Influence of chemical character on GaAs(111) surface reconstruction

Abstract

A surface reconstruction model is presented for GaAs(111)A and B surfaces. The surface reconstruction mechanism is investigated using ab initio Hartree–Fock molecular-orbital calculations. Two model clusters, H3Ga3As3H6 and H6Ga3As3H3, are used to reveal different lateral interactions in the vicinity of the first biatomic surface layer for GaAs(111)A and B surfaces. Lateral interactions originating from the site specific atomic character (Ga/As) are shown to determine the Ga—As—Ga and As—Ga—As bond angles, which differ significantly from those for bulk GaAs. This causes each of the three surface nearest-neighbor Ga (As) atomic rings to become considerably larger (smaller) than the three nearest-neighbor As (Ga) atomic rings lying beneath them. The propagation of such lateral interactions across the surface explains a fundamental inability of Ga (As) -terminated surfaces to match to respective underlying As (Ga) atomic layers, providing the driving force for Ga (As) atom removal from Ga (As) -terminated (111) surfaces. Changes in surface reconstruction are thus attributed to this lateral interaction. It is shown how the 2×2 {2×2, √3×√3, 3×3, and √19 ×√19} reconstructed phases of Ga {As} -terminated surfaces depend on this lateral interaction. Our models for GaAs(111)A and B surface reconstruction are shown to be applicable to the polar surfaces of other III-V compound semiconductors.