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  • 1
    Electronic Resource
    Electronic Resource
    Material and electrical properties of highly mismatched InxGa1−xAs on GaAs by molecular-beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6912-6918 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The material properties of 2-μm-thick InxGa1−xAs epilayers grown on GaAs with 0.28≤x≤1 were investigated. It was found that for x≥0.5, the material quality of the larger lattice-mismatched heterojunction recovers, as evidenced by cross-sectional transmission electron microscopy (XTEM) and double-crystal x-ray diffraction (DXRD). Magnetophotoconductivity measurements were performed on InxGa1−xAs epilayers with 0.75≤x≤1. The dependence of both the cyclotron resonance linewidth and the carrier relaxation time on the material quality is consistent with the XTEM and DXRD results. The transport properties of InxGa1−xAs epilayers with 0.75≤x≤1 were studied using temperature-dependent van der Pauw measurements. It was found that the electron mobility in the low-temperature range is determined by a combination of ionized impurity and dislocation scatterings. The contribution of dislocation scattering to ternary InGaAs epilayers is larger than that to InAs, although InAs has a larger lattice mismatch with respect to GaAs. These four different measurement techniques confirm that the growth mode rather than lattice mismatch determines the density of dislocation for the heteroepitaxy of highly mismatched InxGa1−xAs on GaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355065
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  • 2
    Electronic Resource
    Electronic Resource
    Photoconduction of synthetic pyrite FeS2 single crystals (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2786-2789 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoconduction of synthetic pyrite FeS2 single crystals with low impurity concentration prepared by chemical vapor transport method is reported over a temperature range from 15 K to 300 K. The energy gap is determined from the photoconductive spectral response by the Moss rule. At room temperature the indirect energy gap is found to be 0.83±0.02 eV. According to the experimental evidence for a sharp antibonding p-like state above the Fermi level of FeS2 reported by Folkerts et al. [J. Phys. C 20, 4135 (1987)], the indirect gap is assigned as the transition between Fe 3d t2g and S 3p σ* states. The temperature variation of the indirect band gap shows a linear dependence between 100 K and 300 K with a negative temperature coefficience equal to 1.0±0.1 meV/K. A distinct feature at higher energy side of the spectrum is observed and attributed to the direct band-gap transition. At temperature lower than 60 K, a very sharp peak around 0.9 eV emerged below the absorption edge. This feature might be associated with the excess carriers induced by the photothermal ionization between the impurity levels and conduction band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354627
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  • 3
    Electronic Resource
    Electronic Resource
    Photothermal deflection and photoluminescence studies of CdS and CdSe quantum dots (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3041-3044 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the observation of the quantum confinement effect by using photothermal deflection spectroscopy (PDS) experiment and the time dependence of optically induced degradation in CdS and CdSe semiconductor-doped glasses. The observed absorption peaks in the PDS experiment, together with a simple model, were used to evaluate the average radius of semiconductor microcrystals. It is found that the estimated average radii of quantum dots are consistent with that obtained from other methods. This result demonstrates that the PDS technique provides an alternative tool for the study of the optical properties of semiconductor microscrystals. The time dependence of the luminescence degradation of the impurity band, which is attributed to the process of Auger ionization, follows a stretched-exponential function. The inconsistency with the previously proposed exponential relaxation may be due to the size distribution of CdS and CdSe microcrystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357483
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  • 4
    Electronic Resource
    Electronic Resource
    Morphologies and photoluminescence of porous silicon under different etching and oxidation conditions (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7728-7736 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is found from scanning electron microscopy that the porous silicon samples fabricated under different conditions exhibit different morphologies. Some of them show islands or cracks, but the rest appear to be smooth. It is proposed that the formation of the islands and the cracks depends on the porosity of the porous silicon samples and result from the shrinkage of the porous structure. The photoluminescence spectra of the porous silicon samples also depend on the etching conditions. The peak position of the photoluminescence shifts to higher energy with increasing the porosity of the samples or by rinsing the samples in deionized water for a long time. However, in certain situations the photoluminescence peak shifts to lower energy after the samples are placed in air for a couple of days. It is proposed that not only the quantum size effect but also the transition between oxide levels contribute to the photoluminescence of the porous silicon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356604
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  • 5
    Electronic Resource
    Electronic Resource
    Elimination of light-induced effect in hydrogenated amorphous silicon (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1277-1278 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Light-induced metastable defects in hydrogenated amorphous silicon can be eliminated by atomic hydrogen at the temperature below which the annealing effect occurs. The resulting material has a very high photosensitivity and stability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100404
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  • 6
    Electronic Resource
    Electronic Resource
    Photoluminescence study of hydrogen passivation in GaAs and AlGaAs by the photochemical vapor deposition system (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 70-72 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown for the first time that hydrogen passivation can be made by using a photochemical vapor deposition system. Unlike the common methods, this new method of hydrogenation has no electron or ion bombardment, thus the sample surface will not be damaged during processing. The effects of hydrogenation are confirmed by the enhancement of photoluminescence intensity. A strong increase in the luminescence intensity (a factor of 23) has been observed which is comparable to the results of rf glow discharge systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103581
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  • 7
    Electronic Resource
    Electronic Resource
    An explanation of optically induced excess conductivity in compensated a-Si:H films (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 2578-2579 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to explore the creation process of optically induced excess conductivity in compensated a-Si:H films, we investigated the effect of monochromatic light exposure with different photon energies: 2.54, 1.96, 1.17, and 0.95 eV. The experimental results show that the threshold energy is below 0.95 eV. We suggest that the most likely explanation is the introduction of localized states originating from boron-phosphorus complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339431
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of gap state density distribution in hydrogenated amorphous silicon from light-induced effects (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 1514-1516 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gap state density distribution in hydrogenated amorphous silicon has been obtained from the effect of light illumination on the dark conductivity. This new technique allows us to determine the bulk density of state distribution within approximately 400 meV below the Fermi level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339854
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  • 9
    Electronic Resource
    Electronic Resource
    Optical absorption of ZnSe-ZnS strained layer superlattices (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2142-2144 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of the absorption spectra of excitons in ZnSe-ZnS strained layer superlattices (SLS) with well widths ranging from 0.6 to 7.6 nm is reported. The n=1 heavy hole (hh) and light hole (1h) exciton absorptions are clearly resolved for all samples even near room temperature. A theoretical estimation of the n=1 hh exciton peak energy, which takes account of strain, quantum confinement of free carriers, and exciton binding energy enhancement by reduced dimensionality, is in excellent agreement with the experimental results. The variations in absorption linewidth and energy shift between absorption and emission band peaks, as a function of quantum well width, have also been measured: the experimental results provide evidence that the origin of the so-called "Stokes' shift'' lies in Anderson localization due to monolayer fluctuations in the well width. The temperature dependence of the exciton peak energy and its linewidth are interpreted in terms of electron-phonon and exciton-phonon interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106106
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  • 10
    Electronic Resource
    Electronic Resource
    Strong room-temperature photoluminescence of hydrogenated amorphous silicon oxide and its correlation to porous silicon (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 902-904 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A set of hydrogenated amorphous silicon oxide (a-SiOx:H) films have been fabricated by plasma enhanced chemical vapor deposition. Some of the films exhibit strong room-temperature photoluminescence and others do so only after annealing at high temperature. The variation of photoluminescence after different annealing treatments for these films is found to be similar to that of porous silicon. Assisted by infrared spectra it is concluded that the photoluminescence from a-SiOx:H is originated from the small a-Si clusters or microcrystalline silicon embedded in the amorphous SiOx network. This argument may support a similar model proposed to explain the visible photoluminescence of porous silicon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109867
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