High Performance N-Type Carbon Nanotube Field Effect Transistors with   Chemically Doped Contacts
  Short channel (~80 nm) n-type single-walled carbon nanotube (SWNT) field-effect transistors (FETs) with potassium (K) doped source and drain regions and high-k gate dielectrics (ALD HfO2) are obtained. For nanotubes with diameter ~ 1.6 nm and bandgap ~ 0.55 eV, we obtain n-MOSFET-like devices exhibiting high on-currents due to chemically suppressed Schottky barriers at the contacts, subthreshold swing of 70mV/decade, negligible ambipolar conduction and high on/off ratios up to 10^6 at a bias voltage of 0.5V. The results compare favorably with the state-of-the-art silicon n-MOSFETs and demonstrate the potential of SWNTs for future complementary electronics. The effects of doping level on the electrical characteristics of the nanotube devices are discussed. 
Ali Javey, Ryan Tu, Damon Farmer, Jing Guo, Roy Gordon, and Hongjie   Dai