Velocity of current filament at the high gain mode of GaAs power photoconductive switches

Many of the characteristics, especially transient turn-on, of high gain mode photoconductive semiconductor switches can be explained by a model similar to a gas streamer model in this paper. Based on the gas discharge theory and photoactivated charge domain model, the mechanism of current filament at the high gain mode of GaAs photoconductive semiconductor switches (PCSSs) was discussed. It is pointed out that both the carrier density and the regional electric field satisfy two critical conditions for the formation and development of streamers. Experimental phenomena indicate that the turn-on time is considerably shorter than the time required for the transit of carriers crossing the electrode gap of the device at saturation transfer velocity. Moreover, the transient turn-on characteristic was analyzed and the ultra-fast velocity of current filament was calculated. The calculated results are in agreement with the experimental results.