HYDROGENATION AND ANNEALING EFFECTS ON GAN EPILAYERS GROWN ON SAPPHIRE SUBSTRATES

Photoluminescence (PL) measurements have been carried out to investiga te the hydrogenation and annealing effects of unintentionally doped n- type GaN epitaxial layers grown on sapphire substrates by plasma-assis ted molecular beam epitaxy. When the as-grown GaN/sapphire heterostruc ture is annealed at 800 degrees C. a new peak corresponding to the neu tral donor-bound excitons appears. After hydrogenation, the yellow pea k appeared for the as-grown GaN/sapphire heterostructure annealed at 8 00 degrees C disappears. When the hydrogenated GaN/sapphire heterostru cture is annealed at 950 degrees C, three peaks appears. These results indicate that the crystallinity of the unintentionally doped n-type G aN epilayers grown on sapphire substrates is improved by hydrogenation and annealing.