Modeling of Graphene Nanoribbon FET and Analysis of
Its Electrical Properties
Yangbing Wu
1
, Donghui Guo
2
School of Information Science and Engineering, Xiamen University,
Xiamen, China
1
yangbing11@foxmail.com,
2
dhguo@xmu.edu.cn
Abstract—Graphene devices can be used to electromagnetic
information field base on their peculiar electromagnetic
properties. These devices, which have advantages in terms of
small size, high switching speed, and high switching reliability,
will be instead of the variable capacitances or mechanical
contacts. In this paper, we present a modeling of graphene
nanoribbon field-effect transistor, and a simulation of graphene
devices in weak electrostatic fields, based on the self-consistent
solution of Poisson and Schrödinger equations within the non-
equilibrium Green’s function formalism and a tight-binding
Hamiltonian. The simulation results analyze the electrical
characteristics of GNR-FET with different structures.
Keywords-nonequilibrium Green’s function formalism(NEGF);
graphene; nanoribbon; GNR-FET
I. INTRODUCTION
In the last few years, graphene-based devices have received
considerable attention for their extremely interesting
electromagnetic and physical properties
[1]
and promising
nanoelectronic applications, which have potential to substitute
silicon as the next generation material for transistors beyond
CMOS technology
[2]
. In particular, the possibility of fabricating
stable monolayer graphene sheets, with peculiar electrical
properties, was demonstrated in recent experiments
[3]
. At the
same time, the field-effect transistor (FET) switches are widely
used in radio-frequencies (RF)
[4]
and microwaves
applications
[5]
. These devices have distinguished advantages
compared to conventional variable capacitances or mechanical
contacts in terms of small size, high switching reliability and
high switching speed. In summary, it is feasible and effective
that graphene-based devices are applied to the electromagnetic
information field.
However, monolayer graphene sheets have zero energy gap,
which are used to make transistors is unsuitable. Even though
the energy gap of graphene can be alter by adjusting lateral
border, i.e., that is achieved by etching or lithography
modification of narrow graphene stripes, which is named
graphene nanoribbons (GNRs)
[6,7]
. Only recently experiments
show that graphene FET or graphene nanoribbon field-effect
transistors (GNR-FETs) are fabricated and indicate that is hard
to modulate the conductance of graphene at room temperature.
The most important difficulty is to make an energy gap
sufficient for room temperature operation need to fabricate
extremely narrow nanoribbons (approximately 1 nm) with
atomic precision operation.
At this moment, the theory simulations can be useful to
understand electromagnetic properties of graphene FET or
GNR-FETs and estimate their performance. We will firstly
show a model base on graphene based FET. And then, we
simulate the electromagnetic parameters of the model, based on
the self-consistent solution of Poisson and Schrödinger
equations within the non-equilibrium Green’s function
formalism
[8]
and a tight-binding Hamiltonian in the real space.
At last, the electrical characteristics of the device model will be
demonstrated by the simulation results.
II. P
HYSICAL MODEL
For analysis the electrical properties of graphene based
FET, the model is sketched in Fig.1. It consists of a monolayer
graphene sheet of width W and length L, which could be
graphene nanoribbon (GNR), embedded within two dielectric
substrate (i.e. SiO
2
) both with thickness h and dielectric
constant
d
ε
. One substrate applied voltage V
g
on the top, other
placed over a ground plane, equivalent apply an electrostatic
E
bias
on graphene sheet. The graphene sheet perpendicular to
the z-axis and connect to source and drain electrodes with two
edges.
Figure 1. Graphene Field-Effect Transistor on a Grounded SiO2 Substrate
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978-1-4799-7119-0/14/$31.00 ⓒ2014 IEEE