Subgap State Engineering Using Nitrogen Incorporation to Improve Reliability of Amorphous InGaZnO Thin-Film Transistors in Various Stressing Conditions

Abstract

Instability of amorphous InGaZnO thin-film transistors (a-IGZO TFTs) remains an obstacle for commercialization. Here, we systematically discuss the effect of nitrogen incorporation on a-IGZO TFT stability and developed Ar/O-2/N-2 atmosphere to improve the stability under stressing in different conditions. Based on X-ray photoelectron spectrometer results, it is revealed that the positive gate bias stress (PGBS) stability is significantly improved due to microscopically passivated metal-oxygen bonds. Yet, the negative gate bias and light stress (NBLS) stability is seriously deteriorated with heavily nitrogen incorporation probably due to the bandgap narrowing effect. By optimizing a mixed O-2/N-2 atmosphere, the subgap states are finely tuned to afford optimal performance and stability. The developed IGZO TFTs exhibit mobility (12.67 cm(2)/Vs), small shift of threshold voltage under PGBS (reduced by 64% as compared with the pristine a-IGZO TFTs), and good negative gate bias stability and with NBLS stability as well.