Radiation tests of semiconductor detectors

University dissertation from Stockholm : KTH

Abstract: This thesis investigates the response of Gallium Arsenide (GaAs) detectors to ionizing irradiation. Detectors based on ?-? junction formed by deep level centers doping. The detectors have been irradiated with 137Cs ?-rays up to 110 kGy, with 6 MeV mean energy neutron up to approximately 6 · 1014 n/cm2, with protons and mixed beam up to 1015 p/cm2. Results are presented for the effects on leakage currents and charge collection efficiencies for minimum ionizing electrons and alpha particles. The signal from minimum ionizing electrons was well separated from the noise even after the highest delivered exposures and the diodes are thus still operational as detectors. Saturation of the effects of radiation damage is observed in both the I-V characteristics and charge collection efficiency measurements.The requirements for detectors e.g. at present and planned hadron colliders is very high in terms of radiation hardness. Detectors for tracking applications close to the interaction point will receive charged particle doses in the range of 110 kGy and fast neutron fluences of 1014 n/cm2 during the lifetime of an experiment. In this thesis it is confirmed that GaAs detectors are radiation resistant to neutron irradiation for fluences up to 1015 n/cm2 and that GaAs detectors are feasible as inner trackers. Most of this work was performed in the framework of the RD8 collaboration at CERN.