The impact of acoustic and optical phonon scattering on the performance of CNT-FETs is investigated using a full-quantum transport model within the NEGF formalism. Different gate lengths, dielectric materials and chiralities are considered. It is shown that the use of a high-κ dielectric lowers the off-current dominated by phonon-assisted band-to-band tunneling. The device scalability is demonstrated: with the oxide thickness fixed to 1.5 nm, good performance is obtained with 15 nm and 10 nm gate lengths with SiO2 and HfO2 gate dielectrics, respectively. The role of phonon scattering in CNT-FETs of different chiralities is investigated for the HfO2 devices. A similar analysis has also been carried out for source/drain underlap geometries. The results confirm that the calculation of the off-currents and delay times is strongly influenced by phonon scattering.
Bibliographical noteFunding Information:
The work has been partially supported by EU IST Network SINANO (Contract No. 506844) and PULLNANO project (FP6 IST-026828-IP).
- Band-to-band tunneling
- Carbon nanotube
- Non-equilibrium Green's function formalism
- Phonon scattering
- Quantum transport