Alcohol-Based Sulfur Treatment for Improved Performance and Yield in Local Back-Gated and Channel-Length-Scaled MoS₂ FETs

Achieving good ohmic contacts, with minimum variability, has remained a challenge for field-effect transistors (FETs) using molybdenum disulfide (MoS2). Surface state engineering using ammonium sulfide is a great way to obtain superior and reliable contacts on MoS2 using high-work-function metals such as nickel. However, the process is aggressive to thin gate dielectrics hampering device yield. We report on an improved sulfur treatment process in an alcoholic medium that is less aggressive to thin gate dielectrics and offers a record low Schottky barrier height of 131 meV on Ni-MoS2 contacts. We demonstrate the suitability of this process with channel length scaling (L_G from 500 to 80 nm) on global back-gated FETs with a record low contact resistance of 1.3 kΩ ·μm for 80-nm FET. We also demonstrate the compatibility of the proposed process with local back-gated FETs on thin high-k HfO2 gate dielectrics, which is crucial for scalable process integration in realizing integrated circuits on 2-D materials.