1. D.L. Pulfrey Department of Electrical and Computer Engineering University of British Columbia Vancouver, B.C. V6T1Z4, Canada pulfrey@ece.ubc.ca Carbon Nanotube Field-Effect Transistors: Carbon Nanotube Field-Effect Transistors: Critique of High-Frequency Performance High-Frequency Performance L.C. Castro D.L. John Li Chen http://nano.ece.ubc.ca

2. sp 2 hybridized orbital, 3e - (  -bonds) 2p orbital, 1e - (  -bonds) 1s orbital, 2e - Hybridized carbon atom  graphene monolayer  carbon nanotube Carbon Nanotubes High mobility – quasi-1D, low m*, no surface states Small SCE - coaxial geometry L.C. Castro

3. Employment of metallic CNTs T. Iwai et al., (Fujitsu), 257, IEDM, 2005

4. Fabricated Carbon Nanotube FETs 300 nm SB-CNFET A. Le Louarn et al., APL, 90, 233108, 2007 80nm C-CNFET 80nm C-CNFET A. Javey et al., Nano Lett., 5, 345, 2005 Single-tube drawbacks: I max ~  A Z out ~ k 

5. High-frequency Carbon Nanotube FET A. Le Louarn et al., APL, 233108, 2007

6. Experimental results for f T "Ultimate"

7. Carbon nanotube FETs: model structures C-CNFET D.L. Pulfrey et al., IEEE TNT, 2007 SB-CNFET SB-CNFET K. Alam et al., APL, 87, 073104, 2005

8. Ballistic transport

9. v sig and  SD

10. SB-CNFET: summary of predictions "Ultimate"

11. C-CNFET: summary of predictions (July 2007)

12. C-CNFET: summary of predictions (latest)

13. D.L. John et al., WOCSDICE, 2007 Energy where most ∂Q occurs D.L. Pulfrey et al., IEEE TNT, 2007 Regional delay times 7.6 THz

14. Image charges in transistors QBQB QCQC BJT: q b < |q e | BJT FET: q g  |q e | + _ + + _ Q B +q b Q C +q c qeqe + + + + _ _ _ qeqe Q S +q s Q D +q d Q G +q g FET + ++++ _ _ _

15. Q(E,z) in CNFETs -5.5eV SB-CNFET C-CNFET Insignificant resonance in channel

16. Comparison of v band : Si NW, Si planar and CNT Si NW and planar Si J.Wang et al., APL, 86, 093113, 2005 (11,0) CNT Tight-binding v b,max (CNT) higher by factor of ~ 5

17. FETStatus W (um) Lg (nm) Tox (nm) gm (mS) Cgg (aF) Ft (THz) Si MOSExptl. (IBM)80271.05108520.33 C-CN coaxTheor. (UBC)8072448371.93 Si MOSFET and CNFET: comparison S. Lee et al., IEDM, 241, 2005 CN oxideGate

18. Conclusions Multi-channel CNFETs needed for high current and for impedance matching. HF performance appears to be ultimately limited by v b,max. CNs have a v b,max advantage over Si of ~ 5 times. This could lead to a g m advantage (in C-CNFETs). Translating this advantage into superior f T and f max will necessitate keeping C GG low, which may be a technological issue. Seek applications not suited to Si.