Electric Field Tunable Band Gap in Bi-Axially Strained Graphene/Hexagonal Boron Nitride Super-Lattice

Abstract

In this work, we have reported the tunable band gap of single-layer graphene (SLG) on hexagonal boron nitride (h-BN) monolayer arranged in B3 super-lattice form, as a function of an external electric field perpendicular to the super-lattice plane and an applied external bidirectional stress from the first principle Density Functional theory (DFT). Graphene with its intrinsic high electron mobility poses itself very promising for electronic device application, but absence of band gap and substrate induced mobility degradation limits its application in logic transistor. To reduce the effect of substrate related performance degradation graphene placed on h-BN has been reported in literature. Three super-lattice structures of this bilayer system have been proposed in literature where B3 is reported to have the greatest intrinsic band gap opening among the three but this is not sufficient for logic transistor. To tailor the band gap perpendicular electric field and biaxial stress was applied in this work. It was observed that band gap increases (65.45 meV – 84.5 meV) from compressive to tensile biaxial strain (-5% to +5%) when no electric field was applied. With the application of 5×109 V/m external electric field a band gap of 144.5 meV was found which is promising for logic FET. However, tensile stress and external electric field causes degradation in Fermi velocity and produces higher electron effective mass. Figure 1