Optoelectronic Properties and Excitons in Hybridized Boron Nitride and Graphene Hexagonal Monolayers

TL;DR

This study uses advanced computational methods to analyze the electronic and optical properties of hybridized boron nitride and graphene monolayers, revealing how their band structure and excitons depend on domain size and composition.

Contribution

It provides a detailed theoretical explanation of the optoelectronic behavior of CBN monolayers, challenging previous assumptions about their composition-dependent properties.

Findings

Distinct exciton states localized within C domains.

Optical absorption peaks vary with composition.

Band gap and absorption are not simply composition-dependent.

Abstract

We explain the nature of the electronic band gap and optical absorption spectrum of Carbon - Boron Nitride (CBN) hybridized monolayers using density functional theory (DFT), GW and Bethe-Salpeter equation calculations. The CBN optoelectronic properties result from the overall monolayer bandstructure, whose quasiparticle states are controlled by the C domain size and lie at separate energy for C and BN without significant mixing at the band edge, as confirmed by the presence of strongly bound bright exciton states localized within the C domains. The resulting absorption spectra show two marked peaks whose energy and relative intensity vary with composition in agreement with the experiment, with large compensating quasiparticle and excitonic corrections compared to DFT calculations. The band gap and the optical absorption are not regulated by the monolayer composition as customary for bulk semiconductor alloys and cannot be understood as a superposition of the properties of bulk-like C and BN domains as recent experiments suggested.