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Thin-Film Phototransistor with nc-Si:H/a-Si:H Bilayer Channel

Published online by Cambridge University Press:  15 June 2012

Y. Vygranenko ,
A. Sazonov ,
M. Fernandes ,
M. Vieira  and
A. Nathan
Y. Vygranenko
Affiliation:
Electronics, Telecommunications and Computer Engineering, ISEL, 1949-014 Lisbon, Portugal CTS-UNINOVA, 2829-516 Caparica, Portugal
A. Sazonov
Affiliation:
Electrical and Computer Engineering, University of Waterloo, Waterloo, N2L 3G1, Canada
M. Fernandes
Affiliation:
Electronics, Telecommunications and Computer Engineering, ISEL, 1949-014 Lisbon, Portugal CTS-UNINOVA, 2829-516 Caparica, Portugal
M. Vieira
Affiliation:
Electronics, Telecommunications and Computer Engineering, ISEL, 1949-014 Lisbon, Portugal CTS-UNINOVA, 2829-516 Caparica, Portugal
A. Nathan
Affiliation:
Engineering Department, Cambridge University, Cambridge, CB2 1PZ, United Kingdom
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Abstract

There is significant interest in optical sensors whose fabrication process is fully compatible with existing flat panel display thin film transistor (TFT) technology. Here, we report a field-effect phototransistor with a channel comprising a thin nanocrystalline silicon (nc-Si:H) transport layer and a thicker hydrogenated amorphous silicon (a-Si:H) absorption layer. The implementation of nc-Si:H layer improves device stability in comparison with a-Si:H phototransistors, resulting in reduced threshold voltage shift. Semiconductor and dielectric layers were deposited by radio-frequency plasma enhanced chemical vapor deposition at 280°C. The device characterization included the dark and light transfer characteristics, spectral-response and dynamic measurements. The external quantum efficiency was measured as a function of incident photon flux at different biasing conditions. The phototransistor with channel length of 24 microns and photosensitive area of 1.4 mm2shows an off-current of about 1 pA, and photo-conductive gain up to 200 at low incident intensities. Thus, the results demonstrate the feasibility of the phototransistor for low light level detection.

Keywords

chemical vapor deposition (CVD) (chemical reaction)optoelectronicphotoconductivity
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1426: Symposium A – Amorphous and Polycrystalline Thin-Film Silicon Science and Technology—2012 , 2012 , pp. 205 - 210
Copyright
Copyright © Materials Research Society 2012

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References

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