Effect of substrate surface structure on nucleation of GaAs on Si(100)

We study the effect of surface structure upon the nucleation of GaAs in molecular beam epitaxy growth on vicinal Si(100) surfaces. In general, cross-sectional transmission electron microscopy reveals that nucleation of GaAs islands is associated with surface steps produced by the deliberate substrate misorientation. Furthermore, it is found that standard in situ cleaning of the Si surface prior to deposition can result in steps grouping together, producing local surface facets. GaAs nucleation then occurs on these facets, the nucleation sites being correspondingly further apart than for an equilibrium distribution of monolayer steps.