Improved Contacts and Device Performance in MoS2 Transistors Using a 2D Semiconductor Interlayer

We report a contact engineering method to minimize the Schottky barrier height (SBH) and contact resistivity of MoS2 field-effect transistors (FETs) by using ultrathin 2D semiconductors as contact interlayers. We demonstrate that the addition of a few-layer MoSe2 between the MoS2 channel and Ti electrodes effectively reduces the SBH at the contacts from similar to 100 to similar to 25 meV, contact resistivity from similar to 6 x 10(-5) to similar to 1 x 10(-6) O cm(2), and current transfer length from similar to 425 to similar to 60 nm. The drastic reduction of SBH can be attributed to the synergy of Fermi-level pinning close to the conduction band edge of the MoSe2 interlayer and favorable conduction-band offset between the MoSe2 interlayer and MoS2 channel. As a result of the improved contacts, MoS2 FETs with Ti/MoSe2 contacts also demonstrate higher two-terminal mobility.