Mechanism of oxide film growth on GaAs by plasma anodization

Abstract

The transport of oxygen in the oxide during anodization in oxygen plasma has been investigated using isotopic oxygen. The in-depth profiles measured by IMA for samples anodized in 16O2 and 18O2 indicates that oxygen does not move in the oxide. The growth rate K, which is limited by drift of ionic sites in the oxide, is represented by K=K0exp[−(q/kT)(Wi−ZbEox)] and the values of Wi and Zb have been obtained to be 1.5 ± 0.5 eV and 44 ± 16 Å, respectively, from the dependence of the growth rate and the electric field intensity in the oxide, Eox, on the current density and the substrate temperature during anodization. The current efficiency in anodization is independent of the oxidation time and the current density, but it increases with the substrate temperature and the electron temperature of the plasma. By the relationship between the growth rate and the plasma conditions, it has been concluded that oxidants are supplied from the plasma in the form of neutral atoms, and adsorbed oxygen atoms are ionized by electrons.