Triangular microrings have been formed by selective area epitaxy of GaN and InGaN quantum wells (QWs) on patterned (0 0 0 1) AlN/sapphire. SiO2 patterns consist of triangular ring openings oriented with edges parallel to two different orientations. InGaN QW microrings with each edge parallel to the < 1 (1) over bar 0 0 > direction have very rough sidewalls while microrings with each edge parallel to the < 1 1 (2) over bar 0 > direction exhibit well formed and smooth sidewalls as a result of the generation of a single type of {1 (1) over bar 0 1} facets on the inner and outer sidewalls. These {1 (1) over bar 0 1} facets demonstrate similar cathodoluminescence (CL) spectra that appear to be the superposition of two peaks at photon energies similar to 2.5 eV (500 nm) and 2.7 eV (460 nm). Moreover, spatially matched striations are observed in the CL intensity images and surface morphologies of the {1 (1) over bar 0 1} sidewall facets. The observed striations are found to be related to subtle surface morphologies of the underlying GaN structures. (C) 2010 Elsevier B.V. All rights reserved.