SCANNING-TUNNELING-MICROSCOPY CHARACTERIZATION OF METALORGANIC CHEMICAL-VAPOR-DEPOSITION GROWN GAN

GaN films were grown by metalorganic chemical vapor deposition (MOCVD) on (0001) c-sapphire substrates and their scanning tunneling microsco py (STM) characteristics are reported for the first time. X-Ray charac terization and Hall measurements revealed a full-width-half-maximum (F WHM) value of 288 arcsec and background doping reduction accompanied w ith electron mobility enhancement as the growth temperature increased. STM topography revealed island formations on the growth surface the s ize of which increased again with growth temperature in a manner consi stent with the trends of improved electrical characteristics. STM stim ulated luminescence showed no significant photon emission in the tunne ling mode but moderate value signals in the field-emission mode, where the intensity increased with tip voltage. Finally, scanning tunneling spectroscopy allowed bandgap estimation at 3.5 eV and suggested local ized band-bending fluctuations across the surface. (C) 1997 Published by Elsevier Science S.A.