Anisotropic Interlayer Exciton in GeSe/SnS van der Waals Heterostructure

The observation of interlayer excitons (ILE), where the electron and hole are confined in different layers, in van der Waals (vdW) type II heterostructures has ignited a new interest in investigating the optical properties of these 2D semiconducting materials. Herein, using GW and Bethe−Salpeter equation simulations, we demonstrate the generation of linearly polarized, anisotropic intra- and interlayer excitonic bound states in the transition metal monochalcogenide (TMC) GeSe/SnS vdW heterostructure. The puckered structure of TMC results in the directional anisotropy in the band structure and in the excitonic bound state. Upon the application of compressive/tensile biaxial strain, a dramatic variation in excitonic energies, the indirect-to-direct semiconductor transition, and the red/blue shift of the optical absorption spectrum are observed. The variations in excitonic energies and optical band gap have been attributed to the change in effective dielectric constant and band dispersion upon the application of biaxial strain. The generation and control over the interlayer excitonic energies will find applications in optoelectronics and optical quantum computers and as a gain medium in lasers.