The line-shape of X-ray diffraction rocking curves of GaN layers grown epitaxially onto (00•1)-oriented sapphire substrates was analyzed. Measurements performed using a double- and triple-crystal set-up revealed a q-3 and q-4 intensity decay, respectively, as expected for peak-broadening dominated by randomly distributed dislocations. A model developed on the basis of a restricted random dislocation distribution was fitted to the entire peak shape and used to extract dislocation densities and correlation lengths for edge and screw type threading dislocations. Parameters extracted by double- and triple-crystal X-ray diffraction measurements agreed well with each other but still needed to be verified by systematic cross-sectional transmission electron microscopic measurements.

Dislocation Density Assessment via X-Ray GaN Rocking Curve Scans. I.Booker, K.L.Rahimzadeh, J.F.Woitok, V.Kaganer, C.Mauder, H.Behmenburg, J.Gruis, M.Heuken, H.Kalisch, R.H.Jansen: Physica Status Solidi C, 2010, 7[7-8], 1787–9