The Effect of Oxide and Nitride Passivation on the Behavior of In-Ga-Zn-O Thin-Film Transistors under Negative and Positive Bias Illumination Stress: A Photo-excited Charge Collection Spectroscopic Analysis

Two different types of In-Ga-Zn-O thin-film transistors, each passivated with SiO_x and SiN_x, were studied under negative and positive bias illumination stress (NBIS and PBIS, respectively). Larger shifts in threshold voltage were observed in the SiN_x -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.