Enhancement of the Electrical Performance and Bias Stability of RF-Sputtered Indium Tin Zinc Oxide Thin-Film Transistors with Vertical Stoichiometric Oxygen Control

Indium tin zinc oxide (ITZO) thin-film transistors (TFTs) with different channel structures are investigated. The electrical performance and bias stress stability of bilayer-channel ITZO TFTs are enhanced in comparison with those of single-channel ITZO TFTs. The bilayer channel consists of an oxygen-uncompensated channel layer and an oxygen-compensated capping layer, while the single channel is an oxygen-uncompensated channel layer. The electrical properties of the bilayer-channel films are fine-tuned by adjusting their oxygen stoichiometry using the oxygen-compensated capping layer. The X-ray photoelectron spectroscopy measurements reveal that the bilayer channel shows advantages over the single channel in terms of increased metal oxide concentration and decreased oxygen vacancy and hydroxyl concentration. As a result, the bilayer-channel ITZO TFT exhibits a saturation field-effect mobility of 17.31 cm2/Vs, a sub-threshold swing of 0.24 V/dec, and a good operational bias stress stability in comparison with the single-channel TFT. This work demonstrates that the bilayer-channel ITZO TFTs have great potential for next-generation display applications.