A NEW STRUCTURE FOR CONTROLLING DARK CURRENT DUE TO SURFACE GENERATION IN DRIFT DETECTORS

A new approach has been developed to control dark current due to surfa ce generation in silicon drift detectors. Instead of using a guard ano de to collect current generated at the surface in the areas between th e p(+) rings, these areas are filled with n(+) diffusion rings. This a pproach reduces the depleted area of the silicon/SiO2 interface, which is the source of the surface current, from about 50% of the detector area to less than 2%. Superior robustness to process and material defe cts make this technique preferable to a design using a guard anode to collect surface current in our experiments. The new structure has been applied to an 8 mm diameter cylindrical drift detector. X-ray test re sults show good signal collection from the full detector volume. (C) 1 998 Published by Elsevier Science B.V. All rights reserved.