Highly stable amorphous In-Ga-Zn-O thin-film transistors produced by eliminating deep subgap defects

Highly stable amorphous-In-Ga-Zn-O (a-IGZO) thin film transistors (TFTs) against constant current stress and negative bias light illumination stress were realized by forming a Y2O3 passivation layer. A recent photoemission study revealed that deep defects located above the valence band top are formed at a high density to a depth of ∼2 nm in the surface layer of the a-IGZO channel. Here, we present that these deep defects are responsible for the instability of a-IGZO TFTs, and the instability can be much improved by passivation with Y2O3, which effectively eliminates the deep subgap defects from the surface of a-IGZO.