  We perform an analytical investigation of the bifurcation from static to
traveling current density filaments in a bistable semiconductor structure with
S-shaped current-voltage characteristic. Joule self-heating of a semiconductor
structure and the effect of temperature on electron transport are consistently
taken into account in the framework of a generic reaction-diffusion model with
global coupling. It is shown that the self-heating is capable to induce
translation instability which leads to spontaneous onset of lateral self-motion
of the filament along the structure. This may occur in a wide class of
semiconductor structures whose bistability is caused by impact ionization due
to the negative effect of temperature on the impact ionization rate. The
increment of the translation mode and the instability threshold are determined
analytically.
