Crystals with [¯1¯1¯1] or [111] orientations were investigated by using 3-crystal X-ray diffractometry. Due to the preparation of the substrate surface and the molecular beam epitaxial growth conditions, a concentration of several ppm of large defect clusters appeared. The defects led to considerable diffuse scattering around the reciprocal lattice points. Even in the case of evaporated molecular beam epitaxial layers with a thickness of only about 300nm, a diffusely scattered intensity could be detected.

R.Bloch, D.Bahr, J.Olde, L.Brügemann, W.Press: Physical Review B, 1990, 42[8], 5093-9