Kinematical simulation of high-resolution x-ray diffraction curves of Ge sub x Si sub (1-x) /Si strained-layer superlattices: A structural Assessment.

High-resolution X-ray diffraction (HRXRD) measurements of Ge sub x Si sub (1-x) /Si strained-layer superlattices were carried out using a four-crystal monochromator. A wide asymmetric range of extremely sharp higher order X-ray satellite peaks were observed indicating well-defined strained-layer superlattices with abrupt interfaces. This was further confirmed by cross- section transmission electron microscopy. Using a kinematical diffraction step model which assumes ideally sharp interfaces, the thickness, strain and composition of the Ge sub x Si sub (1-x) well could be extracted. Excellent agreement between measured and simulated X-ray satellite patterns was achieved. These results show that HRXRD together with kinematical simulation provide a powerful tool to evaluate the structural perfection of Ge sub x Si sub (1-x) /Si strained-layer superlattices.