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Influence of Metal/Graphene Coupling on the Operation and Scalability of Graphene Field-Effect-Transistors



Pei Zhao, Qin Zhang, Debdeep Jena, Siyuranga O. Koswatta


We explore the effects of metal contacts on the operation and scalability of 2D Graphene Field-Effect-Transistors (GFETs) using detailed numerical device simulations based on the non-equilibrium Green's function formalism self-consistently solved with the Poisson equation at the ballistic limit. Our treatment of metal-graphene (M-G) contacts captures: (1) the doping effect due to the shift of the Fermi level in graphene contacts, (2) the density-of-states (DOS) broadening effect inside graphene contacts due to Metal-Induced-States (MIS). Our results confirm the asymmetric transfer characteristics in GFETs due to the doping effect by metal contacts. Furthermore, at higher M-G coupling strengths the contact DOS broadening effect increases the on-current, while the impact on the minimum current (Imin) in the off-state depends on the source to drain bias voltage and the work-function difference between graphene and the contact metal. Interestingly, with scaling of the channel length, the MIS inside the channel has a weak influence on Imin even at large M-G coupling strengths, while direct source-to-drain (S D) tunneling has a stronger influence. Therefore, channel length scalability of GFETs with sufficient gate control will be mainly limited by direct S D tunneling, and not by the MIS.
IEEE Transactions on Electron Devices


Graphene, Field-Effect-Transistors, Metal Induced States, Density-of-States Broadening, Source to Drain Tunneling


Zhao, P. , Zhang, Q. , Jena, D. and Koswatta, S. (2011), Influence of Metal/Graphene Coupling on the Operation and Scalability of Graphene Field-Effect-Transistors, IEEE Transactions on Electron Devices, [online], (Accessed March 1, 2024)
Created August 23, 2011, Updated October 12, 2021