High-Performance Carbon Nanotube Field-Effect Transistor with Tunable   Polarities
  State-of-the-art carbon nanotube field-effect transistors (CNFETs) behave as Schottky barrier (SB)-modulated transistors. It is known that vertical scaling of the gate oxide significantly improves the performance of these devices. However, decreasing the oxide thickness also results in pronounced ambipolar transistor characteristics and increased drain leakage currents. Using a novel device concept, we have fabricated high-performance, enhancement-mode CNFETs exhibiting n or p-type unipolar behavior, tunable by electrostatic and/or chemical doping, with excellent OFF-state performance and a steep subthreshold swing (S =63 mV/dec). The device design allows for aggressive oxide thickness and gate length scaling while maintaining the desired device characteristics. 
Yu-Ming Lin, Joerg Appenzeller, Joachim Knoch, and Phaedon Avouris