Desorption of hydrogen from GaN(0001) observed by HREELS and ELS

The bare and hydrogenated GaN(0001) surfaces were characterized using high resolution electron energy loss spectroscopy (HREELS), electron energy loss spectroscopy (ELS), Auger electron spectroscopy (AES) and low energy elect ron diffraction (LEED). AES and LEED show that the GaN surface is clean but faceted. Changes in the surface electronic structure are characterized usi ng ELS. Exposure to atomic hydrogen produces a merging of the double peak c entered near 20 eV and a leveling of the region from 10 to 15 eV. These hyd rogen-induced changes begin to decrease after briefly heating to 260 degree s C and are completely reversed after heating to 380 degrees C. Atomic hydr ogen exposure produces HREELS loss peaks at 2580, 3280 and 3980 cm(-1) due to combinations of the Ga-H stretching vibration at 1880 cm(-1) and Fuchs-K liewer phonons. Briefly heating to 260 degrees C or above produces a decrea se in the intensity of Ga-H vibrations. Heating to 380 degrees C results in a complete disappearance of adsorbate vibrational peaks. Observation of de sorbing molecular hydrogen by mass spectrometry confirms that the disappear ance of Ga-H features in HREEL and ELS spectra is due to recombinative deso rption of hydrogen. Overall this work demonstrates desorption of hydrogen f rom surface Ga sites between 250 and 450 degrees C. (C) 1999 Published by E lsevier Science B.V. All rights reserved.