Initial stages of epitaxial growth: GaAs on Si.

We report on investigations of the formation of the first layers of GaAs grown by molecular beam epitaxy on clean Si(111) substrates. First we observe island formation for Ga on As terminated Si (111). The volume rate of growth of the islands is linearely dependent on time, consistent with an Ostwald ripening mechanism i.e. growth of large clusters at the expense of smaller ones which have a larger free equilibrium concentration at their surface.