X-ray reflectivity investigations of the interface morphology in strained SiGe/Si multilayers

We have studied the lateral and vertical correlation of the interface roughness of Si/SiGe multilayers grown on Si(001) substrates with a miscut between 0.2 degrees and 0.5 degrees using high resolution x-ray reflectivity. The theoretical analysis of the measurements proved that the established phenomenological models for the description of the interface profiles fail in the common case of moderately small miscut angles. We obtained qualitatively correct results for the roughness correlations using a microscopic kinetic step-flow growth model, which accounts for the aggregation of monolayer steps (step bunching) during the hetero-epitaxial growth.