  In this paper we prove the existence of the high-energy tails for electron
distribution function of the Boltzmann equation for semiconductors, in the
stationary and homogeneous regime, in the analytic band approximation and
scattering with acoustic and optical phonons and impurities. We also prove
numerically that the tail is a global maxwellian in the parabolic band
approximation, and in the quasi parabolic band case, a power law of the global
maxwellian.
