Hot electrons in nonparabolic bands with acoustic and polar optical phonon scattering

Abstract

Most compound semiconductors have nonparabolic energy bands, and in pure material the dominant scattering mechanisms are usually by acoustic and polar optical phonons. In this paper, general expressions for the high-field transport properties of such materials are derived, using the balance-of-energy method and assuming a drifted Maxwellian distribution function. Under certain conditions the resultant drift velocity-field curves show a single-band negative differential resistance, arising not only from the increase in effective mass with carrier energy, but also from the change in relative scattering efficiencies of the two mechanisms as the applied field is increased. This effect is more marked at low temperatures. The model gives good agreement with previously reported experimental results on n-type PbTe at 77°K.