Suppression in Negative Bias Illumination Stress Instability of Zinc Tin Oxide Transistor by Insertion of Thermal TiOx Films

This letter examined the insertion effect of thermal TiO2 films on the device performance and photo-bias instability of zinc tin oxide (ZTO) thin-film transistors (TFTs). A 5.0-nm-thick TiOx device inserted at the ZTO/silicon nitride (SiNx) interface exhibited slightly lower mobility (9.4 cm(2)/V . s) compared with that (14.1 cm(2)/V . s) of the reference device with a ZTO/SiNx stack. On the other hand, the negative gate-bias-illumination-stress-induced instability of the TiOx-inserted device was strongly suppressed from 11.0 V (reference device) to 3.0 V. This was attributed to the increase in valence band offset between TiOx and ZTO films, leading to the diminished injection of photoinduced hole carriers into the underlying SiNx bulk region.