Ballistic graphene nanoribbon metal-oxide-semiconductor field-effect transistors: A full real-space quantum transport simulation
A real-space quantum transport simulator for graphenenanoribbon (GNR) metal-oxide-semiconductor field-effect transistors (MOSFETs) has been developed and used to examine the ballistic performance of GNR MOSFETs. This study focuses on the impact of quantum effects on these devices and on the effect of different type of contacts. We found that two-dimensional (2D) semi-infinite graphene contacts produce metal-induced-gap states (MIGS) in the GNR channel. These states enhance quantum tunneling, particularly in short channel devices, they cause Fermi level pinning and degrade the device performance in both the ON-state and OFF-state. Devices with infinitely long contacts having the same width as the channel do not indicate MIGS. Even without MIGS quantum tunnelingeffects such as band-to-band tunneling still play an important role in the device characteristics and dominate the OFF-state current. This is accurately captured in our nonequilibrium Greens’ function quantum simulations. We show that both narrow (1.4 nm width) and wider (1.8 nm width) GNRs with 12.5 nm channel length have the potential to outperform ultrascaled Si devices in terms of drive current capabilities and electrostatic control. Although their subthreshold swings under forward bias are better than in Si transistors,tunneling currents are important and prevent the achievement of the theoretical limit of 60 mV/dec
Date of this Version
J. Appl. Phys. 102, 054307 (2007)
Copyright (2007) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in J. Appl. Phys. 102, 054307 (2007) and may be found at http://dx.doi.org/10.1063/1.2775917. The following article has been submitted to/accepted by Journal of Applied Physics. Copyright (2007) Gengchiau Liang, Neophytos Neophytou, Mark S. Lundstrom and Dmitri E. Nikonov. This article is distributed under a Creative Commons Attribution 3.0 Unported License.