Quantum confinement effects in gallium nitride nanostructures: ab initio investigations.

We present ab initio density functional investigations of the atomic and electronic structure of gallium nitride nanodots and nanowires. With increasing diameter, the average Ga-N bond length in the nanostructures increases, as does the relative stability (heat of formation), approaching the values for bulk GaN. As the diameter decreases, the band gap increases, with the variation for the nanodots greater than that for the nanowires, in qualitative accordance with expectations based on simple geometrical quantum confinement considerations. Interestingly, in contrast to nanowires, the lowest unoccupied states of the nanodots exhibit an extended delocalized (Ga-derived) character, weighted in the centre of the nanodot.