Positive Gate Bias Instability Induced by Diffusion of Neutral Hydrogen in Amorphous In-Ga–Zn-O Thin-Film Transistor

Origin of constant positive gate bias stress instability in amorphous In-Ga-Zn-O thin-film transistor is studied. Threshold voltage shift (AV_th) during the stress test exhibits two different behaviors: 1) a power function-type and 2) a logarithmic function-type depending on thermal treatment atmosphere and temperature. Thermal desorption spectroscopy indicated that the AVth behavior changes from the log-function type to the power-function type as the amount of H₂ desorption increases. Furthermore, the recovery behavior of ΔV_th was not affected by gate bias. These results are explained by a diffusionlimited process of neutral hydrogen, which occurs within 2 nm in the vicinity of the channel-insulator interface.