High-Performance Germanium P-I-N Photodiodes for High-Speed, Hard X-Ray Imaging

Design, fabrication, and measurement of vertical Germanium (Ge) Photodiodes for high-speed, hard X-Ray imaging is presented. The devices used atmospheric-pressure epitaxial absorption layers, varying absorption layer thicknesses (10 – 245 μ m) over bulk-Ge substrates, fabricated in various sizes. Measurements include large-signal and transient-response from X-ray source between 6 keV and 28 keV. The results approach a 100% external quantum efficiency with 245 lm absorption regions and a 22% improvement in temporal response with 10μ m absorption region compared to an Si reference device of the same active area.