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 91 at. %. The extracted activation enthalpy (3.20 +/- 0.2 eV) 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 < X-Ge >=0.91 superlattice is reasonably consistent with a linear interpolation between the recently reported value for an alloy with < X-Ge >approximate to 0.5 and that reported for self-diffusion in pure Ge. (C) 2008 American Institute of Physics.