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  • 1995-1999  (4)
  • 1985-1989  (8)
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  • 1
    Electronic Resource
    Electronic Resource
    Measurements of frequency upconversion and picosecond excitation-correlation luminescence spectra in GaAs quantum wells and determination of time constants describing exciton dynamics (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5921-5931 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the picosecond dynamics of free carriers and excitons in high-quality GaAs quantum wells at 8 K using frequency upconversion (UC) and nonlinear picosecond excitation-correlation (PEC) luminescence spectroscopy under nonresonant excitation conditions with carrier densities of a few 1010 cm−2. We analyze the measurements using a theoretical model of the coupled free electron–hole pair and exciton dynamics, incorporating important density-dependent nonlinear effects, caused by exciton collisions and fermion exclusion. The time-resolved UC photoluminescence (PL) spectra are used to deduce time constants related to free electron–hole (e–h)-pair transformation into excitons and exciton transfer from large K to small K (k is the exciton wave vector). It is shown that unambiguous determination of exciton radiative and nonradiative decay times are possible when both UC and PEC PL spectra are considered simultaneously. We carry out a detailed line-shape analysis of the picosecond UC and PEC PL spectra. We find that while collision broadening is mainly responsible for the observed nonlinear excitonic PEC signal, the PEC PL spectra can be fully explained only when additional nonlinear effects, such as density-dependent radiative lifetime and fermion exclusion, are included in the analysis. From a comparison of the time evolution of both the PEC and UC PL spectra with theory, the time constants introduced in the model to describe free carrier density decay, transfer of excitons with K≠0 to K≈0 states, and their radiative and nonradiative decay are estimated to be about 50, 15, 60, and 1800 ps respectively. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363821
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  • 2
    Electronic Resource
    Electronic Resource
    Erratum: "Measurements of frequency upconversion and picosecond excitation-correlation luminescence spectra in GaAs quantum wells and determination of time constants describing exciton dynamics" [J. Appl. Phys. 80, 5921 (1996)] (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 7077-7077 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365559
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  • 3
    Electronic Resource
    Electronic Resource
    Quasi-ballistic resonant tunneling of minority electrons into the excited states of a quantum well (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2529-2531 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Observation of energy-dependent transmission of nonequilibrium minority electrons through a symmetric double-barrier (DB) quantum well heterostructure is reported. The DB is placed in the base of a GaInAs/AlInAs bipolar transistor. The electrons are launched into the DB with variable kinetic energies using a tunnel barrier in the emitter and varying the emitter-base voltage. The resulting peak in the collector current provides for the first time evidence of quasi-ballistic resonant tunneling of minority carriers into the eigenstates of a quantum well. The small peak-to-valley ratio and the broad peak also demonstrate the importance of scattering and of the anisotropy in momentum space of the incident distribution function in the region between the ballistic electron launcher and the DB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101972
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  • 4
    Electronic Resource
    Electronic Resource
    Transient electrical conductivity of nonequilibrium carriers excited by subpicosecond optical pulses in GaAs (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 323-325 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We calculate the time-dependent electrical conductivity σ(t) for the nonequilibrium carriers excited by a subpicosecond laser pulse in a polar semiconductor like GaAs. The photoexcited carriers are assumed to relax towards equilibrium by emitting longitudinal optical (LO) phonons in a cascade via the strong Fröhlich interaction. We show that σ(t), obtained in the picosecond time domain, has a highly nonlinear time evolution. It develops a pronounced dip, with its value becoming negative, whenever the generated low density carrier distribution is sharply peaked initially at energy ε(approximately-equal-to)m(h-dash-bar)ωLO, m=integer, (h-dash-bar)ωLO being the long wavelength LO phonon energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98990
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  • 5
    Electronic Resource
    Electronic Resource
    Logarithmic detrapping response for holes injected into SiO2 and the influence of thermal activation and electric fields (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4548-4554 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Relaxation of trapped holes that are introduced into silicon dioxide from silicon by the avalanche injection method is studied under various conditions of thermal activation and external electric fields. It is found that the flat band voltage recovery in time follows a universal behavior in that the response at high temperatures is a time scaled extension of the response at low temperatures. Similar universality exists in the detrapping response at different external bias fields. The recovery characteristics show a logarithmic time dependence in the time regime studied (up to 6000 s). We find that the recovery is thermally activated with the activation energy varying from 0.5 eV for a field of 2 MV/cm to 1.0 eV for a field of −1 MV/cm. There is little discharge in 3000 s at room temperature for negative fields beyond −4 MV/cm. The results suggest that the recovery is due to tunneling of electrons in the silicon conduction band into the oxide either to compensate or to remove the charge of trapped holes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340153
