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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical study of time-resolved Raman scattering profiles of hot electrons in semiconductors (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4325-4335 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comprehensive time-resolved electronic Raman scattering theory for nonequilibrium carrier excitations in semiconductors is presented. The following are simultaneously taken into account: (i) the effects of the ultrashort laser pulse for probing the excited carrier distribution function; (ii) the fact that the fluctuation-dissipation theorem is not valid under conditions of nonequilibrium carrier distributions; (iii) the effects of quasiparticle life time via a finite collision time in the Raman scattering cross section; and (iv) the effect of the time-dependent resonant enhancement factor due to the band structure. The single-particle scattering spectra for spin-density fluctuation contribution is found to be significantly broadened by an ultrashort laser pulse, but is substantially narrowed by the finite collision time. The effect of the time-dependent resonant enhancement factor has been demonstrated to broaden the line shape of single-particle scattering spectra for the spin-density fluctuation contribution as the probe photon energy increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352196
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of the single-particle scattering spectra for spin-density fluctuations of electrons in n-GaAs at T=300 K (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3023-3027 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The line shapes of single-particle scattering spectra for spin-density fluctuations of electrons in n-GaAs with carrier concentrations ranging from 5×1015 to 7×1017 cm−3 have been analyzed. We have found that the Raman line shapes can be very well explained by a theory developed by Hamilton and McWhorter which takes into account both the band-structure effects in semiconductors and the effects of carrier collision in a relaxation time approximation. For carrier concentration n≥2×1016 cm−3, the effects of finite collision time has been demonstrated to be very important and these effects must be properly taken into account in order to satisfactorily interpret the line shapes of single-particle scattering spectra for spin-density fluctuations in n-GaAs at T=300 K. We show that although Lindhard–Mermin's expression for dielectric constant as well as Hamilton and McWhorter's theory fit the Raman line shapes equally well for carrier density n=7×1017 cm−3, neglect of band-structure effects of the former tends to underestimate the carrier collision time. An interpretation of the deduced collision time in terms of electron-electron, electron-impurity, and electron-phonon scattering is also given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353008
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  • 3
    Electronic Resource
    Electronic Resource
    Raman scattering by interface phonons in GaAs-AlAs multiple-quantum-well structures: Correlation between Raman and high-resolution electron microscopy results (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 418-421 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of shallow impurity and interface roughness on resonant Raman scattering by interface phonons in GaAs-AlAs multiple quantum-well structures have been studied. By correlating the Raman results with observations by high-resolution electron microscopy, it has been demonstrated that Raman scattering from interface phonons depends strongly on the sample quality. For a relatively smooth interface with about 1–2 monolayers of interface roughness, the Raman signal is governed primarily by the impurity if the impurity concentration inside the GaAs layers is greater than about 2×1016 cm−3. On the other hand, for nominally undoped quantum-well structures, the Raman signal can be dominated by interface roughness if the interfaces are sufficiently distorted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350291
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  • 4
    Electronic Resource
    Electronic Resource
    Critical analysis of the band-shape function of a molecular system imbedded in a host crystal: Application to F centers (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 7574-7585 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present an investigation of the accuracy of the saddle-point method in application to band-shape functions and find that it gives excellent results for most commonly encountered situations. We also present a comparison with a new improved short-time approximation which shows promise in applications. We use this new method to examine the behavior of the band-shape function in a distorted oscillator model. As an application, we have used these methods to explain the absorption and emission spectra of an F-center defect (a prototype defect system) in four different host crystals KCl, KI, KBr, and NaCl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465687
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  • 5
    Electronic Resource
    Electronic Resource
    Transient picosecond/subpicosecond Raman scattering studies of nonequilibrium electron distributions and phonons in CdTe (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3840-3843 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonequilibrium electron distributions and phonons in CdTe have been studied by transient picosecond/subpicosecond Raman spectroscopy at T=300 K. Our experimental results show that for photoexcited electron–hole density of n(approximately-equal-to)1018 cm−3, the electron distributions can be reasonably well described by Fermi–Dirac distribution functions with effective electron temperature substantially higher than the lattice temperature. From an ensemble Monte Carlo analysis of the nonequilibrium phonon population as a function of photoexcited electron–hole pair density, the LO phonon lifetime in CdTe has been deduced to be τ(approximately-equal-to)0.75±0.25 ps. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363338
