The contact properties of van der Waals layered semiconducting materials are not adequately understood, particularly for edge contact. Edge contact is extremely helpful in the case of graphene, for producing efficient contacts to vertical heterostructures, and for improving the contact resistance through strong covalent bonding. Herein, we report on edge contacts to MoS2 of various thicknesses. The carrier-type conversion is robustly controlled by changing the flake thickness and metal work functions. Regarding the ambipolar behavior, we suggest that the carrier injection is segregated in a relatively thick MoS2 channel; that is, electrons are in the uppermost layers, and holes are in the inner layers. Calculations reveal that the strength of the Fermi-level pinning (FLP) varies layer-by-layer, owing to the inhomogeneous carrier concentration, and particularly, there is negligible FLP in the inner layer, supporting the hole injection. The contact resistance is large despite the significantly reduced contact resistivity normalized by the contact area, which is attributed to the current-crowding effect arising from the narrow contact area.

There is a general consensus that the carrier mobility in a field-effect transistor (FET) made of semiconducting transition-metal dichalcogenides (s-TMDs) is severely degraded by the trapping/detrapping and Coulomb scattering of carriers by ionic charges in the gate oxides. Using a double-gated (DG) MoTe FET, we modulated and enhanced the carrier mobility by adjusting the top- and bottom-gate biases. The relevant mechanism for mobility tuning in this device was explored using static DC and low-frequency (LF) noise characterizations. In the investigations, LF-noise analysis revealed that for a strong back-gate bias the Coulomb scattering of carriers by ionized traps in the gate dielectrics is strongly screened by accumulation charges. This significantly reduces the electrostatic scattering of channel carriers by the interface trap sites, resulting in increased mobility. The reduction of the number of effective trap sites also depends on the gate bias, implying that owing to the gate bias, the carriers are shifted inside the channel. Thus, the number of active trap sites decreases as the carriers are repelled from the interface by the gate bias. The gate-controlled Coulomb-scattering parameter and the trap-site density provide new handles for improving the carrier mobility in TMDs, in a fundamentally different way from dielectric screening observed in previous studies.

Many‐body effect and strong Coulomb interaction in monolayer transition metal dichalcogenides lead to intrinsic bandgap shrinking, originating from the renormalization of electrical/optical bandgap, exciton binding energy, and spin‐orbit splitting. This renormalization phenomenon has been commonly observed at low temperature and requires high photon excitation density. Here, the augmented bandgap renormalization (BGR) in monolayer MoS2 anchored on CsPbBr3 perovskite quantum dots at room temperature via charge transfer is presented. The amount of electrons significantly transferred from perovskite gives rise to the large plasma screening in MoS2. The bandgap in heterostructure is red‐shifted by 84 meV with minimal pump fluence, the highest BGR in monolayer MoS2 at room temperature, which saturates with a further increase of pump fluence. Further, it is found that the magnitude of BGR inversely relates to Thomas–Fermi screening length. This provides plenty of room to explore the BGR within existing vast libraries of large bandgap van der Waals heterostructure toward practical devices such as solar cells, photodetectors, and light‐emitting‐diodes.