OXIDATION MECHANISM OF III-V SEMICONDUCTORS

The room temperature oxidation of GaAs, GaSb, and InP(110) surfaces, with and without photon stimulation, was studied by using Auger electron and X-ray photoemission spectroscopy. The oxidation proceeds in two successive stages. Activated adsorption of approximately one monolayer is followed by a layer-by-layer growth of the oxide. The latter mode is characterized by a logarithmic growth law as a function of exposure, and it may be described by the Mott-Cabrera mechanism, i.e. the oxidation is assisted by an electric field across the growing oxide film. Tunneling of electrons from the valence band through that film into adsorbed oxygen is identified as the rate limiting step since the slopes of the uptake vs exposure curves were found to decrease proportionally to the ionization energies of the respective semiconductors. These data compare well with results of model calculations by Fromhold for the oxidation of metals. © 1990 Pergamon Press plc.