Noise characteristics in irradiated multiguard structures

Multiguard structures are designed in order to limit the electrical field intensity around a p-n junction. With these devices the breakdown voltage in silicon microstrip detectors can be greatly enhanced. In this work we investigated the electrical properties of these devices and their noise performance. Four different layouts have been considered, consisting of floating p(+) and/or n(+) guards around the active area, In the best case, such a structure can tolerate bias up to several hundred Volts without breakdown. For each layout the DC electrical characteristics have been compared to the RMS noise measured as a function of the applied voltage. The same measurements were carried out after neutron irradiation, to dose levels similar to those expected in the LHC experiments.