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1976 - 19774

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Publication Type: search.filters.UBSTyp.KonferenzbeitragSubject: search.filters.subject.530Start date: 1966End date: 1979Institute: search.filters.UBSInstitut.1. Physikalisches Institut

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Now showing 1 - 4 of 4
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    Resonance and relaxation attenuation by neutral acceptors in a magnetic field
    (1977) Schad, Hanspeter; Lassmann, Kurt; Zeile, Heinrich
    Fine structure, level splitting, and relaxation times of the acceptor ground state in cubic semiconductors can be deduced from ultrasonic attenuation. By the application of a magnetic field it is possible to vary the coupling strength and the number of acceptors on speaking terms with the ultrasonic wave. Making use of this possibility, we have determined directly effective coupling constants for relaxation attenuation and the temperature dependence of the critical intensity for saturation of the resonant interaction. Results obtained for p-type GaAs and Si are discussed in comparison with analogous results for glasses.
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    Anisotropy of phonon emission from hot electrons in germanium
    (1976) Reupert, Wolfram; Lassmann, Kurt; Groot, Peter de
    We have measured quantitatively the anisotropy of the electron-acoustical phonon scattering in n-germanium in five directions of the (lTO) plane utilizing tunneling junctions for calibrated detection of the phonon radiation emitted from a small avalanche breakdown region in the germanium surface. For comparison and evaluation of phonon focusing a constantan heater and a tunneling junction were also used as phonon sources. A similar experiment has been reported by A. Zylbersztejn, but he could only compare the ratio of the amplitudes of longitudinal and transverse phonon pulses in a given crystal direction to the calculation.
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    High frequency phonon emission from superconducting Al-tunnelling junctions
    (1976) Eisenmenger, Wolfgang
    In single particle tunneling between identical superconductors phonons are generated by relaxation - and recombination transitions of injected quasiparticles. Phonon detection is mediated by the breaking of Cooper-pairs by phonons with energy exceeding the superconducting energy gap 2Δ D. This leads to an increase of the quasiparticle population and a corresponding contribution to the tunneling current in the thermal tunneling regime 0
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    Phonon scattering due to deep acceptors in semiconductors
    (1976) Combarieu, Andre de; Lassmann, Kurt
    We have measured the magnetothermal conductivity in GaAs(Mn) and Si(In) for temperatures between 1.4 K and 90 K at magnetic fields up to 8 T. In both cases the dopants are deep acceptors with binding energy much larger (110 meV and 165 meV respectively) than given by the effective mass theory (~ 35 meV). There is a double interest in such systems: First, an excited level 3 meV (4.2 meV) above the acceptor ground state has been concluded from ultrasonic measurements. Such an excited state might be connected with a Jahn-Teller effect of these deeper acceptors and should be seen by resonant phonon scattering in thermal conductivity. Second, an anomalous behavior of the magnetothermal conductivity has been found for shallowacceptors in Ge (but not in Si) making comparison with systems with different g-factors desirable. The g-factors of acceptors in GaAs are roughly three times, the g-factor of Si(In) about 0.6 times that of Si(B).