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

5. Dose Rate Dependence 85Figure 5.4: Reverse annealing constant k Y 2versus irradiation ux.errors on dosimetry. SA and P0 samples also have a larger error on FDV at late stages ofreverse annealing. Its source is extrapolation of C ;2 versus Vcurve to the plateau value.This was necessary because of breakdown below full depletion voltage.5.3 Results on Reverse CurrentStudy of the leakage current could unfortunately not be performed on the full range of doserates. The reason were problems with guard ring connections that occurred with samplesSA and P0. With guard rings not connected it was not possible to separate the bulkgeneration current from surface current generated on the edge. Since its contribution canbe much larger than the bulk generation current (see g. 3.13), those samples are uselessfor comparisons of the reverse current. Thus only samples K0, K1 and K3, irradiatedwith neutron uxes of 2:310 12 n/cm 2 s, 4:210 11 n/cm 2 sand2:110 9 n/cm 2 s are shown ingure 5.5. The reverse currents were tted according to eq. 4.12 and results are given intable 5.3. Some measured points with bad guard ring connection for sample K1 on thatgure indicate the variability ofthesurface current contribution.Though one can notice some dierence among the samples it is attributed to themeasurement error. It is also not correlated with the irradiation ux.