Fabrication and Characterization of High-Purity Germanium Detectors with Thin (Amorphous Germanium) Contacts*

Large high-purity germanium (HPGe) detectors are widely used in neutrinoless double-beta decay and dark matter experiments. Currently, large (diameter > 11 cm) HPGe crystals can be grown successfully at the University of South Dakota (USD) and small planar detectors with thin contacts can be fabricated and characterized. Compared with lithium contacts, thin contacts (Amorphous Germanium) have a smaller dead layer. This increases the active volume of the detector. Thanks to NSF, USD has purchased a more advanced sputtering system this year, which can make large-size Ge detectors with thin-contacts. We will make detectors and conduct a R&D to deposit a layer of PEN material on the amorphous germanium contacts through this new sputtering system. This talk will report the latest progress in USD detector fabrication.