Atomic geometry of Al−GaAs interfaces: GaAs (110)–p(1 × 1)–Al(ϑ), 0?ϑ?8.5 monolayers

Abstract

The atomic structure of Al on GaAs(110) is studied by soft x-ray photoemission spectroscopy (SXPS) and elastic low energy electron diffraction (ELEED) for coverages ranging from 0.5 to 8.5 monolayers (ML). The core level measurements show a heat-induced chemical shift of Al–2p to higher binding energy consistent with an Al–Ga replacement reaction and the formation of AlAs, and a decrease in emission from Al–2p and Ga–3d, indicating a penetration of Al in the lattice and thermal desorption or formation of islands of Ga freed by the replacement reaction. The ELEED multiple scattering analysis yields a correspondence between the initial experimental coverage and the structure of the interface. The low coverage (0.5–1.0 ML) data are best described by a replacement of Ga in the second layer, the medium coverage (1.5–2.5 ML) data by a replacement in the second and third layers and the high coverage (5.5–8.5 ML) data by replacing Ga in all layers (pure AlAs).