Diffusion of Ge in SiGe alloys

Abstract

Germanium diffusion was measured in SiGe alloys of 100/0, 77.6/22.4, 69.2/30.8, 44.6/55.4, and 22.3/77.7 silicon to germanium atomic-percent ratios by the use of the radioisotope ${}_{}{}^{71}{}_{}{}^{}\mathrm{Ge}$ and a thin-sectioning technique. As expected from the calculated, small, strain-energy contributions from the ${}_{}{}^{71}{}_{}{}^{}\mathrm{Ge}$ impurities, the diffusion is similar to silicon self-diffusion for the silicon end member. Since the results fit an Arrhenius plot for the compositions and temperature ranges studied, activation energies and pre-exponentials were determined. These diffusion parameters indicate that the ${}_{}{}^{71}{}_{}{}^{}\mathrm{Ge}$ diffusion is compatible with the monovacancy mechanism up to 70-at.% silicon in the SiGe alloys. For more silicon-rich material, the diffusion is quite analogous to the extended-defect mechanism previously suggested for high-temperature silicon self-diffusion.