Effects of 5 MeV proton irradiation on 4H-SiC lateral pMOSFETs on-state characteristics

Abstract

Silicon carbide (SiC) MOSFETs are often used in harsh environments where they are exposed to ionizing radiation. This paper investigates the effects of high-energy proton irradiation on SiC MOSFETs, with a particular emphasis on the on-state characteristics of lateral pMOSFETs. By comparing with the lateral 4H-SiC nMOSFET after irradiation in our prior work, we observed the deviations of important electrical parameters. As the irradiation dose increases, the threshold voltage (VTH) of pMOSFETs is negatively shifted and has more negative offsets than that of nMOSFETs. This is due to two factors which affect VTH after irradiation: the near interface oxide traps (NIOTs) and the interface traps (Nit). These two factors compensate each other for nMOSFETs, but strengthen each other for pMOSFETs. It is found that an increase in the density of interface traps (Dit) in both types of MOSFETs after irradiation. However, unlike the nMOSFET, the pMOSFET has a decreasing field effect mobility (μFE) with the increase of irradiation dose. We believed that besides the effect of Dit on μFE, NIOTs have a more profound influence on μFE, resulting in different changes between nMOSFETs and pMOSFETs’ μFE.