New Applications for Graphene Electronics
Han Wang, Daniel Nezich, Jing Kong
and Tomas Palacios
Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology
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This work is sponsored by MIT/Army Institute For Soldier Nanotechnologies (ISN)
and the Interconnect Focus Center (SRC/FCRP IFC).
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What is the best application for
graphene?
Transport properties are not what make this material unique…
• Electron mobility?
µInSb = 80,000 cm2/Vs
− µgraphene = 200,000 cm2/Vs
7
6
5
InSb
CNT
7
- ve,GNT = 5×107 cm/s
Electron velocity (10 cm/s)
- Carrier velocity?
- Ballistic transport?
4
3
InG
aA
sP
InAs
0
0.1
GaN
Si
InP
2
1
CNT
GaAs
1
10
100
Electric field (kV/cm)
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Unique properties of graphene
• Ambipolar transport with very high
1.0m
mobility
Graph F W1R7C01
THfO2 = 40nm
800.0
• Bandgap control through etching Æ
lateral bandgap engineering
• Excellent electrostatic control
+
• Improved transport properties.
600.0
Id (A)
• Flexible and transparent material
W=5µm, L=10µm
VDS = 1 V
400.0
h+
200.0
e-
0.0
-1
0
1
2
Vg (V)
3
3
New graphene devices:
Frequency doublers
e
Holes
h
Electrons
Output signal (2f0)
Vp(Dirac
Voltage)
Input signal (f0)
Graphene
Ambipolar FET
4
•Full wave rectification using a single graphene device
•No bandgap required
•Field effect transistor: Signal amplification possible
•Much higher efficiency than conventional diode or FET frequency doublers
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Fabrication of
Graphene Frequency Multipliers
Optical Interference
Image of graphene flakes
Final Device
Schematic Structure
H. Wang, D. Nezich, J. Kong, and T. Palacios “Graphene Frequency
Multipliers” IEEE Electron Device Letters, May 2009..
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Experimental results…
Graphene frequency doubler
Input
Output
•First demonstration of frequency
doubling
•Excellent spectral purity Æ high
conversion efficiency
•High frequency operation
100
•Large gain possible
•No bandgap required
Graphene is the an excellent
material for high performance
frequency multipliers
Efficiency (%)
Graphene frequency multiplier
Diode frequency
multipliers
10
1
x2
x2x2
x3
x2x2x2
x2x2x3
x2x2x2x2
FET frequency
multipliers
0.1
100
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10006
Frequency (GHz)
?
Conclusion and Future Work
-
Ambipolar frequency multipliers based on graphene demonstrated.
Excellent spectral purity with 94% of the output power at useful frequency.
No filtering elements are needed at the output.
Signal amplification possible.
Many other new devices/applications are possible :
-Analog to digital converters
-Energy harvesting devices
-Advanced photodetectors
-…
H. Wang, D. Nezich, J. Kong, and T. Palacios, IEEE Electron Device Letters, May 2009.
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Ambipolar Frequency Multipliers
Conventional FET Frequency Multipliers
Circuit and Output Waveform
I-V Characteristics
Output Power Spectrum
f
Ambipolar Frequency Multipliers
I-V Characteristics
Circuit and Output Waveform
f
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Output Power Spectrum
Why is spectral purity so
high at the output?
Sub-linear Ids-Vgs characteristics in
fabricated GFETs
78% maximum
Parabolic component of Ids-Vgs
much larger in fabricated GFETs
Less higher order harmonics,
hence higher spectrum purity
94%
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