Reliable Operation in High-Mobility Indium Oxide Thin Film Transistors

Transparent oxide semiconductors (TOSs) based thin-film transistors (TFTs) that exhibit higher field effect mobility (µ_FE) are highly required toward the realization of next-generation displays. Among numerous types of TOS-TFTs, In₂O₃-based TFTs are the front-running candidate because they exhibit the highest µ_FE ≈100 cm² V^-1 s^-1. However, the device operation of In₂O₃ TFTs is unreliable; a large voltage shift occurs especially when negative gate bias is applied due to adsorption/desorption of gas molecules. Although passivation of the TFTs is used to overcome such instability, previously proposed passivation materials do not improve the reliability. Here, it is shown that the In₂O₃ TFTs passivated with Y₂O₃ and Er₂O₃ films are highly reliable and do not show threshold voltage shifts when applying gate bias. Positive and negative gate bias is applied to the In₂O₃ TFTs passivated with various insulating oxides and found that only the In₂O₃ TFTs passivated with Y₂O₃ and Er₂O₃ films do not exhibit threshold voltage shifts. It is observed that only the Y₂O₃ grew heteroepitaxially on the In₂O₃ crystal. This is the origin of the high reliability of the In₂O₃ TFTs passivated with Y₂O₃ and Er₂O₃ films. This finding accelerates the development of next-generation displays using high-mobility In₂O₃ TFTs.