Design and development of a silicon pixel detector for a single-photon counting image sensor

We have designed and developed detectors operating in direct detection of X-ray and a full-depletion mode and having a low noise characteristic attributed to the very small signal generated by a single X-ray photon. In order to improve the X-ray efficiency, the detector was for thicker detectors (1-mm thick) with an optimized electric-field distribution and enhanced breakdown voltage by using alternative techniques of silicon detectors with slight modifications. The proposed structure was fabricated from 4-inch, FZ-refined, N-type, <111>-oriented, 1-mm-thick, high-resistivity (5 k ∼ 10 kΩ·cm) silicon wafers. The fabricated pixel detector had an n ⁺-n-p⁺ structure, a pixel pitch of 100 μm and an active area of 80 × 80 μm. The design of the silicon pixel detector and its performance are presented.