Breakdown voltage analysis of neutron irradiated silicon detectors

The very intense radiation environment of high luminosity future colliding beam experiments (LHC, etc.) makes radiation hardness the most important issue for Si detectors. The crucial question is whether the Si strip detectors can withstand the harsh radiation environment for sufficiently long time (full LHC lifetime) and hence the central issue concerning all LHC experiments is the breakdown performance of these detectors. In this paper the simulations have been performed to analyze electrical parameters for the most deleterious long-term effect of radiation: the change in effective charge carrier concentration and resulting increase in full depletion bias. Detailed calculations using Hamburg Model have allowed the parameterization of these effects, and helped to simulate the operation scenario of Si detectors over 10 years of LHC operation. The systematic studies of the electric field to get an insight into the device behavior provide, for the first time, a possible explanation for the improvement in breakdown performance with radiation. Simulation study is also carried on optimized guard ring structures to study the change in guard voltage distribution after 10 years of neutron radiation damage.