Wide Bandgap Extrinsic Photoconductive Switches

Semi-insulating silicon carbide and gallium nitride are attractive materials for compact high-voltage photoconductive semiconductor switches (PCSSs) due to their large bandgap, high critical electric field strength, and high electron saturation velocity. Carriers must be optically generated throughout the volume of the photoswitch to realize the benefits of the high bulk electric field strength of the 6H-SiC (3 MV/cm) and GaN (3.5 MV/cm) materials. This is accomplished by optically exciting deep extrinsic levels in vanadium-compensated semi-insulating 6H-SiC and iron-compensated semi-insulating GaN. Photoconducting switches with opposing electrodes were fabricated on a-plane 6H-SiC and c-plane GaN substrates. This paper reports what we believe to be the first results of high power photoconductive switching in bulk semi-insulating GaN and reviews the first phase of switch tests of a-plane 6H-SiC PCSS devices.