Segmentation of the Outer Contact on P-Type Coaxial Germanium Detectors

78248S Segmented germanium detector arrays are needed by the DOE for the characterization of low-level radioactive samples. In addition, the same detector arrays could perform important fundamental physics measurements, including the search for rare-events like neutrinoless double-beta decay. However, because of their complexity, these segmented coaxial detectors are expensive and available only after relatively long lead times. Improved fabrication techniques would greatly reduce costs and improve the availability of these segmented detectors for the low-level counting community. Therefore, this project will experimentally investigate alternative techniques for making segmented contacts on p-type coaxial germanium detectors, which would be a much cheaper alternative to the segmented n-type coaxial detectors currently proposed. However, the difficulties associated with the segmentation of conventional thick lithium-diffused contacts must be addressed. Phase I will evaluate amorphous germanium contacts for the hole-injection barrier on small planar test detectors. By making many detectors in rapid succession, the best fabrication parameters will be determined and reconciled with theory. To demonstrate the viability of the fabrication technique, a p-type pseudo-coaxial detector having 8 segments will be fabricated. By the end of Phase II, the best fabrication technique for making segmented p-type coaxial detectors will be determined. Commercial Applications and Other Benefits as described by the awardee: The new germanium-detector technology should enable better detector performance at lower cost. In large low-background arrays, these detectors should find use in the assessment of low-activity radioactive sources of national security and environmental importance. In addition, the same detector arrays will take pure science to new levels of sensitivity in the Majorana search for neutrinoless double-beta decay. Other potential areas of importance to the DOE and the nation include nuclear nonproliferation, medical imaging, and x-ray detectors.