Radiation effects in 1.06-μm InGaAs LED’s and Si photodiodes

Because of the low-intrinsic and radiation-induced attenuation losses in glass fibers in the wavelength range 1.0–1.3 μm, emitters and detectors operating in this range are of practical importance for radiation-environment applications. We have studied the effects of both γ and neutron irradiation on the properties of InGaAs LED’s emitting at 1.06 μm and Si photodiode detectors optimized for this wavelength. While the preirradiation light output of the InGaAs LED’s is low relative to many GaAs LED’s, the InGaAs devices exhibit less sensitivity to radiation than the most radiation-hardened GaAs LED’s. No significant neutron-induced light-output degradation is observed below 1×1013 n/cm2, while 2×107 Co-60 rads are required before any γ-induced degradation is observed. In addition, a significant portion of the γ-induced light-output degradation can be recovered by applying forward-bias currents of the order of 50 mA in magnitude. Although γ irradiation up to 2×108 rads has essentially no effect on the photodiodes, neutron fluences above 2×1014 n/cm2 cause a reduction in responsivity. Analysis of the neutron-induced increases in the photodiode leakage current with the guard ring attached reveals a lifetime-damage constant product of 4×10−12 cm2/n. Laboratory isolators made up of these emitters and detectors have typical preirradiation current-transfer ratios of 5×10−4 which decrease by a factor of 10 after an irradiation of 1.5×1014 n/cm2.