Abstract: Electronic structures of unsaturated and H saturated GaN nanowires with diameters of 9.5Å, 15.9Å and 22.5Å are studied with generalized gradient approximation (GGA) of density functional theory (DFT). Results show that unsaturated and H saturated GaN nanowires have direct band gaps. Band gaps of unsaturated GaN nanowires decrease with the increase of nanowire diameter, but not significantly. Band gaps of H saturated GaN nanowires decrease with the increase of nanowire diameter as well. They are more apparent than unsaturated ones. 2p electrons of N atoms in surface of unsaturated GaN nanowires locate at top of valence band, and 4p electrons of Ga atoms in surface locate at bottom of conduction band. These two kinds of electrons are local which decide the band gap. Surface effect of surface atoms can be eliminated by saturating with hydrogen atoms.

Key words: GaN nanowires, H saturated, electronic structures, density functional theory(DFT)