TRANSMISSION ELECTRON-MICROSCOPY CHARACTERIZATION OF METALORGANIC CHEMICAL-VAPOR-DEPOSITION GROWN GAN LAYERS

GaN layers grown onto sapphire substrates by metalorganic chemical vap our deposition were characterised by optical microscopy, transmission electron microscopy and atomic force microscopy measurements. Mirror l ike surfaces were obtained at certain growth conditions despite the he xagonal based pyramids found on the growth surface. The typical pyrami ds have a base diameter of 20-30 mu m and height of about 1.5-3 mu m. The GaN layers are of the wurtzite type and epitaxially oriented to th e sapphire substrate. Beside the threading dislocations, hexagonal rod s of GaN surrounded by inversion domain boundaries are observed. An Al N layer has been formed at the interface region during the nitridation process of sapphire. (C) 1997 Elsevier Science S.A.