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Towards manufacturing high uniformity polysilicon circuits through TFT contact barrier engineering

Sporea, Radu A., Wheeler, Luke J., Stolojan, Vlad and Silva, S. Ravi P. (2018) Towards manufacturing high uniformity polysilicon circuits through TFT contact barrier engineering Scientific Reports.

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Abstract The predicted 50 billion devices connected to the Internet of Things by 2020 has renewed interest in polysilicon technology for high performance new sensing and control circuits, in addition to traditional display usage. Yet, the polycrystalline nature of the material presents significant challenges when used in transistors with strongly scaled channel lengths due to non-uniformity in device performance. For these new applications to materialize as viable products, uniform electrical characteristics on large areas will be essential. Here, we report on the effect of deliberately engineered potential barrier at the source of polysilicon thin-film transistors, yielding highly-uniform on-current (<8% device-to-device, accounting for material, as well as substantial geometrical, variations). The contact-controlled architecture of these transistors significantly reduces kink effect and produces high intrinsic gain over a wide range of drain voltage (2 – 20V). TCAD simulations associate critical grain boundary position and the two current injection mechanisms in this type of device, showing that, for the geometry considered, the most unfavorable location is ~150nm inside the source area. At this point, grain boundary contributes to increasing the resistance of the source pinch-off region, reducing the current injection from the bulk of the source area. Nevertheless, the effect is marginal, and the probability of a grain boundary existing at this position is low. This new understanding is instrumental in the design of new signal conversion and gain circuits for flexible and low-power sensors, without the need for complex compensation methods.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Electronic Engineering
Authors :
Sporea, Radu
Wheeler, Luke J.
Silva, S. Ravi
Date : 2018
Funders : Royal Academy of Engineering
Grant Title : Research Fellowship
Copyright Disclaimer : © The authors 2018. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit
Uncontrolled Keywords : Electronic properties and devices; Thin-film transistors; Polycrystalline Silicon; Large-area electronics; Metal-semiconductor contacts; Schottky contacts; Device physics
Related URLs :
Depositing User : Clive Harris
Date Deposited : 08 Nov 2018 13:37
Last Modified : 11 Dec 2018 11:24

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