Ambipolar Charge Transport in Two-Dimensional WS₂ Metal–Insulator–Semiconductor and Metal–Insulator–Semiconductor Field-Effect Transistors

Two-dimensional (2D) materials with ambipolar transport characteristics have attracted considerable attention as post-complementary metal–oxide semiconductor (CMOS) materials. These materials allow for electron- or hole-dominant conduction to be achieved in a single channel of the field-effect transistors (FETs) without an extrinsic doping. In this study, all-2D metal–insulator–semiconductor (MIS)-based devices, which were composed of all-2D graphene, hexagonal boron nitride, and WS 2, exhibited ambipolar and symmetrical transport characteristics with a low surface state density ( D it, min ≈ 7 × 10 11 cm –2 ·eV –1 ). Hole- or electron-dominant inversion under the influence of electrostatic doping was obtained in a WS 2 -based 2D capacitor up to a frequency range of 1 MHz. n- and p-channel conductions with enhancement-mode operations were selectively realized in a single MISFET, which presented a current on/off ratio of >10 6 and high field-effect mobility (μ e = 58–67 cm 2 /V·s and μ h = 19–30 cm 2 /V·s). Furthermore, a monolithic CMOS-like logic inverter, which employed a single WS 2 flake, exhibited a high gain of 78. These results can be used to reduce the footprints of the device architectures and simplify the device fabrication processes of next-generation CMOS integrated circuits.