Insights into controllable electronic properties of 2D type-II Twin-Graphene/g-C3N4 and type-I Twin-Graphene/hBN vertical heterojunctions via external electric field and strain engineering

Abstract

Twin-graphene (Twin-G), an accessible carbon allotrope composed of sp2 hybridized carbon atoms, has attracted considerable interest due to its intrinsic bandgap and tunable electronic properties. This work evaluates the near-edge electronic structures and the carrier mobility of the Twin-G/g-C3N4 and Twin-G/hBN vdW heterojunctions employing the first-principles calculations. The results demonstrate that Twin-G/g-C3N4 retains a staggered type-II alignment, which may benefit the highly-efficient photogenerated carrier separation. Whereas the Twin-G/hBN exhibits type-I alignment. An external electrical field induces a semiconductor-to-metal and indirect-to-direct gap transition in Twin-G/g-C3N4 heterostructure. The type-II-to-type-I transition in Twin-G/g-C3N4 under tensile strain can be understood from the near-gap wave functions morphology. G-C3N4 substrate has a more significant effect to enhance the carrier mobility of Twin-G. The electron mobility along the zigzag-direction in Twin-G/g-C3N4 is ∼1751 cm2V−1s−1, far surpassing that of Twin-G monolayer. These results open up promising opportunities for the development of optoelectronic devices based on the Twin-G heterostructures.