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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2227-2229 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Simultaneous measurement of both the conduction- and valence-band dispersion curves in single strained-layer structures is presented. These measurements rely on the application of recent observations regarding breaking of the usual selection rules for interband magnetoluminescence transitions in modulation-doped structures. Low-temperature magneto-luminescence data for three representative InGaAs/GaAs n-type single-strained quantum well structures are presented. For energies approaching 50 meV above the band gap, we find that the conduction band is parabolic with an effective mass of 0.071m0. Over the same energy range, the valence bands are highly nonparabolic.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1324-1326 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report low-field electroreflectance (ER) spectra of an all-semiconductor multilayer optical mirror structure. The structure, consisting of alternating blocks of AlAs/Al0.5Ga0.5 As and Al0.5Ga0.5As/GaAs multiple quantum well layers, was grown by molecular beam epitaxy without wafer rotation. Thickness variations across the wafer produce a position-dependent reflectance spectrum. The observed line shape of the band-edge exciton depends on its wavelength position relative to the mirror spectrum and cannot be explained by ordinary ER theory, due to the rapidly varying background mirror reflectance. Computer simulations, using the matrix method to calculate the reflectance for different layer thicknesses and exciton energies, agree qualitatively with the data. A strong enhancement in ER response is predicted near the minima in the mirror spectrum. This enhancement is important in electo-optic reflectance modulators.
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of built-in biaxial strain on Γ-X transport in n-GaAs/i-InxAl1−xAs/n-GaAs pseudomorphic single-barrier structures (x=0, 0.03, and 0.06) are studied by measuring temperature-dependent I-V characteristics. For the accurate characterization of electron transport across each barrier, a self-consistent numerical model is used to analyze the experimental results. For each structure, the four barrier parameters defined from the thermionic-field-emission theory, the effective Richardson constant A*, the conduction-band offsets ΔEc1,2, and a tunneling mass mn* are extracted by calculating the theoretical I-V characteristics and fitting them to the experimental I-V-T data. The experimentally obtained X-point conduction-band shifts with the addition of indium are compared with the theoretical results calculated based on the model-solid theory. The results indicate that the addition of indium not only splits the degenerate X minima of the InxAl1−xAs barrier, but also shifts the relative barrier heights of both longitudinal and transverse X valleys due to the alloy-dependent band-structure modification. The comparison between the experimental and theoretical results illustrates that the transverse X valleys are the main conduction channel for the Γ-X transport across InxAl1−xAs pseudomorphic barriers. © 1994 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5444-5455 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Poisson's and Schrödinger's equations have been simultaneously solved in cylindrical coordinates for the problem of a cylindrical modulation-doped quantum well, also referred to as a quantum wire. A transfer matrix method for the solution of Schrödinger's equation has been implemented for cylindrical coordinates. For the case of a GaAs wire embedded in an AlGaAs host, a parametric investigation was undertaken to determine the effects of aluminum fraction, temperature, well radius, barrier doping, and spacer layer thickness upon the linear electron density within the quantum wire. Transferred electron densities in excess of 106 electrons per cm are easily achievable for a wide range of parameters.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 717-721 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The critical radius of a strained quantum wire and the potential strain stabilization of quantum wire arrays has been investigated for the InxGa1−xAs/GaAs system. The critical radius of the quantum wire was calculated using an energy balance approach. The wire was found to be more stable than the corresponding two-dimensional quantum well structure. The use of surface tension as a stabilization force during the growth of strained quantum wire arrays is expected to have beneficial effects for arrays with greater than 7% InAs.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6578-6580 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a study of threshold characteristics of as-grown surface-emitting lasers fabricated with molecular-beam epitaxy by the monolithic integration of two quarter-wave high reflectors (mirrors) of AlAs/Al0.4Ga0.6As surrounding an active spacer layer. The spacer was either a multiple quantum well of GaAs/Al0.4Ga0.6As (100 A(ring)/200 A(ring)) or GaAs. Several structures were grown corresponding to different mirror reflectance and different spacer thicknesses from ultrashort 0.9 to 10 μm. One of the structures was chemically etched to form a two-dimensional array of microlasers. All of the structures were photopumped at room temperature, and the lasing threshold was determined. Without any lateral confinement, the threshold irradiance was as low as 2×105 W/cm2. Near-field images of the light emitted slightly above threshold reveal several competing filaments. This competition broadens the lasing linewidth, but can be controlled by lateral confinement schemes.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 8423-8425 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Elastic constants for zinc-blende AlN, GaN, and InN have been estimated from the elastic constants of the wurtzite phase. This has been accomplished by recognizing that the crystal structures of the wurtzite and zinc-blende phases are related by a simple rotation. This rotation was then applied to the elastic constants and a least-squares fit is used to match the results. Using the zinc-blende elastic constants the critical thickness of the nitrides on β-SiC substrates was calculated. The critical thickness of a single overlayer of AlN was calculated to be 14.1 nm, and for GaN the critical thickness was found to be 0.7 nm. In the elastic continuum model used there was no solution for the critical thickness of InN.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 7-9 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report optical tuning (an optically induced shift of the transmittance peak) of an epitaxial Fabry–Perot étalon comprising AlAs/AlGaAs quarter-wave high reflectors surrounding a GaAs/AlGaAs multiple quantum well spacer layer. The reflectors and spacer were produced in a single growth process by using molecular beam epitaxy. Low-power cw reflection and trasmittance spectra as well as higher power pulsed trasmittance spectra were measured at room temperature. A very sharp (∼20 A(ring) full width at half-maximum) Fabry–Perot transmittance peak was observed near the resonant exciton wavelength (8500 A(ring)) at room temperature. The tuning of this transmittance mode under pulsed optical excitation is as large as 27 A(ring). These results indicate that very large on/off switching ratios (∼10:1) can be achieved with these structures.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1395-1397 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report studies of bleaching action in an epitaxial Fabry–Perot resonator grown by molecular beam epitaxy. These new structures hold exciting potential for surface-emitting lasers, optical switches, and optical modulators. The structure consisted of a multiple quantum well of AlGaAs and GaAs surrounded by two quarter-wave high reflectors with alternating layers of AlAs and AlGaAs. The spectral and temporal transmittances under intense optical pulses are reported here. The spectral data provide simultaneous information on nonlinear changes in both real and imaginary parts of the refractive index. The temporal data show that the transmittance can be switched up to three orders of magnitude in less than the experimental resolution of 300 ps, and provide evidence for time compression of optical pulses.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2132-2137 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si-implant activation characteristics in AlxGa1−xAs for Al compositions of 0%–70% AlAs are presented for doses of 5.6×1012 and 2.8×1013 cm−2 at 100 keV. For both doses, the effective activation efficiency (ηeff) is relatively constant from 0% to 20% AlAs (ηeff=64% for 5.6×1012 cm−2 and 37% for 2.8×1013 cm−2 for 20% AlAs), goes through a minimum at 35% AlAs (ηeff=6.6% for 5.6×1012 cm−2 and 2.5% for 2.8×1013 cm−2), and then increases towards 70% AlAs (ηeff=52.8% for 5.6×1012 cm−2 and 31.1% for 2.8×1013 cm−2). The results are explained based on the compositional dependence of the ionization energy and conduction band density-of-states of AlGaAs. The effects of P coimplantation is also studied but demonstrates no significant enhancement of the activation efficiency of Si implantation for 0%–70% AlAs. Finally, data are presented for Se implantation in Al0.2Ga0.8As with a maximum effective activation efficiency of 5.6% achieved. © 1996 American Institute of Physics.
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