title: Determination of the nitrogen vacancy as a shallow compensating center in GaN doped with divalent metals.
abstract: We report accurate energetics of defects introduced in GaN on doping with divalent metals, focusing on the technologically important case of Mg doping, using a model that takes into consideration both the effect of hole localization and dipolar polarization of the host material, and includes a well-defined reference level. Defect formation and ionization energies show that divalent dopants are counterbalanced in GaN by nitrogen vacancies and not by holes, which explains both the difficulty in achieving p-type conductivity in GaN and the associated major spectroscopic features, including the ubiquitous 3.46 eV photoluminescence line, a characteristic of all lightly divalent-metal-doped GaN materials that has also been shown to occur in pure GaN samples. Our results give a comprehensive explanation for the observed behavior of GaN doped with low concentrations of divalent metals in good agreement with relevant experiment.
authors.affiliation: University College London, Kathleen Lonsdale Materials Chemistry, Department of Chemistry, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
authors.forename: J
authors.initials: J
authors.lastname: Buckeridge
authors.affiliation: University College London, Kathleen Lonsdale Materials Chemistry, Department of Chemistry, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
authors.forename: C R A
authors.initials: CR
authors.lastname: Catlow
authors.affiliation: University College London, Kathleen Lonsdale Materials Chemistry, Department of Chemistry, 20 Gordon Street, London WC1H 0AJ, United Kingdom and Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom.
authors.forename: D O
authors.initials: DO
authors.lastname: Scanlon
authors.affiliation: Scientific Computing Department, STFC, Daresbury Laboratory, Daresbury, Warrington WA4 4AD, United Kingdom.
authors.forename: T W
authors.initials: TW
authors.lastname: Keal
authors.affiliation: Scientific Computing Department, STFC, Daresbury Laboratory, Daresbury, Warrington WA4 4AD, United Kingdom.
authors.forename: P
authors.initials: P
authors.lastname: Sherwood
authors.affiliation: University College London, Kathleen Lonsdale Materials Chemistry, Department of Chemistry, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Miskufova
authors.affiliation: Centre for Sustainable Chemical Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Walsh
authors.affiliation: University College London, Kathleen Lonsdale Materials Chemistry, Department of Chemistry, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
authors.forename: S M
authors.initials: SM
authors.lastname: Woodley
authors.affiliation: University College London, Kathleen Lonsdale Materials Chemistry, Department of Chemistry, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
authors.forename: A A
authors.initials: AA
authors.lastname: Sokol