Abnormal Threshold Voltage Modulation Characteristics of Dual-Gate Ingazno Thin-Film Transistor with an Unisolated Top Gate

Abstract

In this study, the unisolated top gate on the performance of dual-gate InGaZnO (IGZO) thin-film transistors (TFT) is investigated. An abnormal threshold voltage modulation characteristic is observed in dual-gate mode operation. This abnormal characteristic is opposite to the threshold voltage modulation characteristics of conventional dual-gate TFTs. This study suggests that the proposed device utilizes mobile electrons between the top gate and channel for threshold voltage modulation, which is different from conventional dual-gate TFTs using capacitive coupling. Moreover, it is found that the unisolated top gate in this study acts as different roles (another source or drain) under different voltage bias. Then, the proposed working mechanism is further verified by using technology computer aided design (TCAD) simulations. The prepared IGZO TFTs also show good electrical stability under the positive gate-bias stress (PGBS). The results of this study may lead to better applications in the circuit design.

Keywords: InGaZnO (IGZO), dual-gate, thin-film transistor (TFT), threshold voltage modulation