Global search for stable screw dislocation cores in III-N semiconductors

The promise of the broad range of direct band gaps of the {Al, Ga, In} N system is limited by the crystal quality of current material. As grown defect densities of InN, when compared with the more mature GaN, are extremely high and InN is strongly influenced by these defects. This is particularly important due to the unusual position of the charge neutrality level of InN, leading to both the well-known surface charge accumulation and difficulties in p-type doping. While impurities and native defects clearly impact on the bulk carrier density in InN, the effects of threading dislocations on the electrical properties are still in dispute. Issues such as whether the dislocation line is charged or contains dangling bonds remain open. We present the results of a global search for possible dislocation core reconstructions for a range of screw dislocations in wurtzite III-N material, utilizing empirical Stillinger-Weber inter-atomic potentials. In addition, we investigate a wide range of non-stoichiometric core structures. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim