Universität Stuttgart
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Item Open Access Influence of defects on the splitting of the acceptor ground state in silicon(1984) Ambrosy, Anton; Lassmann, Kurt; Goer, Anne M. de; Salce, Bernard; Zeile, Heinrich-Item Open Access Resonance and relaxation attenuation by neutral acceptors in a magnetic field(1977) Schad, Hanspeter; Lassmann, Kurt; Zeile, HeinrichFine 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.Item Open Access A study of the ground state of acceptors in silicon from thermal transport experiments(1981) Goer, Anne M. de; Locatelli, Marcel; Lassmann, KurtThermal conductivity measurements of silicon crystals doped with Bor In have shown the presence of several phonon scattering processes. The resonant effect observed below 1 K is ascribed to the existence of a distribution of splittings N(δ) of the Γ8 ground state of the acceptor, which could be related to the presence of oxygen and carbon impurities. In two cases, the maximum of N(δ) occurs for δ max near 6 GHz, in agreement with previous ultrasonic studies.Item Open Access Down-conversion of high-frequency acoustic phonons(1987) Galkina, Tatjana I.; Blinov, A. Y.; Bonch-Osmolovskii, M. M.; Koblinger, Otto; Lassmann, Kurt; Eisenmenger, WolfgangMeasurements of phonon transport in amorphous media can give valuable information on the structural properties of these materials and may be of practical interest for its own concerning the question of thermalization in electronic devices. The existence of two-level systems in a-Si:H as one of these technically important materials has been concluded from measurements of dispersion and attenuation of acoustic surface waves.Item Open Access Shallow traps correlated with deep impurities in silicon as obtained by phonon induced conductance(1986) Burger, Wilfried; Lassmann, Kurt; Holm, Claus; Wagner, PeterAt low temperatures shallow neutral donors and acceptors in silicon can bind an extra carrier to form the so-called D- and A+ centers. With the method of phonon-induced electrical conductivity (PIC) we find the same threshold energies for the detachment of these carriers associated with the shallow impurities P and B, as have been obtained previously by FIR measurements. This shows that the detachment is by a one-phonon process. We find that there is no central cell correction for the binding to the deeper acceptors Al and Ga, whereas for In+ the binding energy is as large as 5,8 meV. We interprete this dependence on acceptor species as another example of the shallow-deep instability of the binding energy with the variation of the central cell potential.Item Open Access Phonon spectroscopy of defects correlated with the diffusion of Zn into Si(1994) Staiger, Joachim; Groß, Peter; Lassmann, Kurt; Bracht, Hartmut; Stolwijk, Nicolaas A.We analyse by phonon spectroscopy low lying phonon scattering states from defects that are introduced by the diffusion of Zn into thick Si wafers.Item Open Access Phonon emission by quasiparticle decay in superconducting tunnel junctions(1970) Kinder, Helmut; Lassmann, Kurt; Eisenmenger, WolfgangImproved measurements on phonon emission and detection by tunnel junctions show qualitative agreement with a numerical evaluation of Tewordt's theory on quasiparticle lifetime.Item Open Access Messung der Hyperschalldämpfung in Quarz(1965) Eisenmenger, Wolfgang; Kinder, Helmut; Lassmann, KurtZur Bestimmung der Hyperschalldämpfung in zylindrischen Quarzstäben für Longitudinalwellen in x-Richtung werden zwei Meßanordnungen für den Frequenzbereich 0,5 GHz bis 2.5GHz sowie für die Frequenz von 1O GHz bei Temperaturen von 4° K bis 273° K beschrieben. Im niedrigeren Frequenzbereich erfolgte eine Rauschbefreiung des Empfangssignals durch elektronische Abtastung und Summation. Neben der Temperatur- und Frequenzabhängigkeit der Dämpfung wurden Geometrieeinflüsse bei der Hyperschallanregung und Ausbreitung näher untersucht. Dabei traten Modeninterferenz und Keilwinkelfehler (Parallelitätsabweichungen der Stabendflächen) besonders deutlich in Erscheinung.Item Open Access Phonon scattering due to deep acceptors in semiconductors(1976) Combarieu, Andre de; Lassmann, KurtWe 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).