The structures of layers of GaSb, grown onto InAs substrates, was investigated by means of high-resolution X-ray diffraction. The samples were grown by using metalorganic vapour-phase epitaxy to produce high-quality monocrystalline layers with thicknesses of between 6 and 300nm. The results showed that the scattering for layers with a thickness below about 125nm was different from the scattering for thicker layers. The scattering from thinner layers showed that the in-plane lattice constant of GaSb was very close to that of the InAs substrate, and that the strain did not vary throughout the film. The measured diffuse scattering was in good agreement with calculations of the scattering from isolated 60º dislocations. The thicker layers exhibited no diffuse scattering but single-Gaussian Bragg peaks and the scattering was that expected from a mosaic layer with a large concentration of 60º dislocations. Analysis of the peak parameters showed that the average in-plane lattice constant was intermediate between those of bulk GaSb and bulk InAs and that there was a changing strain throughout the film. The critical

thickness for GaSb on InAs was calculated to be about 20.4nm. It was argued that, between 20.4 and 125nm, there were only a few dislocations. Thicker films were relaxed by the spontaneous creation of a dislocation network. The results demonstrated the power of high-resolution X-ray scattering for the non-destructive study of the structures of thin films which contained dislocations, and showed that there was a marked change in the scattering for layers of above the critical thickness.

X-Ray Scattering from Epitaxial GaSb/InAs Thin Films below and above the Critical Thickness. A.Y.Babkevich, R.A.Cowley, N.J.Mason, S.Sandiford, A.Stunault: Journal of Physics - Condensed Matter, 2002, 14[28], 7101-21