The structure of GaSb layers grown epitaxially onto GaAs(001) substrates was studied using high-resolution X-ray diffraction. Samples with thicknesses of between 9.5 and 284.5nm were grown by metal–organic vapour-phase epitaxy. The large lattice mismatch was largely relaxed by 2 intersecting regular arrays of 90º dislocations, along the [110] and [1¯10] directions. The density of the dislocations changed with the thickness, but the dislocations remained localized at the interface and both the GaSb layers and the GaAs substrates were distorted. The spacing between the dislocations, in both the [110] and [1¯10] directions, decreased while the relaxation increased as the layer thickness increased. The spacing of the dislocations, and the relaxation and residual in-plane strain along the [110] and [1¯10] directions were found, and this revealed a marked asymmetry in dislocation spacing and relaxation between the 2 directions. This was suggested to be because adjacent {110} planes in the zincblende structure were not equivalent. Due to this asymmetry, the structure of the GaSb layers was orthorhombic. Scattering from the thinner (up to 45nm) layers showed that the GaSb grew first in islands, and their size and distribution were different along the [110] and [1¯10] directions. The 60º dislocations in this system appeared only in thick (greater than 120nm) layers, and their density was significantly higher along the [110] direction. The results revealed the power of high-resolution X-ray diffraction for non-destructively studying the growth, relaxation and dislocation structure of thin films and for providing detailed quantitative information concerning the distortions caused by misfit dislocations in epitaxial layers.

X-ray Scattering from Dislocation Arrays in GaSb. A.Y.Babkevich, R.A.Cowley, N.J.Mason, S.Weller, A.Stunault: Journal of Physics - Condensed Matter, 2002, 14[49], 13505-28