The major limitation of tunneling carbon nanotube field-effect transistors (T-CNTFET) is the ambipolar behavior. In this paper, we show that this problem could be solved by using a partially-gated channel, or Gaussian doping method. The effect of using the two mentioned methods on the electrical characteristics of T-CNTFET has been examined. The non-equilibrium Green's functions (NEGF) in conjunction with Poisson's equation are solved self-consistently. The cutoff frequency (f T ) and power-delay product (PDP) as well as the intrinsic delay (τ) have been considered as key parameters for frequency performance and speed characteristics. The simulation results show an improvement in the OFF-state current and the high-frequency performance as well as a suppression of the ambipolar conduction. These advantages of the proposed techniques make T-CNTFET suitable for low-power and high-speed applications.

The Tunneling Carbon Nanotube FET (T-CNTFET) is one of the most promising alternatives to the conventional MOSFET. However, T-CNTFET suffers mainly from low ON-current. In this paper, we propose a modified hetero-dielectric T-CNTFET in which a dielectric pocket is inserted near the source-channel interface. The impact of the length of the dielectric pocket and its shift from source/channel barrier on DC and high-frequency performance is investigated. The performance parameters are studied by examining ON-current (I ON) and cutoff frequency (f T ) as measures for the DC and high frequency behavior, respectively. It is demonstrated that the condition of an optimum design for the pocket position concerning I ON is different from that regarding f T and a compromise should be met in order to obtain the best performance. Based on our developed 2D quantum simulations, it is shown that a high-k pocket having a length of 12.5% of the channel length may result in an increase of 65% in I ON with no deterioration in f T . Moreover, a little shift of 20% of the pocket length towards the source region doesn’t degrade I ON and enhances f T .