Rare-metal-free high-performance Ga-Sn-O thin film transistor

Tokiyoshi Matsuda,Daiki Nishimoto,Mutsumi Kimura,Mamoru Furuta,Yuta Kato,Kenta Umeda

doi:10.1038/srep44326

Tokiyoshi Matsuda, Daiki Nishimoto + Show 4 more

Open Access

https://doi.org/10.1038/srep44326

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Abstract

Oxide semiconductors have been investigated as channel layers for thin film transistors (TFTs) which enable next-generation devices such as high-resolution liquid crystal displays (LCDs), organic light emitting diode (OLED) displays, flexible electronics, and innovative devices. Here, high-performance and stable Ga-Sn-O (GTO) TFTs were demonstrated for the first time without the use of rare metals such as In. The GTO thin films were deposited using radiofrequency (RF) magnetron sputtering. A high field effect mobility of 25.6 cm2/Vs was achieved, because the orbital structure of Sn was similar to that of In. The stability of the GTO TFTs was examined under bias, temperature, and light illumination conditions. The electrical behaviour of the GTO TFTs was more stable than that of In-Ga-Zn-O (IGZO) TFTs, which was attributed to the elimination of weak Zn-O bonds.

Highlights

Oxide semiconductor materials such as In-Ga-Zn-O (IGZO)[1,2,3,4], In-Sn-Zn-O (ITZO)[5,6], In-Ga-O (IGO)[7], and In-Sn-O (ITO)[8] have several advantages as active layer of thin film transistors (TFTs) such as steep subthreshold swing (S factor), transparency, and extremely low leak current in off state when compared to conventional semiconductors such as hydrogenated amorphous silicon (a-Si:H)[9] and polycrystalline silicon[10]
Amorphous IGZO TFTs has been attributed to the electron path formed by the broad In 5 s orbital
High field effect mobility TFT with a low S factor was prepared using GTO, where the rare earth In was replaced by Sn

Summary

Introduction

Oxide semiconductor materials such as In-Ga-Zn-O (IGZO)[1,2,3,4], In-Sn-Zn-O (ITZO)[5,6], In-Ga-O (IGO)[7], and In-Sn-O (ITO)[8] have several advantages as active layer of thin film transistors (TFTs) such as steep subthreshold swing (S factor), transparency, and extremely low leak current in off state when compared to conventional semiconductors such as hydrogenated amorphous silicon (a-Si:H)[9] and polycrystalline silicon[10]. Oxide TFTs have high field effect mobility (μFE) and can be fabricated on large-area substrates by deposition processes with low cost, low toxicity, and low risk of explosion, such as radiofrequency (RF) or direct current (DC) magnetron sputtering. These techniques are used in the TFT fabrication processes to deposit IGZO as semiconductor, ITO as the transparent electrodes for displays, and metallic materials (Cr, Mo, and Al) for electrodes.

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