New Applications for Graphene Electronics New Applications for - PowerPoint PPT Presentation

New Applications for Graphene Electronics 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 tpalacios@mit.edu This work is sponsored by MIT/Army Institute For Soldier Nanotechnologies (ISN) and the Interconnect Focus Center (SRC/FCRP IFC). tpalacios@mit.edu

What is the best application for graphene? Transport properties are not what make this material unique… • Electron mobility? µ InSb = 80,000 cm 2 /Vs − µ graphene = 200,000 cm 2 /Vs 7 - Carrier velocity? - v e,GNT = 5×10 7 cm/s 6 7 cm/s) InSb 5 CNT Electron velocity (10 4 InGaAsP 3 CNT - Ballistic transport? InAs GaN InP 2 Si GaAs 1 0 0.1 1 10 100 Electric field (kV/cm) tpalacios@mit.edu

Unique properties of graphene • Ambipolar transport with very high 1.0m mobility Graph F W1R7C01 T HfO2 = 40nm 800.0 W=5 µ m, L=10 µ m • Bandgap control through etching � V DS = 1 V lateral bandgap engineering 600.0 I d (A) • Flexible and transparent material 400.0 h + e - • Excellent electrostatic control 200.0 + 0.0 -1 0 1 2 3 • Improved transport properties. V g (V) 3

New graphene devices: Frequency doublers e h Holes Electrons Output signal (2f 0 ) V p (Dirac Voltage) Input signal (f 0 ) Graphene 4 Ambipolar FET •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 tpalacios@mit.edu

Fabrication of Graphene Frequency Multipliers Final Device Optical Interference Schematic Structure Image of graphene flakes H. Wang, D. Nezich, J. Kong, and T. Palacios “Graphene Frequency Multipliers” IEEE Electron Device Letters , May 2009.. tpalacios@mit.edu

Experimental results… Graphene frequency doubler Input Output •First demonstration of frequency doubling •Excellent spectral purity � high conversion efficiency •High frequency operation 100 •Large gain possible Graphene frequency multiplier ? Diode frequency •No bandgap required multipliers Efficiency (%) 10 Graphene is the an excellent FET frequency multipliers x2 1 material for high performance x2x2 x3 x2x2x2 frequency multipliers x2x2x3 x2x2x2x2 0.1 6 100 1000 Frequency (GHz) tpalacios@mit.edu

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 : Many other new devices/applications are possible : -Analog to digital converters -Analog to digital converters -Energy harvesting devices -Energy harvesting devices -Advanced photodetectors -Advanced photodetectors -… -… H. Wang, D. Nezich, J. Kong, and T. Palacios, IEEE Electron Device Letters , May 2009. tpalacios@mit.edu

tpalacios@mit.edu

Ambipolar Frequency Multipliers Conventional FET Frequency Multipliers Output Power Spectrum I- -V Characteristics V Characteristics Circuit and Output Waveform Circuit and Output Waveform Output Power Spectrum I f Ambipolar Frequency Multipliers Output Power Spectrum I- I -V Characteristics V Characteristics Circuit and Output Waveform Circuit and Output Waveform Output Power Spectrum f tpalacios@mit.edu

Why is spectral purity so high at the output? Sub-linear I ds -V gs characteristics in fabricated GFETs 78% maximum Parabolic component of I ds -V gs much larger in fabricated GFETs Less higher order harmonics, hence higher spectrum purity 94% tpalacios@mit.edu