Radiation effects on floating rings of voltage terminating structure in Si p-on-n detectors

In the 1990s a suggestion was put forward that the space charge limited current mechanism is responsible for stabilization of the I-V characteristics in irradiated Si p-on-n detectors. This mechanism is switched on in the case of high concentration of radiation induced deep traps which via holes accumulation will reduce the electric field in the regions of breakdown. The present study shows that voltage terminating structure (VTS) consisting of the floating p+ rings as a main element for stabilization of I-V characteristics in nonirradiated detectors is still active being irradiated to the fluence beyond space charge sign inversion. This characteristic of VTS can be accounted for by the double peak electric field distribution in heavily irradiated detectors and the punch-through mechanism of current flow between the floating p+ rings in the silicon bulk with high concentration of deep traps. It is shown that VTS operates as a potential divider up to the fluence of 1×1015 neq/cm2 and it is at higher fluences that the detector stability is maintained only by the space charge limited current mechanism.