The initial oxidation of sputter etched AlxGa1−xAs(100) surfaces investigated by soft x-ray photoelectron spectroscopy

Abstract The chemisorption of oxygen at exposures of up to 10 9 L on ion-bombarded Al x Ga 1− x As(100) surfaces was studied at room temperature. Core level shifts and intensity ratios of the spectra of ZrMζ (151.4 eV) excited photoelectrons were used to describe the oxide growth on samples with different x values. The formation of aluminum oxide begins already at low exposures of unexcited oxygen. At higher exposures an outdiffusion of aluminum takes place. It depends on the x value of the substrate and determines the further oxide growth. After 10 9 L oxygen exposure the sample surfaces were covered by a compact aluminum oxide surface layer. As a consequence of the preferential interaction of oxygen with group III atoms elemental arsenic appears. Experiments with excited oxygen show a strong increase in the oxidation rate, particularly in the case of aluminum atoms.