Radiation-Enhanced Dislocation Glide: The Current Status of Research

Abstract

Dislocations in most semiconductors exhibit radiation-enhanced dislocation glide (REDG) which is a cause of serious degradation in bipolar devices under forward biasing. Phenomenologically, REDG is characterized by the remarkable reduction of activation energy for glide velocity and the pre-exponential factor controlled by radiation intensity. Although the REDG shares features common with similar effects in point defects known as the recombination-enhanced defect reaction (REDR) that is well interpreted in terms of the phonon kick mechanism, it is not as yet established whether the REDG and the REDR share or not the same microscopic mechanism due to the lack of knowledge concerning electronic levels associated with the dislocations showing the REDG. Recent progress, however, has been achieved by studies of REDG in 4H-silicon carbide (4H-SiC) in which the dislocation component that exhibits the REDG is identified as 30°-Si(g) partial dislocation. Nevertheless, the driving force for the REDG in 4H-SiC is not the mechanical stress as in usual cases but an anomalous reversal of the sign of the Shockley stacking-fault (SSF) energy depending on the radiation intensity. An attempt was made in our recent experiments of photoinduced REDG to separate the intensity-dependent REDG effect and also the intensity-dependent driving force by simultaneous measurements of SSF expansion velocity (hence, the glide velocity of 30°-Si(g) partials) and the intensity of photoluminescence from the same SSFs (the latter allows us to deduce the driving force for the SSF expansion and hence the REDG). A comment, inspired by the studies of REDG in 4H-SiC, is given also to the mechanism of radiation-enhanced dislocation climb, another cause of degradation induced by minority-carrier injection.