Influence of contact geometry on NTD sensor performance

A cryogenic bolometer with Neutron Transmutation Doped Ge as mK thermometer is being developed to study neutrinoless double beta decay (NDBD) in 124Sn. The performance and sensitivity of the sensor strongly depends on the irradiation as well as fabrication (etching, annealing, contact deposition) process. The role of contact fabrication on the sensor performance is presented here. The performace of NTD Ge sensors with wrap-around contact and face-type contacts is compared at T < 100 mK. It is observed that NTD Ge sensors with face-type contacts show Mott behaviour upto lower temperature ~35 mK as compared to that for sensors with wrap-around contacts. Further, detailed noise measurements on several indigeously developed NTD Ge sensors have been carried out in temperature range of 20-70 mK to understand its impact on bolometer resolution and have been described in following section.