Effect of Tunable Sub-Source and Sub-Drain Device Behavior in Four-Terminal Operation Using Metal-Capping Thin-Film Transistors

We report on a metal-capping (MC) structure with threshold voltage (Vth) tunability via four-terminal driving. Amorphous oxide semiconductors (AOSs) are emerging as promising next-generation semiconductor materials due to their remarkable properties, such as high field-effect mobility, uniformity, and excellent transmittance in the visible light region. The MC structure is a simple structure that can improve the characteristics of a thin-film transistor (TFTs) based on AOSs. By applying additional voltage to this MC layer, we were able to control the amount and direction of carrier flow during the I–V operation. With the four-terminal drive, the Vth of the MC TFT can be modulated according to the voltage applied to the MC layer. When a negative voltage is applied to the MC layer, the Vth shifts to the negative region, and when a positive voltage is applied, the Vth shifts to the positive region. With the four-terminal MC TFT, we expect to be able to compensate for Vth modulated by external stresses that significantly affect the display pixels. Furthermore, it is expected that this operating principle can be utilized in many application systems, such as sensors.