MoS$_{2}$ Field-effect Transistors with Graphene/Metal Hetero-contacts

MoS$_{2}$, as one of the mostly studied transition-metal dichalcogenides, has already revealed a series of new physics and potential device applications. However, the performance of the MoS$_{2}$ field-effect transistors is limited by the large contact resistance at metal/MoS$_{2}$ interface due to the non-negligible Schottky barrier. In this study, n-type few-layer MoS$_{2}$ field-effect transistors with graphene/Ti as the metal contacts have been fabricated showing more than 160 mA/mm drain current at 1 $\mu$m gate length and on-off current ratio of 10$^{7}$. Different metal contacts (Ti, Ni, Au, and Pd) from low work function to high work function metals on MoS$_{2}$/graphene hetero contacts have been performed and studied. Moreover, for the first time, 2D Fermi-level pinning concept is introduced to understand the band alignment of hetero-structured metal/graphene/MoS$_{2}$ or other 2D semiconductor interfaces. Temperature dependent, noise, and stress measurement results will also be presented.