Strain relief at the GaSb/GaAs interface versus substrate surface treatment and AlSb interlayers thickness

Using transmission electron microscopy we investigate the influence of AlSb monolayers and substrate surface preparation on the microstructure of GaSb grown on GaAs (001) by molecular beam epitaxy. The geometric phase analysis method is used to analyze the interface dislocation type and the residual strain, as well as the dislocation core behavior versus the thickness of the AlSb interface layer. A quantitative measurement of the local Burgers vectors shows that the misfit dislocations at the GaSb/GaAs interface are always 60 degrees dislocations. They are arranged in pairs which are more or less distant. For the samples with the lower threading dislocation density, the average distance between the 60 degrees pairs is smaller, the interface is flatter and the local strain is more relieved. These results show that understanding the atomic structure of interfaces may be of great help in improving the quality of GaSb grown on GaAs substrates. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3532053]