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
$\hbox{TiO}_{2}$
films on the device performance and photo-bias instability of zinc tin oxide (ZTO) thin-film transistors (TFTs). A 5.0-nm-thick
$\hbox{TiO}_{x}$
device inserted at the ZTO/silicon nitride
$(\hbox{SiN}_{x})$
interface exhibited slightly lower mobility (9.4
$\hbox{cm}^{2}/\hbox{V}\cdot \hbox{s}$
) compared with that (14.1
$\hbox{cm}^{2}/\hbox{V}\cdot \hbox{s}$
) of the reference device with a ZTO/
$\hbox{SiN}_{x}$
stack. On the other hand, the negative gate-bias-illumination-stress-induced instability of the
$\hbox{TiO}_{x}$
-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
$\hbox{TiO}_{x}$
and ZTO films, leading to the diminished injection of photo-induced hole carriers into the underlying
$\hbox{SiN}_{x}$
bulk region.