Radiation sensitivity of light emitting diodes (LED), laser diodes (LD) and photodiodes (PD)

Commercially available diodes were irradiated at a flash X-ray source, a ⁶⁰Co gamma ray source, and a 14-MeV neutron generator. During irradiation at the ⁶⁰Co source, the light output of the LEDs and LDs was measured continuously. From time to time their emission spectrum was also observed. With the PDs the authors measured the preamplifier output during ⁶⁰Co irradiation as well as dark current noise before and after irradiation. Determination of the sensitivity against neutrons was made offline. After pulsed irradiation of PDs the authors measured how long a certain type of preamplifier was overdriven by the induced photocurrent. LEDs and LDs showed a maximum decrease of output power of only 0.5 dB up to a total gamma dose of 10⁶ Gy or neutron fluences of 4×10¹³ cm^-2 (1 MeV), respectively. Irradiations of PDs with ⁶⁰Co gammas up to a total dose of 10⁶ Gy as well as irradiations with neutrons up to fluences of ⩽4×10¹³ cm^-2 (1 MeV) lead to significant changes of the device parameters. The main effect is a strong increase of the dark current by factors of two up to 5000