X-ray photoelectron spectroscopy surface oxidation study of remote plasma-enhanced chemical vapor deposition-grown Ge1−xSnx/Si alloys

Abstract

Recent progress in the remote plasma-enhanced chemical vapor deposition of Ge1−xSnx grown directly on Si substrates has improved crystal structure quality. To understand the impact of postgrowth storage, we study oxidation states of Ge1−xSnx alloys, for x values of 7.5%, 8.8%, 12.5%, and 19.3%. A surface oxidation layer formed naturally at room temperature over five months is quantified using angle-resolved x-ray photoelectron spectroscopy. The GeSn alloys exhibit a high surface oxide concentration with a minimum of 77% in Sn 3d peak analysis. Ge is less susceptible to oxidation than Sn, with oxidation percentages ranging from 25% to 86%. The Sn dopant enhances the oxidation features associated with the Ge 3p peak, aiding surface oxidation and penetrating further into the film. It is feasible that the 4+ state Sn from the precursor readily oxidizes postgrowth resulting in an oxide-rich surface layer.