Micro-twinning in (111) epitaxial films was studied by using X-ray diffraction methods. The films had been grown onto (00•1) sapphire substrates by means of metalorganic chemical vapor deposition. It was found that the concentration of twins was high at points near to the interface, but fell off rapidly with distance. In the case of films with thicknesses of up to about 0.01mm, the micro-twin density was constant at less than 1vol%, at points away from the interface. In the case of films with thicknesses that were greater than 0.01mm, there was a marked increase in the micro-twin content. These micro-twins were located at points that were close to the film surface.

H.L.Glass, M.R.A.Woods: Applied Physics Letters, 1992, 60[21], 2619-21