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.