We report on the characterization of GaSb layers grown on silicon substrates using an AlSb nucleation layer. In particular, we investigate the influence of the AlSb layer thickness when this nucleation layer is grown at low temperature (400 degrees C). X-ray diffraction techniques, atomic force microscopy and transmission electron microscopy were used to characterize the material properties. We demonstrate that there exists a correlation between the micro-twin density, the surface roughness and the broadening of the x-scan GaSb peaks. Moreover, the AlSb thickness has a strong influence on the micro-twin density, and must be carefully optimized to improve the GaSb quality. (C) 2017 Elsevier B.V. All rights reserved.