Investigations on damage of GaAs detectors caused by neutrons (peak energy 1 MeV) and Co-60 photons

In April 1994 we irradiated more than 60 GaAs detectors made from the same wafer with different fluencies in the ISIS neutron source at the Rutherford Appleton Laboratory. The detectors were produced in Aachen from SI-GaAs from American Xtal Technology (AXT). All detectors remained functional after irradiation with up to 1 x 10(15) n/cm(2). Even at the highest radiation level the reverse current density of the detectors is below 50 nA/mm(2) at 200V bias voltage, only a factor of four higher than before irradiation. After 1 x 10(15) n/cm(2) the signal for minimum ionising particles is a factor of two lower than before irradiation. No difference was seen beween detectors that were biased during the exposure and those that were not. The detectors were operated at room temperature during and after the exposure.