Seed surface orientation dependence of the defect formation at the initial stage of physical vapor transport growth of 4H-SiC crystals

The influence of the seed crystal surface orientation on the defect formation at the initial stage of physical vapor transport (PVT) growth of 4H-SiC crystals was investigated using X-ray topography and Raman scattering microscopy. To examine the detailed influence of the seed surface orientation, a seed crystal having a groove on the growth surface was used for PVT growth; the seed crystal with a groove provides a continuously varying seed surface orientation from (0 0 0 1¯) (on-axis c-face growth) to (1 1 2¯ 0) (a-face growth), and using the seed crystal, the effect of the seed surface orientation can be examined in a single growth experiment. X-ray topography observations revealed that a number of threading screw dislocations (TSDs) were formed at the bottom corners of the groove, while their formation was largely suppressed at the bottom of the groove, indicating that an off-oriented (0 0 0 1¯) seed crystal surface tends to generate TSDs. Characteristic dopant striations were also observed in the crystal portions grown on the off-oriented seed crystal surface, and the generated TSDs were found to propagate along the boundaries of these dopant striations. Based on these results, we discuss the TSD formation mechanism on an off-oriented (0 0 0 1¯) seed crystal surface at the initial stage of PVT growth of 4H-SiC crystals and suggest an important role of macrostep formation on the surface.