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  • Articles  (1,494,347)
  • 2000-2004  (1,494,347)
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  • 1
    Electronic Resource
    Electronic Resource
    Micro-Raman scattering in laterally epitaxial overgrown GaN (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5840-5852 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this study, micro-Raman spectroscopy has been used to investigate the vibrational properties of laterally epitaxial overgrown (LEO) GaN. The LEO GaN films were grown by metal organic chemical vapor deposition on a 2 in. sapphire substrate with SiN mask. Photoluminescence and polarized Raman scattering measurements have been performed in the two regions of GaN growth (wing and window regions). Raman scattering results are consistent with the lateral growth of GaN in the overgrown region. We have observed second-order Raman scattering in the wing and window regions of GaN. The observations of longitudinal optical phonon plasmon modes in the overgrown region demonstrate that LEO GaN is doped. We have carried out micro-Raman mapping of the local strain and free carrier concentration in the LEO GaN. Anharmonicity due to temperature in LEO GaN has also been investigated. The anharmonicity was found to increase with increasing temperature, and such temperature-induced anharmonicity introduces changes in the linewidth and line center position of the Raman active phonons. The phonon lifetimes in GaN are estimated in the LEO region as well as in the coherently grown region (window region). © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1467952
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  • 2
    Electronic Resource
    Electronic Resource
    Latent track formation in GaAs irradiated with 20, 30, and 40 MeV fullerenes (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5853-5857 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microstructural observations of gallium arsenide single crystals irradiated with a few tens of MeV C60 incident clusters (fullerenes) were performed. Normal and grazing incidences were investigated. Similar to in the case of silicon and germanium, cylindrical amorphous tracks whose diameters vary as a function of the projectile energy were found. However, for a given energy of the clusters, the track diameters are slightly different from one material to another. Also depending on the fullerene, energy is the length of the amorphous cylinder that formed along the projectile's path. The recrystallization process under an electron beam during transmission electron microscopy observation was analyzed and a higher growth rate for gallium arsenide compared to that of germanium was seen. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1467962
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  • 3
    Electronic Resource
    Electronic Resource
    Response of silicon carbide to high velocity impact (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5858-5866 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article presents an analysis of the response of silicon carbide to high velocity impact. This includes a wide range of loading conditions that produce large strains, high strain rates, and high pressures. Experimental data from the literature are used to determine constants for the Johnson–Holmquist constitutive model for brittle materials (JH-1). It is possible to directly determine the strength and pressure response of the intact material from test data in the literature. After the ceramic has failed, however, there are not adequate experimental data to directly determine the response of the failed material. Instead, the response is inferred from a comparison of computational results to ballistic penetration test results. After the constants have been obtained for the JH-1 model, a wide range of computational results are compared to experimental data in the literature. Generally, the computational results are in good agreement with the experimental results. Included are computational results that model interface defeat, which occurs when a high velocity projectile impacts a ceramic target and then dwells on the surface of the ceramic with no significant penetration. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1468903
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  • 4
    Electronic Resource
    Electronic Resource
    Chemical origin of the yellow luminescence in GaN (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5867-5874 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of ion-beam-produced lattice defects as well as H, B, C, N, O, and Si, introduced by ion implantation, on the luminescence properties of wurtzite GaN is studied by cathodoluminescence spectroscopy. Results indicate that intrinsic lattice defects produced by ion bombardment mainly act as nonradiative recombination centers and do not give rise to the yellow luminescence (YL) of GaN. Experimental data unequivocally shows that C is involved in the defect-impurity complex responsible for YL. In addition, C-related complexes appear to act as efficient nonradiative recombination centers. Implantation of H produces a broad luminescent peak which is slightly blueshifted with respect to the C-related YL band in the case of high excitation densities. The position of this H-related YL peak exhibits a blueshift with increasing excitation density. Based on this experimental data and results reported previously, the chemical origin of the YL band is discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1467605
