ELECTRONIC GAP STATES ON GAN(0001)-(1 X-1) SURFACES STUDIED BY ELECTRON SPECTROSCOPIES

GaN(0001)-(1 x 1) surfaces are grown by RF plasma-assisted MBE and cha racterized in situ by electron spectroscopy. A consistent picture of t he energy distribution of occupied and empty electronic states in the gap of the GaN is deduced by a combined photoemission- and high-resolu tion electron energy loss spectroscopy study. Surface electronic state s near the valence and conduction band edges are assessed and an overa ll picture of the wurtzite GaN surface emerges which is similar to tha t of ZnO surfaces. Electronic states in the upper half of the forbidde n band are assumed to be responsible for the observed upwards band ben ding with the Fermi level pinning at E-F - E-v = (2.4 +/- 0.1) eV.