Structural, vibrational and electronic properties of faceted GaN (000(1)over-bar) surfaces

We report on our investigations of the structural, vibrational and electronic properties of GaN epilayers grown on sapphire(0001). By a combination of high-resolution electron energy-loss spectroscopy (HREELS) and angular-resolved X-ray photoelectron spectroscopy (ARXPS) the orientation of the layers is determined to be (0001). Parts of the surface contain facets that are made of (10 (1) over bar (2) over bar)-type planes, as found using low-energy electron diffraction (LEED). We observe the dissociative adsorption of water from the residual gas at the GaN(000 (1) over bar) surface. N-H and Ga-H stretching vibrations observed in hydrogenation experiments can be correlated to adsorption on terraces and facets, respectively. Finally, we report the observation of the conduction-band surface plasmon and use theoretical simulation of the HREEL spectra to extract Important semiconductor parameters such as band bending, doping level and electron mobility. (C) 1999 Elsevier Science B.V. All rights reserved.