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 microscopy (STM) characteristics are reported for the first time. X-Ray characterization and Hall measurements revealed a full-width-half-maximum (FWHM) value of 288 arcsec and background doping reduction accompanied with electron mobility enhancement as the growth temperature increased. STM topography revealed island formations on the growth surface the size of which increased again with growth temperature in a manner consistent with the trends of improved electrical characteristics. STM stimulated luminescence showed no significant photon emission in the tunneling 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 localized band-bending fluctuations across the surface.