Simulation studies of persistent photoconductivity, filamentary conduction and optical pulse positioning on the high voltage response of semi-insulating GaAs photoconductive switches

A self-consistent, two-dimensional, time-dependent, drift-diffusion model is developed to simulate the response of high power photoconductive switches. Effects of spatial inhomogeneities associated with the contact barrier potential are shown to foster filamentation. Results of the dark current match available experiments. Persistent photoconductivity is shown to arise at high bias even under conditions of spatial uniformity. Filamentary currents require an inherent spatial inhomogeneity, and are more likely to occur for low optical excitation. Finally, it is shown that the switch response can be varied by changing the spatial position of the optical excitation pulse.