EFFECTS OF ANNEALING ON ANODIC OXIDES OF GAP

The surface topography and the chemical composition of anodic oxides on GaP have been studied. The surface of the as grown anodic oxide was featureless but annealing at T greater-than-or-equal-to 600-degrees-C causes the formation of hollow bumps and blisters which increase in size with temperature or duration of the anneal. The oxide composition was investigated by x-ray photoelectron spectroscopy (XPS) and was found to be a nonuniform mixture of P2 O5, Ga2 O3, and GaPO4. There is some evaporation of phosphorus oxide near the surface when annealed at T greater-than-or-equal-to 300-degrees-C but little or none from the bulk of the oxide film.