Pulsed Irradiation of Optimized, MBE Grown, AlGaAs/GaAs Radiation Hardened Photodiodes

We report here new results including the effects of neutron irradiation of AlGaAs/GaAs double hetero-junction photodiodes and special, small active volume, PIN silicon photodiodes. Results from high energy electron irradiations are also presented. Finally we report on improvements in processing and growth of these radiation hardened, AlGaAs/GaAs, double heterojunction, photodiodes. Neutron irradiation studies have shown that the double heterojunction, AlGaAs/GaAs photodiodes degrade only slightly after exposure to 3.6 × 1015 n/cm2. The special "rad-hard" silicon PIN photodiodes showed considerably greater degradation in both optical responsivity and leakage current characteristics after exposure to neutron fluences of 1.0 × 1015 n/cm2. Measurements of ionizing-radiation induced photocurrent during exposures to pulsed electron beams and pulsed x-rays show that the AlGaAs/GaAs structures generate only a fraction (0.03 to 0.1) of the current generated by the small active volume, radhard, silicon photodiodes. Optimization of the device growth and fabrication processes have resulted in significantly better electrical characteristics while maintaining good optical properties. The irradiation test results reported here expand our knowledge of the radiation hardness of these devices to include other types of irradiation threats beyond previously published work.