INSITU STUDIES OF THE ANODIC-OXIDATION OF INDIUM-PHOSPHIDE

The anodic oxidation of indium phosphide has been investigated using ellipsometric measurements. The in situ measurements revealed a two-layer system: an outer indium-rich oxide layer and, close to the substrate, a phosphorus-rich oxide layer. This two-layer composition was obtained with different electrolytes: a complex glycol-based solution and pure water. Considering these experimental results, a tentative explanation for the oxidation mechanism is proposed. The oxide growth is controlled by the drift of ionic species under the electric field. The anodic efficiency, which is defined as the ratio of ionic charge to total charge, is dependent on the barrier height at the electrolyte/oxide interface. Therefore the reduction of the growth rate as the oxidation proceeds is explained by the change in the surface composition.