Permanent Damage Effects in Si and AlGaAs/GaAs Photodiodes

We report here on a study of permanent damage effects in photodiodes due to total dose exposures of 108 rad (Si) ionizing-radiation from a Co60 source. Specifically, we compare the degradation of optical quantum efficiency and increases in photodiode leakage current in Si PIN structures with specially designed and fabricated, double heterostructure AlGaAs/GaAs photodiodes. Results indicate some degradation in quantum efficiency (20-30%) for both types of devices. Leakage currents were found to increase signficantly after 108 rad in the Si PIN structures but only increase slightly in the AlGaAs/GaAs structures.