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

Surface barrier detectors processed in Aachen using SI-GaAs from sever al manufacturers have been irradiated with high fluences of neutrons ( mean energy 1 MeV, fluence up to Phi(p) similar to 5 x 10(14) cm(-2)), pions (191 MeV, fluence up to Phi(r) similar to(pi) 0.6 x 10(14) cm(- 2)) and protons (23 GeV, fluence up to Phi(p) similar to 2 x 10(14) cm (-2)). The detectors have been characterized in terms of macroscopic q uantities like I-V characteristic curves and charge collection efficie ncies for incident minimum ionizing- (mip) as well as alpha-particles. All detectors work well after the exposure. At the highest fluences a sizable degradation concerning the charge collection efficiencies has been observed for all investigated materials. SI-GaAs material with l ow carbon content (LC material from FCM, Freiberg) seems to be less af fected than substrates with a higher carbon concentration. At the high est irradiation level the mip signal from a 250 mu m thick detector ma de of LC material amounts to 8000 electrons (at 400 V bias voltage) in dependent of peaking times between 40 ns and 2.2 mu s. The leakage cur rents for this material are even reduced after the irradiation.