The intrinsic As diffusion properties have been determined in relaxed ${\mathrm{Si}}_{1-x}{\mathrm{Ge}}_x$ epilayers. The properties were studied as a function of composition x for the full range of materials with $x=0,$ 0.20, 0.35, 0.50, 0.65, 0.8, and 1. The activation enthalpy $E_a$ was found to drop systematically from 3.8 eV $\mathrm{}(x=0\mathrm{})\mathrm{}$ to 2.4 eV $\mathrm{}(x=1\mathrm{}).$ Comparisons with other impurity atom- and self-diffusion results in Si, Ge, and SiGe show that both interstitials and vacancies contribute as diffusion vehicles in the composition range $0<~x<~0.35$ and that vacancy mechanism dominates diffusion in the composition range $0.35<x<~1.$

• Received 27 May 2003

DOI:https://doi.org/10.1103/PhysRevB.68.155209