CV and Hall effect analysis on neutron irradiated silicon detectors

Abstract

Four contact bulk samples and p + n junction diodes produced from high resistivity n-type silicon wafers of the same ingot have been irradiated with 1 MeV-neutron fluences between 10 12 and 3 × 10 13cm −2. The effective impurity concentration N eff has been calculated from CV measurements in irradiated diodes, and bulk resistivity has been measured with the Van der Pauw method on four contact samples. The experimental resistivity and N eff dependence on the irradiation fluence, self-annealing time and storage temperature have been modeled considering the exponential shallow donor decay and the creation of acceptor traps in the irradiated silicon. A numerical fit to the experimental data, based on the solution of the neutrality and Poisson equations, has been carried out considering an equivalent deep acceptor defect created during and after irradiation in the silicon lattice. The energy level and the introduction rate of this defect, evaluated as best-fit parameters in the numerical procedure, are E t = 0.60–0.65eV above the valence band edge defect, evaluated as best-fit parameters in the numerical procedure, are E t = 0.60–0.65eV above the valence band edge and b ∼ 0.06 cm −1.