Electronic structure and metallization effects at threading dislocation cores in GaN

We have carried out a complete and consistent study on core configurations of the three types of threading dislocations in wurtzite GaN. Their atomic and local electronic structures were analyzed and systematically compared, at the level of Density Functional Theory. Screw and mixed threading dislocations were found to introduce both deep and shallow gap states, while most of core configurations of the edge dislocation introduce only shallow states. We demonstrated that the existence of an extended one-dimensional metallization, associated with unoccupied gap states, is a specific feature of threading screw dislocations. The extended metallization along with the high dispersion of the energy gap states are at the origin of the experimentally observed high electric conduction along threading screw dislocations in GaN. The presence of nitrogen vacancies in the core of screw dislocations is predicted to enhance their electric conduction.