Silicon-germanium interdiffusion in high-germanium-content epitaxial heterostructures

We report on multilayer x-ray reflectivity measurements of the Si–Ge interdiffusivity in epitaxial SixGe1−x∕SiyGe1−y superlattices that have an average Ge composition of 91at.%. The extracted activation enthalpy (3.20±0.2eV) is substantially smaller than that previously reported for Si-rich SiGe alloys and the interdiffusivity value at typical dopant anneal temperatures is, therefore, much larger for the Ge-rich heterostructures. The activation enthalpy for interdiffusion measured for the ⟨XGe⟩=0.91 superlattice is reasonably consistent with a linear interpolation between the recently reported value for an alloy with ⟨XGe⟩≈0.5 and that reported for self-diffusion in pure Ge.