Selective electron beam irradiation of high purity semi-insulating 4H silicon carbide substrates to characterize the effects on photoconductive semiconductor switch operation

High energy electron beam irradiation of bulk SiC creates crystal defects within the material which act as deep traps. These deep traps capture charge carriers and in turn increase the resistivity/blocking voltage of SiC photoconductive semiconductor switches (PCSS). Irradiation has been shown to increase the blocking field of a vertical SiC PCSS to 705 kV/cm when the entire sample region is irradiated with a 1×10¹⁸ cm^-2 fluence from a 1 MeV electron beam. This paper investigates selectively irradiating specific regions of a SiC PCSS gap to characterize the effects on DC operation. Lateral switches were fabricated on a high-purity semi-insulating 4H-SiC sample and subsequently irradiated to form three sample types of differing irradiation regions. The selectively irradiated regions are: 1) mid-gap, 2) both contact-gap interfaces, and 3) a single gap-contact interface used for both anode and cathode testing configurations depending upon the polarity of the applied voltage.