Abstract
Local-density-functional methods are used to examine the atomic geometries, energetics, and electrical properties of different models for domain boundaries on {112̄0} planes in wurtzite GaN. In agreement with recent experiments, we find that the energetically most favorable model is characterized by a displacement of 1/2<101̄1> and has no inversion of polarity. In this model all atoms at the boundary are fourfold coordinated and form strong Ga-N bonds, which results in a band gap free from deep states. However, our calculations also suggest that electrically active point defects, in particular gallium vacancies, may segregate to the boundary and thus introduce deep acceptor states.