Hot-electron anisotropy of microwave conductivity in nonparabolic semiconductors

Abstract

Using the equilibrium distribution function obtained from the Boltzmann transport equation, and the collision term given by Matz [D. Matz, Solid State Commun. 4, 491 (1966); J. Phys. Chem. Solids 28, 373 (1967)], expressions have been derived for microwave conductivity (in parallel and perpendicular orientations to an externally applied, high-dc electric field) in III-V semiconductors with nonparabolic energy bands. Electron scattering with phonons, via the polar optical mode and with ionized impurities, has been considered to be the dominant scattering mechanism. Numerical evaluation of the results for a typical case of n InSb shows that, for the same dc field, the perpendicular microwave conductivity is always greater than the parallel one. An interesting reduction to the case of parabolic-band semiconductors has also been made for the sake of comparison; it reveals that the band nonparabolicity has the effect of reducing the magnitude of conductivity anisotropy.