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  • 1990-1994  (9)
  • 1993  (9)
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  • 1990-1994  (9)
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  • 1
    Electronic Resource
    Electronic Resource
    Terrace width evolution during step-flow growth with multiterrace adatom migration (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7351-7357 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a computer-solvable model of step-flow growth that includes both anisotropic multiterrace adatom migration and asymmetric step edge attachment. We find that terrace widths equalize not only when each adatom preferentially attaches to the ascending step edge of the terrace that it lands on, but also when adatoms preferentially migrate over ascending step edges. This latter process can equalize long-range terrace width nonuniformities much more rapidly than can the former process. We also find that a slow lateral movement of terrace width distributions occurs when each adatom adheres to the step edges of the terrace that it lands on. More significantly, we find that a rapid lateral movement of terrace width distributions occurs when adatoms cross multiple step edges. This motion is especially fast when adatoms migrate distances that are comparable to or greater than the terrace width distribution period. We simulated the evolution of an experimentally observed (Al,Ga)Sb lateral superlattice (LSL) terrace width distribution, which led to quantitative estimates of the adatom migration characteristics present during the LSLs growth. At least one type of adatom, probably Ga, migrates nearly isotropically over many terraces. This method of determining adatom migration characteristics can be extended to any material system that allows LSL layers to be grown as terrace width markers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354026
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Capacitance-voltage profiling through graded heterojunctions: Theory and experiment (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 251-260 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Starting from the general equations for capacitance-voltage (CV) profiling through a graded heterojunction, we obtain numerical solutions to yield thermal-equilibrium energy-band diagrams, real electron profiles, and apparent electron profiles (i.e., the profile extracted from a CV measurement) for modulation-doped square, triangular, and parabolic potential wells. Room-temperature CV measurements are performed on parabolic potential wells grown by molecular beam epitaxy in the AlxGa1−xAs system, and the measured apparent electron profiles fitted to computer reconstructions whence the real electron distributions are deduced. These measurements reflect a uniform electron distribution in a parabolic well, with 3D electron density determined by well curvature. Data analysis also suggests the presence of a doping asymmetry in the modulation doping of the well. Appropriate corrections to growth conditions remove these asymmetries, as reflected in CV measurements. Besides its importance in the analysis of potential wells of different shapes, the theory presented is applicable to the determination of band offsets by the CV profiling technique where the unintentional grading of the band gap and/or doping in the neighborhood of the isotype abrupt heterojunction is known.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353897
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Growth and characterization of (111) and (001) oriented MgO films on (001) GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3276-3283 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of substrate preparation on the structure and orientation of MgO films grown on (001) GaAs using pulsed laser deposition has been investigated. Textured MgO films displaying a (111)MgO(parallel)(001)GaAs orientation relation with x-ray rocking curve full width at half maximum (FWHM) values as low as 1.8° were obtained in cases where the native GaAs surface oxide was only partially desorbed prior to growth. Reflection high-energy electron diffraction, transmission electron microscopy (TEM), and x-ray pole figure analysis of these films reveals a preferential orientation within the plane of the substrate: [11¯0]MgO(parallel)[11¯0]GaAs and [112¯]MgO(parallel)[110]GaAs. An interfacial layer (∼5 nm thick) was observed in high resolution TEM analysis, and was attributed to a remnant native GaAs oxide layer. Complete desorption of the native GaAs oxide at ∼600 °C in vacuum prior to MgO growth led to significant surface roughening due to Langmuir evaporation, and resulted in randomly oriented polycrystalline MgO films. Growth of MgO on Sb-passivated GaAs substrates, which provided smooth, reconstructed surfaces when heated to 350 °C in vacuum, resulted in cube-on-cube oriented films [i.e., (001)MgO(parallel)(001)GaAs,[100]MgO(parallel)[100]GaAs] with x-ray rocking curve FWHM values as low as 0.47°. TEM analysis of the cube-on-cube oriented films revealed evidence of localized strain fields at the MgO/GaAs interface, indicating the presence of misfit dislocations in the MgO layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352975
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Conductance fluctuations and quantum chaotic scattering in semiconductor microstructures (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 3 (1993), S. 643-653 
    Details
