Radiation Response of Negative Gate Biased SiC MOSFETs

Silicon carbide (SiC) metal-oxide-semiconductor field effect transistors (MOSFETs) are expected as power electronic devices for high radiative conditions, including nuclear plants and space. Radiation response of commercial-grade prototype SiC MOSFETs with applying the gate bias is of interest, in terms of installation of the device in robots or sensors working under such radioactive circumstances. Due to gamma-rays irradiation, the threshold voltages (V_th) of samples with un- and negative-biased up to -4.5 V slightly shift toward the negative voltage side. In contrast, the positive bias of 2.25 V shifts V_th more negatively. Positive charge densities trapped in the gate oxide of un- and positive-biased samples increased with increasing dose. However, no significant increase was observed for negative-biased samples of -2.25 and -4.5 V. We calculated characteristic parameters for the accumulation of holes in the gate oxide, σ_pJ_p which is defined as the product of current density due to holes generated by irradiation and capture cross section for a hole in a trap, and it is lower for these negative biased samples compared with the unbiased case. Application of appropriate negative gate biases to SiC MOSFETs during irradiation suppresses accumulation of positive charges in the gate oxide and negative shift of V_th, due to irradiation.