The Evolution of Strain Relaxation Close to The Critical Thickness

Abstract

ABSTRACTHigh resolution X-ray diffraction space mapping has been used to follow the change in the distribution of residual strain and localised relaxation in low mismatched epitaxial layers. Using this new technique, we have obtained a series of diffraction space maps of partially relaxed epitaxial layers of In.1Ga.9As on GaAs. The layers have different thicknesses and hence different degrees of strain relaxation. The diffuse scatter close to the Bragg peaks provides information about the imperfect and distorted regions in the structure and this has allowed us to examine the extent and distribution of residual strain close to the dislocations. We have followed the evolution of local relaxation, which is confined initially to regions around isolated dislocations, through to the case of overlapping dislocation strain fields, leading to a more homogeneous strain field distribution and microscopic and macroscopic tilting of the layers.