Spatial distribution of In during the initial stages of growth of InAs on GaAs(001)-c(4x4)

The initial stages in the growth of InAs by molecular beam epitaxy (MBE) on GaAs(001)-c(4x4) have been studied by in situ scanning tunnelling microscopy (STM) and reflection high energy electron diffraction (RHEED). Deposition of 0.1 ML at 420 degrees C gives rise to a low number density of two dimensional (2D) islands on top of domains of locally disordered (1 x 3) structures which decorate the step edges. The size of the (1 x 3) domains increase as more InAs is deposited, consistent with the development of a (1 x 3) RHEED pattern. The results show that a 2D growth mode operates with strong evidence for alloying in the surface layer. The spatial distribution of In in the surface layer has also been investigated by varying the substrate temperature for InAs deposition. The implication is that growth at similar to 420 degrees C provides the optimal condition for growing high quality InAs monolayers on GaAs(001).