Oxide layers on GaAs prepared by thermal, anodic and plasma oxidation: In-depth profiles and annealing effects

Abstract

The in-depth profiles of oxide layers prepared by thermal, anodic or plasma oxidation were investigated by means of simultaneous Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS) measurements. With the AES measurements it was found that the oxides grown by thermal oxidation consisted only of Ga 2O 3; a large pile-up of arsenic was found near the interface between the oxide layer and the substrate. In contrast, oxides formed by anodic and plasma oxidation contained both Ga 2O 3 and As 2O 3 and showed a much smaller pile-up of arsenic. The annealing of as-grown oxide layers at relatively low temperatures (around 300°C) caused the oxide composition to become more uniform with depth and made the interface thinner. Annealing at relatively higher temperatures gave rise to a deficiency of arsenic in the oxide and created a pile-up of arsenic near the interface. Preliminary X-ray photoelectron spectroscopy measurements revealed the presence of unoxidized arsenic in the sputterer surfaces of anodic and plasma oxides. The SIMS measurements revealed that the relative intensity of the secondary ions varied in a complicated way in the oxide and near the interface, where no appreciable changes in composition were observed by AES. The SIMS results suggest the existence of different oxides having different physiochemical properties; these differences probably alter the ionization yield and/or the process of emission of the secondary ions.