Strain mediated reconstructions and indium segregation on InGaAs∕GaAs(001) alloy surfaces at intermediate lattice mismatch

In vacuo scanning tunneling microscopy is used to investigate the surface reconstructions of pseudomorphic InGaAs alloys at intermediate values of compressive strain. The coverage of different reconstructions varies with film thickness, concomitant with changes in composition and strain at the surface arising from In segregation and changes in surface morphology. Thin samples exhibit mainly disordered (1×3) reconstructions along with small regions of incommensurate (1×2). With increasing thickness, the (1×3) transforms into more regular (4×3) or c(4×6), whose coverage mirrors the increase and saturation of In surface composition. Regions of α2(2×4) reconstructions are also present, and their coverage initially increases with In surface composition, but later decreases upon saturation of In at the surface. This decrease is concurrent with the onset of surface roughening, suggesting that the α2(2×4) reconstruction is strain stabilized.