Speaker
Description
High purity germanium (HPGe) detectors remain the state of the art technology for high resolution gamma ray spectroscopy, yet conventional lithium diffused contacts impose intrinsic limitations on device performance and segmentation due to their ~1 mm inactive layer and poor thermal stability. To address these constraints, a new fabrication approach based on magnetron sputtered dopants incorporated into germanium via Pulsed Laser Melting (PLM) has been developed at INFN-LNL and the University of Padova. PLM temporarily melts a thin Ge layer, enabling epitaxial regrowth and substitutional dopant incorporation, resulting in an ultra thin, thermally stable, and fully segmentable contact/junction.
A series of prototypes from 2 mm devices to 2 cm thick crystals was fabricated to validate the technique. Across all samples, PLM formed junctions exhibited excellent thermal stability, including after neutron damage recovery annealing cycles. Process optimization (surface preparation, photolithography, chemical mechanical polishing, and mechanical contacting) yielded devices with breakdown voltages significantly above depletion voltage.
These results demonstrate that PLM based doping can effectively replace lithium diffused contacts, enabling next generation segmented HPGe detectors with improved performance for applications in nuclear physics, imaging, security, and astrophysics.