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  • 1
    Electronic Resource
    Electronic Resource
    Breakdown of crystallinity in low-temperature-grown GaAs layers (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2153-2155 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic study of the change in structural quality of as-grown GaAs layers deposited at temperatures between 180 and 210 °C by molecular beam epitaxy was performed using transmission electron microscopy, double-crystal x-ray rocking curves, and particle-induced x-ray emission. We found that the crystal quality was correlated strongly with growth temperature near 200 °C. The lattice parameter and the amount of As incorporated in the layer were observed to increase at lower growth temperatures. After exceeding a certain growth-temperature-dependent layer thickness, large densities of pyramidal-type defects are formed, which at lowest growth temperature result in the breakdown of crystallinity and in columnar polycrystalline growth. The lattice expansion is ascribed to the excess As in the layers. The mechanisms of breakdown of crystallinity are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104990
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  • 2
    Electronic Resource
    Electronic Resource
    Microstructure of GaN layers grown on (001) GaAs by plasma assisted molecular-beam epitaxy (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2931-2933 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High resolution electron microscopy has been applied to characterize the structure of β-GaN epilayers grown on (001) GaAs substrates by plasma-assisted molecular-beam epitaxy. An rf plasma source was used to promote chemically active nitrogen. An exposure of the layer surface to the As flux during the growth of the first few monolayers was shown to result in remarkably flat GaN–GaAs interface. The best quality GaN layers were achieved by near-stoichiometric nucleation with optimal Ga-to-N ratio. Deviation from these nucleation conditions leads to interface roughening and formation of the wurtzite phase within the GaN layer. All the layers contained a high density of stacking faults near the interface which sharply decreases toward the surface. Stacking faults were anisotropically distributed within the GaN layer probably due to different properties of α compared to β dislocations in cubic GaN. The majority of stacking faults intersect the interface along lines parallel to the major flat of the GaAs wafer. The stacking faults are often associated with atomic steps at the GaN–GaAs interface. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120219
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  • 3
    Electronic Resource
    Electronic Resource
    Schottky barrier contacts on defect-free GaAs (110) (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2507-2509 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High resolution transmission electron microscopy and analytical electron microscopy show direct evidence for defect-free interfaces produced by in situ cluster deposition of Au, Ag, and Ti onto ultrahigh vacuum-cleaved n-GaAs. In contrast to interfaces produced by atom-by-atom deposition, no specific interface reconstruction or orientation relationship and no change of stoichiometry of the GaAs near the interface was observed. Schottky barrier heights correspond to unusual Fermi level pinning positions in the upper half of the GaAs band gap, in clear contrast to values obtained for atom deposition and for diodes prepared by standard technology on GaAs (100). These results give clear evidence that Fermi level pinning for metal/GaAs interfaces formed without defects does not follow the predictions of current metal-induced gap-state models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102873
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  • 4
    Electronic Resource
    Electronic Resource
    Rapid thermal annealing of low-temperature GaAs layers (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2086-2088 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron microscopy studies of annealed GaAs layers grown by molecular beam epitaxy at low temperature (200 °C) were used to monitor growth of As precipitates. Ostwald ripening kinetics was used to deduce a migration enthalpy of 1.4±0.3 eV for the diffusion mediating defect. A conclusive picture of the dominant diffusion mechanism can be given, attributing this value to the migration enthalpy of gallium vacancies (VGa), which is well established by other experiments. The present studies indicate that growth of As precipitates is driven by supersaturation of VGa. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113911
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of Si doping on the dislocation structure of GaN grown on the A-face of sapphire (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 990-992 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscopy, x-ray diffraction, low-temperature photoluminescence, and Raman spectroscopy were applied to study stress relaxation and the dislocation structure in a Si-doped GaN layer in comparison with an undoped layer grown under the same conditions by metalorganic vapor phase epitaxy on (11.0) Al2O3. Doping of the GaN by Si to a concentration of 3×1018 cm−3 was found to improve the layer quality. It decreases dislocation density from 5×109 (undoped layer) to 7×108 cm−2 and changes the dislocation arrangement toward a more random distribution. Both samples were shown to be under biaxial compressive stress which was slightly higher in the undoped layer. The stress results in a blue shift of the emission energy and E2 phonon peaks in the photoluminescence and Raman spectra. Thermal stress was partly relaxed by bending of threading dislocations into the basal plane. This leads to the formation of a three-dimensional dislocation network and a strain gradient along the c axis of the layer. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117105
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  • 6
    Electronic Resource
    Electronic Resource
    Nucleation and evolution of misfit dislocations in ZnSe/GaAs (001) heterostructures grown by low-pressure organometallic vapor phase epitaxy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 346-348 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscopy and x-ray diffraction were used to study strain relaxation and the evolution of the dislocation structure in ZnSe epilayers grown by low-pressure organometallic vapor phase epitaxy on a (001) surface of semi-insulating GaAs. Before the ZnSe growth, the substrate surface was exposed to a flow of tertiarybutylarsine to promote an As-terminated surface. This surface treatment results in a low density of stacking faults; 60° misfit dislocations were observed at a layer thickness as low as 0.05 μm. This agrees well with the theoretical critical value for misfit dislocation formation in the ZnSe/GaAs system, but is much lower than experimental critical thicknesses reported earlier. Various mechanisms of misfit dislocation generation were observed at different growth stages. The evolution of the dislocation structure is discussed in relation with the morphology of the ZnSe layers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116711
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