We have investigated the effects of high energy nitrogen ion (N +) irradiated n-GaAs Schottky barrier diodes using deep level transient spectroscopy. The diodes have been irradiated (fluences of 1 × 1012 and 1 × 1013 cm-2) at 77 K. Three electron trap levels (labeled as En1, En2 and En3) are observed for the diodes irradiated with the fluence of 1 × 1012 cm2. Activation energies and capture cross-sections of the levels are calculated. The electron trap level En2 (691 meV) is attributed to NGa defects produced by the irradiation. Trap level and shallow level concentrations of the irradiated diodes are found to be decreased. It is due to trapping of charge carriers by the irradiation induced defects. Photo carrier life times of the control and irradiated samples have been measured using time resolved photoluminescence spectroscopy. After the irradiation, a decrease in the PL decay time of the sample has been observed. © 2003 Elsevier B.V. All rights reserved.