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Hydrogenated Nanocrystalline Silicon Thin Film Transistor Array for X-ray Detector Application

Published online by Cambridge University Press:  01 February 2011

Kyung-Wook Shin
Affiliation:
TalezShin@Gmail.com, University of Waterloo, Electrical and Computer Engineering, 200 University Avenue West, Waterloo, N2L 3G1, Canada, 519-888-4567 ext. 38183
Mohammad R. Esmaeili-Rad
Affiliation:
mresmaei@uwaterloo.ca, University of Waterloo, Department of Electrical and Computer Engineering, 200 University Avenue West, Waterloo, Ontario, N2L 3G1, Canada
Andrei Sazonov
Affiliation:
A.Sazonov@venus.uwaterloo.ca, University of Waterloo, Department of Electrical and Computer Engineering, 200 University Avenue West, Waterloo, Ontario, N2L 3G1, Canada
Arokia Nathan
Affiliation:
anathan@ee.ucl.ac.uk, University College London, London Centre for Nanotechnology, 17-19 Gordon Street, London, WC1H 0AH, United Kingdom
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Abstract

Hydrogenated nanocrystalline silicon (nc-Si:H) has strong potential to replace the hydrogenated amorphous silicon (a-Si:H) in thin film transistors (TFTs) due to its compatibility with the current industrial a-Si:H processes, and its better threshold voltage stability [1]. In this paper, we present an experimental TFT array backplane for direct conversion X-ray detector, using inverted staggered bottom gate nc-Si:H TFT as switching element. The TFTs employed a nc-Si:H/a-Si:H bilayer as the channel layer and hydrogenated amorphous silicon nitride (a-SiNx) as the gate dielectric; both layers deposited by plasma enhanced chemical vapor deposition (PECVD) at 280°C. Each pixel consists of a switching TFT, a charge storage capacitor (Cpx), and a mushroom electrode which serves as the bottom contact for X-ray detector such as amorphous selenium photoconductor. The chemical composition of the a-SiNx was studied by Fourier transform infrared spectroscopy. Current-voltage measurements of the a-SiNx film demonstrate that a breakdown field of 4.3 MV/cm.. TFTs in the array exhibits a field effect mobility (μEF) of 0.15 cm2/V·s, a threshold voltage (VTh) of 5.71 V, and a subthreshold leakage current (Isub) of 10−10 A. The fabrication sequence and TFT characteristics will be discussed in details.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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References

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