ELECTRONIC-STRUCTURE, SURFACE-COMPOSITION AND LONG-RANGE ORDER IN GAN

We present a study of hexagonal GaN thin films grown by low-pressure c hemical vapor deposition on sapphire substrates. We used synchrotron r adiation photoemission spectroscopy to probe the electronic density of states and test the validity of existing band structure calculations. Parallel studies of surface composition and atomic structure by means of Auger spectroscopy and reflection high-energy electron diffraction were performed following sputtering/annealing cycles using argon, xen on and nitrogen ions. We found that sputtering with nitrogen ions foll owed by annealing in vacuum is an effective method to reduce nitrogen surface depletion and produce quasi-stoichiometric ordered GaN(0001)1 x 1 surfaces.