Effects of High-Field Velocity Saturation on the Performance of V-Doped 6H Silicon-Carbide Photoconductive Switches

Velocity saturation characteristics of a V-doped 6H silicon-carbide (SiC) photoconductive switch under high electric field are presented. A vertical-geometry switch device based on vanadium-compensated SiC is triggered by a 532-nm laser pulse with light peak power of several hundred kW and operational voltages from 2 to 20 kV. The maximum electrical peak power achieved by the device is up to 1 MW (similar to 50-A, 20-kV, 1.1-ns pulsewidth). When the working voltage is increased to increase output power, the carrier-velocity saturation under high electric field unavoidably impedes the current growth and directly limits the peak power. The parameters of parallel high-field-dependent mobility are obtained with different fields and laser energies: low-field mobility mu = 227 cm(2)/V s and fitting parameter beta = 1.7. With working voltage increasing steadily, a crack-forming process results in device degradation as a result of large current and high electric field. The I-V characteristic curves of the simulations and tests show current saturation and possible damage under high electric field.