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  • 1
    Electronic Resource
    Electronic Resource
    Infrared study of OH− defects in KTiOPO4 crystals (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5371-5380 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Variations in the concentrations and distributions of the OH− defects present in flux and hydrothermal KTiOPO4 (KTP) crystals, measured by infrared spectroscopy of single crystals, are attributed to differences in the growth environments and other nonhydrogenic defects present in the crystals. The concentrations of OH− have been estimated from the infrared data to be approximately 400 ppma (parts per million atomic) (3.0×1019 cm−3) in the flux crystals, 1100–1500 ppma (0.74–1.1×1020 cm−3) in the high-temperature hydrothermal and 600 ppma (4.3×1019 cm−3) in the low-temperature hydrothermal crystals. A 3566 cm−1 peak and a 3575 cm−1 band are observed in all crystals. The integrated intensity of the OH− absorption band at 3566 cm−1 increases at the expense of the 3575 cm−1 band at higher temperatures in the high-temperature hydrothermal crystals. Several OH− peaks (3490, 3455, 3428, 3420, and 3333 cm−1), which have strongly temperature-dependent linewidths, are present in the hydrothermally grown KTP crystals. The temperature dependencies of their peak frequencies and widths are consistent with the presence of mobile protons in the lattice. The protons located in the 3490 and 3428 cm−1 sites are believed to contribute to the ionic conductivity of the high-conductivity high-temperature hydrothermal crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351976
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  • 2
    Electronic Resource
    Electronic Resource
    Diffusion, release, and uptake of hydrogen in magnesium-doped gallium nitride: Theory and experiment (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3195-3202 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusion and release of H and its uptake from the gas phase are modeled for Mg-doped, wurtzite GaN using formation energies and vibration frequencies from the density-function theory. Comparison is made with rates of deuterium release and uptake measured by nuclear-reaction analysis of deuterium concentration. Good agreement is found when account is taken of a surface permeation barrier. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1347410
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  • 3
    Electronic Resource
    Electronic Resource
    Equilibrium state of hydrogen in gallium nitride: Theory and experiment (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4676-4687 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Formation energies and vibration frequencies for H in wurtzite GaN were calculated from density-functional theory and used to predict equilibrium state occupancies and solid solubilities at elevated temperatures for p-type, intrinsic, and n-type material. The solubility of deuterium (D) was measured in p-type, Mg-doped GaN at 600, 700, and 800 °C as a function of D2 pressure and compared with theory. Agreement was obtained by reducing the H formation energies 0.22 eV from ab initio theoretical values. The predicted stretch-mode frequency for H bound to the Mg acceptor lies 5% above an observed infrared absorption attributed to this complex. More limited solubility measurements were carried out for nominally undoped material rendered n-type by donors provisionally identified as O impurities, and results agree well with theory after the aforementioned adjustment of formation energies. It is concluded that currently recognized H states and physical processes can account for the equilibrium, elevated-temperature behavior of H examined in this work. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1309123
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of H2 on morphology evolution during GaN metalorganic chemical vapor deposition (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3114-3116 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In situ optical reflectance transients reveal that the morphology evolution of the initial low-temperature buffer layer strongly influences the structural and electrical quality of the high-temperature GaN films. Moreover, the morphology evolution of that buffer layer, specifically evolution of the spatial and orientational distributions of the nuclei, is strongly affected by H2. The growth conditions for which surface smoothness is maintained throughout the two-step growth do not necessarily produce the best quality final GaN films; instead, there may be an optimal roughness and incubation period en route to the best quality final films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120263
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  • 5
    Electronic Resource
    Electronic Resource
    Morphology and photoluminescence improvements from high-temperature rapid thermal annealing of GaN (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 200-202 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rapid thermal annealing of GaN in an Ar or N2 ambient up to 1100 °C is shown to improve surface morphology and photoluminescence intensity. For both ambients the average rms surface roughness as determined by atomic force microscopy decreases from ∼4 nm on the as-grown material to ∼1 nm after a 1100 °C anneal. The band-edge luminescence intensity was increased by a factor of 4 after a 1100 °C anneal in a N2 ambient and a factor of 2 for annealing at 1100 °C in an Ar ambient as compared to as-grown material. The 1100 °C anneal improves the ratio of band edge to deep-level luminescence and also reduces the electron concentration and mobility. The reduction in mobility can be explained in terms of a two-band conduction mechanism where defect band conduction dominates at the lower carrier densities or an increase in the free-carrier compensation ratio. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116459
