Thick layers with atomically flat surfaces were successfully grown directly onto sapphire substrates by metal-organic vapour phase epitaxy at between 1300C and 1600C. Dislocations such as those of edge, screw and mixed types exhibited differing behaviours in the AlN epilayers. The dislocation density of AlN was less than 2 x 109/cm2. Free and bound excitons of AlN were observed, with peak energies of 6.084 and 6.063eV, respectively.Microstructure of Thick AlN Grown on Sapphire by High-Temperature MOVPE. M.Imura, K.Nakano, T.Kitano, N.Fujimoto, N.Okada, K.Balakrishnan, M.Iwaya, S.Kamiyama, H.Amano, I.Akasaki, K.Shimono, T.Noro, T.Takagi, A.Bandoh: Physica Status Solidi A, 2006, 203[7], 1626-31