Observation and modeling of the initial fast interdiffusion regime in Si/SiGe multilayers

X-ray diffraction is used to probe interdiffusion in asymmetrically strained, low concentration Si/SiGe superlattices. The results are shown to be in good agreement with a model developed from literature data for Ge diffusion in SiGe alloys. Using this model, it is shown that the initial fast interdiffusion frequently observed in Si/SiGe superlattices results primarily from the concentration dependence of the activation enthalpy for SiGe interdiffusion. Time dependent strain relaxation is shown to play a discernible, but secondary role in the transition from fast to slow interdiffusion. The linear proportionality constant relating the activation enthalpy of SiGe interdiffusion to biaxial strain is found to be similar to19 eV/unit strain. (C) 2002 American Institute of Physics.