Simulation studies of persistent photoconductivity and filamentary conduction in opposed contact semi-insulating GaAs high power switches

A self-consistent, two-dimensional, time-dependent, drift-diffusion model i s developed to simulate the response of high power photoconductive switches . Effects of spatial inhomogeneities associated with the contact barrier po tential are incorporated and shown to foster filamentation. Results of the dark current match the available experiment data. Persistent photoconductiv ity is shown to arise at a high bias even under the conditions of spatial u niformity. Filamentary currents require an inherent spatial inhomogeneity, and are more likely to occur for low optical excitation. Under strong unifo rm illumination, the spatial nonuniformities were quenched as a result of a polarization-induced collapse in the internal fields. However, strong elec tric fields resulting at the contacts create a bipolar plasma, and hence, a virtual "double injection." (C) 1999 American Institute of Physics. [S0021 -8979(99)05119-1].