This paper deals with the diffusion approximation of the Boltzmann equation for semiconductors in the presence of spatially oscillating electrostatic potential. When the oscillation period is of the same order of magnitude as the mean free path, the asymptotics leads to the driftdiffusion equation with a homogenized electrostatic potential and a diffusion matrix involving the small-scale information. The convergence is proven rigorously for Boltzmann statistics, while it is incomplete for Fermi-Dirac statistics.
Introduction.The drift-diffusion equation is a standard model of particle transport in many applications such as neutron transport [17,18], plasmas [14,22], semiconductors [25,26,33,34,41,42,40,44], gas discharges [39], etc. The driftdiffusion model, very well suited for numerical simulations, is designed to describe the macroscopic behavior of the device. It consists of a mass balance equation relying on the particle and current densities,