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

We report on our investigations of the structural, vibrational and electron ic properties of GaN epilayers grown on sapphire(0001). By a combination of high-resolution electron energy-loss spectroscopy (HREELS) and angular-res olved X-ray photoelectron spectroscopy (ARXPS) the orientation of the layer s 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-ener gy electron diffraction (LEED). We observe the dissociative adsorption of w ater 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 corre lated to adsorption on terraces and facets, respectively. Finally, we repor t the observation of the conduction-band surface plasmon and use theoretica l simulation of the HREEL spectra to extract Important semiconductor parame ters such as band bending, doping level and electron mobility. (C) 1999 Els evier Science B.V. All rights reserved.