Bias and Temperature Dependence of Radiation-Induced Degradation for SiC MOSFETs

The influence of bias and temperature on total ionizing dose (TID) effects are studied for SiC MOSFETs. The TID degradations are manifested as the negative threshold voltage shift and leakage current increase. The radiation-induced positive trapped charge in the gate oxide, but not the interface trap, is the main contributor to the degradation of SiC MOSFET under different bias and temperature conditions. The generation rate and trapping probability of radiation-induced holes under different bias conditions are different, resulting in differences in the severity of TID degradations. A positive gate bias leads to more radiation-induced hole generation in the gate oxide, so worse degradations are observed under positive on bias than the other biases. However, when the gate bias voltage is too high, the probability of radiation-induced holes being captured by trap centers decreases, which in turn leads to smaller degradation. A model considering the generation rate and trapping efficiency of the radiation-induced hole is used to calculate the radiation-induced trapped charge density in the gate oxide. Good agreement is achieved between the measured data and model calculation under different bias conditions. Low-temperature enhanced TID effect is observed for SiC MOSFETs, which is manifested as a larger negative threshold voltage shift at lower temperatures. Temperature primarily affects the TID effect by altering the transport rate of holes in the gate oxide. With the slower transport rate of radiation-induced holes at lower temperatures, some additional holes cannot be removed from the gate oxide after irradiation, ultimately leading to a greater threshold voltage shift.