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  • 6
    Electronic Resource
    Electronic Resource
    Contrasts in electron and hole trapping phenomena in pyrogenic oxides grown with different H2O partial pressures on silicon (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 2337-2341 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Trapping characteristics of both electrons and holes in pyrogenic oxides grown on silicon with different H2O partial pressures in the oxidizing ambient are studied by using the avalanche injection technique. The electron- and hole-trapping phenomena show opposite dependence on the pyrogenic oxide growth conditions. It is found that the electron-trap density increases with the H2O partial pressure, whereas the hole-trap density decreases. On the basis of the above, and from the results of further experiments on water-diffused oxides, the effect of post-metallization annealing, and infrared absorption, we examine different models of possible defects in silicon-dioxide films grown on Si for a consistent explanation. From the analysis SiH and SiOH centers appear to be the most likely hole and electron traps, respectively, in our pyrogenic oxides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339494
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of test signal frequency on the determination of band discontinuity of GaAs/AlGaAs heterojunctions from capacitance-voltage measurements (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1552-1554 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have simulated the effects of deep donors in AlGaAs (DX centers) in the determination of band discontinuity (ΔEc) of GaAs/AlGaAs heterojunctions using the capacitance-voltage measurements. In addition to the partial ionization of the deep donors, the ability of the traps (deep donors) to respond to the test signal used for capacitance measurement has also been included in the analysis. We find that the deep-level effects lead to an underestimation or overestimation of ΔEc, depending upon whether the frequency of the test signal is low or high, respectively, as compared to the emission rate of the traps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341832
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  • 8
    Electronic Resource
    Electronic Resource
    Nonlinear temperature dependence of the refractive index of polycrystalline silicon films and the influence of microstructural disorder (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 2072-2076 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical properties of thin films are known to be affected by microstructural inhomogeneities. In this paper we study, using ellipsometry, the influence of microstructural disorder on the refractive index at 632.8 nm and on its dependence on temperature in the range 300–700 K in the case of thin noncrystalline low-pressure chemical-vapor deposition silicon films. It is found that films with large amorphous component have a behavior distinct from that shown by polycrystalline films. In particular, both the refractive index n and the thermo-optic coefficient dn/dT at room temperature have larger values for amorphous films than for polysilicon films. Furthermore, the thermo-optic coefficient dn/dT is found to vanish at about 500 K in the case of highly noncrystalline films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341110
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  • 9
    Electronic Resource
    Electronic Resource
    Picosecond time evolution of photoexcited hot-electron mobility in GaAs and the speed of photoresponse (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3189-3196 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transient mobility of hot electrons photoexcited in undoped GaAs by subpicosecond laser pulses is calculated. For this, we solve the time-dependent Boltzmann transport equation in the presence of a low-frequency, weak electric field. The attention is focused mainly on the role of intracentral Γ valley scattering in determining the delay in the mobility rise on the picosecond time scale, and the hot-electron energies are assumed to be below the thresholds for possible side-valley transfers (Γ→L,X). We consider the mobility response under two separate conditions of excited carrier density, namely, (1) low-density excitations for which the electron–longitudinal phonon (LO) Fröhlich interaction initially dominates in the carrier relaxation and (2) high-density excitations for which the electron-electron interaction is faster than all other collisions. The mobility of hot electrons is very small (〈1000 cm2/V s) just after photogeneration. It rises to its maximum value with a time constant decided by the various scattering processes which are influenced by the values of the carrier density and the lattice temperature. We find that the mobility rise can be quite slow up to the scale of several picoseconds, even when the possible delay due to side-valley scattering is absent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342670
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  • 10
    Electronic Resource
    Electronic Resource
    Exciton-phonon scattering in GaAs/AlAs quantum wires (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2474-2476 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We perform temperature-dependent photoluminescence measurements on a GaAs/AlAs quantum wire array (QWR-A) with a very low disorder. Using these, we deduce the temperature dependence of the homogeneous linewidth of the quasi-one-dimensional exciton to show that exciton scattering rates with optical phonons are enhanced in the QWR-A in comparison with a reference quantum well. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123012
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