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  • 6
    Electronic Resource
    Electronic Resource
    A computational study of laser-supported detonation waves propagating up an oblique incident beam (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 805-807 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We conducted a series of numerical experiments to study the propagation of laser-supported detonation waves (LSDWs) in the case that a CO2 laser beam strikes an aluminum surface obliquely in air. A reflected shock formed at the aluminum surface was more prominent at higher angles of incidence θ of the beam, but otherwise the hydrodynamics of the plasma and the LSDW were insensitive to θ. Furthermore, the total impulse delivered to the aluminum varied approximately as 1/cos θ, a result that can be modeled with elementary blast-wave theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338187
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of water vapor on the susceptibility to electric-field damage of KTiOPO4 (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 799-801 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate that the susceptibilities of hydrothermal and flux grown KTiOPO4 (KTP) crystals to electric-field induced darkening increase with increasing water vapor content of the atmosphere surrounding the crystals. Infrared spectroscopy shows that hydrogen ions from the atmosphere migrate into the crystals in the presence of the applied electric field and charge compensate the formation of Ti3+ defects which are responsible for damage. These observations suggest that KTP-based electro-optic devices should be operated in a dry environment to reduce their susceptibility to damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108582
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  • 8
    Electronic Resource
    Electronic Resource
    High temperature electron cyclotron resonance etching of GaN, InN, and AlN (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1761-1763 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron cyclotron resonance etch rates for GaN, InN, and AlN are reported as a function of temperature for Cl2/H2/CH4/Ar and Cl2/H2/Ar plasmas. Using Cl2/H2/CH4/Ar plasma chemistry, GaN etch rates remain relatively constant from 30 to 125 °C and then increase to a maximum of 2340 A(ring)/min at 170 °C. The InN etch rate decreases monotonically from 30 to 150 °C and then rapidly increases to a maximum of 2300 A(ring)/min at 170 °C. This is the highest etch rate reported for this material. The AlN etch rate decreases throughout the temperature range studied with a maximum of 960 A(ring)/min at 30 °C. When CH4 is removed from the plasma chemistry, the GaN and InN etch rates are slightly lower, with less dramatic changes with temperature. The surface composition of the III–V nitrides remains unchanged after exposure to the Cl2/H2/CH4/Ar plasma over the temperatures studied. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113359
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  • 9
    Electronic Resource
    Electronic Resource
    Transient photoinduced absorption in (AlxGa1−x)0.5In0.5P fractal quantum well heterostructures (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 966-968 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Picosecond photoinduced absorption measurements have been performed on four different (AlxGa1−x)0.5In0.5P fractal quantum well heterostructures. The results of these measurements reveal that, at early times following pulsed excitation, the carriers remain near the surface layer in which they were photogenerated, and populate the higher lying branches of the V-shaped fractal structure. With increasing time, the carrier population relaxes toward the lowest energy, central wall. The rate at which the relaxation occurs is governed by the characteristic layer of widths of the fractal structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117097
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  • 10
    Electronic Resource
    Electronic Resource
    Pseudomorphic InAsSb multiple quantum well injection laser emitting at 3.5 μm (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1332-1334 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A pseudomorphic, compressively strained InAs0.94Sb0.06 multiple quantum well injection laser, emitting in the 3.5–3.6 μm range is reported. The device was grown by metalorganic chemical vapor deposition, and x-ray and optical characterization indicate that the active region has a very low dislocation density. In pulsed mode, the laser operated at 135 K and displayed a characteristic temperature of 33 K, equaling the highest value reported for molecular-beam epitaxy grown, InAsSb/InAlAsSb active region lasers of comparable wavelength. Factors limiting the performance of these lasers are discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115925
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