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

74 4. Time Development of DefectsLower full depletion voltages for MESA processed samples as compared to planarones have also been reported by G. Casse et al. [48]. They observed systematically betterradiation hardness of MESA samples as compared to planar ones. The dierence shows asan about factor of two lower introduction rate of acceptor-like defects, lower introductionrate of reverse annealing defects and lower damage constant. Those eects are howevernot induced by increased oxygen concentration only, since results on oxygenated planarsamples (up to several 10 17 cm ;3 ) show no decrease in FDV or value as compared tonon-oxygenated planar samples [48]. Agreement of FDV after irradiation for standardand oxygenated materials was also reported by L. Beattie et al. [49], while B. Dezillie etal. [32] reports better radiation resistivity of MESA samples and M. Moll et al. [50] forCzochralski samples, both having an increased oxygen concentration (order of 10 18 cm ;3 ).4.4 Annealing of Reverse CurrentAs with N eff , the time development of bulk generation current was studied in two parts:fast annealing at various temperatures during the rst week after irradiation and longterm annealing at 60 C to accelerate time development.4.4.1 Fast AnnealingSample T 0 0 1 1 2 2[ C] [10 ;17 A/cm] [10 ;17 A/cm] [h] [10 ;17 A/cm] [h]D3 15 C 4.6 2.0 4.2 1.9 55D1 15 C 4.1 1.2 15. 1.4 180B3 0 C 4.1 1.2 9.7 1.1 220K0 5 C 5.4 14. 1.4 2.5 20K3 5 C 5.1 7.4 2.2 1.9 38Table 4.9: List of samples and irradiation temperatures with values of the t parametersaccording to eq. 4.11. For easier comparison between samples and with other authors, values ofthe parameter are normalised to 20 C.Fast annealing of reverse current was studied on samples D3, D1, B3, K0 and K3.Their irradiation conditions are given in tables 4.1 and 4.3. The rest of the diodes had noguard ring structures, guard rings were not connectable or had some other problems thatprevented reliable determination of the bulk current.As with N eff , short term annealing can be tted with a constant part and two