Interfacial Defect Characteristics and Low-temperature Electrical Properties of the Germanium Oxynitride Passivation Film for Ge-Based Metal Oxide Semiconductor and High-Purity Germanium Detectors

Germanium-based devices with high electron/hole mobility at low temperatures have extensive application value in the detection field. Among them, high-purity germanium (HPGe) detectors are a kind of γ-ray detector with the highest energy resolution. The germanium passivation is the bottleneck in the application of cryogenic electronics in germanium-based devices. In this article, we study the mechanism of the germanium oxynitride (GeOxNy) passivation layer to realize low surface defects of Ge-based devices and HPGe detectors. To establish the optimal experimental conditions and passivation mechanism, GeOxNy films were prepared by magnetron sputtering in different O₂/N₂ ratios. Then, the surface defects of Ge/GeOxNy were analyzed by constructing Al/GeOxNy/Ge MOS devices. Their electrical characteristics were tested at room temperature and 77 K. The interface state density (<i>D</i> _it) reflected the surface defects with passivation. The border traps between the GeOxNy/Ge surface were the most important factor causing the <i>D</i> _it to increase at 77 K. The highest minority lifetime of 16.588 μs shows that the GeOxNy film can effectively reduce interface defects. The leakage current and energy resolution of the HPGe detector were further tested after GeOxNy passivation, which achieved a relatively higher energy resolution. This exploration of GeOxNy films gives potential applications for the surface modification of Ge-MOS devices and HPGe detectors.