Radiation damage in silicon particle detectors: Microscopic defects and macroscopic properties
M. Moll
Abstract
Silicon microstrip and pixel detectors are the key devices for the measurement of particle trajectories in elementary particle collision experiments. In present-day and future high luminosity experiments (e.g. ATLAS, CMS, LHCb and HERA-B) they have to operate in extremely intense hadronic radiation fields where radiation damage of the detector bulk material leads to severe deterioration of the detector properties. It is even foreseeable that some of the devices produced from standard detector grade silicon and exposed to the highest irradiation levels will not survive the envisaged operational period of the experiments. Hence, the improvement of the radiation tolerance of the detector bulk material is of prime importance and was the main goal of this thesis. The radiation induced changes in the effective doping concentration and the leakage current have been systematically investigated and parameterized as function of particle fluence, annealing temperature and annealing time. Furthermore, as a possibility for defect engineering, the dependence on the oxygen content and the resistivity of the bulk material was studied. The oxygen concentration of the investigated materials reached from 1 clow 2 x 10"1"4 cm"-"3 to 9 x 10"1"7 cm"-"3 and the resistivity of the n-type silicon from 110 #OMEGA#cm to about 25 k#OMEGA#cm. It has been found that a high oxygen concentration leads to an improved radiation hardness of the bulk material with respect to the changes in the effective doping concentration for neutron and especially charged hadron irradiation