On a One-Dimensional Hydrodynamic Model for Semiconductors with Field-Dependent Mobility

We consider a one-dimensional, isentropic, hydrodynamical model for a unipolar semicon-ductor, with the mobility depending on the electric field. The mobility is related to the momentum relaxation time, and field-dependent mobility models are commonly used to describe the occurrence of saturation velocity, that is, a limit value for the electron mean velocity as the electric field increases. For the steady state system, we prove the existence of smooth solutions in the subsonic case, with a suitable assumption on the mobility function. Furthermore, we prove uniqueness of subsonic solutions for sufficiently small currents.