Strip detector design for ATLAS and HERA-B using two-dimensional device simulation

Abstract

Irradiation scenarios were simulated in order to evaluate different technology and design options for silicon strip detectors exposed to a high luminosity environment. Two-dimensional process and device simulations were performed to get an insight into the device behaviour. The boundary condition of the free oxide regions between the strips was evaluated thoroughly to obtain correct field distributions. Using these results the formation of electron accumulation layers on the surface of the p-side and the depletion voltage dependence on the strip geometry can be explained. We investigated the “blocking implant” and the “spray implant” techniques as promising candidates for the n-side isolation of irradiated detectors. The main drawback of the “blocking implanted” devices is the increase of the electric field with increasing oxide charges. This implies the danger of impact ionization in irradiated devices. A “spray implanted” isolation layer leads to the highest electric field in the non-irradiated state which has the advantage of a better testability. Small gaps between strips as used in charge division readout reduce electric fields and leakage currents.