Development of Germanium Detectors for Rare Event Physics Searches*

High-purity germanium (HPGe) detectors have been widely recognized for their high performance in gamma-ray spectroscopy. Due to their low electrical capacitance, semiconductor detectors made of germanium have been favored as they provide significantly better energy resolution compared to other radiation detection materials. As a result, HPGe detectors have proven to be crucial for the investigation of dark matter and neutrinoless double beta decay experiments. This work introduces the research that I have been pursuing at the University of South Dakota (USD), one of the leading institutions for facilitating the fabrication and characterization of HPGe planar detectors. The home-grown crystals at USD using the Czochralski technique are utilized for fabricating detectors rare-event searches. The fabrication of detector is implemented in Patterson 124. The amorphous germanium contacts are created using the sputtering machine to block both electron and hole injection while providing a sufficient passivation layer on the surface of the HPGe crystal. After fabrication, the detectors are cooled down to approximately the temperature of liquid nitrogen (79 K) and assessed using I-V and C-V characteristics as performance metrics. Further research conducted at USD aims to optimize detector performance by minimizing noise induced by charge injection leakage current, resulting in higher charge collection efficiency.