Monolayer Short-Channel Transistors Defined by Nonmetallic van der Waals Contact

Two-dimensional (2D) semiconductors have excellent immunity to short-channel effects and are therefore promising for ultrascaled field-effect transistors. However, ultrascaled transistors necessitate simultaneous minimization of the channel length and contact resistance, which is a significant challenge for atomically thin 2D semiconductors. In this work, a facile angle evaporation technique is developed to fabricate ultrashort channel monolayer 2D transistors with nonmetallic van der Waals (vdW) contacts. By precisely controlling the evaporation angle and the thickness of the physical vapor deposition-grown nonmetallic PbTe, which owns ultrasharp edges due to its perfect and stable periodic crystal structure, the channel length of 2D transistors can be controlled reproducibly. Moreover, due to the nonmetallic contact properties of PbTe, there are negligible metal-induced gap states (MIGS) between PbTe and 2D semiconductors; thus, almost no additional Fermi-level pinning (FLP) at the heterostructure interface. The short-channel MoS₂ transistor with PbTe vdW contact exhibits superior performance, including excellent ohmic contacts, near-Boltzmann-limit subthreshold swing, high on/off current ratio (∼10⁹), and negligible drain-induced barrier lowering (∼82 mV V^-1). In addition, the device can also operate at a low voltage of 0.01 V with a desirable on/off ratio of ∼10⁸, providing a facile technique to fabricate 2D material-based low-power ultra-scaled transistors.