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Enhanced Blue Sensitivity in ITO/a-SiNx:H/a-Si:H MIS Photodetectors

Published online by Cambridge University Press:  01 February 2011

S. Tao ,
Y. Vygranenko  and
A. Nathan
S. Tao
Affiliation:
Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
Y. Vygranenko
Affiliation:
Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
A. Nathan
Affiliation:
Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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Abstract

We report an ITO/a-SiNx:H/a-Si:H MIS photodetector with improved performance in terms of its dark current, stability, and spectral response in the blue region. The a-Si:H and a-SiNx:H thin film layers were deposited by plasma-enhanced chemical vapor deposition (PECVD) on a glass substrate with patterned Mo back contact. The ITO was polycrystalline with a wide band gap (>3.75 eV) and was deposited at room temperature by magnetron sputtering. SIMS (Secondary Ion Mass Spectrometer) measurements show that an ultra thin a-SiNx:H film (a few nm) can effectively block the diffusion of oxygen from the ITO to the a-Si:H. In addition, the insulator layer provides a barrier for electrons, which serves to reduce the dark current. This is in contrast to the ITO/a-Si:H Schottky photodiode whose electrical and optical performance is impaired by the large defect density at the interface due to impurity diffusion from the ITO layer. At a reverse bias of 1 V, the dark current density of the MIS photodetector is as low as 4 nA/cm2. Photoresponse measurements show a dramatically enhanced sensitivity in the UV/blue spectral region. A high quantum efficiency (∼80%) is achieved at a wavelength of 440 nm, which can be attributed to reduction of both optical and recombination loses by virtue of the highly transparent polycrystalline ITO and the low defect density at the a-SiNx:H/a-Si:H interface.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 762: Symposium A – Amorphous and Nanocrystalline Silicon-Based Films – 2003 , 2003 , A21.6
Copyright
Copyright © Materials Research Society 2003

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