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Proceedings Paper

Lateral amorphous selenium metal-semiconductor-metal photodetector for large-area high-speed indirect-conversion medical imaging applications
Author(s): Kai Wang; Feng Chen; Kyung-Wook Shin; Nicholas Allec; Karim S. Karim
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Paper Abstract

Thick amorphous selenium (a-Se) as an excellent photoconductor has been used in direct conversion X-ray imaging modalities such as mammography. However, due to substantial charge trapping, such detectors experience a long X-ray response time and as a result, suffer from a slow speed of operation. Therefore, its deployment to speed-required applications such as real-time fluoroscopy remains a challenge. In this work, we aim to investigate a lateral a-Se MSM photodetector as an indirect conversion X-ray imager and its utilization in high speed, high energy medical applications. The dark current density of the newly-fabricated detector is below 20 pA/mm2 for a 200 μm×50 μm pixel pitch at electric field strengths ranging from 6 to 12 V/μm. The photoresponsivity reaches up to 2.3A/W towards blue wavelength of 468 nm at an electric field strength of 20 V/μm. Furthermore, the photocurrent has a fast speed of photoresponse, demonstrating rise time, fall time and time constant of 50 μs, 60 μs and 30 μs, respectively. Given that low dark current and high photoresponsivity this detector holds, coupled with fast photoresponse, it is believed that lateral a-Se MSM photodetector is promising for indirect conversion X-ray imager integrated with either CMOS or TFT arrays.

Paper Details

Date Published: 18 March 2010
PDF: 9 pages
Proc. SPIE 7622, Medical Imaging 2010: Physics of Medical Imaging, 762217 (18 March 2010); doi: 10.1117/12.843980
Show Author Affiliations
Kai Wang, Univ. of Waterloo (Canada)
Thunder Bay Regional Research Institute (Canada)
Feng Chen, Univ. of Waterloo (Canada)
Kyung-Wook Shin, Univ. of Waterloo (Canada)
Nicholas Allec, Univ. of Waterloo (Canada)
Karim S. Karim, Univ. of Waterloo (Canada)


Published in SPIE Proceedings Vol. 7622:
Medical Imaging 2010: Physics of Medical Imaging
Ehsan Samei; Norbert J. Pelc, Editor(s)

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