Electronic structure of 1X1 GaN(0001) and GaN(000(1)over-bar) surfaces - art. no. 035305

The electronic structure of clean and Ga- or N-covered 1 x 1 GaN(0001) and GaN(000 (1) over bar) surfaces is studied using the local-density approxima tion of density-functional theory employing ab initio pseudopotentials toge ther with Gaussian orbital basis sets. We use both standard and self-intera ction- and relaxation-corrected pseudopotentials. The latter allow for a mo st accurate description of the electronic structure of these surfaces. Comp aring the formation energies for the clean and adatom-covered 1x1 configura tions, we determine optimal surface structures for various growth condition s. For the GaN(0001) surface in the Gn-rich case, we iind a structural mode l consisting of Ga adatoms adsorbed in T-4 positions above the substrate su rface to be most favorable. In the N-rich case, the clean GaN(0001) surface is the most stable 1x1 configuration. For the GaN(000 (1) over bar) surfac e, our results for both Ga- and N-rich growth conditions indicate that a fu ll monolayer of Ga adatoms adsorbed in on top positions is the most stable configuration. Our theoretical results allow for a comparison of full calcu lations of the surface electronic structure for a number of optimized struc tural models with most recent angle-resolved photoemission spectroscopy dat a.