Bipolar Degradation of 6.5 kV SiC pn-Diodes: Result Prediction by Photoluminescence

The stability of 6.5 kV pn-diodes is dependent on the absence of critical crystal defects, such as basal plane dislocations. In this paper, we present a method to detect these defects on wafer level by utilizing photoluminescence (PL). The PL scan is performed immediately after epitaxy and also after the implantation process steps with subsequent high temperature annealing. The analysis of both scans enables the prediction of devices that will drift due to bipolar degradation, and devices that will exhibit non-drifting behaviour. To validate this PL scanning technique, forward bias electrical stress tests have been performed on the fabricated 6.5 kV pn-diodes.