep levels display thermal activation energies for electron emission of 0.49 and 0.18 eV.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.112337

    Articles: DFG German National Licenses
  12. 12
    Götz, W. ; Johnson, N. M. ; Walker, J. ; Bour, D. P. ; Amano, H. ; Akasaki, I.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1995
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The effects of the deliberate hydrogenation of GaN were investigated for heteroepitaxial layers grown by metalorganic chemical vapor deposition. The GaN layers were either Mg-doped, p-type after thermal activation, or Si-doped, n type. Elemental depth profiles from secondary ion mass spectroscopy reveal a striking contrast after a deuteration at 600 °C: the deuterium concentration in Mg-doped GaN is ∼1019 cm−3 while there is no detectable deuterium incorporation in the n-type material. Variable temperature Hall effect measurements provide the most direct evidence to date for Mg–H complex formation with the decrease in the hole concentration upon hydrogenation accompanied by an increase in the hole Hall mobility. © 1995 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.114330

    Articles: DFG German National Licenses
  13. 13
    Ponce, F. A. ; Bour, D. P. ; Götz, W. ; Johnson, N. M. ; Helava, H. I. ; Grzegory, I. ; Jun, J. ; Porowski, S.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1996
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Bulk single crystals of GaN were used for epitaxial growth of GaN by metalorganic chemical vapor deposition. Photoluminescence (at 2 K) from polished substrates yields a broad near-band-edge emission band centered at 3.32 eV and the commonly observed yellow luminescence band. In contrast, the epitaxial layer displays a strong, sharp bound exciton line at 3.458 eV and a weak yellow band. Transmission electron microscopy reveals a sharp, planar interface between substrate and epilayer: The substrate contains small Ga inclusions, and the epilayer consists of less than 108 dislocations per cm2, mostly in the form of dislocation loops, which originate at the interface. © 1996 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.116230

    Articles: DFG German National Licenses
  14. 14
    Ponce, F. A. ; Bour, D. P. ; Götz, W. ; Wright, P. J.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1996
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The spatial dependence of the luminescence intensities at the band edge (364 nm) and at the "yellow'' defect-band (centered at 560 nm) regions for epitaxial GaN films have been studied using cathodoluminescence microscopy at room temperature. The films were grown by metalorganic chemical vapor deposition on (0001) sapphire substrates and were not intentionally doped. Significant nonuniformities in the band-to-band and in the yellow band emissions were observed. Yellow luminescence in small crystallites appears to originate from extended defects inside the grains and at low-angle grain boundaries. The size of band-to-band emission sites correlates with low-angle grain sizes observed by transmission electron microscopy. © 1996 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.116756

    Articles: DFG German National Licenses
  15. 15
    Götz, W. ; Johnson, N. M. ; Bremser, M. D. ; Davis, R. F.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1996
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Si-doped, n-type heteroepitaxial layers of Al0.12Ga0.88N grown by metalorganic chemical vapor deposition on SiC substrates were characterized by capacitance transient spectroscopies. Conventional deep level transient spectroscopy (DLTS) reveals the presence of a dominant deep level with an activation energy for electron emission to the conduction band of (0.61±0.02) eV. The activation energy of this deep level displays a pronounced field dependence as determined from double-correlation DLTS (DDLTS), which is indicative of a deep donor level in n-type semiconductors. A deep level is observed by optical-DLTS (O-DLTS) with a threshold energy for electron photoemission to the conduction band of 0.77 eV, which appears to be of identical origin as the dominant deep level detected by DLTS. Two additional deep levels are detected with O-DLTS in the upper half of the band gap of our Al0.12Ga0.88N sample with threshold energies of 0.83 and 1.01 eV. © 1996 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.117643

    Articles: DFG German National Licenses
  16. 16
    Götz, W. ; Romano, L. T. ; Krusor, B. S. ; Johnson, N. M. ; Molnar, R. J.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1996
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The electronic and structural properties of GaN were investigated for heteroepitaxial layers grown by hydride vapor phase epitaxy. Uniform film nucleation on the sapphire substrates was facilitated by a GaCl pretreatment. The films were all unintentionally doped n type. Variable temperature Hall effect measurements reveal electron concentrations as low as 2×1017 cm−3 and electron mobilities as high as 460 cm2/V s at 300 K. The films exhibit bound exciton photoluminescence lines with a full width at half-maximum (FWHM) of 2.42 meV at 2 K. Transmission electron microscopy studies of the GaN/sapphire interface reveal a ∼200 nm thick, highly defective GaN layer consisting predominantly of stacking faults. The excellent quality of these GaN films is attributed to this "auto-buffer'' layer which enables growth of GaN cells with a dislocation density of ∼3×108 cm−2 after ∼12 μm of film growth. © 1996 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.117937

