AbstractStructural defects in aluminium nitride (AlN) get visible in panchromatic cathodoluminescence (CL) maps as luminescence at 340 nm and 630 nm is locally enhanced. Low‐angle grain boundaries (LAGBs) and dislocations can be detected as long as they are sufficiently decorated and the defect‐related contrast is higher than local variations in background CL intensity. We applied the method to c ‐plane and a ‐plane cuts of one of our off‐oriented grown AlN crystals and describe occurrence, routes, and dissolution into dislocation bunches of LAGBs. We found that the vast majority of LAGBs are uneven a ‐planes which extend in a preferential m ‐ as well as in c ‐direction. As a consequence, their density decreases only slightly during growth (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)