Formation energies and charge transition levels of amphoteric defects in GaAs giving rise to Fermi-level pinning are calculated with hybrid functionals. The hybrid functional results indicate that previously identified defects involving the bistable nature of Ga and As vacancies cannot account for the experimentally observed pinning at 0.6 eV in damaged bulk GaAs. A stable defect complex involving an extra As antisite bound to a Ga vacancy is identified and shown to possess bistable and amphoteric behavior leading to Fermi-level pinning in accord with experiment. (C) 2013 Elsevier B.V. All rights reserved.