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Achieving low contact resistance (RC) is one of the major challenges in producing 2D FETs for future CMOS technology applications. In this work, the electrical characteristics for semimetal (Sb) and normal metal (Ti) contacted MoS2 devices are systematically analyzed as a function of top and bottom gate‐voltages (VTG and VBG). The semimetal contacts not only significantly reduce RC but also induce a strong dependence of RC on VTG, in sharp contrast to Ti contacts that only modulate RC by varying VBG. The anomalous behavior is attributed to the strongly modulated pseudo‐junction resistance (Rjun) by VTG, resulting from weak Fermi level pinning (FLP) of Sb contacts. In contrast, the resistances under both metallic contacts remain unchanged by VTG as metal screens the electric field from the applied VTG. Technology computer aided design simulations further confirm the contribution of VTG to Rjun, which improves overall RC of Sb‐contacted MoS2 devices. Consequently, the Sb contact has a distinctive merit in dual‐gated (DG) device structure, as it greatly reduces RC and enables effective gate control by both VBG and VTG. The results offer new insight into the development of DG 2D FETs with enhanced contact properties realized by using semimetals. [ABSTRACT FROM AUTHOR]

Surface charge transfer doping (SCTD) using oxygen plasma to form a p‐type dopant oxide layer on transition metal dichalcogenide (TMDs) is a promising doping technique for 2D TMDs field‐effect transistors (FETs). However, patternability of SCTD is a key challenge to effectively switch FETs. Herein, a simple method to selectively pattern degenerately p‐type (p+)‐doped WSe2 FETs via electron beam (e‐beam) irradiation is reported. The effect of the selective e‐beam irradiation is confirmed by the gate‐tunable optical responses of seamless lateral p+–p diodes. The OFF state of the devices by inducing trapped charges via selective e‐beam irradiation onto a desired channel area in p+‐doped WSe2, which is in sharp contrast to globally p+‐doped WSe2 FETs, is realized. Selective e‐beam irradiation of the PMMA‐passivated p+‐WSe2 enables accurate control of the threshold voltage (Vth) of WSe2 devices by varying the pattern size and e‐beam dose, while preserving the low contact resistance. By utilizing hBN as the gate dielectric, high‐performance WSe2 p‐FETs with a saturation current of −280 µA µm−1 and on/off ratio of 109 are achieved. This study's technique demonstrates a facile approach to obtain high‐performance TMD p‐FETs by e‐beam irradiation, enabling efficient switching and patternability toward various junction devices. [ABSTRACT FROM AUTHOR]

Even though atomically thin 2D semiconductors have shown great potential for next‐generation electronics, the low carrier mobility caused by poor metal–semiconductor contacts and the inherently high density of impurity scatterings remains a critical issue. Herein, high‐mobility field‐effect transistors (FETs) by introducing few‐layer PdSe2 flakes as channels is achieved, via directly depositing semimetal antimony (Sb) as drain–source electrodes. The formation of clean and defect‐free van der Waals (vdW) stackings at the Sb–PdSe2 heterointerfaces boosts the room temperature transport characteristics, including low contact resistance down to 0.55 kΩ µm, high on‐current density reaching 96 µA µm−1, and high electron mobility of 383 cm2 V−1 s−1. Furthermore, metal–insulator transition (MIT) is observed in the PdSe2 FETs with and without hexagonal boron nitride (h–BN) as buffer layers. However, the layered h–BN/PdSe2 vdW stacking eliminates the interference of interfacial disorders, and thus the corresponding device exhibits a lower MIT crossing point, larger mobility exponent of γ ∼ 1.73, significantly decreased hopping parameter of T0, and ultrahigh electron mobility of 2,184 cm2 V−1 s−1 at 10 K. These findings are expected to be significant for developing high mobility 2D‐based quantum devices. [ABSTRACT FROM AUTHOR]