Expressions for the independent galvanomagnetic resistance tensor components in weak magnetic fields are obtained for p-Te type semiconductors, using a variational method. Carrier scattering by optical lattice vibrations is considered without using the relaxation time approximation. With p-Te as an example, the temperature dependence of the tensor components ; ( H ) is studied both theoretically and experimentally for temperatures between 77 and 300 "K. From comparison between the calculated and measured values of $(If)
Strain-induced metal-insulator (MI) transitions have been observed in degenerately doped Si:Sb and Ge:Sb crystals at T = 4.2 K and for extremely high uniaxial pressures up to 5 GPa. It is shown that in both Si and Ge the transition from a metallic-type to an activated conductivity is determined by strain-induced changes of the conduction band parameters. The data obtained demonstrate that the effective mass donor approach and the scaling theory of localization describe well the MI transition phenomenona observed.
The effect of appearance of a constant current (at a closed circuit) in anisotropic semiconductors at propagation of longitudinal oscillations with an external carrier-heating electric field applied to the sample is investigated. The departure of the energy dispersion law from the isotropic parabolic one (as, e.g., in tellurium) is ascertained to result in an additional term in the expression for the current, which is absent for an equilibrium plasma; its contribution can be determined under certain conditions. Consideration of the energy dependence of the relaxation time as well brings about additions to the constant current, which may also be in an equilibrium plasma. Dependences of the current on the oscillation frequency and wave vector as well as on orientation of the external electric field relative to crystallographic axes are derived.Es wird das Auftreten eines konstanten Stroms (im geschlossenen Stromkreis) in anisotropen Halbleitern bei Ausbreitung von longitudinalen Oszillationen mit einem auDeren, die Ladungstrager aufheizenden elektrischen Feld an der Probe untersucht. Die Abweichung des Energiedispersionsgesetzes von der isotropen parabolischen Form (wie z. B. in Tellur) fiihrt zu einem zusatzlichen Term im Ausdruck fur den Strom, der fur ein Gleichgewichtsplasma fehlt; unter bestimmten Bedingungen kann sein Beitrag bestimmt werden. Die Beriicksichtigung der Energieabhangigkeit der Relaxationszeit ruft ebenfalls Zusatze zum konstanten Strom hervor, die auch in einem Gleichgewichtsplasma vorhanden sein konnen. Die Abhangigkeit des Stromes sowohl von der Oszillationsfrequenz-und Wellenvektor als auch von der Orientierung des auDeren elektrischen Felds relativ zu den kristallographischen Achsen wird abgeleitet.
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