Epitaxial van der Waals contacts for low schottky barrier MoS₂ field effect transistors

Small contact resistance and low Schottky barrier height (SBH) are the keys to energy-efficient electronics and optoelectronics. Two-dimensional (2D) semiconductors-based field effect transistors (FETs), holding great promise for next-generation information circuits, still suffer from poor contact quality at the metal–semiconductor junction interface, which severely hinders their further applications. Here, a novel contact strategy is proposed, where Bi₂Te₃ nanosheets with high conductivity were in-situ epitaxially grown on MoS₂ as van der Waals contacts, which can effectively avoid the damage to MoS₂ caused during the device manufacturing process, leading to a high-performance MoS₂ FET. Moreover, the small work function difference between Bi₂Te₃ and MoS₂ (Bi₂Te₃: 4.31 eV, MoS₂: 4.37 eV, measured by Kelvin probe force microscopy (KPFM)), enables small band bending and Ohmic contact at the junction interface. Electrical characterizations indicate that the MoS₂ FET device with Bi₂Te₃ contacts possesses a high current on/off ratio (5 × 10⁷), large effective carrier mobility (90 cm²/(V·s)), and low flat-band SBH (60 meV), which is favorable as compared with MoS₂ FET with traditional Cr/Au electrodes contacts, and superior to the vast majority of the reported chemical vapor deposition (CVD) MoS₂-based FET device. The demonstration of epitaxial van der Waals Bi₂Te₃ contacts will facilitate the application of 2D MoS₂ nanosheet in next-generation low-power consumption electronics and optoelectronics.