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of growth temperature on strain barrier for metalorganic vapor phase epitaxy grown strained InGaAs quantum well with lattice matched InGaAsP barriers (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5875-5881 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InGaAs strained quantum well (SQW) samples with lattice matched InGaAsP quaternary barriers are grown on GaAs substrates by metalorganic vapor phase epitaxy. These SQW samples are characterized using photoluminescence, photomodulated reflectance, surface photovoltage spectroscopy and high-resolution x-ray diffraction techniques. The results based on numerical calculations are used to identify the various transitions seen in the spectra. The effect of growth temperature on the indium content of the InGaAs SQW with lattice matched InGaAsP quaternary barriers is studied. Contrary to the reported higher value of indium incorporation in InGaAs SQW with GaAs (In-free) barriers when the growth is performed at low temperatures, we find that the indium content of the InGaAs SQW with InGaAsP (In-based) quaternary barriers decreases if the SQW is grown at lower growth temperatures. A possible explanation for this behavior is provided. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1464210
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  • 6
    Electronic Resource
    Electronic Resource
    Band gap in epitaxial NaCl-structure CrN(001) layers (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5882-5886 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: B1–NaCl-structure CrN(001) layers were grown on MgO(001) at 600 °C by ultrahigh vacuum reactive magnetron sputter deposition in pure N2 discharges. X-ray diffraction analyses establish the epitaxial relationship as cube-on-cube, (001)CrN(parallel)(001)MgO with [100]CrN(parallel)[100]MgO, while temperature-dependent measurements show that the previously reported phase transition to the orthorhombic Pnma structure is, due to epitaxial constraints, absent in our layers. The resistivity increases with decreasing temperature, from 0.028 Ω cm at 400 K to 271 Ω cm at 20 K, indicating semiconducting behavior with hopping conduction. Optical absorption is low (α〈2×104 cm−1) for photon energies below 0.7 eV and increases steeply at higher energies. In situ ultraviolet photoelectron spectra indicate that the density of states vanishes at the Fermi level. The overall results provide evidence for CrN exhibiting a Mott–Hubbard type band gap. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1466528
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of dual-band quantum well photodetectors (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5887-5891 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a simple model for quantum well photodetectors for simultaneous middle infrared and near infrared or visible dual-band detection. We derive analytical formulas for the responsivity and detectivity as functions of the material and structural parameters. It is shown that the characteristics of near infrared and visible radiation detection can be sensitive to parameters of the hole transport, capture into quantum wells, and reflection from the electron emitting contact. We demonstrate that a properly designed photodetector can exhibit comparable performance for both middle infrared and near infrared (or visible) detection. The obtained results can be used to optimize the photodetector design and characteristics in both spectral ranges. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1467604
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  • 8
    Electronic Resource
    Electronic Resource
    Interaction of As impurities with 30° partial dislocations in Si: An ab initio investigation (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5892-5895 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated through ab initio total energy calculations the interaction of arsenic impurities with the core of a 30° partial dislocation in silicon. It was found that when an arsenic atom sits in a crystalline position near the dislocation core, there is charge transfer from the arsenic towards the dislocation core. As a result, the arsenic becomes positively charged and the core negatively charged. The results indicate that the structural changes around the impurity are very small in both environments, namely, the crystal and the dislocation core. In this scenario, the interaction between arsenic and the core is essentially electrostatic, which eventually leads to arsenic segregation. The segregation energy was found to be as large as 0.5 eV/atom. Additionally, it was found that arsenic pairing inside the core is not energetically favorable. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1466877
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  • 9
    Electronic Resource
    Electronic Resource
    Inelastic electron tunneling spectroscopy: Capabilities and limitations in metal–oxide–semiconductor devices (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5896-5901 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on inelastic electron tunneling spectroscopy of a tunneling metal–oxide–semiconductor (MOS) device over an extended energy range compared to previous results. We have clearly observed the vibrations of the hydrogen-passivated (111)Si Pb center in this extended energy range. The assignment of this mode has been confirmed by a comparison with infrared experiments. Capabilities and limitations of the technique to detect and observe molecular vibrations in tunneling MOS devices are discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1462423
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  • 10
    Electronic Resource
    Electronic Resource
    Rapid thermal annealing in GaNxAs1−x/GaAs structures: Effect of nitrogen reorganization on optical properties (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5902-5908 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the effect of rapid thermal annealing (RTA) on the photoluminescence (PL) properties of GaNxAs1−x/GaAs structures. In particular, a blueshift of the PL peak energy is observed when annealing the samples. The results are examined as a consequence of a RTA-induced nitrogen diffusion inside the GaNxAs1−x material rather than diffusion out of the alloy, which homogenizes initial nitrogen composition fluctuations. We propose a simple model that describes the RTA-induced blueshift of the low temperature PL peak energy. This model is in good agreement with experimental results and is consistent with recent studies in which lateral composition fluctuations in the GaNAs alloy were reported. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1467957
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