GAAS FORMATION BY REDUCTION OF AS2O3 AND GA2O3 AT SIO2 GAAS OXIDES/GAAS INTERFACES/

SiO2/GaAs interfaces have been obtained by deposition of Si on oxidize d GaAs(110) surfaces, with the reduction of As and Ga oxides to form S i oxide. High resolution photoemission studies have been performed to elucidate the chemical state of the atoms liberated from the oxide. Th e reduction of As oxides, faster than that of Ga oxides, produces an A s enrichment at the interface, that creates deviations from GaAs stoic hiometry. This As excess appears in the high resolution spectra as a c omponent with an energy shift between 0.45 and 0.65 eV from the GaAs s ubstrate signal. Subsequent reduction of Ga oxides produces the decrea se of the component related to As excess. In any stage of the process no segregation of Ga appears from the spectra. Finally the As-excess c omponent vanishes, showing that it reacts with the liberated Ga atoms to form again GaAs. A quantitative analysis of the photoemission inten sities has allowed the establishment of a structural model of the atom ic arrangement during the chemical changes.