Effects of Annealing Atmosphere on Electrical Performance and Stability of High-Mobility Indium-Gallium-Tin Oxide Thin-Film Transistors

In this study, we examined the effects of the annealing atmosphere on the electrical performance and stability of high-mobility indium-gallium-tin oxide (IGTO) thin-film transistors (TFTs). The annealing process was performed at a temperature of 180 degrees C under N-2, O-2, or air atmosphere after the deposition of IGTO thin films by direct current magnetron sputtering. The field-effect mobility (mu(FE)) of the N-2- and O-2-annealed IGTO TFTs was 26.6 cm(2)/V.s and 25.0 cm(2)/V.s, respectively; these values were higher than that of the air-annealed IGTO TFT (mu(FE) = 23.5 cm(2)/V.s). Furthermore, the stability of the N-2- and O-2-annealed IGTO TFTs under the application of a positive bias stress (PBS) was greater than that of the air-annealed device. However, the N-2-annealed IGTO TFT exhibited a larger threshold voltage shift under negative bias illumination stress (NBIS) compared with the O-2- and air-annealed IGTO TFTs. The obtained results indicate that O-2 gas is the most suitable environment for the heat treatment of IGTO TFTs to maximize their electrical properties and stability. The low electrical stability of the air-annealed IGTO TFT under PBS and the N-2-annealed IGTO TFT under NBIS are primarily attributed to the high density of hydroxyl groups and oxygen vacancies in the channel layers, respectively.