Effect of strain on the performance of MOSFET-like and p–i–n carbon nanotube FETs

The effects of both uniaxial and torsional strain are investigated on the performance of carbon nanotube field effect transistors (CNTFETs) in which the carbon nanotube (CNT) is doped near the source and the drain contacts. The Non-Equilibrium Green’s Function formalism (NEGF) is used to derive the transport equations in the mode space basis. In order to calculate the electrostatic potential within the proposed structures the Poisson equation is solved by means of the non-linear finite difference method. Final results are obtained by the self consistent solution of the Poisson and the NEGF equations. The strain affects the bonding length between carbon atoms which leads to the change of the tight-binding Hamiltonian and the corresponding bandgap. Since the bandgap variation of a semiconductoring (n, m) CNT with respect to the applied strain is strongly dependent upon its n–m mod 3 value, we have considered both a (13, 0) and a (14, 0) CNT in our calculations. The bandgap variation due to the external strain leads to a significant change of electronic properties which can be used to achieve the desired device characteristics at a particular bias range.