Tuning the inhomogeneous charge transport in ZnO interfaces for ultrahigh on/off ratio top-gated field-effect-transistor
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Tuning the inhomogeneous charge transport in ZnO interfaces for ultrahigh on/off ratio top-gated field-effect-transistor arrays Thanh Luan Phan1, Dinh Loc Duong2,3, Tuan Khanh Chau2,3, Sidi Fan2,3, Won Tae Kang1, Thi Suong Le2,3, Hyun Yong Song2,3, Linfeng Sun3, Van Tu Vu1, Min Ji Lee1, Quoc An Vu2,3, Young Hee Lee2,3,4, and Woo Jong Yu1 () 1
Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea 3 Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea 4 Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea 2
© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 8 June 2020 / Accepted: 1 July 2020
ABSTRACT The interface between oxide/oxide layers shows an inhomogeneous charge transport behavior, which reveals a high conductivity owing to interface-doped. One typical example is the hetero-interface between ZnO film and other wide band gap oxides (e.g., Al2O3, TiO2, and HfO2). It is thus quite evident that the ZnO/other oxides hetero-interface contains high density electron carriers effectively screening the gate-induced electric field. Thus, an extremely weak gate modulation in ZnO film was showed, resulting in very low on/off ratio of 1.69 in top-gate field-effect-transistor (TG-FET) configuration. So, to extend the usage of ZnO TG-FET is not quite possible toward further practical application. Herein, we clarified the correlation of inhomogeneous region in oxide/oxide hetero-junction by systematically study. Our work suggests that a self-assembly of molecules (SAM) buffer layer is suitable for tuning the inhomogeneous charge transport in ZnO film, which not only reduces the interface trap density, but also effectively enhances the gate electric field modulation at the hetero-interface. We further report the robust fabrication of TG-FET arrays based on ZnO thin film, using an ultra-thin alkylphosphonic acid molecule monolayer as buffer layer. Our device demonstrates a pronounced ultrahigh on/off ratio of ≥ 108, which is 8-order of magnitude higher than that of a device without buffer layer. For the highly reliable arrays, our device exhibits a high yield of over 93% with an average on/off ratio of ~107 across the entire wafer scale, mobility (18.5 cm2/(V·s)), an extended bias-stressing (~ 2,000 s) and long-stability (~ 150 days) under ambient conditions.
KEYWORDS zinc oxides, thin-film field-effect-transistor, self-assembly molecule, inhomogeneous charge transport, interface engineering
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Introduction
During the past few decades, metal oxide thin films have been proposed as potential candidates in the post-silicon era [1–7]. Zinc oxide (ZnO) is a typical n-type semiconductor material, which has received significant attention owing to its exceptional electrical and optical properties [8–10]. It offers numerous advantages compared to silico
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