BAND-WARPING-INDUCED TRANSVERSE POPULATION-INVERSION OF HOT HEAVY HOLES IN GERMANIUM AT HIGH ELECTRIC-FIELDS

The steady-state distribution functions of hot heavy and light holes i n germanium in the presence of a strong static electric field have bee n calculated simultaneously by solving the full Boltzmann equation wit h an iterative method. The theoretical model employs a warped paraboli c valence-band structure. The hole scattering mechanisms are limited t o 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 st reaming 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.