Design and modeling of a lateral a-Se MSM photoconductor as indirect conversion X-ray imager

Kai Wang; Feng Chen; George Belev; Safa O. Kasap; Karim S. Karim

doi:10.1117/12.829299

17 September 2009 Design and modeling of a lateral a-Se MSM photoconductor as indirect conversion X-ray imager

Kai Wang, Feng Chen, George Belev, Safa O. Kasap, Karim S. Karim

Proceedings Volume 7449, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XI; 74491W (2009) https://doi.org/10.1117/12.829299
Event: SPIE Optical Engineering + Applications, 2009, San Diego, California, United States

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.

Citation Download Citation

Kai Wang, Feng Chen, George Belev, Safa O. Kasap, and Karim S. Karim "Design and modeling of a lateral a-Se MSM photoconductor as indirect conversion X-ray imager", Proc. SPIE 7449, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XI, 74491W (17 September 2009); https://doi.org/10.1117/12.829299

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