Low dark current and high dynamic range a-Si:H MSM photodetector for large area medical imaging

Sina Ghanbarzadeh; Shiva Abbaszadeh; Michael Adachi; Karim S. Karim

doi:10.1117/12.2007973

6 March 2013 Low dark current and high dynamic range a-Si:H MSM photodetector for large area medical imaging

Sina Ghanbarzadeh, Shiva Abbaszadeh, Michael Adachi, Karim S. Karim

Proceedings Volume 8668, Medical Imaging 2013: Physics of Medical Imaging; 86683U (2013) https://doi.org/10.1117/12.2007973
Event: SPIE Medical Imaging, 2013, Lake Buena Vista (Orlando Area), Florida, United States

Abstract

Previously a-Si:H metal-semiconductor-metal (MSM) lateral detectors for indirect medical imaging applications had been proposed by our research group. These lateral detectors are attractive due to their ease of fabrication primarily because there is no p+ doped semiconductor layer, thus making it compatible with industry standard amorphous silicon thin film transistor electronics processing. However the earlier devices exhibited high dark current which is problematic for integration mode imaging. In the other words, they were limited in term of dynamic range. In this study, we demonstrate an a-Si:H MSM lateral structure with low dark current, high dynamic range and comparable sensitivity and quantum efficiency to conventional p-i-n photodiodes. These improvements are achieved by the introduction of a thin polymer layer as a blocking contact. The fabricated amorphous silicon based MSM detector exhibits a photo-response of more than 3 orders of magnitude to a green light source (λ = 525nm). In comparison to vertical p-i-n structures, the reported MSM lateral devices show gains in terms of dynamic range, ease of fabrication (no p+ layer), faster speed at the cost of a slightly reduced quantum efficiency. The experimental results of dark and photocurrent measurements as well as the responsivity for two in-house fabricated MSM structures at different bias voltages and light intensity are presented. This results are promising and encourage the development of a-Si:H lateral MSM devices for indirect conversion large area medical imaging applications and especially low cost flat panel computed tomography.

Citation Download Citation

Sina Ghanbarzadeh, Shiva Abbaszadeh, Michael Adachi, and Karim S. Karim "Low dark current and high dynamic range a-Si:H MSM photodetector for large area medical imaging", Proc. SPIE 8668, Medical Imaging 2013: Physics of Medical Imaging, 86683U (6 March 2013); https://doi.org/10.1117/12.2007973

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