Zn-In-O based thin-film transistors: Compositional dependence

• Published in: Physica status solidi. A, Applications and materials science Applications and materials science, 2008-08, Vol.205 (8), p.1915-1919
• Main Authors: Itagaki, N., Iwasaki, T., Kumomi, H., Den, T., Nomura, K., Kamiya, T., Hosono, H.
• Format: Article
• Language: English
• Subjects: 68.55.−a; 73.61.Jc; 73.61.Le; 81.05.Gc; 81.15.Cd; 85.30.Tv; Applied sciences; Electronics; Exact sciences and technology; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Transistors
• ISSN: 1862-6300; 0031-8965; 1862-6319
• DOI: 10.1002/pssa.200778909

The compositional dependence of sputter‐deposited Zn–In–O (ZIO) film properties and the TFT performance were studied by means of a combinatorial technique. Both the characteristics of ZIO‐TFTs and the ZIO film properties are very sensitive to the Zn:In ratio. The best TFT performances are obtained at Zn:In ∼60:40 at%, where the saturation mobility (μsat), subthreshold swing (S.S.), on–off current ratio (Ion/Ioff), and threshold voltage (Vth) are 26.5 cm2/V s, 0.24 V/dec., 1010, and +2 V, respectively. The TFT characteristics peak at this compositional ratio. Specifically, μsat, Ion/Ioff and Vth reach maximum, while S.S. reaches minimum at this ratio. The air stability of ZIO‐TFTs was also examined for active channel layers with different Zn:In ratios, which clarified that the TFTs with high stability are obtained around the same composition ratio where the best characteristics are obtained. It was confirmed by X‐ray diffraction and transmission electron microscopy that the ZIO films with this composition ratio have amorphous structure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)