    Articles: DFG German National Licenses
  17. 17
    Götz, W. ; Johnson, N. M. ; Walker, J. ; Bour, D. P. ; Street, R. A.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1996
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The activation kinetics of acceptors was investigated for heteroepitaxial layers of GaN, doped with Mg. After growth, the samples were exposed to isochronal rapid thermal anneals in the temperature range from 500 to 775 °C. The samples were studied by variable temperature Hall effect measurements and photoluminescence (PL) spectroscopy in the as-grown condition and after each temperature step. The thermal treatment reduced the resistivity by six orders of magnitude and the p-type conductivity was found to be dominated by an acceptor with an activation energy of ∼170 meV. This acceptor is attributed to Mg atoms substituting for Ga in the GaN lattice and the activation process is consistent with dissociation of electrically inactive Mg–H complexes. It is shown that the appearance of a blue emission band in the PL spectrum of Mg-doped GaN does not directly correlate with the increase in p-type conductivity. © 1996 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.116503

    Articles: DFG German National Licenses
  18. 18
    Götz, W. ; Johnson, N. M. ; Bour, D. P. ; McCluskey, M. D. ; Haller, E. E.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1996
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Local vibrational modes (LVMs) are reported for Mg-doped GaN grown by metalorganic chemical vapor deposition. Hetero-epitaxial layers of GaN:Mg, either as-grown, thermally activated, or deuterated, were investigated with low-temperature, Fourier-transform infrared absorption spectroscopy. The as-grown material, which was semi-insulating, exhibits a LVM at 3125 cm−1. Thermal annealing increases the p-type conductivity, as established with Hall effect measurements, and proportionally reduces the intensity of this LVM. Deuteration of the activated material creates a LVM at 2321 cm−1. The isotopic shift establishes the presence of hydrogen in the vibrating complex. The new LVMs are assigned to the stretch modes of the Mg–H and Mg–D complexes in GaN, with the vibrational frequencies indicative of a strong N–H bond as recently proposed from total-energy calculations. © 1996 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.117202

    Articles: DFG German National Licenses
  19. 19
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Data are presented on high-power AlGaInN flip-chip light-emitting diodes (FCLEDs). The FCLED is "flipped-over" or inverted compared to conventional AlGaInN light-emitting diodes (LEDs), and light is extracted through the transparent sapphire substrate. This avoids light absorption from the semitransparent metal contact in conventional epitaxial-up designs. The power FCLED has a large emitting area (∼0.70 mm2) and an optimized contacting scheme allowing high current (200–1000 mA, J∼30–143 A/cm2) operation with low forward voltages (∼2.8 V at 200 mA), and therefore higher power conversion ("wall-plug") efficiencies. The improved extraction efficiency of the FCLED provides 1.6 times more light compared to top-emitting power LEDs and ten times more light than conventional small-area (∼0.07 mm2) LEDs. FCLEDs in the blue wavelength regime (∼435 nm peak) exhibit ∼21% external quantum efficiency and ∼20% wall-plug efficiency at 200 mA and with record light output powers of 400 mW at 1.0 A. © 2001 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.1374499

    Articles: DFG German National Licenses
  20. 20
    Götz, W. ; Dittjen, O. ; Wicke, M. ; Biereder, S. ; Krüger, U. ; Von Lengerken, G.

    Oxford UK : Blackwell Science Ltd.
    Published 2001
    Staff View
    ISSN:
    1439-0264
    Source:
    Blackwell Publishing Journal Backfiles 1879-2005
    Topics:
    Medicine
    Notes:
    The insulin-like growth factor (IGF) system plays an important role in postnatal somatic and skeletal muscle growth in pigs. There is little information on the occurrence and distribution of components of the IGF system in postnatal porcine skeletal muscle. IGF-I, IGF receptor 1 (IGF1R) and the IGF-binding proteins IGFBP-1 and -3 in longissimus dorsi and triceps brachii were localized in muscle biopsies from 12 commercially crossbred pigs aged from 28 to 199 days as well as from the sire generation, by immunohistochemistry. Plasma IGF-I concentrations were also determined using radioimmunoassays. Unlike other species, IGF-I was localized in porcine skeletal muscle fibres. Staining intensity correlated with the highest plasma IGF-I levels and phases of intensive muscle growth from the 11th to 22nd week. The pattern of IGF1R immunostaining, which was strong, correlated with that of IGF-I. IGF1R was also localized in endomysial tissues. IGFBP-1 was not detected within muscle fibres, but was found in the endomysium and vessel walls, while IGFBP-3 was localized with IGF-1 and its receptor. Higher magnification revealed that IGF1R, IGFBP-3 and probably IGF-I appeared in the tubular system. Inhibitory as well as stimulating controls of IGFBP-1 and -3 on IGF functions are discussed, which may maintain a balance between autocrine growth promoting activities of IGF-I and IGF1R.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1046/j.1439-0264.2001.00297.x

    Articles: DFG German National Licenses