We report the results of a theoretical study of AlnNn GanNn and InnNn (with n = 4, 5, 6) clusters, focusing on their structural properties, stability, and electronic structure. For AlnNn clusters, the metal-nitrogen bond is found to dominate the lowest energy configurations, with a transition from planar to bulklike three-dimensional structures, as the cluster size increases from Al4N4 to Al6N6. However, for GanNn and InnNn clusters, the lowest energy configurations are mostly planar, and they are dominated either by N3(-) or N-2 subunits. It strongly suggests that N-segregation may occur during quantum dot or thin film deposition processes, due to the low atomic coordination and abundance of dangling bonds.