Electronic structures of GaN edge dislocations

We investigate atomic and electronic structures of the threading edge dislocations of GaN using self-consistent-charge density-functional tight-binding approaches. Full-core, open-core, Ca-vacancy, and N-vacancy edge dislocations are fully relaxed in our total-energy scheme. The Ca-vacancy dislocation is the most stable in a wide range of Ga chemical potentials, whereas full-core and open-core dislocations are more stable than others in the Ga-rich region. Partial dehybridization takes place during the lattice relaxation near the dislocation in all cases. The dangling bonds at Ga atoms mostly contribute to the deep-gap states, whereas those at N atoms contribute to the valence-band tails. All the edge dislocations can act as deep trap centers, except the Ga-vacancy dislocation, which may act as an origin of yellow luminescence.