Strain nonuniformity in GaAs heteroepitaxial films on Si(001) studied by x-ray diffraction

High-resolution x-ray diffraction measurements are used to fully characterize the strain state of relaxed highly mismatched GaAs films, grown on vicinal Si (001) substrates by molecular beam epitaxy. The nonuniformity of the misfit dislocation network at the GaAs∕Si (001) interface is studied by analyzing the profiles of x-ray diffraction peaks and the reciprocal space maps for different reflections. The detailed analysis of the peak positions shows a dependence of the relaxation on the crystallographic direction, with the relaxation being larger in the direction perpendicular to the α-dislocation lines. Based on analytical expressions for the full width at half maximum in the longitudinal and transverse sections, an advanced version of the Williamson-Hall plot [Acta Metall. 1, 22 (1953)] is proposed that takes into account the geometry of dislocation distribution and the scattering geometry. We show that this type of analysis can reveal both the type and density of misfit dislocations. The measured peak ...