Abstract
Using a firstβprinciples band structure approach, we have investigated the electronic structures of edge dislocations associated with the $\left\langle {11\overline {2} 0} \right\rangle { 0001]$ slip system. This edge dislocation has been simulated using a 4βΓβ4βΓβ3 supercell from which a halfβplane perpendicular to the basal plane along the $\left\langle {1\overline {1} 00} \right\rangle $ 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/4β=β3.216βΓ
, C/3β=β5.234βΓ
compared to experiment and the GaN bond lengths, d~GaβN~β=β1.965 and 1.973βΓ
. A detailed analysis of the partial density of states (DOS) shows that the edge atoms along the ${\left[ {1\overline {1} 00} \right]}$ 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 0.5βeV 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 electronβhole pairs is discussed in detail.