Composition and band structure of the native oxide nanolayer on the ion beam treated surface of the GaAs wafer

Detailed information on GaAs oxide properties is important for solving the problem of passivating and dielectric layers in the GaAs-based electronics. The elemental and chemical compositions of the native oxide layer grown on the atomically clean surface of an $n$-GaAs (100) wafer etched by Ar$^+$ ions have been studied by synchrotron-based photoelectron spectroscopy. It has been revealed that the oxide layer is essentially enriched in the Ga$_2$O$_3$ phase which is known to be a quite good dielectric as compared to As$_2$O$_3$. The gallium to arsenic ratio reaches the value as high as [Ga]/[As] = 1.5 in the course of oxidation. The Ga-enrichment occurs supposedly due to diffusion away of As released in preferential oxidation of Ga atoms. A band diagram was constructed for the native oxide nanolayer on the $n$-GaAs wafer. It has been shown that this natural nanostructure has features of a $p$–$n$ heterojunction.