BGaN ternary alloys with 0.7% and 1.7% boron grown on GaN/sapphire template substrates by metalorganic vapour phase epitaxy (MOVPE) have been investigated through HAADF-STEM. At low boron content, 0.7%, no compositional fluctuations were observed with XRD or STEM measurements. Photoluminescence at room temperature was measured. At higher boron content, cubic BGaN nano-sized clusters were identified. The clusters are 3 nm wide, homogeneously distributed in size and in density and coherent with the surrounding wurtzite BGaN matrix. Their boron composition was estimated by EDX. (C) 2010 Elsevier B.V. All rights reserved.