Response Properties of Silicon Trench Photodiodes to Single α- and γ-Ray in Pulse Mode

Abstract

This study proposes a new silicon X-ray sensor structure for photon-counting computed tomography (CT), which is a next-generation low-dose X-ray imaging technique. Silicon, which is inexpensive and has excellent processability and a lower reverse bias voltage of several tens of volts, as well as charge transport properties, is used as the sensor material. Using silicon trench photodiodes and horizontal X-ray irradiation method, we can achieve the performance required for photon-counting CT, including a signal response time of less than 100 ns and an exposure dose two orders of magnitude lower than that of conventional CT at a low cost, long device lifetime, and high reliability. The proposed sensor was fabricated, and its photon-counting effectiveness was estimated using 4.2 MeV single $\alpha $ -ray and 60 keV single $\gamma $ -ray photon. The pulse height spectra derived from the $\alpha $ -rays and $\gamma $ -rays were obtained with a low bias voltage of 20 V. For the first time, a single radiation detection pulse was observed, and the pulse height spectra were obtained using silicon trench photodiodes. Furthermore, $\gamma $ -ray count rate, detection efficiency, and pulse rise time proportional to the signal charge collection time were estimated using 60 keV $\gamma $ -rays.

Keywords

• X-ray detectors
• silicon radiation detectors
• photodiodes
• semiconductor device
• microfabrication
• single γ-ray photon counting