High Performance of Y-doped Sn-Zn-O Films Fabricated by Solution-process for Amorphous Thin Film Transistors
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High Performance of Y-doped Sn-Zn-O Films Fabricated by Solution-process for Amorphous Thin Film Transistors Yunxuan Yu1 , Xian Gong1 ,Dong Liu1,2, Yan Wang1,*Jinfeng Kang1 1 Institute of Microelectronics, Peking University, Beijing 100871, China 2 Peking University Shenzhen Graduate School, Shenzhen, 518055, China ABSTRACT The effect of Y dopant incorporated into ZTO with different Y ratios in Y-ZTO system on the performances of ZTO-based TFTs is investigated by using sol-gel process. The proper Y doped ZTO present both high film crystallization temperature and superior electrical properties as an active channel layer of TFTs. The fabricated YZTO-based TFTs with 11% Y show the excellent devices performance such as the channel field effect mobility of 1.756 cm2/Vs, SS of 2.13 V/dec, threshold voltage of 0.8V and on/off ratio of 3.12×106. INTRODUCTION Amorphous oxide-based semiconductor (AOS) thin-film transistors (TFTs) as active channel material for transparent display and large scale Panel devices have been widely studied due to their good uniformity, high stability and transparency. Particularly, indium-gallium-zinc-oxide (IGZO) system has been given significant attention because of its high mobility and good on/off ratio [1]. Nevertheless, the large amount of indium in the IGZO system has the disadvantages of high cost and toxicity. Thus, the close study of indium-free amorphous oxide channel material has been conducted. Several promising candidates have been addressed including Zn-Sn-O system and ZnO. In the Zn-Sn-O (ZTO) system, Sn acts as a mobility enhancer that makes the high turn-on current possible [2], but may suffer from the poor on/off ratio [3]. It has been demonstrated that using proper dopant into ZTO to suppress the carrier generation may be effective to achieve the high on/off ratio [4]. In this study, the effect of Y dopant incorporated into ZTO on the properties of Y-ZTO films and the performance of YZTO-based TFTs are investigated. Y doped In-Zn-O thin film was studied and the effect of Y as carrier suppressor in IZO system was demonstrated [5-6]. In this article, the effect of Y incorporation into the In-free ZTO system as the active channel layer of TFTs are demonstrated. EXPERIMENT In the study, the sol-gel process is used to fabricate the Y-ZTO films. A 0.5M YZTO solution was prepared in 2-methoxyethanol using a mixture of zinc acetate dehydrate [Zn(CH3COO)2·2H2O], tin chloride [SnCl2], and yttrium nitrate hexahydrate [Y(NO3)3·6H2O]. The mole ratios of Y-ZTO were Y:Sn:Zn=x:2:2, and yttrium was doped as x=0.1-0.8. The YZTO solution was stirred at 40℃ for half an hour and the prepared solution was spin-coated at 3000 rpm for 30 s in a spin coater. After coating, the films were immediately dried at 120℃ for 10 min to remove the 2-methoxyethanol solvent, then were annealed in a hot plate at 450 ℃ for 2 hrs under atmosphere ambient. For the fabrication of the YZTO-based TFTs, a bottom-gate and top contact TFT structure has been used by spin-coating YZTO precursor solutions on heavily
doped n+-
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