Radiation effects in GAAS MIS schottky diodes

The electrical characteristics of GaAs MIS Schottky barrier diodes using a thin (∼60 Å) native oxide layer were evaluated before and after ionizing ∝-ray irradiation and fast-neutron irradiation. No change in electrical behavior could be observed with a Cobalt-60∝ irradiation level as high as 1.5 × 10⁷ rads (Si) absorbed dose. The MIS diodes together with reference MS diodes were progressively irradiated with neutrons from a fluence of 5 × 10¹³ n/cm² to 8 × 10¹⁴ n/cm². Carrier compensation in GaAs is negligible at these radiation levels, but significant changes were observed in I-V characteristics. The low-voltage forward I-V exhibited an appreciable increase in depletion region recombination current resulting from a decrease in carrier lifetime, while the diode ideality factor was found to increase at higher forward voltages. The reverse current showed orders of magnitude increase with irradiation, and its strong field dependence and relatively weak temperature dependence suggests field emission through traps as possible mechanism of current flow. The attenuation in reverse current caused by the oxide layer is seen to be reduced after neutron irradiation. Finally, the increase in reverse current is found to vary approximately in proportion to the neutron fluence. The implications of radiation results on practical devices are briefly discussed.