The dissociation modes of threading screw dislocations in 4H-SiC

Abstract

In 4H-SiC, which is currently considered as a most promising candidate for the power devices, four types of threading dislocation (TD) have been identified. Apart from a threading edge dislocation with b = a, it has been shown recently that there are at least three types of TDs whose Burgers vectors b are parallel or nearly parallel to the c axis, i.e. a threading pure screw dislocation (TpSD) with b = [0001], a threading near screw dislocation (TnSD) with and a threading mixed dislocation (TMD) with . These dislocations have been called simply as threading screw dislocations (TSDs). Since the total Burgers vector, and hence the energy, increases in the order of TpSD, TnSD and TMD, it is expected that the occurrence should decrease in the order of TpSD, TnSD and TMD. This is not the case. The reason why high-energy TnSD and TMD are as abundant as low-energy TpSD has been discussed based on the dissociation models. As a result of dissociation, the difference of energy among these three types of TSD is reduced considerably.