Characteristic features of surface-damage related threading dislocations in epitaxial layers were investigated by means of transmission electron microscopy. It was found that most of the observed threading dislocations were of perfect edge-type, with line directions along [00▪1] and a Burgers vector of a/3<11▪0>. The edge dislocations were arranged in the form of cellular structures, with cell walls that were aligned preferentially along <1¯1▪0> directions. Small isolated cells were also observed in areas of lower dislocation density. The density of elementary screw dislocations in the overgrowth was about 105/cm2, and was some 2 orders of magnitude lower than the edge dislocation density. The screw dislocations appeared in pairs, with opposite-sign Burgers vectors, separated by about 0.3µm. The formation of threading dislocations was associated with sub-surface damage caused by plastic deformation during mechanical polishing.

Surface-Damage-Induced Threading Dislocations in 6H-SiC Layers Grown by Physical Vapor Transport. J.Q.Liu, E.K.Sanchez, M.Skowronski: Journal of the Electrochemical Society, 2003, 150[3], G223-7