Comparative Study on Light-Induced Bias Stress Instability of IGZO Transistors With and Gate Dielectrics

This letter examines the effect of the gate dielectric material on the light-induced bias-temperature instability of an In-Ga-Zn-O (IGZO) thin-film transistor (TFT). After applying positive and negative bias stresses, the SiNx-gated TFT exhibited inferior stability to the SiO₂-gated TFT, which was explained by the charge trapping mechanism. However, light illumination under a negative bias stress accelerated the negative displacement of the threshold voltage (V_th) of the SiN_x-gated IGZO TFT compared to that of the SiO₂-gated TFT. This was attributed to the injection of photocreated hole carriers into the underlying gate dielectric bulk region as well as the hole trapping at the gate/channel interface.