Current-voltage characteristics of process-damaged p-n junction diodes are investigated for the purpose of damage evaluation. In this technique, damage is assessed by examining its effect on the diode characteristics of the peripheral portion of Zn-diffused p-n junctions. The depth information for the current-voltage measurements is obtained by wet etching. This technique is applied to determine the extent of damage caused by Ar bombardment during Ar-ion beam etching and film deposition of sputtered SiO2. The forward-bias current-voltage characteristics are found to be more effective for damage-depth evaluation than the reverse-bias ones. The depth of the damaged layer is determined from the behavior of the ideality factor (n) of the forward-bias current-voltage characteristics. This technique was used to probe a damaged layer to a depth of up to 350 nm in Ar-ion beam etching, which is much deeper than the 60 nm that is typically evaluated by the current-voltage characteristics of Schottky diodes. This thickness is equivalent to that evaluated by the photoluminescence intensity and cathodoluminescence properties of multiquantum well structures. In addition, the damage depth profile can be represented quantitatively by considering the n similar or equal to 2 recombination current deduced from the diameter dependence of the diode current-voltage characteristics. Three damaged regions with different recombination current densities are revealed in both Ar-ion beam etching and film deposition of sputtered SiO2.