High-resolution X-ray diffraction study of highly mismatched III–V heterostructures by analysis of the layer Bragg peak width

Abstract

Recently, a method has been proposed in order to measure the threading dislocation density in epitaxial layers, based on X-ray diffraction and the analysis of the layer Bragg peak width β. According to this model, β is broadened by the rotation of the lattice planes and the modification of the lattice parameter near the threading dislocation lines. In the present work, this method is applied on GaAs/InAs and InAs/GaAs heterostructures. Different geometrical conditions and reflections, including (004), (115), (335), (444) and (117), have been investigated, showing a strong difference in β when, for a fixed reflection, the grazing incidence or grazing emergence geometry is chosen. Reciprocal lattice maps on the same samples demonstrate that this effect cannot be explained unless some degree of correlation between strain and tilt is assumed. The experimental findings are explained in term of lateral non-uniformity of the layer due to the misfit dislocation distribution. Further, the first results of a study about the effects of the layer roughness on β, performed on a InGaAs/GaAs sample, are presented.