Populations and propagation behaviors of pure and mixed threading screw dislocations in physical vapor transport grown 4H-SiC crystals investigated using X-ray topography

The populations and propagation behaviors of pure and mixed threading screw dislocations (TSDs) in physical vapor transport (PVT) grown 4H-SiC crystals were investigated using X-ray topography. The X-ray topography studies revealed that mixed TSDs, which have a Burgers vector component within the basal plane in addition to thec-component, were dominant in PVT-grown 4H-SiC crystals, even though they have a higher energy contained in the elastic field around them compared to pure TSDs. The studies also revealed that mixed TSDs tended to propagate in a specific direction inclined from thec-axis, whereas pure TSDs were often converted into helical dislocations during the PVT growth. Based on these results, we discussed the nature and propagation behavior of pure and mixed TSDs in PVT-grown 4H-SiC crystals and suggested an importance of the interaction between TSDs and point defects during PVT growth of 4H-SiC.