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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 990-992 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron populations induced by spontaneous and piezoelectric polarization in semiconductor heterostructures can be estimated simply by using elementary electrostatic theory. The method is illustrated for the AlGaN/GaN system in which the AlGaN barrier is either undoped, or doped n type, and the effect of a GaN overlayer is described. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2485-2487 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple rigorous analytical theory of two-dimensional (2D) nonequilibrium electrons occupying an arbitrary number of subbands in a quantum well is developed. The electric-field dependence of electron mobility and the average kinetic energy for AlN/GaN quantum wells are presented. At temperatures below 200 K the electron mobility is controlled mainly by the acoustic phonon scattering and it is a nonmonotonous function of the electric field, which has a maximum. At room and higher temperatures the interaction with both acoustic and polar optical phonons determine the hot-electron mobility and it depends very weakly on the electric field. Both the mobility and average energy of 2D electrons are smaller than that for three-dimensional (3D) electrons in the bulk semiconductor. Our theory provides a self-consistent transition from the 2D to the 3D regime of electron transport with increasing electric field accompanied by the occupation of an increasingly large number of subbands by the electrons. © 1998 American Institute of Physics.
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  • 3
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For high-power electronics applications, GaN is a promising semiconductor. Under high electric fields, electrons can reach very high energies where polar optical phonon (POP) emission is the dominant scattering mechanism. So, we undertake a full-band analysis of POP scattering of conduction-band electrons based on an empirical pseudopotential band structure. To uncover the directional variations, we compute POP emission rates along high-symmetry directions for the zinc-blende (ZB) crystal phase of GaN. We also compare the results with those of the wurtzite phase. In general, the POP scattering rates in the zinc-blende phase are lower than the wurtzite phase. Our analysis also reveals appreciable directional dependence, with the Γ–L direction of ZB GaN being least vulnerable to POP scattering, characterized by a scattering time of 11 fs. For both crystal phases, we consider the negative differential conductivity possibilities driven by the negative effective mass part of the band structure. According to our estimation, for the ZB phase the onset of this effect requires fields above ∼1 MV/cm. © 2000 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3633-3635 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The continuum theory of optical-mode hybrids in multilayered structures is applied to the case of a quantum well containing a centrally placed monolayer of a semiconductor whose optical frequencies are very different from those of the host. It is shown that antisymmetric modes are strongly modified whereas symmetric modes are not modified at all. As a consequence, the intersubband scattering rate is expected to be reduced. © 1995 American Institute of Physics.
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  • 5
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical model that uses simple, analytic valence band equations to calculate the differential gain in strained layer InGaAs/GaAs quantum wells shows good agreement with experimental differential gain values obtained from multiple quantum well strained layer lasers. The differential gain in these devices is 7 times greater than in bulk, p-type doped InGaAsP lasers. Calculations including nonlinear damping effects indicate that modulation bandwidths exceeding 60 GHz should be achievable in strained layer quantum well lasers.
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  • 6
    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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  • 7
    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.
    Type of Medium: Electronic Resource
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  • 8
    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 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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  • 10
    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.
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