Pd/n-GaAs Schottky barrier diodes (SBDs) have been fabricated using liquid-encapsulated Czochralski (LEC) grown silicon-doped GaAs (100) single-crystal substrates. The diodes were implanted using low-energy (70 keV) alpha particles of fluence 1×1014, 1×1015 and 1x1016cm-2 to study the effect of irradiation-induced defects very close to the interface. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of control, irradiated and annealed diodes have been carried out under dark conditions and analyzed. After the irradiation, the rectifying behavior of the diode deteriorates with the fluence. The irradiated diodes annealed at 573 and 673 K show a decrease in the reverse leakage current and an enhancement in the barrier height due to the reduction of the irradiation-induced defects. The capacitance values of the irradiated diodes have been observed to be less than those of the control diodes and they increase with increasing ion fluences whereas those of the irradiated and annealed diodes decrease for all fluences due to passivation on the GaAs surface and/or the removal of the irradiation-induced defects in the SBDs. © 2000 Elsevier Science Ltd. All rights reserved.