Formation of composite oxides on III-V semiconductors

A method of forming a composite oxide on III-V compound semiconductors is disclosed. An oxidizable metal such as Al, Ni, Ta, Ti, Zn or alloys including said metals is deposited on the surface of the semiconductor or on a native oxide grown on the semiconductor. The structure is subjected to an electrolytic oxidation so that all the metal is oxidized and a native oxide is grown into the surface resulting in a composite oxide comprising the native oxide and the metal oxide. This composite oxide can serve to passivate the semiconductor as well as provide a stable mask for etching and diffusion processes. In addition, the composite oxide appears to have a high dielectric strength for use in MOS devices.