Dislocation density assessment via X-ray GaN rocking curve scans

The line shape of X‐ray diffraction (XRD) rocking curves of GaN layers grown epitaxially on (0001) oriented sapphire substrates is analyzed. Measurements performed with double‐ and triple‐crystal setup show a q‐3 and q‐4 intensity decay, respectively, as expected for peak broadening dominated by randomly distributed dislocations. A model developed in [2], based on a restricted random dislocation distribution is 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 agree well with each other but still must be verified by systematic cross‐sectional TEM measurements. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)