Gettering Effect Induced by Oxygen-Deficient Titanium Oxide in InZnO and InGaZnO Channel Systems for Low-Power Display Applications

Abstract

This paper reported the IGZO and IZO thin-film transistor (TFT) with titanium-oxide semiconductor as channel capping layer. After the ${\hbox{TiO}}_{x}$ Gettering process, the oxygen vacancies in IGZO channel were successfully modified to maximize the carrier concentration and device mobility. The superior transfer characteristics included a low sub-threshold swing of 79 mV/decade, a very high mobility of ${\hbox{68}}~{\hbox{cm}}^{2}/{\hbox{V}}{\cdot}{\hbox{s}}$ , and good on/off-current ratio of ${\hbox{5.61}}\times {\hbox{10}}^{6}$ . However, the IZO channel with nano-crystallized grains and without Ga atom doping showed unfavorable transistor characteristics. In addition to apparently degraded transfer properties, the spontaneously oxidized ${\hbox{TiO}}_{x}$ capping layer also lead to an increase of channel parasitic resistance that limits the output driving current. Therefore, we believe that the existence of Ga–O bonds among IGZO channel would be helpful to stabilize oxygen diffusion behavior and electric structure during Gettering process.