High Resolution X-Ray Triple Axis Diffractometry of Short Period SimGen Superlattices

Abstract

Double crystal and triple axis X-ray reciprocal space mapping were used to characterize in detail the structural properties of short period Si9Ge6 superlattices grown by molecular beam epitaxy (MBE) on 1.3 µ m thick step-graded SiGe alloy buffers resulting in reduced dislocation densities. Precise strain data were extracted from two-dimensional reciprocal space maps around (004) and (224) reciprocal lattice points (RELP's). From the distribution of diffusely scattered intensity around reciprocal lattice points the correlation function of the deformation field due to structural defects was calculated using a model based on the kinematical theory of X-ray diffraction and on a formalism from statistical optics. Two types of extreme models were defined for the defect structure, and from simulations to the correlation function calculated from the diffuse X-ray scattering (DXS) limiting mosaicity parameters were extracted.