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 TiO 2 films on the device performance and photo-bias instability of zinc tin oxide (ZTO) thin-film transistors (TFTs). A 5.0-nm-thick TiO x device inserted at the ZTO/silicon nitride (SiN x ) 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/SiN x stack. On the other hand, the negative gate-bias-illumination-stress-induced instability of the TiO x -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 TiO x and ZTO films, leading to the diminished injection of photo-induced hole carriers into the underlying SiN x bulk region.