Expansion of Shockley Stacking faults in high doped 4H-SiC epilayers

Shockley Stacking fault (SSF) expansion from basal plane dislocations (BPDs) occurs during forward bias operation in 4H-Silicon Carbide (SiC) and causes forward voltage drift in minority carrier SiC devices [1, 2]. Reverse bias breakdown voltage degradation with SSF expansion has also been reported [3]. The SSFs expansion occurs via the electron-hole recombination enhanced dislocation glide (REDG) process [4]. In order to mitigate the influence of these SSFs in the active drift layer, a high doped buffer layer was grown to convert most of the BPDs to threading edge dislocations (TED) within it. This confines the BPD to the buffer and only the relatively benign TED passes through the drift layer. Previously it was thought that SSF expansion would not occur in these high doped epilayers and propagate into the drift layer. However, this assumption that BPDs within the buffer do not affect the drift layer during carrier injection has not been previously studied. In this work using electron-hole creation by UV excitation, we image the motion and faulting of BPDs buried in the buffer layer and show that SFs originating in that layer expand into the device drift region.