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  • 1
    Electronic Resource
    Electronic Resource
    Photoreflection study on the surface electric field of delta-doped GaAs grown by molecular beam epitaxy (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1468-1472 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance spectroscopy has been used to study the surface electric-field strength and the surface potential of delta-doped GaAs. Franz–Keldysh oscillations in the reflectance spectra were clearly observed and the oscillation periods were used to calculate the internal electric fields of the delta-doped samples. Based on the measured results and the self-consistent calculation, a surface potential of 0.6 eV is obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351710
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  • 2
    Electronic Resource
    Electronic Resource
    Franz–Keldysh oscillations of δ-doped GaAs (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1065-1069 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si-δ-doped GaAs (N2D ≈ 1011 cm−2) samples grown by molecular-beam epitaxy are investigated by using photoreflectance spectroscopy. The oscillations observed above the GaAs fundamental band gap are attributed to the Franz–Keldysh effect in the region between the δ-doped layer and the crystal surface. This ascription is confirmed by detailed studies through varying the cap thickness (250–2500 A(ring)), temperature (10–450 K), and laser pump power (0.05–7 mW/cm2). The surface potential deduced from the Franz–Keldysh oscillations is found to be temperature and laser pump power dependent, which is explained by taking the surface photovoltaic effect into account. The surface Fermi level has been measured by this method and is found to have the value 0.73±0.02 V.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351780
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  • 3
    Electronic Resource
    Electronic Resource
    A study of Franz–Keldysh oscillations in the photo reflectance spectrum of the δ-doped GaAs film (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7183-7185 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Our photo reflectance (PR) spectroscopy measurements of the δ-doped GaAs film at 300 K reveal many Franz–Keldysh oscillations (FKOs) above the valence band edge, E0 and the spin-orbit split energy, E0+Δ0, which enables us to determine the electric field strength from periods of FKOs provided reduced masses of the electron and holes are known. The reduced masses can be determined unambiguously at E0+Δ0, but not at E0, at which the heavy- and light-hole transitions are degenerate. However, the ambiguity at E0 can be resolved by applying the fast Fourier transform to the PR spectrum to separate the contributions from the heavy and light holes. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361433
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  • 4
    Electronic Resource
    Electronic Resource
    Modeling temperature-dependent photoreflectance spectra of single AlGaAs/GaAs modulation-doped heterojunctions (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6197-6202 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We attempt to deal with the physical processes involved in the temperature-dependent photoreflectance of single AlGaAs/GaAs modulation-doped heterojunction structures. Building on the assumption that photomodulation mechanism is due chiefly to modification of the band bending in the buffer layer, we apply the Franz–Keldysh theory to simulate the temperature-dependent photoreflectance spectra of single AlGaAs/GaAs modulation-doped heterojunction structures. In view of the nonuniformity of the electric field within the buffer layer, the field profile of which is calculated through the application of self-consistent variational approach, the WKB method is used to approximate the effective change in the dielectric function. A comparison between the experimental and the simulated results attests the validity of our assumption. The effects of temperature on the electric-field strengths, estimated from the extrema of the Franz–Keldysh oscillations, can be accounted for by considering the temperature dependence of the Fermi level. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360565
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  • 5
    Electronic Resource
    Electronic Resource
    Differential photoreflectance of Si-δ-doped GaAs (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3030-3033 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The signals from buried layer in Si-δ-doped GaAs of different undoped cap thickness have been studied by differential photoreflectance. The first-derivative-like line shape of differential photoreflectance is attributed to the energy transitions related to the modulations of two-dimensional electron gas density. We have observed a change of line shape at low temperatures. This change of line shape is probably due to the change of potential distribution in the conduction band, which is caused by the surface Fermi-level pinning and surface photovoltaic effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356148
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  • 6
    Electronic Resource
    Electronic Resource
    Photoreflectance study of Si delta-doped low-temperature GaAs grown by molecular beam epitaxy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2124-2127 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance spectroscopy has been used to study the surface electric field of Si delta-doped GaAs grown by molecular beam epitaxy at a low substrate temperature (230 °C). Franz–Keldysh oscillations in the reflectance spectra are observed for samples annealed above 700 °C for 10 min. The deduced surface electric field increases with annealing temperatures and with a decrease in spacer thickness between surface and the delta-doped plane. The evolution of photoreflectance spectra can be explained by the activation of Si donors and Fermi level pinned at surface due to the redistribution of As precipitates. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358788
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  • 7
    Electronic Resource
    Electronic Resource
    Line shape of electromodulation in uniform electric field of δ-doped GaAs (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7489-7492 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The line shape of electromodulation in uniform electric field of δ-doped GaAs has been calculated and compared with the experiments. The calculations show that the Franz–Keldysh oscillations (FKO) beats observed in experiments are contributed form the interference of heavy-hole and light-hole transitions. The calculations also show that the linear equation of extrema is a good approximation to analyze the electric field from the FKO line shape, although the equation only considers the heavy-hole transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356620
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  • 8
    Electronic Resource
    Electronic Resource
    p-d hybridization of the valence bands of copper indium disulfide (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3772-3774 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The p-d hybridization of the valence bands of copper indium disulfide has been studied by photoreflectance. A simple model has been used to measure the separation E between the p and d levels, the interaction strength M between these levels, the d-electron contributions x0 to the E0 energy level, and x1 to the E0 + Δ0 energy level. Our results confirm that the d-electron contributions decrease when the temperature is increased. Our measurements of x0 and x1 agree with the calculation of Yoodee et al. [Phys. Rev. B 30, 5904 (1984)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348475
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  • 9
    Electronic Resource
    Electronic Resource
    Photoreflectance of sulfur-annealed copper indium disulfide (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 283-287 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of the energy gaps for sulfur-annealed copper indium disulfide has been studied by photoreflectance in the temperature range of 10–300 K. The sulfur-annealed sample has been found to have larger transition energies, smaller positive temperature coefficients of energy gaps, and larger spin-orbit splitting energy than the as-grown sample. This can be explained by the reduction of d-level contributions in the upper valence band probably caused by the variation of lattice distance due to native defects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347128
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  • 10
    Electronic Resource
    Electronic Resource
    Room temperature study of low temperature grown Al0.3Ga0.7As/GaAs multiple quantum wells by modulation reflectance (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8589-8593 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We studied the subband energy levels in AlGaAs/GaAs multiple quantum wells grown at different temperatures (200–600 °C) by using the piezoreflectance and photoreflectance in room temperature. Under subsequent 30 s rapid-thermal annealing at different temperatures (600–1000 °C), we observed a large energy blueshift in samples with growth temperature below 400 °C. This blueshift energy may be attributed to the modification of quantum wells caused by gallium vacancy enhanced Al–Ga interdiffusion. The energy blueshifts were analyzed by solving Fick's second law for Al diffusion in quantum wells, obtaining an effective activation energy of 0.75 eV. We discuss our results using the nonequilibrium diffusion equation and comparing them with other experiments. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373583
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