Radiation effects in light emitting diodes, laser diodes, photodiodes, and optocouplers

A variety of commercially available LEDs, LDs, PDs, and optocouplers from two German manufacturers were irradiated at a flash X-ray source, a ⁶⁰Co gamma ray source, and a 14 MeV neutron generator. Light output and emission spectrum of the LEDs and LDs were measured before and after irradiation at the ⁶⁰Co source. With the PDs we measured the dark current and the photo current before and after ⁶⁰Co irradiation. Determination of the sensitivity against neutrons was made off-line. With PDs we measured the photo current induced by pulsed X-rays. The GaAs LED showed a maximum decrease of output power of 28 dB after a total gamma dose of 10⁶ Gy and LDs a threshold current shift of 80% after neutron fluences of 4·10¹⁴ cm^-2 (1 MeV). Irradiations of PDs and APDs with ⁶⁰Co gammas up to a total dose of 10⁶ Gy as well as irradiations with neutrons up to fluences of ≲4·10¹⁴ cm^-2 (1 MeV) led to significant changes of the device parameters. The main effect was a strong increase of the dark current. The consequence was a reduction of the minimum detectable light power. Optocouplers are very sensitive to ionizing radiation. Gammas as well as neutrons led to a decrease of the CTR and a change of the bandwidth up to a complete failure (after neutron irradiation)