Improving the Current Ratio and Ambipolar Behavior of Junctionless CNTFETs Using Graded Metal Gate Work Function: A Quantum Simulation

In this paper, a new improvement technique based on an upward gate work function is computationally suggested to boost the current ratio of junctionless carbon nanotube field-effect transistors. The simulation method is based on the non-equilibrium Green's function formalism. It has been found that the dilation in the band-to-band tunneling (BTBT) window near the source induced by the electrostatic effects of the upward gate work function, is efficient in mitigating the BTBT mechanism as well as its associated detrimental effects. As result, improvements in terms of switching characteristics have been reached, where lower leakage current, reduced ambipolar behavior, and improved current ratio are recorded. The obtained results indicate that the upward gate work-function technique is an intriguing improvement method that can be applied to boost the performance of other nano-FETs suffering from the BTBT such as the graphene nanoribbon field-effect transistors.