Influence of Ga Doping on Electrical Performance and Stability of ZnO Thin-Film Transistors Prepared by Atomic Layer Deposition
Qi Tang, Xue Chen, Jiaxian Wan, Hao Wu, Chang Liu
Abstract
Ga-doped ZnO (GZO) thin-film transistors (TFTs) with different doping concentrations (n_Ga :n_Zn =0 , 1:150, 1:75, 1:50) were successfully fabricated by atomic layer deposition. Among them, GZO TFTs with the doping concentration of 1:75 exhibited a high field-effect mobility of 16.2 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , a small subthreshold swing of 0.22 V dec <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , a high ON-/ OFF-current ratio of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> , and a proper threshold voltage of 6.0 V as well as a small threshold voltage shift of 0.14 V under positive bias stress. Compared to ZnO (ZO) TFTs, GZO TFTs exhibit excellent bias stability and electrical properties, which can be attributed to appropriate Ga doping concentration suppressing the oxygen vacancy defects, decreasing the trap density at the Al2O3/ZO interfaces, and broadening energy band of the ZO thin films.