A reduction in the threading dislocation density, due to mutual interactions, was investigated in GaSb thin films which had been grown onto (001) GaAs substrates by means of molecular beam epitaxy. The effectiveness of various buffer layers, including GaSb/AlSb strained-layer superlattices and Ga0.89In0.11Sb/GaAs, for the suppression of threading dislocations was evaluated. High-resolution transmission electron microscopy showed that the GaSb/GaAs interface consisted of a highly periodic network of 90° pure edge misfit dislocations, with an average spacing which was close to that for a fully relaxed system. This led to relatively low threading densities in the GaSb epilayer, in spite of the large lattice-mismatch of 8.2%. The threading dislocation density, as a function of GaSb film thickness, was determined by means of plan-view transmission electron microscopy and was found to decrease with film thickness; due to mutual interactions among dislocations. It was found that a strained-layer superlattice of GaSb/AlSb, within which each layer was close to the critical thickness, was most effective in reducing the threading dislocation density.

W.Qian, M.Skowronski, R.Kaspi: Journal of the Electrochemical Society, 1997, 144[4], 1430-6