Study of radiation damage in silicon detectors for high ... - F9

AbstractRadiation damage of the silicon bulk will play an important role in the vertex detectorsin the future experiments at LHC. To study its macroscopic eects, high resistivityp + -n-n + diodes were irradiated with neutrons at the TRIGA research reactor of JozefStefan Institute in Ljubljana. Irradiation uences were in the range from 10 13 to 2.510 14/cm 2 of equivalent 1 MeV neutrons. Development of eective doping concentration andreverse current during and after irradiations was studied under controlled conditions (bias,temperature).Long term annealing of eective doping concentration was studied to determine thedynamics of the process responsible. Results obtained from a set of unbiased diodes keptat 20 Cgave conclusive evidence that, at least during the initial stage, time developmentcan be described by a rst order process.Flux dependence of defect creation has been checked in the ux range from 210 8 to 510 15 n/cm 2 s. No signicant dierence among the samples was observed in any ofthestudied properties.Inuence of bias voltage on defect development was discovered. Fully biased sampleswere found to have about a factor 2 higher values of N eff after benecial annealing. Afterremoval of bias, the dierence anneals out exponentially with two time constants of about40h and 6weeks at 20 C. No inuence of bias voltage on reverse current was observed.Keywords: silicon detectors, radiation hardness, neutron irradiation, LHCPACS 29.40.Gx, 29.40.Wk