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We review recent experiments on aperiodic conductance fluctuations in ballistic GaAs/AlGaAs microstructures in the shape of a stadium billiard and a circle with point-contact leads, measured at millikelvin temperatures. Much of the observed behavior can be analyzed within a semiclassical approach to quantum chaotic scattering. After a brief review of the Landauer–Büttiker formulation of coherent transport, a variety of novel experimental phenomena and comparisons to semiclassical theory are presented. In particular, we discuss quantum-enhanced backscattering, the power spectrum of conductance fluctuations, crossover to the high-magnetic-field and tunneling regimes, and an application allowing the rate of phase-randomizing scattering to be measured in chaotic ballistic microstructures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.165927
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Observation of arsenic precipitates in GaInAs grown at low temperature on InP (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2209-2211 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single-crystal Ga1−xInxAs (x=0.4) grown on InP by molecular-beam epitaxy at low substrate temperatures (250–150 °C) has been examined by transmission electron microscopy. Arsenic precipitates were observed following an ex situ anneal at 550 °C. The precipitates coarsen during higher-temperature anneals at 600 and 700 °C. Microstructure dependence on the growth temperature was similar to that observed in low-temperature grown GaAs. Arsenic precipitate volume fraction increased with decreasing growth temperature, with a measured maximum value of ∼0.4%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109418
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Band-gap engineered digital alloy interfaces for lower resistance vertical-cavity surface-emitting lasers (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3411-3413 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on a technique of grading the heterobarrier interfaces of a p-type distributed Bragg reflector mirror to reduce the operating voltages of vertical-cavity surface-emitting lasers (VCSELs). We report VCSELs with lower operating voltages (2–3 V) and record continuous-wave room-temperature power-conversion efficiencies (17.3%). We experimentally demonstrate that by using a parabolic grading and modulating the doping correctly, a flat valence band is generated that provides low voltage hole transport. The low resistance mirrors are achieved using low Be doping, digital-alloy grading and 600 °C growth temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110156
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Optical gain anisotropy in serpentine superlattice nanowire-array lasers (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2015-2017 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report optical gain measurement from a serpentine superlattice nanowire-array laser sample, grown by molecular beam epitaxy on a 2°-off (100)GaAs vicinal substrate. Gain spectra, obtained from in-plane ridge-waveguide lasers with stripes either parallel or perpendicular to the nanowire arrays at 1.4 K, showed that the optical gain for the TM mode became greater than that of the TE mode when the optical cavity was placed along the nanowire direction. This provides strong evidence that the lateral quantum confinement in the serpentine superlattice is stronger than the vertical quantum confinement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110629
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Observation of impurity effects on the nucleation of arsenic precipitates in GaAs (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 169-171 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The precipitation of arsenic in low temperature GaAs uniformly doped with Si and Be has been studied by transmission electron microscopy. Following an in situ anneal at 600 °C, precipitate size and density is found to be strongly dependent on the dopant type. Impurities at the epilayer/substrate interface lead to heterogeneous nucleation of precipitates. Although precipitates were observed to nucleate heterogeneously at threading dislocations, the precipitates predominantly form homogeneously. These results are consistent with the general theory of precipitation in solids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109360
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Capacitive detection of subband structure in the electron gas in a wide parabolic GaAs/AlxGa1−xAs quantum well (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 390-392 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Profiles of the capacitance C(Vg) between a front gate and the electron gas in a wide parabolic well and its derivative dC/dVg are used to study the subband structure and uniformity of the electron gas layer. Subband depopulation events are detected as peaks in the derivative profile dC/dVg as the width of the electron gas is reduced by application of the gate voltage Vg. To separate depopulation events from nonuniformities in electron density, derivative profiles are repeated for increasing in-plane magnetic fields: depopulation peaks move to smaller gate voltages and disappear at characteristic fields, while nonuniformities remain fixed and are accentuated in strong fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108966
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