Dc Field-Induced Anisotropy of Microwave Conductivity in Nonparabolic Semiconductors at Low Temperatures

Abstract

dc field-induced anisotropy of small-signal microwave conductivity has been theoretically studied and some calculations are presented in the microwave frequency region at low temperatures (77°K) in an n-InSb sample. Above a certain minimum value of the electric field, the spontaneous emission of optical phonons in the active region (ε>ℏωl), and elastic scattering by ionized impurities and by acoustic phonons in the passive region (ε>ℏωl) have been assumed to be the dominant scattering mechanisms. Comparison is made with the theoretical results at high temperatures (300°K) and, qualitatively, with the experimental results of Bonek and Richter. It is seen that the effect of electric field is much more appreciable at low temperatures than at high; many of the qualitative features of the experimental results are explained by the theory. An interesting reduction is made to the case of a parabolic semiconductor, which reveals that the anisotropy effects are greater for a nonparabolic semiconductor than the parabolic one in analogous situations.