Diffusive semiconductor moment equations using Fermi�CDirac statistics

Diffusive moment equations with an arbitrary number of moments are formally derived from the semiconductor Boltzmann equation employing a moment method and a Chapman?CEnskog expansion. The moment equations are closed by employing a generalized Fermi?CDirac distribution function obtained from entropy maximization. The current densities allow for a drift-diffusion-type formulation or a ??symmetrized?? formulation, using dual-entropy variables from nonequilibrium thermodynamics. Furthermore, drift-diffusion and new energy-transport equations based on Fermi?CDirac statistics are obtained and their degeneracy limit is studied.