Effect of the intra-layer potential distributions and spatial currents on the performance of graphene SymFETs

Mehdi Hasan,Berardi Sensale-Rodriguez

doi:10.1063/1.4930200

Abstract

In this paper, a two-dimensional (2-D) model for a graphene symmetric field effect transistor (SymFET), which considers (a) the intra-graphene layer potential distributions and (b) the internal current flows through the device, is presented and discussed. The local voltages along the graphene electrodes as well as the current-voltage characteristics of the device are numerically calculated based on a single-particle tunneling model. Our numerical results show that: (i) when the tunneling current is small, due to either a large tunneling thickness (≥ 2 atomic layers of BN) or a small coherence length, the voltage distributions along the graphene electrodes have almost zero variations upon including these distributed effects, (ii) when the tunnel current is large, due to either a small tunneling thickness (∼ 1 atomic layer of BN) or due to a large coherence length, the local voltage distributions along the graphene electrodes become appreciable and the device behavior deviates from that predicted by a 1-D approximation. These effects, which are not captured in one-dimensional SymFET models, can provide a better understanding about the electron dynamics in the device and might indicate potential novel applications for this proposed device.

Highlights

Graphene is a zero-bandgap two-dimensional (2-D) semiconductor with linear energy dispersion and a symmetric band structure.[1,2] By means of field effect the carrier density in graphene (n) can be continuously tuned between electrons and holes attaining values as high as 1013 cm−2 and mobilities (μ) exceeding 15,000 cm2/Vs, even under ambient conditions.[1,3] The truly exceptional features of graphene: (i) μ can remain relatively high even at the highest electric-field-induced concentrations, and (ii) the intrinsic symmetry of its band structure symmetric electronic properties for electrons and holes, justify the potential of graphene for electronic applications.[2]
The local voltages along the graphene electrodes as well as the current-voltage characteristics of the device are numerically calculated based on a single-particle tunneling model
Our numerical results show that: (i) when the tunneling current is small, due to either a large tunneling thickness (≥ 2 atomic layers of by an insulator (BN)) or a small coherence length, the voltage distributions along the graphene electrodes have almost zero variations upon including these distributed effects, (ii) when the tunnel current is large, due to either a small tunneling thickness (∼ 1 atomic layer of BN) or due to a large coherence length, the local voltage distributions along the graphene electrodes become appreciable and the device behavior deviates from that predicted by a 1-D approximation

Summary

INTRODUCTION

Graphene is a zero-bandgap two-dimensional (2-D) semiconductor with linear energy dispersion and a symmetric band structure.[1,2] By means of field effect the carrier density in graphene (n) can be continuously tuned between electrons and holes attaining values as high as 1013 cm−2 and mobilities (μ) exceeding 15,000 cm2/Vs, even under ambient conditions.[1,3] The truly exceptional features of graphene: (i) μ can remain relatively high even at the highest electric-field-induced concentrations, and (ii) the intrinsic symmetry of its band structure symmetric electronic properties for electrons and holes, justify the potential of graphene for electronic applications.[2]. The I-V characteristic of the device is dominated by a Dirac–delta function like peak at this critical interlayer voltage and smaller currents at all other voltages This symmetric graphene tunneling field-effect transistor (SymFET) was analyzed in most previous works employing a single particle tunneling model and assuming a 1-D approximation of the device. We introduce a rigorous distributed circuit model to represent these 2-D electrostatic effects, which takes into consideration: (a) the intra-graphene-layer potential distributions, and (b) the internal current flows through the device, as suggested in the work of Zhao et al.[7] as a future element to be considered in further work.

Employed value

RESULTS AND DISCUSSIONS

CONCLUSION