The local atomic structure of the oxide coating on polished GaAs(100)

The local atomic structure of the surface oxide on a polished GaAs(100) wafer is investigated using glancing-angle X-ray absorption spectroscopy. Measurements show Ga to be coordinated to oxygen both tetrahedrally and octahedrally while As appears to occupy only tetrahedral sites. Close structural correlation is seen between the second nearest neighbours around Ga and As atoms, indicative of a single phase non-stoichiometric oxide. Depth sensitive measurements reveal the oxide to be about 7 A in thickness with a concentration gradient of As into the surface.