On the driving force for recombination-induced stacking fault motion in 4H-SiC

The formation and expansion of recombination-induced stacking faults (SFs) within 4H-SiC bipolar and unipolar devices is known to induce a drift in the forward voltage during forward bias operation. This drift renders devices unsuitable for commercial applications. While the expansion of SFs in 4H-SiC occurs by the recombination-enhanced dislocation glide mechanism, why SF expansion occurs, i.e., the energetic driving force, remains unclear. Recent experiments have revealed that SF contraction and a recovery of the forward voltage drift can be induced under many conditions, including forward bias operation. Such observations have enabled the identification of SF-related degradation in devices where imaging methods are not possible and are inconsistent with the previously reported energetic driving force models. We present a model that qualitatively explains these recent experimental observations, which is based on the quasi-Fermi energy of the electron population during forward bias operation. Device simulation results and further experiments are also reported in support of this model. [doi:10.1063/1.3467793]