Cross-sectional observations of 6H-type samples, on the basal plane, revealed 2 forms of planar defect. One was triangular, while the other looked like a thin rectangle with its long edge parallel to the interface. These defects were related to edge dislocations. Micro-pipes induced planar defects, and the screw dislocations changed into edge dislocations. Consequently, micro-pipes disappeared or shrank. A mixed (6H, 4H, 15R) polytype layer was observed in high N-doped layers. It was possible to decrease the micro-pipe density by means of N incorporation. The fact that other polytypes were observed in highly N-doped layers suggested that polytypes might change easily due to N-doping.

Polytype and Defect Control of Two Inch Diameter Bulk SiC. M.Sasaki, H.Shiomi, H.Harima, S.Nishino: Materials Science Forum, 2000, 338-342, 485-8