Ni/n-GaAs Schottky barrier diodes (SBDs) have been irradiated using low energy proton ions of fluences 1 × 1014, 1 × 1015 and 1 × 1016cm-2 to study the effect of irradiation damages very close to the interface. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of control and irradiated diodes have been carried out. The change in the reverse leakage current increases with increasing ion fluences. The barrier height of the SBDs has been found to decrease and the ideality factor deviates from the ideal behavior with increasing ion fluences. This non-rectifying behavior is due to the irradiation induced defects at the interface. The rectifying behavior of the SBDs improved, upon annealing at 573 and 673K. The capacitance value of the irradiated diodes has been found to be less than the control diodes and it increases with increasing ion fluences. The capacitance of the irradiated and annealed diode decreases for all fluences due to the removal of the irradiation induced defects in the depletion region. The carrier concentration reduces by the proton irradiation through the mechanism of passivation and defects trapping at the interface and within in the depletion region. The time resolved luminescence spectrum in proton irradiated GaAs has been carried out in order to measure the life times of the photo excited carriers as a function of fluence. It is observed the carrier lifetimes decrease with increasing fluences. © 2002 Elsevier Science B.V. All rights reserved.