SEM and Raman studies of annealed nanocrystalline GaN and amorphous GaN:O

We report annealing studies of thin films of GaN and GaN:O prepared by ion assisted deposition. As-prepared films of stoichiometric tetrahedrally bonded GaN form nanocrystalline networks, but amorphous networks result with the inclusion of more than 10 at.% of oxygen. The annealed nc-GaN films show an increased average crystallite size, though even after a 700 °C anneal the crystals are no larger than about 10 nm. Annealed a-GaN:O films remain amorphous even after a 700 °C anneal, after which they display a weak photoluminescence.