Degradations of Gamma-Irradiated SiC MOSFETs Under Repetitive Short-Circuit Stress

SiC MOSFETs are expected to be exposed to irradiation when applied in harsh environments such as space. Therefore, it is important to understand the ionization radiation effects on the short-circuit (SC) reliability of SiC MOSFETs. In this work, the degradation modes and degradation mechanisms in the atomic scale of Gamma-irradiated SiC MOSFETS under repetitive short-circuit stress are investigated. Compared to single-stress scenarios, the synergistic effect of irradiation and short-circuit stress significantly accelerates the negative shift of threshold voltage of irradiated devices and thus results in the degradations of switching performances. The cyclic SC stress results in the dominate hole trapping in the oxide over the annealing of active oxide defects from the self-heating. The Electro-thermal simulations and Hybrid-functional density functional theory (DFT) calculations are performed and demonstrate that the hole injection into the oxide and the subsequent hole trapping by electrically active oxygen vacancies (VO) are main cause for the enhanced formation of positively charged oxide-trap after irradiation and SC stress, where the irradiation and repetitive SC stress promote the structural transformation of VO and hole trapping of VO by overcoming the thermal barrier, respectively.