GAMMA-RADIATION EFFECTS OF LIGHT-EMITTING AND VARIABLE CAPACITANCE DEVICES

Gamma radiation doses as low as a few krads caused significant increas es in the output of light-emitting diodes (LEDs). Further irradiation, above 10 krad, produced permanent radiation damage associated with th e degradation of light emitted and the output electrical characteristi cs. Capacitance-voltage and current-voltage measurements have shown th at LED devices are sensitive to the gamma-ray dose. Such behavior sugg ests that LED devices can be successfully employed for the determinati on of absorbed dose in the relatively low gamma dose range. Following irradiation, shelf annealing of the damaged cells, at room temperature for 200 days, leads to recovery of 17-18% of their initial output lig ht intensity. Oven annealing at different temperatures ranging up to 5 00-degrees-C, for 50 minutes, shows that the output light intensity le vels recover to around 22%, 25%, 33%, 43%, and 67.5% of the initial va lues under the influence of annealing temperature levels of 100-degree s-C, 200-degrees-C, 400-degrees-C, and 500-degrees-C respectively. Var actor type ''BA102'' offered a high resistance to gamma exposure. The response of its (C-V) and (I-V) relationships to radiation started onl y in the Mrad range, where the change is found to occur over a relativ ely wide radiation dose range (up to 130 Mrads). The ratio of capacita nce variation (C/C(o)) due to gamma irradiation is increased from 2.7, at zero dose, to 4.5 after exposure to 50 Mrads and at a reverse bias of 10 volts.