Pre-firing electric field distribution in semi-insulating GaAs bulk avalanche switches

The prefiring electric field distribution within a bulk avalanche semiconductor switch has a strong bearing upon the propagation of current filaments that form during the conduction state, the voltage breakdown limits for the off-state, and thus the overall peak power scalability of the switch. In this paper, we apply a detailed numerical model for semi-insulating GaAs which includes the full electronic structure of the deep levels to calculate the internal field distribution under prefiring bias voltages. We demonstrate that the electric field is far from homogeneous, with a potential barrier being formed at the cathode end, and the maximum field occurring at the anode end. The more specific details of this electric field distribution are found to depend greatly upon the type of semi-insulating compensation mechanism present in the GaAs substrate. This electric field distribution agrees qualitatively with that determined by a novel optical imaging technique based upon the Franz-Keldysh effect.