NONDISRUPTIVE OXIDE OVERLAYER GROWTH ON GAAS(110)

Three different ways of forming oxide overlayers on GaAs(110) have been examined with x-ray photoemission. First, Cr atoms were deposited onto cleaved GaAs(110) at 300 K, producing a disrupted region over which Cr metal grew. Subsequent exposure to O2 resulted in an inhomogeneous overlayer with areas of thick Cr2O3-like oxides in addition to As and Ga oxides. GaAs oxidation was enhanced by Cr-induced surface disruption, but there was no evidence of a catalytic process. Second, metallic clusters of Cr containing hundreds of atoms were condensed onto GaAs(110). In this case, no substrate disruption was observed at low temperature. O2 exposure resulted in Cr2O3 formation with small amounts of Ga2O3 and no detectable As2O3. Third, Cr atoms and O2 molecules were condensed onto a Xe buffer layer on GaAs(110) to produce Cr2O3-like species out of contact with the semiconductor. Buffer layer desorption brought these Cr2O3 aggregates into contact with the substrate. The overlayer produced in this manner was abrupt, and there was no evidence of GaAs oxidation.