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 MoS field-effect transistors (FETs) by using ultrathin 2D semiconductors as contact interlayers. We demonstrate that the addition of a few-layer MoSe between the MoS channel and Ti electrodes effectively reduces the SBH at the contacts from ~ 100 meV to ~ 25 meV, contact resistivity from ~6×10 Ω cm to ~1×10 Ω cm, and current transfer length from ~ 425 nm 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 MoSe interlayer and favorable conduction-band offset between the MoSe interlayer and MoS channel. As a result of the improved contacts, MoS FETs with Ti/MoSe contacts also demonstrate higher two-terminal mobility.