Effects of Ge concentration on SiGe oxidation behavior

Abstract

The oxidation of SiGe layers grown by molecular beam epitaxy was studied. Auger depth profile showed that after oxidation, Ge was completely rejected from the oxide and Ge-rich layers were formed. However, the Ge concentration in the SiGe layer was found to play an important role in the formation of these Ge-Rich layers. For SiGe with Ge concentration below 50%, Si was preferentially oxidized and only one Ge-rich layer was formed at the oxide/substrate interface. On the other hand, for SiGe with Ge concentration above 50%, two Ge-rich layers were formed after oxidation with one at the oxide/substrate interface and the other at the oxide surface. X-ray photoelectron spectroscopy studies showed that Ge at the oxide/substrate interface is in elemental form, while Ge at the oxide surface is in an intermediate oxidized state. A classical binary alloy oxidation theory is employed to explain the overall oxidation behavior qualitatively.