The segregation and diffusion of Au are examined during ion‐beam‐induced solid phase epitaxial crystallization of Au‐implanted amorphous silicon layers. Epitaxy was induced at temperatures as low as 220 °C by irradiation with 1.5 MeV Ar ions. At these temperatures Au is segregated to form a narrow layer at the moving crystal/amorphous interface. The size of the segregated layer depends on the velocity of the interface compared to the Au diffusivity in amorphous Si. The growth rate for ion‐beam‐induced epitaxy is found to be independent of Au concentration and near‐complete epitaxial crystallization of the amorphous layers can be achieved, even for Au concentrations ∼2 at. %.