The effects of radiation damage on the properties of Ni-nGaAs Schottky diodes—II Terminal characteristics

Abstract

The effects of radiation damage on the electrical characteristics of Ni-nGaAs Schottky diodes are studied, the damage being introduced by implanting various ions (B, O, He, Ge) into the depletion layer. Current-voltage characteristics show excess current flow after irradiation, this being explained in terms of a recombination-generation process. A trap assisted-tunnelling mechanism is also believed responsible for conduction in reverse bias for voltages greater than a few volts. Reverse voltage-capacitance measurements indicate the presence of a compensated layer within the depletion region which strongly affects the capacitance of deeply implanted diodes. For shallower implants, however, the capacitance becomes dominated by surface state effects at the interface. In forward bias the capacitance-voltage characteristics are very similar to those expected for a p-i-n structure, becoming more p-i-n like in behaviour as the damage is increased. Finally a model is proposed to explain the observed characteristics in terms of a change in the physical nature of the barrier region due to damage produced defect states.