Annealing amorphous GaN - a way to nano-crystalline state

The effects of thermal annealing on structural and optical properties of amorphous GaN thin films obtained by Ion Assisted Deposition (IAD) have been investigated. Thermal annealing. was carried out in flowing nitrogen and respectively under water vapour pressure (1.7-2.4 torr), at temperatures up to 800/spl deg/C. From SEM observations of the annealing processes in real time it appears that formation of nano-crystallites in the amorphous environment occurs at about 400/spl deg/C. XRD and Raman scattering performed on the annealed films prove the presence of nano-crystallites (2-4 nm). Optical measurements show a weak absorption edge in the as prepared film, and the deepening edge and reduced sub-band absorption after annealing.