Solitary-wave dynamics in extrinsic semiconductors under dc voltage bias

Numerical-simulation results are presented for a simple drift-diffusion model which describes time-dependent and nonlinear electrical transport properties of extrinsic semiconductors under time-independent (dc) voltage bias. Simulations for finite-length samples with Ohmic boundary conditions yield dynamically stable solitary space-charge waves that travel periodically across the sample. Numerical estimates of wave speed, the wave size, and onset phenomena are in excellent agreement with recent experiments in p-type germanium.