  We studied and optimized the molecular beam epitaxy of GaSb layers on vicinal
(001) Si substrates using a GaAs nucleation layer. An in-depth analysis of the
different growth stages under optimized conditions revealed the formation of a
high density of small GaAs islands forming a quasi-two-dimensional layer. GaSb
then nucleated atop this layer as three-dimensional islands before turning to
two-dimensional growth within a few nanometers. Moreover, reflexion high-energy
electron diffraction revealed a fast relaxation of GaAs on Si and of GaSb on
GaAs. The GaSb layer quality was better than that of similar layers grown on Si
through AlSb nucleation layers.