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  • 6
    Electronic Resource
    Electronic Resource
    Quantitative assessment of the effects of carrier screening on the average electric field in a GaAs-based p–i–n nanostructure under subpicosecond laser excitation (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 406-408 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used electric-field-induced Raman scattering to quantitatively assess the effects of carrier screening on the average electric fields in a GaAs-based p–i–n nanostructure semiconductor under subpicosecond laser photoexcitation. Our experimental results demonstrated that the effects of carrier screening on the average electric field were negligible for a photoexcited electron–hole pair density of n≤1015 cm−3. As the density of photoexcited carriers increased, we observed a significant decrease of the average electric field. In particular, for n=1018 cm−3, a decrease of electric field of about 50% was found. All of these experimental results were explained by ensemble Monte Carlo simulations and very good agreement has been obtained. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364072
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  • 7
    Electronic Resource
    Electronic Resource
    Time-resolved Raman studies of the decay of the longitudinal optical phonons in wurtzite GaN (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2132-2134 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Decay of the longitudinal-optical (LO) phonons in wurtzite GaN has been studied by subpicosecond time-resolved Raman spectroscopy. Our experimental results show that among the various possible decay channels, the LO phonons in wurtzite GaN decay primarily into a large wave-vector TO and a large wave-vector LA or TA phonon. These experimental results are consistent with the recent theoretical calculations of the phonon dispersion curves for wurtzite GaN. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121299
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  • 8
    Electronic Resource
    Electronic Resource
    Transport properties of excitons in GaAs quantum wells−time-resolved Raman probe (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1666-1668 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time-resolved, space-imaged Raman spectroscopy has been employed to study the transport properties of excitons in GaAs quantum wells. For an injected exciton density of nex (approximately-equal-to)1.5×1011 cm−2, the experimental results show that exciton transport can be well described by a simple diffusion model. Based on the temperature and well-width dependence of the deduced diffusion constant, we demonstrate that at low temperatures, i.e., T ≤60 K, the transport of excitons in GaAs quantum wells is primarily governed by two dominant mechanisms: acoustic phonon scattering and interface roughness scattering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104080
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  • 9
    Electronic Resource
    Electronic Resource
    Determination of the local Al concentration in AlxGa1−xAs-GaAs quantum well structures using the (200) diffraction intensity obtained with a 10 A(ring) electron beam (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1454-1456 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel method for determining the local concentration of Al in the AlxGa1−xAs layer of AlxGa1−xAs-GaAs multiple quantum well structures is reported. By scanning a 10 A(ring) electron beam across the interface, the (200) dark-field scanning transmission electron microscopy (STEM) image shows the contrast of the AlxGa1−xAs-GaAs multilayer since the intensity of the (200) diffraction is sensitive to the Al concentration. The line scan intensity profile of the (200) diffraction, along a uniform specimen region of known thickness, shows the intensity variation of the (200) diffraction and reflects the local content of Al in each region. The simulation of the nanodiffraction patterns produces a chart of the (200) diffraction intensity versus the Al concentration for the determination of the local change of the Al concentration. A molecular beam epitaxy grown AlxGa1−xAs-GaAs specimen (x=0.57 as determined from Raman spectroscopy) is tested and the dark-field STEM studies show two thin layers of x=0.46 at the 1/3 and 2/3 height level within every AlxGa1−xAs layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100695
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  • 10
    Electronic Resource
    Electronic Resource
    Electron–phonon interactions in the wide band-gap semiconductor GaN (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1757-1759 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Picosecond Raman spectroscopy has been employed to study electron–phonon interactions in the wide band-gap semiconductor GaN. By using very intense picosecond laser pulses in the visible spectral range, electron-hole pairs were generated through the two-photon absorption in GaN. The relaxation of these high energy electrons and holes were used to interrogate electron–phonon interactions. We have found that electrons thermalize toward the bottom of the conduction band by emitting primarily longitudinal optical phonons. Our work demonstrates that the Fröhlich interaction is much stronger than the deformation potential interaction in wurtzite GaN. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115040
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