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New type of defects in SiC grown by the PVT method

The quality of SiC crystals grown by the physical vapour transport (PVT) method was studied by means of optical microscopy and scanning electron microscopy (SEM) observations with the aid of etching by molten KOH. New types of defects were found, including triangular etching pits, shallow hexagonal etching pits and dendritic silicon inclusions in 4H-SiC. The triangular etching pits usually appear on the C face with a size comparable with the irregular dark etching pits due to the micropipes, while the shallow hexagonal etching pits were observed on the Si face with a size comparable with that due to the micropipes. The silicon inclusions exhibit dendritic shape up to several microns like those usually observed in metal alloys. In addition, 4H-SiC and 6H-SiC domains with different polarities in the growth surface were found to develop from the same seed. The interface of 4H-SiC and 6H-SiC was one of the sources for inducing the micropipes.