Theoretical analysis of short-circuit capability of SiC power MOSFETs

The short-circuit capability of Si power devices, defined in terms of critical energy density, is the product of the heat capacity in the heat generation region and the increase in temperature. However, for SiC power devices, the heat generation region is significantly smaller than that for Si power devices, because the drift-region thickness is about 10 times less in SiC power devices. Therefore, the formulae used for Si devices are not directly applicable to SiC devices. In this study, analytical formulae are derived for the short-circuit capability of a SiC power device and its dependence on the ambient temperature and the thickness of the n− drift region, on the basis of the thermal diffusion equation. The calculated results are found to be in good agreement with those of direct measurements.