Computational study of bilayer armchair graphene nanoribbon tunneling field-effect transistors for digital circuit design

Abstract

This study investigates the effects of a structural defect, specifically a single vacancy (SV), on the performance of bilayer armchair graphene nanoribbon tunnel field-effect transistors (BL-AGNR TFETs). Simulations are conducted using the Non-Equilibrium Green's Function (NEGF) formalism and the tight-binding Hamiltonian, along with a self-consistent solution of the Poisson and Schrödinger equations, to evaluate key performance parameters, including subthreshold swing (SS), ON-current (I_ON), OFF-current (I_OFF), and the ON/OFF-current ratio (I_ON/I_OFF). The results indicate that single vacancies have a negligible effect on ON-current (I_ON) but cause a significant increase in OFF-current (I_OFF) and subthreshold swing (SS), leading to a degradation in the I_ON/I_OFF ratio and overall switching performance. The subthreshold swing (SS) for a defect-free transistor is 65 mV/dec; however, in the presence of a single vacancy located near the source or in the middle of the channel, the SS increases to 97 mV/dec and 75 mV/dec, respectively. This study highlights the negative impact of structural defects on TFET performance and emphasizes the importance of precise device engineering to enhance performance in the presence of defects.