We report on the molecular beam epitaxy and characterization by X-ray diffraction techniques of GaSb layers grown on silicon substrates. AlSb and Al nucleation layers were used with different thicknesses and growth temperatures. Reciprocal space maps and a modified version of the Williamson-Hall analysis allowed for a characterization of the misfit dislocations properties. Finally, a post-growth annealing step is studied in order to further improve the material quality. Using this technique, a full-width-at-half maximum of the GaSb peak of 235 arc sec was obtained for a layer thickness of 1 mu m, which is comparable to the best results for GaAs or Ge on Si. (C) 2016 Elsevier B.V. All rights reserved.