Comparative Study on Light-Induced Bias Stress Instability of IGZO Transistors With $\hbox{SiN}_{x}$ and $ \hbox{SiO}_{2}$ 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
$\hbox{SiN}_{x}$
-gated TFT exhibited inferior stability to the
$\hbox{SiO}_{2}$
-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
$(V_{\rm th})$
of the
$\hbox{SiN}_{x}$
-gated IGZO TFT compared to that of the
$\hbox{SiO}_{2}$
-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.