High Resolution X-Ray Diffraction Investigations of Si/SiGe Quantum Well Structures and Si/Ge Short-Period Superlattices

Double crystal and triple axis X-ray diffractometry was used to characterize the structural properties of Si/Si$\text{}_{1-x}$Ge$\text{}_{x}$ multiquantum well samples grown pseudomorphically on Si(001) substrates, as well as of short-period Si$\text{}_{9}$Ge$\text{}_{6}$ superlattices grown by molecular beam epitaxy on rather thick step-graded Si$\text{}_{1-x}$Ge$\text{}_{x}$ (0 < x < 0.4, 650 nm thick) buffers followed by 550 nm Si$\text{}_{0.6}$ Ge$\text{}_{0.4}$ layers. Reciprocal space maps around the (004) and (224) reciprocal lattice points yield direct information on the strain status of the layers in the heterostructure systems and in particular on the amount of strain relaxation.