Real atomic structures on the GaAs(001) surface grown by molecular-beam epitaxy

Abstract

The techniques of scanning tunnelling microscopy and reflection diffraction of fast electrons have been used for the study of atomic structures on GaAs(001) surfaces grown by molecular beam epitaxy (MBE). The phases (2×4)-α, β, γ and c (4 × 4) are formed on the GaAs(001) surface with the As coating of the various thickness. It has been shown that the phases (2 × 4)-α, β and γ are based on the same unit structure in the surface layer consisting of two As dimers and a pair of As dimer vacancies. The structure model of the As-enriched GaAs(001) surface has been proposed. Phases (4 × 2) and (4 × 6) have been studied on Ga-enriched GaAs(001) surfaces. The unified model, according to which the (4 × 2) phase consists of two Ga dimers in the upper layer and one Ga dimer in the third layer, and the (4 × 6) phase is situated in agreement with periodically arranged Ga clusters in the corners of unit cell, has been proposed.