The electrical properties and deep level spectra in undoped n-GaN films irradiated by fast neutrons are reported. The electron removal rate was similar to 5 cm(-1), and the dominant deep states introduced by neutron damage were electron traps with activation energy of 0.75 eV. For high doses of 1.7 X 10(17) - 10(18) cm(-2) the material becomes semi-insulating n-type with the Fermi level pinned near E-c-0.85 eV. Deep level spectra are dominated by electron traps with activation energy of 0.75 eV, close to the energy of the Fermi level pinning in heavily irradiated material. Neutron irradiation also introduces a high density of centers giving rise to strong persistent photocapacitance. The observed phenomena are explained under the assumption that the dominant defects in neutron irradiated GaN are disordered regions produced by high-energy recoil atoms. (c) 2007 American Vacuum Society.