NOISE CHARACTERISTICS IN IRRADIATED MULTIGUARD STRUCTURES

Multiguard structures are designed in order to limit the electrical fi eld intensity around a p-n junction. With these devices the breakdown voltage in silicon microstrip detectors can be greatly enhanced. In th is 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 h undred Volts without breakdown. For each layout the DC electrical char acteristics 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 L HC experiments.