X-ray double-crystal characterization of molecular beam epitaxially grown Si/Si1−xGex strained-layer superlattices

Abstract

We report the first study of Si/Si1−xGex strained-layer superlattices using x-ray double-crystal diffractometry. Symmetric rocking curves (400) were used to determine the structural parameters and strain distribution. All the superlattices were found to have excellent crystalline quality and uniformity both in thickness and alloy composition. Kinematical simulations of rocking curves revealed that most of the misfit between Si and Si1−xGex is accommodated by lattice deformation of the alloy layers. A small tensile strain (∼0.05%) in the growth direction was also found in Si and was attributed to the difference in thermal expansion coefficients of Si and Si1−xGex.