Predominant ionized impurity scattering of warm carriers in semiconductors

Abstract

At large carrier concentrations and about equally large impurity concentrations in nondegenerate semiconductors, a Maxwell-Boltzmann distribution may be used for the calculation of the warm-carrier coefficient β. Acoustic and optical deformation potential scattering, piezoelectric, and polar optical mode scattering are considered as mechanisms of energy transfer from the carriers to the lattice. In all cases of predominant ionized impurity scattering β is positive, proportional to the product of mobilities with and without impurity scattering, which includes an inverse proportionality to the impurity concentration, and inversely proportional to the square of a velocity. For acoustic scattering this velocity is the sound velocity while for optical mode scattering it is essentially the constant drift velocity of carriers at high field intensities. Since the treatment is based on the simple model of band structure no anisotropy of β or carrier transfer effects are obtained.