Study Of High Power Silicon Carbide Photoconductive Semiconductor Switches

Semi-insulating silicon carbide (SiC) is an attractive material for application as power compact photoconductive semiconductor switches (PCSS) due to its large band gap, high critical electric field strength, high electron saturation velocity and high thermal conductivity. The critical field strength of 300 MV/m for 4H-SiC makes it particularly attractive for compact, high voltage, fast switching applications.A lateral 4H-SiC photoconductive semiconductor switches (PCSS) device model was built based on the Drift-diffusion Model, and then the I-V characteristics of intrinsic and vanadium doped extrinsic semi-insulating 4H-SiC photoconductive semiconductor switches were simulated respectively under instant input optical intensity. The results indicated that when 10V bias voltage across the intrinsic SiC-PCSS was set, the photocurrent was produced using the 300 nm wavelength light. There was no evident photocurrent as a result of the energy of excitation photons were less than the band gap of 4H-SiC when the wavelength of the illumination light exceeded 500 nm, and the PCSS worked in intrinsic absorption model. For the compensated 4H-SiC PCSS, simulation also successfully observed the compensation effect of vanadium as deep level traps to capture free carriers on n-type impurity N, which further validated the vanadium's compensation function in SiC reported before. The maximum absorption coefficient value reached at 1020 nm wavelength for this compensated 4H-SiC PCSS, which suggested that semi-insulating 4H-SiC photoconductive semiconductor switches could be switched by the lights with the wavelength below the band gap of it and worked in the extrinsic absorption model.At the end of this paper, Ohm contact, one of the key technologies of PCSS fabrication, was discussed with the details of fabrication processing and corresponding parameters based on lateral structure, which could provide some instruction for fabricating the SiC PCSS device.