Steady State Properties Current Filaments

Collective impact ionization has been used to exT1ain lock-on in semi-insulating GaAs under highvohage bias. W7ehave used this theory to study some of the steady state properties of lock-on current filaments. In steady state, the heat gained from the field is exactly compensated by the cooling due to phonon scattering. In the simplest approximation, the carrier distribution approaches a quasi-equ~lbrium Ma.xwell-Boltzmann distribution. In this repom we examine the validity of this approximation. \Ye fmd that this approximation leads to a filament carrier density which is much lower than the high density needed to achieve a quasiequilibrium distribution. Further work on this subject is in progress.