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

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).