HREELS of H/GaN(0001): evidence for Ga termination

Two issues relevant to the growth and processing of GaN are the termination of the GaN(0001) surface and its reaction with hydrogen. We have used high-resolution electron energy loss spectroscopy (HREELS), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES) to study the adsorption of hydrogen on MOCVD-grown GaN(0001). LEED of the sputtered and annealed surface shows evidence of facetting. No adsorbate vibrations are observed on the clean surface by HREELS, only Fuchs-Kliewer phonons at intervals of 700 cm(-1) Following exposure of the clean GaN surface to hydrogen atoms, HREEL spectra show adsorbate loss peaks at 2580, 3280, and 3980 cm(-1). The Ga-H stretching vibration at 1880 cm(-1) becomes evident when the HREEL spectrum is deconvoluted to remove the phonon multiple-loss peaks. We assign the 2580, 3280, and 3980 cm(-1) peaks to combination modes of the Ga-H stretch and phonon(s). Upon dosing with deuterium, the Ga-D bending mode is observed at 400 cm(-1). No vibrational peaks due to N-H (N-D) species are observed after H (D) exposure. We conclude that sputtered and annealed GaN(0001) is Ga-terminated. (C) 1999 Elsevier Science B.V. All rights reserved.