Assessing Lock-On Physics in Semi-Insulating GaAs and InP Photoconductive Switches Triggered by Sub-Bandgap Excitation

The time-dependent photocurrent responsein semi-insulating GaAs and InP was studied basedon 1-D, time-dependent simulations with a focus on theLock-On phenomenon. The results underscore the role oftrap-to-band impact ionization from deep traps in rapidcharge creation and its subsequent propagation muchlike a streamer. The numerical results compare well withthe actual data. The main findings are that deeper trapsnearer the valence band at higher densities, materials withlarger high-field drift velocity, and cathode-side illuminationwould all aid in attaining Lock-On. These could be usefulguidelines for producing Lock-On in new materials such asGaN for high-power applications.