Space‐and‐surface charge neutralization of cryogenic Ge detectors using infrared LEDs

Operation of the germanium cryogenic detectors for dark matter search requires an efficient procedure for surface and space‐charge cancellation. Methods of detector reset have been studied for use with the newly commissioned coplanar grid detectors of the EDELWEISS collaboration. To this end, we have investigated several reset procedures, using both penetrating gamma radiation, and infrared LEDs of different wavelengths (1.65, 1.45, and 1.3 μm) to inject carriers at varying depths from the detector surfaces. Criteria are defined to characterize the efficiency of these different reset procedures, and the resulting performances of charge collection are discussed.