Critical temperature and failure mechanism of SiC Schottky rectifiers in Unclamped Inductive Switching (UIS)

We report measurements of specific avalanche energies as function of time in avalanche, perform thermal analysis and verify the results by temperature-dependent UIS tests. We demonstrate that linear thermal analysis is inaccurate in application to UIS in SiC due to much higher critical temperatures in SiC as compared to silicon. An activation-type dependence with an apparent energy of 1.3 eV is established between time in avalanche and critical failure temperature. The failure mechanism for UIS is shown to be unrelated to electronic instability.