Wide bandgap extrinsic photoconductive switches

Semi-insulating Silicon Carbide and Gallium Nitride are attractive materials for compact, high voltage, photoconducting semiconductor switches (PCSS) due to their large bandgap (3.0 – 3.4 eV), high critical electric field strength (3.0 – 3.5 MV/cm) and high electron saturation velocity (2.0 – 2.5×10⁷ cm/s). 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 aplane, 6H-SiC substrates and c-plane, GaN substrates. This work reports the initial fabrication and test of extrinsic GaN switches excited at a wavelength of 532 nm, and a review of the first phase [1] of switch tests of a-plane, 6H-SiC PCSS.