We have studied the kinetics and mechanism of oxidation of SiGe alloys deposited epitaxially onto Si substrates by lowhyphen;temperature chemical vapor deposition. Ge is shown to enhance oxidation rates by a factor of about 3 in the linear regime, and to be completely rejected from the oxide so that it piles up at the SiO2/SiGe interface. We demonstrate that Ge plays a purely catalytic role, i.e., it enhances the reaction rate while remaining unchanged itself. Electrical properties of the oxides formed under these conditions are presented, as well as microstructures of the oxide/substrate, Gehyphen;enriched/SiGe substrate, and SiGe/Si substrate interfaces, and xhyphen;ray photoemission studies of the early stages of oxidation. Possible mechanisms are discussed and compared with oxidation of pure silicon.
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