INVESTIGATION OF THE RADIATION-DAMAGE OF GAAS DETECTORS BY PROTONS, PIONS AND NEUTRONS

Surface barrier detectors processed in Aachen using semi-insulating (S I) GaAs from several manufacturers have been irradiated with high flue nces of neutrons (mean energy 1 MeV, fluence up to Phi(n) similar to 5 x 10(14) cm(-2)), pions (191 MeV, fluence up to Phi(pi) similar to 0. 6 x 10(14) cm(-2)) and protons (23 GeV, fluence up to Phi(p) similar t o 2 x 10(14) cm(-2)). The detectors have been characterized in terms o f macroscopic quantities like I-V characteristic curves and charge col lection efficiencies for incident minimum ionizing- (mip) as well as a lpha-particles. All detectors work well after the exposure. At the hig hest fluences a sizable degradation in the charge collection efficienc ies has been observed for all investigated materials. SI-GaAs material with low carbon (LC) content seems to be less affected than substrate s with a higher carbon concentration, Al the highest irradiation level the mip signal from a 250 mu m thick detector made of LC material amo unts to 8000 electrons (at 400 V bias voltage) independent of peaking times between 40 ns and 2.2 mu s. The leakage currents for this materi al are even reduced after the irradiation.