Boron diffusion ininsitudoped Si1−xGexand Si, subjected to inert‐ambient furnace annealing at 800 °C, was investigated. For Si1−xGex, the effect of biaxial compressive and tensile strain on boron diffusion was studied using Si1−xGexlayers with a constant Ge content (x≊0.10 andx≊0.20) grown epitaxially on various relaxed Si1−yGey(0≤y≤0.20) substrates. Boron diffusion is primarily a function of Ge content,xin the Si1−xGexlayers, and does not show a strong dependence on macroscopic biaxial strain. For Si, the effect of biaxial tension was investigated using relaxed Si1−yGeylayers as substrate templates for epitaxial Si layers. As in Si1−xGex, boron diffusion in Si does not depend strongly on biaxial strain. ©1995 American Institute of Physics.