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  • 1
    Electronic Resource
    Electronic Resource
    Lattice parameter variation in doped GaAs substrates determined using high resolution photoluminescence spectroscopy (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 6305-6311 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Variations in the lattice parameters of commercially available undoped and Si-doped GaAs substrates have been studied using high resolution photoluminescence (PL) spectroscopy. The lattice parameter difference between high quality epitaxial layers of GaAs and the doped substrates upon which they are grown induces a biaxial strain in the epitaxial layer which can be detected with remarkable sensitivity using low temperature PL. The PL results show that a lattice mismatch as low as 0.0013% can cause significant and well-resolved changes in the features of donor (D°X) and acceptor (A°X) bound exciton spectra, which are consistent with results obtained from samples subjected to externally applied biaxial stress. In addition to studying a variety of low lattice mismatch GaAs/GaAs:Si heterostructures, the technique is also successfully employed in the case of more highly strained GaAs grown on an In0.004Ga0.996As substrate. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368953
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  • 2
    Electronic Resource
    Electronic Resource
    Substrate photoluminescence: An aid in the evaluation of pulsed laser evaporation and epitaxial growth of Cd1−xMnxTe epilayers on (111)GaAs (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3045-3048 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence (PL) emitted from (111)Cd1−xMnxTe/(111)GaAs:Si heterojunctions produced using pulsed laser evaporation and epitaxy (PLEE) has been studied at 11.5 K. The heterojunctions show PL from the substrate E0 and E0+Δ0 gap regions as well as from the epilayer. The substrate E0+Δ0 signal is particularly sensitive to the epilayer growth temperature and is strongest for samples grown on substrates held at Tg=290 °C. The heterojunction PL also includes a component produced by Si dopant atoms in the substrate that undergo clustering changes as the growth temperature is raised. Through comparison with annealing studies of the substrate, it is argued that the PLEE ablated material possesses sufficient kinetic energy to increase the effective temperature above Tg at the growth surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356151
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  • 3
    Electronic Resource
    Electronic Resource
    Impact ionization rate calculations in wide band gap semiconductors (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 8178-8185 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An algorithm for calculating impact ionization rates in the semiclassical Fermi's Golden Rule approximation which is efficient close to threshold is presented. Electron and hole initiated rates are calculated for three semiconductors with particular band structure characteristics, as are the distributions of the generated carriers. Simple analytic expressions of the form R=A(E−E0)P are fitted to the calculated rates. The role of the matrix elements in influencing the distribution of final states is investigated. In the direct gap materials, they act to significantly enhance the low-q transitions, while in the indirect gap case they have a lesser effect on the distribution. Results for GaAs obtained here and by several other workers are compared and possible causes of the discrepancies examined, including differences in band structure and approximations made in evaluation of the matrix element. It is found that these differences do not influence the rate sufficiently to account for the wider variation between authors, and so it is concluded that differences in the implementation of the rate integration algorithm are the main cause. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370657
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  • 4
    Electronic Resource
    Electronic Resource
    Characteristics of impact ionization rates in direct and indirect gap semiconductors (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 8186-8192 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Impact ionization rates for electrons and holes in three semiconductors with particular band structure characteristics are examined to determine underlying factors influencing their qualitative behavior. The applicability of the constant matrix element approximation is investigated, and found to be good for the indirect gap material studied, but overestimates threshold softness in the direct gap materials. The effect that final states in the Γ valley have in influencing characteristics of the rate in the direct gap materials is investigated, and it is found that they play a significantly greater role than the low density of Γ valley states would suggest. The role of threshold anisotropy in affecting threshold softness is examined, and it is concluded that it plays only a small part, and that softness is controlled mainly by the slow increase in available phase space as the threshold energy is exceeded. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370658
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  • 5
    Electronic Resource
    Electronic Resource
    Raman investigation of molecular beam epitaxy grown InGaAlAs epilayers lattice matched to InP for low Al concentrations (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 2266-2271 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room temperature Raman measurements on a series of molecular beam epitaxy grown In0.53Ga0.47−xAlxAs epilayers lattice matched to InP substrates have been carried out for the composition range 0≤x≤0.08. This low Al composition range is important for tailoring the well gap energy in communication device fabrication. The Raman data show three-mode phonon behavior for films with Al concentrations as low as x=0.03. In addition to detecting the fundamental one-phonon scattering processes, overtone, and combinations of the GaAs-like and AlAs-like optic phonon modes are recorded. These are then used to determine the composition dependent phonon mode shifts. By comparing the separate estimates of the free carrier band-gap energy using low temperature absorption and photoluminescence measurements, unintentional doping of the epilayers by the substrate is revealed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366967
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  • 6
    Electronic Resource
    Electronic Resource
    High resolution spectroscopy of free-standing GaAs films prepared by epitaxial liftoff (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 5772-5775 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Free-standing layers of high purity GaAs prepared by epitaxial liftoff are investigated using high resolution photoluminescence, optical transmission, and x-ray diffraction techniques. Low temperature (1.5 K) optical measurements of these thin, strain-free films yield spectra rich in structure, revealing much about the fundamental properties of the materials. X-ray diffraction analysis of layers as thin as 2000 Å produce well-resolved Pendellösung fringes, in excellent agreement with dynamical theory simulations. Once removed from their underlying substrates, these thin semiconductor cavities constitute unique systems for a variety of novel spectroscopic studies not possible in as-grown heterostructures. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368842
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  • 7
    Electronic Resource
    Electronic Resource
    Large photoluminescence enhancements from epitaxial GaAs passivated by postgrowth phosphidization (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 3275-3277 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dramatic enhancements of over 300× in the room temperature photoluminescence signal obtained from high purity GaAs epitaxial layers were recorded after a brief heat treatment in tertiarybutylphosphine vapor. Low temperature photoluminescence spectra indicate that, unlike other passivation techniques, the surface layer formed during this simple treatment does not induce any appreciable strain on the underlying epilayer. The increases in photoluminescence intensity are indicative of a reduction in surface recombination brought about by the formation of a very thin GaP layer that protects against surface oxidation. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118426
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