Effect of Indium Doping on Bias Stability in Dual-Target Co-Sputtering InZnSnO Thin-Film Transistors

Despite increasing indium content improves the field-effect mobility of metal–oxide thin-film transistors (TFTs), it is usually accompanied by the deterioration in bias stability. In this work, we achieve enhanced mobility and stability together within a certain range by controlling the sputtering power in the co-sputtering system. Due to the difference in electronegativity and binding energy between indium and zinc, the increase of indium content at lower sputtering power reduces the oxygen vacancy defects and smooth interfacial quality. In0.45Zn0.42Sn0.13O TFTs exhibit excellent stability threshold voltage variation of only 0.58 and −0.12 V under positive bias stress (PBS) and negative bias stress (NBS). However, excess indium could lead to high carrier concentrations in the channel, which introduced new defects, while defects between active and gate insulator (GI) layer interface trap electrons and lead to decreased stability. In addition, the maximum temperature in this work does not exceed 150 °C and the transmittance of all thin films is greater than 80% in the visible range, which has great potential for application in the next generation of transparent flexible electronics. These results indicate that optimizing the ratio of indium doping is an effective strategy for achieving simultaneous enhancement of mobility and stability.