Epitaxial van der Waals contacts for low schottky barrier MoS_(2) 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 Bi_(2)Te_(3)nanosheets with high conductivity were in-situ epitaxially grown on MoS_(2)as van der Waals contacts,which can effectively avoid the damage to MoS_(2)caused during the device manufacturing process,leading to a high-performance MoS_(2)FET.Moreover,the small work function difference between Bi_(2)Te_(3)and MoS_(2)(Bi_(2)Te_(3):4.31 eV,MoS_(2):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 MoS_(2)FET device with Bi_(2)Te_(3)contacts possesses a high current on/off ratio(5×107),large effective carrier mobility(90 cm^(2)/(V·s)),and low flat-band SBH(60 meV),which is favorable as compared with MoS_(2)FET with traditional Cr/Au electrodes contacts,and superior to the vast majority of the reported chemical vapor deposition(CVD)MoS_(2)-based FET device.The demonstration of epitaxial van der Waals Bi_(2)Te_(3)contacts will facilitate the application of 2D MoS_(2)nanosheet in next-generation low-power consumption electronics and optoelectronics.