Epitaxial misorientations in thin films on sapphire were studied. The symmetry theory of line defects at interfaces was used to show that a large number of differing interfacial dislocations was possible. Coordinate transformation matrices were derived, using the 4-vector method for hexagonal crystals, and were used to identify the Burgers vectors of plausible dislocations. A geometrical model was developed which predicted that the dislocations which formed at substrate surface features, due to vicinal off-cut and substrate surface roughness, could lead to a misorientation, of the epitaxial deposit, away from the nominal orientational relationship. An X-ray goniometric method was used to measure the substrate vicinal angle and the misorientation angle of wafers on sapphire. It was found that there was a marked correlation between vicinal angle and misorientation. The data agreed well with the geometrical model.

M.Aindow, R.C.Pond: Philosophical Magazine A, 1991, 63[4], 667-94