han wang, daniel nezich, jing kong and tomas palacios · han wang, daniel nezich, jing kong and...
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New Applications for Graphene ElectronicsNew Applications for Graphene Electronics
Han Wang, Daniel Nezich, Jing Kong and Tomas Palacios
Department of Electrical Engineering and Computer ScienceMassachusetts Institute of Technology
This work is sponsored by MIT/Army Institute For Soldier Nanotechnologies (ISN) and the Interconnect Focus Center (SRC/FCRP IFC).
What is the best application for graphene?
• Electron mobility?− µgraphene = 200,000 cm2/Vs
- Carrier velocity?- ve,GNT = 5×107 cm/s
- Ballistic transport?
0.1 1 10 1000
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2
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CNT
InSb
GaN
GaAs
InPSi
InAs
Elec
tron
vel
ocity
(107 c
m/s
)
Electric field (kV/cm)
CNT
InGaAsP
µInSb = 80,000 cm2/Vs
Transport properties are not what make this material unique…
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Unique properties of graphene
• Ambipolar transport with very high mobility
• Bandgap control through etchinglateral bandgap engineering
• Flexible and transparent material
• Excellent electrostatic control+
• Improved transport properties.-1 0 1 2 3
0.0
200.0
400.0
600.0
800.0
1.0m
I d (A)
Vg (V)
Graph F W1R7C01THfO2 = 40nmW=5µm, L=10µmVDS = 1 V
e-h+
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Holes Electrons
New graphene devices: Frequency doublers
•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
he
Graphene Ambipolar FET
Input signal (f0)
Output signal (2f0)Vp(Dirac Voltage)
Fabrication of Graphene Frequency Multipliers
Final DeviceOptical Interference Image of graphene flakes
Schematic Structure
H. Wang, D. Nezich, J. Kong, and T. Palacios “Graphene Frequency Multipliers” IEEE Electron Device Letters, May 2009..
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OutputInput
•First demonstration of frequency doubling
•Excellent spectral purity high conversion efficiency
•High frequency operation
•Large gain possible
•No bandgap required
Experimental results…Graphene frequency doubler
Graphene is the an excellent material for high performance
frequency multipliers100 1000
0.1
1
10
100
FET frequencymultipliers
Effic
ienc
y (%
)
Frequency (GHz)
x2 x2x2 x3 x2x2x2 x2x2x3 x2x2x2x2
Graphene frequency multiplier
Diode frequency multipliers
?
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-…
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.
Ambipolar Frequency Multipliers
Ambipolar Frequency Multipliers
Conventional FET Frequency Multipliers
II--V CharacteristicsV Characteristics Circuit and Output WaveformCircuit and Output Waveform Output Power SpectrumOutput Power Spectrum
II--V CharacteristicsV Characteristics Circuit and Output WaveformCircuit and Output Waveform Output Power SpectrumOutput Power Spectrum
f
f
Why is spectral purity so high at the output?
Parabolic component of Ids-Vgsmuch larger in fabricated GFETs
Less higher order harmonics, hence higher spectrum purity
Sub-linear Ids-Vgs characteristics in fabricated GFETs 78% maximum
94%