Bilayer graphene vertical tunneling field effect transistor

Abstract

Electronic devices have been explored in the past based on resonant single-electron CB (conduction band) to CB tunneling between parallel quasi-two dimensional (2D) quantum wells within III-V heterostructures and their accompanying negative differential resistance (NDR) [1]. Such devices are attractive for high speed electronics, and digital logic circuits also have been demonstrated using a combination of conventional and such NDR FETs [2]. For two graphene layers separated by a tunnel barrier, we recently proposed the ultra-low-voltage Bilayer pseudoSpin FET (BiSFET) which would employ enhanced nonresonant VB (valence band) to CB tunneling, with a nevertheless very sharp NDR characteristic based on a predicted room-temperature many-body superfluid state [3]. However, NDR due to resonant single-particle CB-to-CB or VB-to-VB tunneling may also be achievable in such a structure. Furthermore, the atomically near-perfect 2D nature of the component graphene layers and the conduction/valence band symmetry may offer advantages over III-Vs. Here, we model the I-V characteristics due to single-particle tunneling in such a structure, Fig. 1, using a perturbative tunneling Hamiltonian approach [4,5], and deviations from this simple theory using atomistic tight-binding nonequilibrium Green's function (NEGF) simulation.