Carrier Type Control of WSe₂Field-Effect Transistors by Thickness Modulation and MoO₃Layer Doping

KGaA, Weinheim Control of the carrier type in 2D materials is critical for realizing complementary logic computation. Carrier type control in WSe2field-effect transistors (FETs) is presented via thickness engineering and solid-state oxide doping, which are compatible with state-of-the-art integrated circuit (IC) processing. It is found that the carrier type of WSe2FETs evolves with its thickness, namely, p-type (<4 nm), ambipolar (≈6 nm), and n-type (>15 nm). This layer-dependent carrier type can be understood as a result of drastic change of the band edge of WSe2as a function of the thickness and their band offsets to the metal contacts. The strong carrier type tuning by solid-state oxide doping is also demonstrated, in which ambipolar characteristics of WSe2FETs are converted into pure p-type, and the field-effect hole mobility is enhanced by two orders of magnitude. The studies not only provide IC-compatible processing method to control the carrier type in 2D semiconductor, but also enable to build functional devices, such as, a tunable diode formed with an asymmetrical-thick WSe2flake for fast photodetectors.