Copper phthalocyanine-based organic thin-film transistors (OTFTs) with gate dielectric made by different combinations of ZrO2 and Al2O3 are fabricated. Experimental results show that as compared to the OTFTs with ZrO2/Al2O3 stacked and Al2O3/ZrO2/Al2O3 sandwiched gate dielectric, the device fabricated with the Al2O3/ZrO2 stacked gate dielectric manifests better electrical properties such as larger on/off ratio, smaller subthreshold slope, and higher carrier mobility. This could be explained by the fact that Al2O3 has good interface properties with CuPc and can act as a barrier layer, which prevents intermixing of materials at the organic/insulator interface and can slow oxygen diffusion through Al-O matrix, thus suppressing interfacial trap density. The gate-bias stress effect on the performance of OTFTs is also investigated. It is found that the threshold voltage shifts toward positive direction with stress time under a negative gate bias voltage. Longer stress times cause more degradation of the subthreshold and on/off ratio, probably due to more defect-state creation in the channel and an increase of interfacial traps and oxide charges in the dielectric during stress. Results also indicate that OTFTs with Al2O3 interlayer between the high-k dielectric and the gate electrode have less degradation in subthreshold and on/off ratio after a 3600-s stress. The involved mechanism lies in that the Al2O3 interlayer at the high-k dielectric/gate electrode interface can effectively block the injection of electrons from the gate electrode into the high-k material during electrical stress and thus less stress-induced interfacial traps and negative oxide charges in the devices. The electrical characteristics of the OTFTs after the removal of gate bias for a period of time are also studied.
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January 2013
Research Article|
December 03 2012
Comparison of CuPc-based organic thin-film transistors made by different dielectric structures
Wing Man Tang;
Wing Man Tang
a)
Department of Electrical and Computer Engineering,
University of Toronto
, 10 King's College Rd., Toronto, Ontario M5S 3G4, Canada
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Wai Tung Ng;
Wai Tung Ng
Department of Electrical and Computer Engineering,
University of Toronto
, 10 King's College Rd., Toronto, Ontario M5S 3G4, Canada
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Mark T. Greiner;
Mark T. Greiner
Department of Materials Science and Engineering,
University of Toronto
, Ontario M5S 3E4, Canada
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Jacky Qiu;
Jacky Qiu
Department of Materials Science and Engineering,
University of Toronto
, Ontario M5S 3E4, Canada
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Michael G. Helander;
Michael G. Helander
Department of Materials Science and Engineering,
University of Toronto
, Ontario M5S 3E4, Canada
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Zheng-Hong Lu
Zheng-Hong Lu
Department of Materials Science and Engineering,
University of Toronto
, Ontario M5S 3E4 Canada
and Department of Physics, Yunnan University
, 2 Cuihu Beilu, Yunnan, Kunming 650091, China
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a)
Electronic mail: wmtang@vrg.utoronto.ca
J. Vac. Sci. Technol. B 31, 012201 (2013)
Article history
Received:
June 23 2012
Accepted:
November 09 2012
Citation
Wing Man Tang, Wai Tung Ng, Mark T. Greiner, Jacky Qiu, Michael G. Helander, Zheng-Hong Lu; Comparison of CuPc-based organic thin-film transistors made by different dielectric structures. J. Vac. Sci. Technol. B 1 January 2013; 31 (1): 012201. https://doi.org/10.1116/1.4769259
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