Excitonic effects on the optical response of monolayer and bilayer graphene-like silicon carbide

Abstract

The graphene-like silicon carbide (SiC) has attracted much attention recently owing to its potential application in optoelectric devices. In this work, we have theoretically investigated the excitonic effects on the dielectric constants [ε(ω)] of monolayer (ML-) and bilayer (BL-) SiC using the first principle calculations with solving the Bethe-Salpeter equation. The Tran-Blaha modified Becke-Johnson exchange potential combined with the Perdew and Wang correlation potential is used to overcome the underestimate of bandgap. Within the independent particle approximation, BL-SiC not only has the same intralayer π→π∗ transition in the transverse ε(ω) as ML-SiC but also has an interlayer π→π∗ transition in the longitudinal ε(ω). The excitonic effects dramatically change the absorption spectra of two polarization directions (transverse and longitudinal). For the transverse ε(ω), BL-SiC has a similar excitonic absorption profile to ML-SiC but shows a blue-shift relative to ML-SiC and an apparent decrease in the binding energy of bright exciton. For the longitudinal ε(ω), ML-SiC has a bright exciton with a large binding energy of 1.87eV related to the σ→π∗ transition band, and BL-SiC has a bright exciton with a small binding energy of 0.41eV related to the interlayer π→π∗ transition.