Contact Resistivity in Edge-Contacted Graphene Field Effect Transistors

A great challenge is presented when metals have contact with a 2D semiconducting material because the contact resistances (R-c) induced at the metal-graphene interfaces hinder the performances of 2D devices, and therefore low resistance Ohmic contacts need to be developed to achieve unique and high performance of the 2D devices. This study demonstrates that edge-contacted graphene devices of multiple stacked 2D hetero-structures with hexagonal boron nitride (hBN) exhibit superior performances in carrier transport across channel and contact regions, compared to surface-contacted devices. In surface-contacted graphene devices, R-c and contact resistivity (rho(c)) are calculated by applying the modified transfer length (L-T*) obtained from the contact-end-resistance method, while R-c and rho(c) in edge-contacted graphene devices are estimated by replacing the L-T* with the thickness of graphene. The edge-contacted device is fabricated via a controlled plasma etching that allows each layer of graphene and hBN consisting hetero-structures to be removed evenly at a uniform speed. Four-point probe measurements are conducted in addition to transmission line method and confirms that rho(c) is lower for edge contact than surface contact. rho(c) of a graphene edge-contacted device (approximate to 10 omega mu m(2)) is much lower than that of a surface-contacted device (approximate to 230 omega mu m(2)).

Automated summary

This study demonstrates that edge-contacted graphene devices of multiple stacked 2D hetero-structures with hBN exhibit superior performances in carrier transport and have lower contact resistivity compared to surface-contacted devices.