Two possible nucleation mechanisms for threading edge and screw dislocations during physical vapour transport growth were investigated. Growth over intentionally deposited C inclusions led to edge and screw dislocation densities which were orders of magnitude higher than those in the surrounding crystal. Seeds which exhibited mechanical polishing damage were shown to lead to a dislocation density which was nearly 3 orders of magnitude higher than that in seeds that were H-etched. A new linear step source was observed and was correlated with an increase in the dislocation density. The seed-surface quality before growth was directly related to the dislocation density in the physical vapour transport-grown material. Second-phase precipitates on the seed growth surface led to the nucleation of both screw dislocations and threading edge dislocations. This formation appeared to involve the nucleation of SiC islands on top of second-phase material. There was also a direct relationship between the surface polish and the dislocation density. The use of H-etching removed this damage and thus lowered the dislocation density. When the seed surface was cleaned, and the damage removed, the main step-source was related to a newly discovered defect. Long narrow defects which were aligned along <11▪0> directions acted as step sources and were related to increased populations of both threading edge and screw dislocations.

Nucleation of Dislocations during Physical Vapor Transport Growth of Silicon Carbide. E.K.Sanchez, V.D.Heydemann, D.W.Snyder, G.S.Rohrer, M.Skowronski: Materials Science Forum, 2000, 338-342, 63-6