Two different types of In-Ga-Zn-O thin-film transistors, each passivated with SiOx and SiNx, were studied under negative and positive bias illumination stress (NBIS and PBIS, respectively). Larger shifts in threshold voltage were observed in the SiNx -passivated device under both NBIS and PBIS. Photo-excited charge collection spectroscopy analyses suggest that the incorporation of hydrogen during the nitride deposition induces a larger concentration of sub-bandgap trap sites within the oxide semiconductor and/or at the semiconductor/dielectric interface. These are suspected to trap holes during NBIS and electrons during PBIS, which induce negative and positive shifts in the threshold voltage, respectively.
- Device Instability