Fabrication of an In-rich IGZO TFT by Co-sputtering of In₂O₃ and IGZO and Characterization of its Compensated Positive Bias Stress Properties

We report on the fabrication and characterization of In-rich indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) prepared by the co-sputtering of In₂O₃ and IGZO. The co-sputtering strategy successfully mitigates the tradeoff between switching characteristics and operation speed: the device exhibits a low OFF current (~ 10^–10 A) comparable to that of an IGZO TFT and a high electron mobility (37.3 cm²/Vs) comparable to that of an In₂O₃ TFT. Interestingly, the co-sputtered device demonstrates a minimal threshold voltage shift under a positive bias stress (PBS) test, whereas the IGZO TFT shows a typical positive PBS and the In₂O₃ TFTs show an abnormal negative shift of the threshold voltages. The chemical composition of the co-sputtered film is analyzed by X-ray photoelectron spectroscopy (XPS). The proposed co-sputtering strategy is expected to provide a simple and scalable method that enables the easy fabrication of high-performance and reliable TFTs and can be generalized for further industrial applications.