Effects of Carrier Concentration in the Back and Front Channels of Hf-In-Zn-O Thin Film Transistors

Abstract: The effects of carrier concentrations in the front and back channels were comparatively studied in Hf-In-Zn-O thin film transistors by controlling the concentration of In. Although the field effect mobility is mainly controlled by the front channel composition, Vth is dominantly affected by the composition of the back channel. For instance, the use of an In-rich back channel that contains a large carrier concentration results in negatively shifted Vth while a relatively In-poor back channel that contains a small carrier concentration doesn’t. Also, the Vth of an In-rich front channel device was near 0 V by applying an In-poor back channel. These results indicate that the adjustment of back channel carrier concentration and conductivity allows the control of Vth in Hf-In-Zn-O devices.