Influence of irradiation with neutrons on the characteristics of the voltage terminating structure in silicon radiation detectors

The distribution of potentials over a voltage terminating structure (VTS) has been studied in silicon nuclear-radiation detectors irradiated with neutrons in the range of doses from 1 $\times$ 10$^{10}$ to 5 $\times$ 10$^{15}$ neq/cm$^2$, where the VTS represents a system of floating ring $p^+$–$n$ junctions. It is shown that variation in the profile of an electric field in the bulk of the detector as the radiation dose is increased is the determining factor in the distribution of potentials over the VTS. The mechanisms of VTS operation at irradiation doses lower than 5 $\times$ 10$^{14}$ neq/cm$^2$ are established: the distribution of potentials between the rings is accomplished by a punch-through mechanism in the inter-ring gap, while, at higher doses, the distribution is controlled by a current-related mechanism, which is based on the density of the electron–hole generation current flowing in the bulk of the detector. The suggested mechanisms of VTS operation are confirmed experimentally and by simulation.