Improved optical quantum efficiency and temporal performance of a flat-panel imager with avalanche gain

Corey Orlik; Adrian F. Howansky; Sébastien Léveillé; Anastasiia Mishchenko; Safa Kasap; Jann Stavro; Amir H. Goldan; James R. Scheuermann; Wei Zhao

doi:10.1117/12.2582035

15 February 2021 Improved optical quantum efficiency and temporal performance of a flat-panel imager with avalanche gain

Corey Orlik, Adrian F. Howansky, Sébastien Léveillé, Anastasiia Mishchenko, Safa Kasap, Jann Stavro, Amir H. Goldan, James R. Scheuermann, Wei Zhao

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Proceedings Volume 11595, Medical Imaging 2021: Physics of Medical Imaging; 1159516 (2021) https://doi.org/10.1117/12.2582035
Event: SPIE Medical Imaging, 2021, Online Only

Abstract

Active matrix flat panel imagers (AMFPIs) with thin film transistor (TFT) arrays are becoming the standard for digital x-ray imaging due to their high image quality and real time readout capabilities. However, in low dose applications their performance is degraded by electronic noise. A promising solution to this limitation is the Scintillator High-Gain Avalanche Rushing Photoconductor AMFPI (SHARP-AMFPI), an indirect detector that utilizes avalanche amorphous selenium (a-Se) to amplify optical signal from the scintillator prior to readout. We previously demonstrated the feasibility of a large area SHARP-AMFPI, however there are several areas of desired improvement. In this work, we present a newly fabricated SHARP-AMFPI prototype detector with the following developments: metal oxide hole blocking layer (HBL) with improved electron transport, transparent bias electrode for increased optical coupling, and detector assembly allowing for a back-irradiation (BI) geometry to improve detective quantum efficiency of scintillators. Our measurements showed that the new prototype has improved temporal performance, with lag and ghosting below 1%. We also show an improvement in optical coupling from 25% to 90% for cesium iodide (CsI) scintillator emissions. The remaining challenge of the SHARP-AMFPI is to reduce the dark current to prevent dielectric breakdown under high bias and further increase optical quantum efficiency (OQE) to CsI scintillators. We are proposing to use a newly developed quantum dot (QD) oxide layer, which shows to reduce the dark current by an order of magnitude, and tellurium doping, which could increase OQE to 85% to CsI at avalanche fields, in future prototype detectors.

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Corey Orlik, Adrian F. Howansky, Sébastien Léveillé, Anastasiia Mishchenko, Safa Kasap, Jann Stavro, Amir H. Goldan, James R. Scheuermann, and Wei Zhao "Improved optical quantum efficiency and temporal performance of a flat-panel imager with avalanche gain", Proc. SPIE 11595, Medical Imaging 2021: Physics of Medical Imaging, 1159516 (15 February 2021); https://doi.org/10.1117/12.2582035

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