Dynamic Degradation of Planar-Gate SiC MOSFETs After Total Ionizing Dose Radiation

SiC MOSFETs are increasingly gaining attentions from aerospace industry due to their superior radiation tolerance and low loss. The influences of total ionizing dose (TID) radiation on static characteristics of SiC MOSFETs have been extensively studied in recent years. However, the influence on their switching behaviors has seldom been comprehensively studied yet. In this article, we comparatively studied the switching characteristics of SiC MOSFETs pre and after <tex-math notation="LaTeX">γ</tex-math> -ray radiation. It is observed that their turn-on time and turn-on loss ( <tex-math notation="LaTeX">E_ON)</tex-math> decrease by 12.78% and 9.19%, and turn-off time and turn-off loss ( <tex-math notation="LaTeX">E_OFF)</tex-math> increase by 15.92% and 20.79%, respectively, after 500-krad radiation under gate bias ( <tex-math notation="LaTeX">VGS</tex-math> <tex-math notation="LaTeX">$=$</tex-math> 15 V and <tex-math notation="LaTeX">VDS</tex-math> <tex-math notation="LaTeX">$=$</tex-math> 0 V), while they are 9.91%, 13.31%, 14.87%, and 28.51% with the same tendency after 500-krad radiation under drain bias ( <tex-math notation="LaTeX">VGS</tex-math> <tex-math notation="LaTeX">$=$</tex-math> 0 V and <tex-math notation="LaTeX">VDS</tex-math> <tex-math notation="LaTeX">$=$</tex-math> 400 V). The compensation effect of <tex-math notation="LaTeX">Δ E_ON</tex-math> and <tex-math notation="LaTeX">Δ E_OFF</tex-math> is beneficial to power electronic systems from thermal budget point of view. Further investigation indicates that the negative shift of threshold voltage and increment in parasitic capacitances, both of which are induced by accumulation of positive charges in gate oxide, should be responsible for dynamic degradation of SiC MOSFETs after <tex-math notation="LaTeX">γ</tex-math> -ray radiation. Besides, TCAD simulation reveals that the differences in electric field magnitude and distribution under <tex-math notation="LaTeX">VGS</tex-math> and <tex-math notation="LaTeX">VDS</tex-math> bias could be the physical mechanism for their different radiation responses. These results provide fundamental knowledge to predict radiation reliability of SiC MOSFETs through switching parameters.