NEUTRON-INDUCED RADIATION-DAMAGE IN SILICON DETECTORS

Ion-implanted silicon pad detectors fabricated on different n-type and p-type silicon wafers with initial resistivities between 2.6 and 12.9 kOMEGAcm have been irradiated with neutrons of approximately 1 MeV energy, up to a fluence of 5 10(13) n cm-2. The evolution of diode leakage current and capacitance characteristics is presented as a function of the neutron fluence. The reverse diode current increases proportionally to the neutron fluence. There is evidence that the doping of the initial n-type material evolves towards intrinsic and inverts to an apparent p-type at fluences between 1 10(13) and 3 10(13) n cm-2, depending on the initial silicon resistivity. There is also evidence that p-type material remains of the same conduction type with a slight increase of the acceptor doping with fluence. The signal shape and the charge collection efficiency for incident beta particles have also been measured. Results from this work may contribute to show the feasibility of silicon detectors in the supercolliders, in particular, for a silicon tracker and preshower under study for the LHC.