Potential distribution in voltage terminating structures with floating p–n junction rings of silicon radiation detectors

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

“…As was shown in studies of the mechanisms of the distribution of potentials over the detector's VTS before irradiation, the value of the electric field in the region of the inter ring gap is the most important fac tor, which determines the difference in potentials between neighboring rings [1]. Irradiation of silicon diode structures brings about the generation of radia tion defects with energy levels that affect the effective concentration N eff in the space charge region (SCR) and the corresponding profile of the electric field.…”

“…In what follows, the sign of the space charge is changed from positive to negative, i.e., inversion of the space charge's sign takes place. The dependence of the effective concentration N eff on the dose of irradia tion with neutrons Φ can be calculated using the fol lowing parametric equation [2]: (1) here, N d0 is the effective concentration before irradia tion with N d0 = N eff (Φ = 0); γ = 8.8 × 10 -14 cm 2 is the coefficient of donor removal; and β = 0.022 cm -3 is the coefficient of acceptor introduction. According to Eq.…”

“…As was shown previously [1], the distribution of the potentials over the VTS of unirradiated detectors is described in terms of an injection model of current flow through the inter ring gaps in the VTS. In the case where the sensitive p + -n junction is reverse biased, the ring potential remains equal to zero until a high critical voltage V bias = V cr .…”

“…In the simulation, we disregarded the introduction of deep levels as a result of irradiation and, as a result, we disregarded the formation of the electric field profile with two maximums near the p + and n + type contacts in the case of irradiation with high doses. The adjustable parameter was the effective impurity concentration, which was calculated as a function of the dose of irradiation using formula (1). For detectors irradiated with doses of no higher than 10 13 n eq /cm 2 , i.e., prior to inversion of the space charge sign, the detector model corresponded to the p + -n-n + structure.…”

“…In thus study, we investigated the effect of irradia tion with neutrons at doses as high as 5 × 10 15 n eq /cm 2 on the properties of ring structures, which surround the sensitive area of the detector and are designed to provide a gradual decrease in the potential from the central sensitive area to the detector's periphery (in what follows, we use the abbreviation VTS, which stands for voltage terminating structure [1]). This makes it possible to prevent the formation of regions with a high electric field at the radiation sensitive con tact and the flow of surface and peripheral currents, thus attaining stabilization of the device's operation.…”