First‐principles investigation of the electronic structures of edge dislocations in GaN

Using a first‐principles band structure approach, we have investigated the electronic structures of edge dislocations associated with the 112̄ 0 \ 0001] slip system. This edge dislocation has been simulated using a 4 × 4 × 3 supercell from which a half‐plane perpendicular to the basal plane along the 11̄ 00 direction was removed in every unit cell. The electronic structures were then calculated within the framework of density functional theory with a plane wave basis set using the projector augmented wave technique as implemented in the Vienna ab initio simulation package (VASP). The optimized structure yields slightly larger lattice parameters A/4 = 3.216 Å, C/3 = 5.234 Å compared to experiment and the GaN bond lengths, dGa‐N = 1.965 and 1.973 Å. A detailed analysis of the partial density of states (DOS) shows that the edge atoms along the [ 11̄ 00 ] direction and the surface atoms on either side of the missing plane introduce new states in the band gap. The edge atoms introduce more localized states inside the gap, which could act as electron and hole traps. The highest occupied and lowest unoccupied states are N 2p like edge states and above these states at about 0.5 eV we find 4s like surface states of Ga. The band gap for the defect system vanishes due to states introduced by the dislocation. How the localized states introduced by the dislocation would affect the recombination of electron–hole pairs is discussed in detail.