X-ray diffraction peaks from misfit dislocations in double-and triple-crystal diffractometry

We propose a common description of the full widths at half maximum of X-ray diffraction peaks obtained in different scans of triple-crystal diffractometry and as well as for glancing incidence and glancing exit double-crystal measurements. Calculations are compared with measurements of GaAs/Si(001) heteroepitaxial films. We show that the diffraction peak broadening is entirely due to random 60° misfit dislocations that provide only a minor part of the misfit relaxation. The remaining relaxation is due to periodic edge misfit dislocations that do not contribute to the peak broadening.