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) are highly required toward the realization of next-generation displays. Among numerous types of TOS-TFTs, InO-based TFTs are the front-running candidate because they exhibit the highest µ ≈100 cm V s. However, the device operation of InO 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 InO TFTs passivated with YO and ErO films are highly reliable and do not show threshold voltage shifts when applying gate bias. Positive and negative gate bias is applied to the InO TFTs passivated with various insulating oxides and found that only the InO TFTs passivated with YO and ErO films do not exhibit threshold voltage shifts. It is observed that only the YO grew heteroepitaxially on the InO crystal. This is the origin of the high reliability of the InO TFTs passivated with YO and ErO films. This finding accelerates the development of next-generation displays using high-mobility InO TFTs.