Analysis of strain and mosaicity in a short-period Si9Ge 6 superlattice by x-ray diffraction

Abstract

Triple axis x-ray diffractometry was employed for the structural characterization of a 100 period Si9Ge6 superlattice grown by molecular beam epitaxy on a thick step-graded SiGe alloy buffer. From the distribution of diffusely scattered intensity around reciprocal lattice points the correlation function of the deformation field due to structural defects has been calculated using kinematical theory of x-ray diffraction. From the extension of the correlation function it turns out that on the average the entire superlattice (0.2 μm thick) scatters coherently along growth direction, whereas laterally the coherently scattering regions are extended only over about 40 nm.