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Rational Hydrogenation for Enhanced Mobility and High Reliability on ZnO-based Thin Film Transistors: From Simulation to Experiment Lei Xu,†,‡ Qian Chen,# Lei Liao,*,† Xingqiang Liu,† Ting-Chang Chang,∥ Kuan-Chang Chang,§ Tsung-Ming Tsai,§ Changzhong Jiang,† Jinlan Wang,*,# and Jinchai Li† †
Department of Physics and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China ‡ School of Mathematics and Information Sciences, North China University of Water Resources and Electric Power, Zhengzhou 450046, China # Department of Physics, Southeast University, Nanjing 211189, China ∥ Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan § Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung 804, Taiwan S Supporting Information *
ABSTRACT: Hydrogenation is one of the effective methods for improving the performance of ZnO thin film transistors (TFTs), which originate from the fact that hydrogen (H) acts as a defect passivator and a shallow n-type dopant in ZnO materials. However, passivation accompanied by an excessive H doping of the channel region of a ZnO TFT is undesirable because high carrier density leads to negative threshold voltages. Herein, we report that Mg/H codoping could overcome the trade-off between performance and reliability in the ZnO TFTs. The theoretical calculation suggests that the incorporation of Mg in hydrogenated ZnO decrease the formation energy of interstitial H and increase formation energy of O-vacancy (VO). The experimental results demonstrate that the existence of the diluted Mg in hydrogenated ZnO TFTs could be sufficient to boost up mobility from 10 to 32.2 cm2/(V s) at a low carrier density (∼2.0 × 1018 cm−3), which can be attributed to the decreased electron effective mass by surface band bending. The all results verified that the Mg/H codoping can significantly passivate the VO to improve device reliability and enhance mobility. Thus, this finding clearly points the way to realize high-performance metal oxide TFTs for low-cost, large-volume, flexible electronics. KEYWORDS: thin film transistors, ZnO, hydrogenation, mobility, reliability objection.6 Among them, ZnO has advantages in relatively cheap, abundant, simple composition and nontoxic, which are expected to avoid mechanical instability problem and electrical property variations for fully transparent flexible electronic applications.7,8 However, several reports have indicated that the undoped ZnO TFTs exhibit a low on-state current and high subthreshold slope, which is indicative of low mobility (
