1. Graphene Transistors for Microwave Applications and Beyond Mahesh Soni1, Satinder Kumar Sharma1, Ajay Soni2 1School of Computing and Electrical Engineering, Indian Institute of Technology-(IIT), Mandi, H.P, , India 2 School of Basic Sciences, Indian Institute of Technology–(IIT), Mandi, H.P, , India
ABSTRACT
Gr-FET: MODELING
Graphene (Gr) based dual (top and back) gated depletion mode n-type field effect transistor (Gr-FET) exhibiting unipolar current characteristics is extensively simulated using High-k HfO2 as gate dielectric. The model describes the functionality of the transistor for electron conduction in Gr channel, taking into account the effects of longitudinal and lateral electric field for charge carrier control. Excellent transport properties and the potential to modify the carrier concentration using electrical coupling enables Gr to be used as a most promising material to meet the demands of power optimal, high performance nano electronic regime microwave devices.
A dual gate model of n-Gr-FET with Al/HfO2(~15 nm)/Gr(~5 nm)/SiO2 (~300 nm)/(highly doped) p-Si is presented.
Simulation results resembles :-
Control of charge carriers in Gr channel.
Unipolar current saturation.
Increase in Ids for higher values of Vgs.
Excellent transport properties
enabling its use in high frequency
applications.
DEVICE SCALING &
PRESENT TECHOLOGY CHALLENGES
EVOLUTION
Materials & Challenges
Silicon (Si)
Short Channel Effects (SCE).
Drain Induced Barrier Lowering (DIBL).
Increased Power consumption.
Not feasible to scale beyond 11 nm.
Nano-wires FET (NWFET)
Prone to changes in temperature.
Control over the dimension of nano-wire.
Accuracy to position it on the substrate.
Carbon Nanotube FET (CNFET)
Chirality Control (band gap related).
Orientation in specific direction.
Individual assemblies of CNT.
Figure 4. Forward bias characteristics of n-Gr-FET for Vback=40V(BLACK), 20V(RED), 5V(BLUE) at Vgs (a) 0V (b) 2V (c) 10V
CONCLUSIONS
Figure 1. Device Scaling History & Future Projection [1]
MOTIVATION
Proposed model for n-Gr-FET exhibits unipolar current characteristics. Owing to excellent transport properties and current saturating behavior enables the n-Gr-FET structure to be a potentially used for analog devices operating in microwave region.
Graphene (Gr) is possibly a potential break-though aspirant to meet the nanoelectronics scaling challenges over the CNT, NWFET and has attracted significant attention from the scientific community recently.
International Technology Roadmap for Semiconductors (ITRS) 2009 proposes Gr to be one of the most potential candidate beyond 11 nm to replace Si technology due to transport properties [2] like:-
Higher Fermi velocities ( ~108 cm/s) almost 10 times higher than Si.
High carrier mobilities (~105 cm2/V-s).
Ballistic transport of electrons and holes.
Challenges
Gr has zero band gap.
Gr devices has low Ion/Ioff ratio.
Ambipolar Characteristics.
Zero/Negative transconductance(gm).
Figure 5. Cut off frequency (fT) variation with gate length (L) for Gr-FET
POSSIBLE GRAPHENE APPLICATIONS
Figure 6. General Gr Applications [8]
Figure 7. Gr Applications for micro wave region
REFERENCES
1) G.E.Moore. Electronics, 1965, 38.
2)The International Technology Roadmap for Semiconductors Links/2009ITRS/Home2009.htm (Semiconductor Industry Association, 2009).
3) F. Schedin, A. K. Geim, S. V. Morozov, E. W. Hill, P. Blake, M. I. Katsnelson, K. S. Novoselov. Nat. Mater. 2007, 6:652.
4) F. Schwierz. Nature Nanotechnology. 2010, 5:487
5) A. K. Geim, K. S. Novoselov. Nat. Matter. 2005, 6 :183.
6)A. H. C. Neto, F. Guinea, N. M. R. Peres, K. S. Novoselov, A. K. Geim. Rev. Mod. Phys. 2009, 81 :109.
7) I.Meric, M. Y. Han, A. F. Young, B. Ozyilmaz, P. Kim, K. L. Shepard. Nat Nano. 2008, 3:654.
8) Comprehensive Report on Global Graphene Market
Figure 2. Cross-sectional view of n-type dual gated depletion mode Gr-FET
Figure 3. Ids as a function of Vds for n-type
top gated Gr-FET (as in [4])