Ballistic Graphene Nanoribbon MOSFETs: a full quantum real-space simulation study

TL;DR

This study develops a quantum transport simulator for graphene nanoribbon MOSFETs, revealing quantum effects like MIGS and tunneling significantly impact device performance, with certain CNRs outperforming scaled silicon devices.

Contribution

The paper introduces a full quantum real-space simulation method for CNR MOSFETs and analyzes quantum effects on their performance, highlighting the role of MIGS and tunneling.

Findings

MIGS cause performance degradation in short-channel devices.

Quantum tunneling dominates off-state current in CNR MOSFETs.

Certain narrow CNRs outperform scaled silicon transistors.

Abstract

A real-space quantum transport simulator for carbon nanoribbon (CNR) MOSFETs has been developed. Using this simulator, the performance of carbon nanoribbon (CNR) MOSFETs is examined in the ballistic limit. The impact of quantum effects on device performance of CNR MOSFETs is also studied. We found that 2D semi-infinite graphene contacts provide metal-induced-gap-states (MIGS) in the CNR channel. These states would provide quantum tunneling in the short channel device and cause Fermi level pining. These effects cause device performance degradation both on the ON-state and the OFF-state. Pure 1D devices (infinite contacts), however, show no MIGS. Quantum tunneling effects are still playing an important role in the device characteristics. Conduction due to band-to-band tunneling is accurately captured in our simulations. It is important in these devices, and found to dominate the off-state current. Based on our simulations, both a 1.4nm wide and a 1.8nm wide CNR with channel length of 12.5nm can outperform ultra scaled Si devices in terms of drive current capabilities and electrostatic control. Although subthreshold slopes in the forward-bias conduction are better than in Si transistors, tunneling currents are important and prevent the achievement of the theoretical limit of 60mV/dec.