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High-Mobility, High-Photostability Tetravalent-Terbium-Doped Indium-Tin-Zinc-Oxide Thin-Film Transistors with a
Huimin Su1, Linfeng Lan1,2, Jintao Xu1
1State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Wushan Road 381, Guangzhou 510640, China.
Abstract:
The trade-off between mobility and stability is the main problem for amorphous oxide semiconductor (AOS) thin-film transistors (TFTs). In this work, a high-mobility and good-photostability Tb-doped indium-tin-zinc oxide (Tb:ITZO) AOS is studied. The ITZO TFT without Tb doping had a mobility of as high as 49.4 cm2·V-1·s-1 but exhibited poor stability under negative bias illumination stress (NBIS). After Tb doping, the NBIS stability of the TFTs improved greatly, but the mobility reduced to 37.9 cm2·V-1·s-1. The great improvement of the NBIS stability of the Tb:ITZO TFTs is attributed to the charge-transfer transition between Tb4f 7O2p 6 and Tb4f 8O2p 5 that would reduce the lifetime of the photoinduced electrons and the ionized oxygen vacancies. Increasing O2 flow rates during sputtering would further enhance the NBIS stability but decrease the mobility seriously. To further improve the mobility of the Tb:ITZO TFTs, a stacked-channel TFT was fabricated by using the same Tb:ITZO target (sputtering with different O2 flow rates). The mobility increased to 40.4 cm2·V-1·s-1, and it also exhibited good NBIS stability. The mobility increment of the stacked-channel TFTs is ascribed to the conduction path confinement of the front channel by the conduction band barrier at the bilayer interface. This work provides a prominent AOS material and a simple way to break the trade-off between the mobility and stability of the AOS-TFTs.
