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D.L. Pulfrey

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

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D.L. Pulfrey

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

  2. Carbon Nanotubes • Hybridized carbon atom  graphene monolayer  carbon nanotube 1s orbital, 2e- sp2 hybridized orbital, 3e-(-bonds) 2p orbital, 1e-(-bonds) • 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 Single-tube drawbacks: Imax~ A Zout ~ k 80nm C-CNFET A. Javey et al., Nano Lett., 5, 345, 2005

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

  6. Experimental results for fT "Ultimate"

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

  8. Ballistic transport

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

  14. FET QG+qg _ + + + + _ + _ QD+qd QS+qs qe + _ + + _ + qe QB+qb QC+qc Image charges in transistors BJT _ + _ + _ + QB QC FET: qg |qe| BJT: qb < |qe|

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

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

  17. CN oxide Gate Si MOSFET and CNFET: comparison S. Lee et al., IEDM, 241, 2005

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

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