Search

Control of the carrier type in 2D materials is critical for realizing complementary logic computation. Carrier type control in WSe2 field-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 WSe2 FETs 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 WSe2 as 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 WSe2 FETs 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 WSe2 flake for fast photodetectors. [ABSTRACT FROM AUTHOR]

Self‐driven photodetectors have wide applications in wireless sensor networks and wearable physiological monitoring systems. While 2D materials have different bandgaps for potential novel application fields, the self‐driven photodetectors are mainly built on PN junctions or heterostructures, whose fabrication involves doping or reliable multiple transfer steps. In this study, a novel metal–semiconductor–metal (MSM) WSe2 photodetector with asymmetric contact geometries is proposed. A high responsivity of 2.31 A W−1 is obtained under zero bias, and a large open‐circuit voltage of 0.42 V is achieved for an MSM photodetector with a large contact length difference. The MSM photodetector can overcome the disadvantage of high dark current in traditional MSM photodetectors. A small dark current of ≈1 fA along with a high detectivity of 9.16 × 1011 Jones is achieved. The working principles and finite element analysis are presented to explain the origin of the self‐driven property and its dependence on the degree of asymmetry. A self‐driven metal–semiconductor–metal (MSM) WSe2 photodetector with a planar structure by using asymmetric contact geometry is achieved. A high responsivity of 2.31 A W−1 is obtained under zero bias. The MSM photodetector avoids the disadvantage of the high dark current of traditional MSM photodetector, and a small dark current of ≈1 fA along with a detectivity of 9.16 × 1011 Jones is achieved. [ABSTRACT FROM AUTHOR]