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Proceedings Paper

Design and modeling of a lateral a-Se MSM photoconductor as indirect conversion X-ray imager
Author(s): Kai Wang; Feng Chen; George Belev; Safa O. Kasap; Karim S. Karim
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Paper Abstract

Amorphous selenium (a-Se) has been widely used as a direct conversion X-ray detection material. Vertical structures are employed in most cases, where >200 μm thick a-Se photoconductor layer is inserted between top and bottom electrodes. In this paper, we design a lateral metal-semiconductor-metal (MSM) structure in which a relatively thin layer of a-Se (~ 8 μm) is coated on top of two lateral electrodes. The simulation results indicate that dark current of such a structure stays extremely low level and external quantum efficiency (EQE) reaches over 30% with wavelengths ranging from 320 to 680 nm. We further fabricate the lateral MSM photoconductor by a two-mask photolithography process. The fabricated photoconductor exhibits a dark current below 40 fA under electric fields ranging from 6 V/μm to 9 V/μm, a responsivity up to 0.06 A/W, a measured EQE of 18% towards a short wavelength of 468 nm, and a high photoresponse speed at 500 Hz with a rise time of 250 μs, fall time of 350 μs, and time constant of 250 μs, respectively. Furthermore, an architecture of indirect conversion X-ray imager is proposed with the use of such a lateral MSM structure and a blue-emitting scintillator material atop.

Paper Details

Date Published: 17 September 2009
PDF: 8 pages
Proc. SPIE 7449, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XI, 74491W (17 September 2009);
Show Author Affiliations
Kai Wang, Univ. of Waterloo (Canada)
Thunder Bay Regional Research Institute (Canada)
Feng Chen, Univ. of Waterloo (Canada)
George Belev, Univ. of Saskatchewan (Canada)
Safa O. Kasap, Univ. of Saskatchewan (Canada)
Karim S. Karim, Univ. of Waterloo (Canada)

Published in SPIE Proceedings Vol. 7449:
Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XI
Ralph B. James; Larry A. Franks; Arnold Burger, Editor(s)

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