Atomic core structure of 90° -bent screw threading dislocations in wurtzite GaN

The atomic and electronic structures of the c threading dislocations with an edge or screw character were compared using a tight binding formalism which takes into account charge transfer. The two dislocations do not exhibit dangling bonds. While the screw dislocation contains only constrained Ga-N bonds, the edge dislocation contains Ga-Ga and N-N wrong bonds. Both dislocations are found to induce shallow and deep gap states.