Transmission electron microscopy, high-resolution X-ray diffraction and KOH etching were used to study the dislocation structure of 4H-type crystals which had been grown by means of physical vapour transport. Many of the observed etch pits formed arrays which extended along the <11▪0> and <¯11▪0> directions on (00▪1) wafers. Plan-view conventional and high resolution transmission electron microscopy showed that both types of array consisted of pure edge dislocations which threaded along the c-axis; with identical Burgers vectors of a/3<11▪0> type. The former arrays were suggested to be slip bands which formed via dislocation glide in the slip system, <11▪0>{¯11▪0}, of hexagonal material during post-growth cooling. The latter arrays made up low-angle tilt boundaries with their tilt axis parallel to the [00▪1] direction. It was concluded that such boundaries could form via polygonization of the threading edge dislocations which were introduced by plastic deformation.

Origin of Threading Dislocation Arrays in SiC Boules Grown by PVT. S.Ha, N.T.Nuhfer, M.De Graef, G.S.Rohrer, M.Skowronski: Materials Science Forum, 2000, 338-342, 477-80