On the Driving Force of Shockley Stacking Fault Motion in 4H-SiC

Shockley stacking faults (SSFs) are extended, planar defects in silicon carbide SiC that are the cause of the observed drift in the forward voltage that occurs during bipolar injection within both bipolar or unipolar SiC devices. Efforts to understand the primary driving force for SSF nucleation and expansion have been put forth in an effort to eradicate the incorporation of the basal plane dislocations from which the SSFs nucleate and/or to minimize the expansion of the SSFs themselves. Up until recently, the reported driving force models were all based on the hypothesis that SSFs were thermodynamically stable with respect to the 4H-SiC host lattice. Therefore, these prior models focused on explaining the reason for the improved stability of the material in the faulted state. However, annealing 4 and high temperature device operation 5 experiments illustrated that SSFs could be contracted and the Vf drift recovered. The results of these experiments therefore clearly showed that SSFs are not the preferred state of 4H-SiC at thermal equilibrium and T>30C. Here, we introduce and discuss a possible mechanism describing the primary driving force governing SSF expansion and contraction that is consistent with the previously reported experimental observations. Further, we also will present further experimental and simulation results that strengthen support for this model. Finally, we report simulation results that imply SSF-induced degradation of the Vf is due to a reduction in the carrier lifetime within the 3C-SiC material of the SSFs, which act as electron traps within the host lattice material. The model we present builds upon the mechanisms reported by Lambrecht and Miao and Galeckas et al., where the relative energy associated with the filling of the two-dimensional density of states of the SSFs under