title: Nitrogen vacancies as major point defects in gallium nitride.
abstract: We present results of ab initio calculations for vacancies and divacancies in GaN. Particular attention is paid to nitrogen vacancies and mixed Ga-N divacancies in negatively charged states, which in n-type GaN are found to be energetically comparable with gallium vacancies. We also demonstrate that the activation energy for self-diffusion over the nitrogen sublattice is lower than over the gallium one for all Fermi-level positions, which implies the nitrogen vacancies are major defects in samples annealed at high temperatures. Possibilities for direct observations of nitrogen vacancies through positron annihilation experiments are discussed.
authors.affiliation: COMP/Laboratory of Physics, Helsinki University of Technology, Espoo, Finland.
authors.forename: M G
authors.initials: MG
authors.lastname: Ganchenkova
authors.forename: R M
authors.initials: RM
authors.lastname: Nieminen