GROWTH OF ANODIC AL2O3/NATIVE OXIDE DOUBLE-LAYERS ON INP

Models of the controlling mechanisms of anodic growth of native oxides under an anodized Al film on InP are presented. These models for constant current anodization use charge flow over and through the oxide-InP interfacial energy barrier to explain the observed oxide growth behavior. They account for changes in the interfacial barrier height due to variations in substrate doping type and concentration and for changes in illumination conditions. For anodization to proceed on low-doped n-type InP, holes must be generated by either impact ionization or illumination. With low-doped p-type, the interfacial barrier must be reduced by applying an overvoltage or creating energetic carriers with illumination. Increasing the doping concentration reduces the barrier to current flow; thus, neither illumination or increased voltage is required.