Band-warping-induced transverse population inversion of hot heavy holes in germanium at high electric fields.

Abstract

The steady-state distribution functions of hot heavy and light holes in germanium in the presence of a strong static electric field have been calculated simultaneously by solving the full Boltzmann equation with an iterative method. The theoretical model employs a warped parabolic valence-band structure. The hole scattering mechanisms are limited to nonpolar optical and acoustical phonons and are treated on the basis of the deformation-potential theory in a way consistent with the band structure of the solid. The numerical computations show that under streaming conditions the distribution function of the heavy holes may be inverted transverse to the direction of the applied electric field as a consequence of band warping.