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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    JETP letters 63 (1996), S. 464-470 
    ISSN: 1090-6487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Due to the lack of transverse momentum conservation for the electron-acoustic-phonon interaction in quantum wires this interaction becomes strongly inelastic within a wide range of electron energies. As a result the electron distribution function has to be found from an integro-differential equation. We derive the new nonequilibrium distribution functions for these conditions and present the electric field dependences for the kinetic coefficients. Our approach can be applied as well for two-dimensional electron systems or for electrons subjected to an external quantizing magnetic field.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3089-3097 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Scattering and well-width nonuniformities in double-barrier structures introduce level broadening, particularly in the quantum-well region, and the effect of this level broadening on coherent and sequential transmission of electrons through these structures has been examined. First, it is shown that resonant energies are eigenenergies of the overall system, so that it is the same energy level which is involved in both tunneling mechanisms. This explains why the negative differential resistance (NDR) peak occurs at the same voltage for coherent and sequential tunneling. Expressions for the transmission coefficients and, consequently, for the current density are derived, and it is shown that the effect of broadening is to reduce the peak current and the peak-to-valley ratio for both tunneling processes, this reduction being quite remarkable for the case of coherent tunneling through the structures with thick barriers. Based on this, ways are suggested to distinguish between the two tunneling phenomena. This broadening-induced reduction in peak current and peak-to-valley ratio leads to a reduction in the NDR-related maximum operating frequency in these structures. On the other hand, the effect of broadening on coherent tunneling itself is to reduce the resonant tunneling time, thus allowing higher-frequency operation in optical devices. Above a critical amount of broadening the assumption of coherent tunneling breaks down, and sequential tunneling takes over. Critical broadenings for a number of cases are estimated. It is emphasized that the form of the NDR and hence the frequency response is dependent on whether the emitter density of states is two- or three-dimensional-like.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6135-6139 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron transport in a channel separated from the surface by a thin insulating barrier layer is shown to be profoundly affected by electrical conditions on the surface. Nonuniformities in the coupled surface and channel systems lead to depletion and accumulation regions in the channel and the depletion regions can cause the current to saturate at unusually low voltages. Even when there are no nonuniformities it is shown that the coupled system exhibits a density instability that leads to similar phenomena. These effects are described in terms of an analytical model that takes into account diffusion and hot-electron transport applied to the AlGaN/GaN system. It is noted that the effect of any extension of the channel under the cathode (source) can produce depletion and current saturation that can be mistaken for the result of a nonohmic contact resistance. © 2001 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2579-2588 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple analytical model is obtained to describe the effect of carrier heating on the frequency response of a quantum well laser. The principal factors are taken to be injection heating, recombination heating, and hot phonons. The model is applied to the GaAs/GaInAs strained layer system and is shown to qualitatively account for many of the nonideal features observed. The nonlinear effects cannot be described satisfactorily by a single phenomenological "gain suppression'' factor. However, at low drives the conventional gain suppression factor can be expressed in terms of the phonon lifetime and the temperature-relaxation time. The response is mediated by several time constants which, in our example, combine to give an effective time constant of about 10 ps. The modulation frequency response becomes seriously impaired when the differential gain is lowered by a factor of 2 and the time constants describing scattering and phonon lifetime are increased by a factor of 2.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3491-3499 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The suppression of longitudinally polarized optical-phonon (LOP) electron scattering in multiple quantum wells (MQWs) was sought in short periodic AlAs/GaAs with well widths of 12, 15, and 20 monolayers and AlAs barrier widths of 2 and 4 monolayers, based on a study of electron mobility in the plane of the MQW. Two-dimensional electron-gas structures with MQWs of up to eight wells in their channel were grown. Their mobilities at room temperature were slightly reduced, as compared to samples without MQW channel, due to interaction with interface polaritons from AlAs barriers, while mobility at temperatures 〈50 K improved due to reduction of remote ionized impurity scattering. The theoretical analysis of the results based on the model of hybridon-electron interaction in an infinite superlattice is presented. The reduction of room-temperature mobility in the MQWs is believed to be caused by the interaction of electrons with both barrier interface-polariton (IP) -like modes and the well LOP-IP hybrids. An alternative explanation of the results of a similar experiment done elsewhere is offered denying the evidence of strong suppression of LOP scattering there.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 5546-5550 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interaction between holes confined in a strained Si1−xGex quantum well and acoustic and optical phonons is investigated in an effort to elucidate in-plane carrier transport. This treatment utilizes conventional deformation potential theory within the context of the momentum conservation approximation in the confinement direction to obtain analytical expressions for both acoustic and optical phonon scattering rates as functions of carrier energy. The optical phonon interaction explicitly accounts for the three vibrational modes: Si-Si, Si-Ge, and Ge-Ge by incorporating experimentally determined longitudinal optical (LO) phonon frequency shifts in the calculation of the matrix elements. The oscillator strengths for each of these LO (short wavelength) modes are approximated using a binomial distribution to describe the local atomic arrangement of a unit cell. The two-dimensional scattering rates are evaluated and compared with bulk scattering calculations for a well of fixed width and varying Ge content. It is found that the overall hole-phonon scattering rate in a SiGe well is higher than that of holes in strained SiGe layers due to the combined effects of similar two- and three-dimensional density of states and large inter-sub-band scattering. A qualitative description of high field transport within the well is obtained by calculating the relative contributions of particular optical phonon modes to the overall scattering rate at high carrier energies.
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 72 (1968), S. 1844-1845 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 5606-5621 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experimental and theoretical study has been made of electron transport over a wide AlGaAs barrier with graded interfaces sandwiched between GaAs contact layers. The width of the central barrier region was varied between 700 and 2100 A(ring). Two series of samples with nominally identical structures but from different sources were investigated. Extensive measurements of both the voltage and temperature dependence of the current were made, as well as measurements of capacitance and magnetoresistance. Drift-diffusion thermionic emission theory has been used to interpret the data. Both numerical and analytical solutions of the model have been developed and were found to be in good agreement with each other. The presence of space charge in the barrier region, which has the effect of increasing the barrier height, was seen to be crucial to an understanding of the data. When the effect of space charge was included in the model good agreement was obtained between theory and experiment for electric fields up to 10 kV cm−1. The numerical solution required only one adjustable parameter, namely the value of the space-charge density. The parameters used in the analytical model were all derived from the experimental data.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4667-4673 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The problem of calculating the valence-band structure of strained-layer quantum wells in the effective-mass approximation is reviewed. Using the spherical approximation and exploiting the simplicity of the infinitely deep well model we show that the in-plane effective mass is determined by two factors—a splitting contribution which is dominant at large strains, and a quantum confinement contribution. A model for finite-depth wells is presented which gives analytic expressions for the zone-center in-plane mass and associated nonparabolicity factor, and it is applied to the system InxGa1−xAs/GaAs. The model allows the computation of valence-band structure using no more than a pocket calculator. It is shown to give results in reasonable agreement with experiment.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 4020-4021 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Boltzmann equation was solved exactly for the case of low-field electron transport in bulk GaN at 300 K in the presence of polar-optical phonon scattering only, giving a mobility at low electron densities of 2200 cm2 V−1 s−1 (m*=0.22m0), or 2500 cm2 V−1 s−1 (m*=0.2m0). The effect of increasing the electron concentration to around 1019 cm−3 was found to reduce the mobility to 640 cm2 V−1 s−1. This new result was shown to be a consequence of there being at high densities, a greater proportion of electrons able to emit phonons. © 1998 American Institute of Physics.
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