Th. Kehagias¹, Ph. Komninou¹, J. Kioscoglou¹, E. Sarigiannidou¹, G.P. Dimitrakopulos¹, S. Mikroulis^2,3, K. Tsagaraki^2,3, A. Georgakilas^2,3, Th. Karakostas^1
1Department of Physics, Aristotle University, GR-54006 Thessaloniki, Greece
²IESL, FORTH, P.O. Box 1527, GR-711 10 Heraklion-Crete, Greece
³Physics Department, University of Crete, Heraklion-Crete, Greece

Abstract. Transmission Electron Microscopy (TEM) is employed in order to investigate the morphological and structural aspects of GaN films grown on sapphire, by Molecular Beam Epitaxy (MBE). The sapphire surface was nitridated at high temperature and then a 20–25 nm low temperature buffer layer of AIN was deposited . The buffer layer was annealed at high temperature and then the epitaxial GaN was grown under various conditions. The correlation between structural and morphological properties of GaN and MBE grown conditions is investigated at microscopic level. A significant reduction in the GaN surface roughness with increasing Ga/N ratio is observed.

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