RELAXATION AND MOSAICITY PROFILES IN EPITAXIAL LAYERS STUDIED BY HIGH-RESOLUTION X-RAY-DIFFRACTION

A novel nondestructive method correlating the strain gradient in partially relaxed epilayers with a profile of crystalline mosaicity is demonstrated by using high resolution X-ray diffraction. By reciprocal space mapping, a distribution of the scattered intensity near reciprocal lattice points was found, which is characteristic for partially relaxed layers. This distribution is described by a relaxation-mosaicity triangle which is modified in a characteristic way for different reflection orders. The increase in mosaicity with progressive relaxation is quantified from diffraction profiles recorded along selected directions in reciprocal space. The determination of the depth profile of strain implies also the knowledge of the depth gradient of the mosaicity. The method is demonstrated for a partially relaxed ZnSe layer grown by MBE on (001) GaAs.