Self-Diffusion ofS31iandG71ein RelaxedSi0.20Ge0.80Layers

Self-diffusion of implanted ${}^{\mathrm{31}}\mathrm{S}\mathrm{i}$ and ${}^{\mathrm{71}}\mathrm{G}\mathrm{e}$ in relaxed ${\mathrm{S}\mathrm{i}}_{0.20}{\mathrm{G}\mathrm{e}}_{0.80}$ layers has been studied in the temperature range $730–950°\mathrm{C}$ by means of a modified radiotracer technique. The temperature dependences of the diffusion coefficients were found to be Arrhenius-type with activation enthalpies of 3.6 eV and 3.5 eV and preexponential factors of $7.5\times {10}^{-3}{\mathrm{m}}^2{\mathrm{s}}^{-1}$ and $8.1\times {10}^{-3}{\mathrm{m}}^2{\mathrm{s}}^{-1}$ for ${}^{\mathrm{31}}\mathrm{S}\mathrm{i}$ and ${}^{\mathrm{71}}\mathrm{G}\mathrm{e}$, respectively. These results suggest that, as in Ge, in ${\mathrm{S}\mathrm{i}}_{0.20}{\mathrm{G}\mathrm{e}}_{0.80}$ both ${}^{\mathrm{31}}\mathrm{S}\mathrm{i}$ and ${}^{\mathrm{71}}\mathrm{G}\mathrm{e}$ diffuse via a vacancy mechanism. Since in ${\mathrm{S}\mathrm{i}}_{0.20}{\mathrm{G}\mathrm{e}}_{0.80}$ ${}^{\mathrm{71}}\mathrm{G}\mathrm{e}$ diffuses only slightly faster than ${}^{\mathrm{31}}\mathrm{S}\mathrm{i}$, in self-diffusion studies on Si-Ge ${}^{\mathrm{71}}\mathrm{G}\mathrm{e}$ radioisotopes may be used as substitutes for the “uncomfortably” short-lived ${}^{\mathrm{31}}\mathrm{S}\mathrm{i}$ radiotracer atoms.