Annealing studies of AlN capped, MOCVD grown GaN films

•We developed an AlN capping process to anneal C-plane GaN up to 1300°C for 30min.•AFM roughness increases in GaN when annealed at 1200–1300°C for 30min.•XRD rocking curves showed decrease in FWHM of GaN after annealing.•Changes in XRD FWHM and film bow suggest that film became more relaxed during anneal.