Interdiffusion in coherent Si0.90Ge0.10/Si0.95Ge0.05 superlattices

This work presents the use of x-ray scattering from Si1-XGeX/Si1-YGeY superlattices as a tool for measuring the concentration dependence of interdiffusivity in Si/SiGe epitaxial thin films. Although x-ray scattering from compositionally modulated films is well established as an ultra-high-sensitivity technique for measuring interdiffusion in a variety of systems, the concentration dependence of Si/SiGe interdiffusion complicates its interpretation. It is shown that these complications can be avoided using Si1-XGeX/Si1-YGeY superlattices with a small compositional modulation. This strategy is assessed using numerical modeling of both interdiffusion and dynamical x-ray diffraction. Its effectiveness is demonstrated by measuring the activation enthalpy and exponential prefactor for interdiffusion in compressively strained Si0.925Ge0.075. The results are 4.38 +/- 0.05 eV and 36 +/- 9 cm(2)/s respectively.