Tunable band alignment in boron carbon nitride and blue phosphorene van der Waals heterostructure

Abstract

The hybrid monolayer of boron nitride and graphene, namely the BCxN monolayer, has been recently revealed as a direct bandgap semiconductor with exceptional thermal, mechanical and optical properties. The integration of such monolayer with other 2D materials into a van der Waals heterostructure (VDWH), however, remains largely unexplored thus far. In this work, we investigate the electronic and structural properties of a new class of VDWH obtained via the vertical stacking of BCxN (x = 2, 6) and blue phosphorene monolayers. By using first-principle density functional theory (DFT) simulation, we show that BCxN couples to the blue phosphorene layer via weak van der Waals interactions and exhibits a type-II band alignment which is beneficial for electron-hole pair separation in photodetection and solar cell applications. Intriguingly, changing the interlayer separation induces a indirect-to-direct band gap transition which changes the band alignment types of the VDWH. The interlayer separation, which can be readily tuned via a vertical strain, thus provides a useful tuning knob for switching the heterostructures between type-I and type-II VDWHs. Our findings reveals the BCxN-based VDWH as a versatile material platform with tunable band alignments, thus opening a route towards novel VDWH-based optoelectronic devices.