GaN nanowires are grown as templates for pendeoepitaxial coalescence overgrowth at substrate temperatures between 720 and 820 degrees C on Si(111) by molecular beam epitaxy. The unintentional coalescence of nanowires is suppressed with increasing substrate temperature. Simultaneously, the width of the donor-bound-exciton transition at 3.472 eV decreases down to 1.6 meV. The length distribution of the GaN nanowires strongly influences the morphology of the pendeoepitaxial layer after coalescence. (C) 2011 Elsevier B.V. All rights reserved.