The document discusses graphene-based transistors for digital and analog applications through simulation. It provides motivation for exploring new channel materials beyond CMOS due to limitations of existing technologies. Graphene is introduced as a potential channel material due to its high carrier mobility and other desirable electronic properties. The document outlines plans to simulate graphene field-effect transistors using the NanoTCAD ViDES software to model device performance and optimize design parameters.

1. Graphene Based Transistors For Digital And
Analog Application
:A Simulation Study
Vishal Anand Agam Gupta Abhishek Anand
1204059 1204056 1204055
Project Supervisor: Dr. M. W. Akram

2. Contents:-
• Motivation
• Introduction
• Basics of Graphene
• Simulation on Software
• Project Roadmap

3. Motivation:-
Moore’s Law observed in 1965 by Gordon
Moore suggested that, over the history of
computing hardware, the number of
transistors in a dense integrated circuit has
doubled approximately every two years.
The trend that was followed so far in the
electronics industry but with devices
becoming increasingly small and reaching the
limit we now had to explore other frontiers for
this.
The shortcomings of some devices with
respect to some parameters forced us to
consider the introduction of new channel
material. By using this new channel material,
new FET devices can be optimized. Ref:[1].www.intelcorporations.com

4. Beyond C-MOS
Ref:-[2] Roadmap for 22 nm and beyond H. Iwai * Frontierl Research Center, Tokyo Institute of Technology,

5. So What’s The Way Out ???
TWO
OPTIONS
NEW
DEVICE
STRUCTURE
FinFET
NEW
CHANNEL
MATERIAL
CARBON
NANOTUBE GRAPHENE SHEETFinFET
Ref:-[3] www.google.com

6. What Is Graphene ?
Thermodynamically stable graphene sheet was first
discovered in 2004 by Giem and Novoselov.
Graphene is a two –dimensional sheet of sp2 bonded
carbon atoms arranged ina honeycomb crystal structure
with two carbon atoms in each unit cell.
Sp2 hybrids of each carbon atom contribute to form
sigma bond with three other carbon atoms in triangular
planar structure of Graphene,P orbitals are normal to
planar structure and can bind to form half filled pi-band.
Ref:- [4]Fabrication and Characterization of Graphene Field Effect Transistors by Sam Vaziri

7. Graphite
Single-layer Graphene
Single-wall Carbon Nanotub
Ref:- [5] K. S. Novoselov et al., “Electric Field Effect in Atomically Thin
Carbon Films,” Science, 306 (2004) 666.

8. Graphene Electronic Properties :
• Semi-metal or zero-gap semiconductor
• Linear dispersion relation Optoelectronics
• Massless dirac fermions, v ~ c/300 Intrinsic carrier mobility
(suspended graphene in vacuum 2,00,000 cm2 V-1s-1
• Carrier mobility of graphene on SiO2 at room-temperature 10,000-
20,000 cm2 V-1s-1
• Maximum current density J > 108 A/cm2
• Velocity saturation vsat = 5 x 107 cm/s (10 x Si, 2 x GaAs)
Fig:-Dispersion relation of graphene in fist Brillouin zone
Ref:-[6] Fabrication and Characterization of Graphene Field Effect Transistors by Sam Vaziri

9. 1. Mechanical properties
• Young’s modulus: ~1.10 TPa (Si ~ 130 GPa)
• Elastically stretchable by 20%
• Strongest material known
• Flexible
2. Thermal conductivity
• ∼5.000 W/m•K at room temperature
Diamond: ∼2000 W/m•K, 10 x higher than Cu, Al
3. Transparent (only 1 atom thin)
Transparent flexible conductive electrodes
4. High surface to volume ratio
5. Most important advantage of Graphene technology is that it is compatible with standard sllicon technology
making it easy and cost effective to integrate with the existing CMOS fabrication plants.

10. Comparison Between Graphene And Sillicon Mosfet
• GFET has higher switching speed due to high mobility of carriers
• GFET’s Thermodynamically more stable
• Shorter and thin channel length resulting in high packing density
Ref:-[7] A. Betti, G. Fiori, and G. Iannaccone, “Atomistic investigation of lowfield mobility in graphene nanoribbons,”
IEEE Trans. Electron Devices,
vol. 58, no. 9, pp. 2824–2830, Sep. 2011.

11. Unconventional Use Of Unconventional Properties :
• 1 Transistor Rectifier
• 1 Transistor Frequency Doubler
[8] I. Imperiale, S. Bonsignore, A. Gnudi, E. Gnani, S. Reggiani, and G. Baccarani, “Computational study of
graphene nanoribbon FETs for RF applications,” in Proc. IEEE IEDM, Dec. 2010, pp. 732–735.

12. Simulation Side
• We will be using NanoTCAD ViDES as our simulation software.
• The current version of NanoTCAD ViDES is a python module, which integrates the
C and Fortran subroutines already developed in the past version of the NanoTCAD
ViDES simulator, which is able to simulate nanoscale devices, through the self-
consistent solution of the Poisson and the Schroedinger equations, by means of the
Non-Equilibrium Green’s Function (NEGF) formalism.

13. Why device simulation???
They allow to:
• predict the device behaviour
• understand the physical mechanisms underlying
the device operation
• test the impact of device design parameters on the device
performance (device optimization)

14. The module developed so far has a set of predefined functions, which
allow to compute transport in:-
• Two-dimensional materials (2D materials like MoS2, WSe2 and metal
dichalcogenides in generals)
• Silicene
• Graphene Nanoribbons
• Carbon Nanotubes
• Two-dimensional graphene FET
• Two-dimensional bilayer graphene FET

15. The user can anyway define his own device and material through the
exploitation of the Hamiltonian command
Hamiltonian
Synopsys: Hamiltonian(n,Nc)
Hamiltonian is the NanoTCAD ViDES class, which allow the definition of
a general Hamiltonian within the semi-empirical tight-binding model. As
inputs, it requires the number of atoms n in the slice, and the number of
slices Nc of the material to be considered. Nc must be at least larger than
4.

16. Some of the attributes of Hamiltonian class are as follows:-
• Nc : (int) the number of slices
• n : (int) the number of atoms within each slice
• x: (numpy array of length n*Nc) x coordinates of the atoms
• y: (numpy array of length n*Nc) y coordinates of the atoms
• z: (numpy array of length n*Nc) z coordinates of the atoms
• Phi: (numpy array of length n*Nc) potential of the atoms
• Eupper : (double) the upper energy limit for which the NEGF is computed in the
nanoribbon
• Elower : (double) the lower energy limit for which the NEGF is computed in the
nanoribbon
• charge_T : (function) function which computes the free charge and the
transmission coefficient in the energy interval specified by Eupper and Elower with
an energy step equal to dE in correspondence of each C atoms of the nanoribbon

17. Template of 2D Metal Di Chalcogenides Field Effect Transistor.
Ref:-[9] ViDES manual

18. Ref:-[10] ViDES manual

19. Structure of top gated graphene field-effect transistor is used in our
simulations
Ref:-[11] ViDES manual

20. The Id-Vds characteristics of the top gate graphene field-effect
transistor at VG = 0.1V, 0.2V, 0.4V, 0.6V, 0.8V (bottom to up).
Ref[12]:- ViDES manual

21. Ref:-[13] ViDES manual

22. Source:-[14] ViDES manual

23. Project Roadmap