Design and characterization of silicon carbide photoconductive switches for high field applications

Characteristics of a silicon carbide photoconductive switch designed for high field applications have been studied. Analyses show that premature breakdown occurs primarily due to impact ionization and subsequent charge accumulation near the anode. For the shallow donor, deep-acceptor-type compensated material, a p+ layer next to the cathode results in field homogenization in the bulk. As a result, the blocking or hold off voltage of the switch could increase beyond the experimentally determined value of 18kV (0.45MV∕cm). Simulations also show that a minimum thickness, equivalent to a diffusion length, of the p+ layer is necessary to avoid premature breakdown. Following illumination, the photocurrent rise time of the switch would also improve by about 25% with the p+ layer near the cathode.