Temperature Dependence of Shockley Stacking Fault Expansion and Contraction in 4H-SiC p-i-n Diodes

The nucleation and expansion of Shockley stacking faults (SSFs) in 4H-SiC is known to induce an increase in the forward voltage drop (V-f) of bipolar devices such as pin diodes. However, recent annealing experiments have shown that SSFs can not only expand, but that low temperature annealing (210-700 degrees C) induces a contraction of the SSFs that is coupled with a full and repeatable recovery of the V-f drift. Here we report that following extended periods of forward bias operation that the V-f drift of 10kV 4H-SiC pin diodes saturates, with the saturation V-f drift dropping with increasing stressing temperature. Upon reaching saturation, increases in temperature during forward bias operation at the same injection conditions also lead to a partial recovery of the V-f drift. Furthermore, the magnitude of this current-induced recovery is dependent upon the injection current, as reductions in the current cause a slower, but larger overall V-f drift recovery. All of these results clearly indicate that the current driving force models for SSF expansion are either incomplete or incorrect and that further efforts are required for a more complete understanding of SSF dynamics to be obtained.