Domain velocity in semiconductors with field-dependent carrier diffusion

Recently several analytical formulas for the velocity of high-field domains in materials with bulk negative differential conductivity and field-dependent carrier diffusion have been published. The formulas were derived under the conventional "invariant domain" condition, and they thus represent solutions of the fundamental equations which are not necessarily stable. Numerical calculations of mathematically stable domains, allowing independence of one space dimension and time, have been made and are reported here. The results are consistent with the analytical formulas.