Energy band gap tuning in Te-doped WS₂/WSe₂ heterostructures

Understanding the possibility of band-gap engineering in multilayers composed of two-dimensional materials is extremely important for modeling and creation of novel electronic and photonic devices. Stacking of WS₂ and WSe₂ monolayers looks particularly attractive for applications due to direct gap of resulting heterostructure, especially taking into account the indirect-gap nature of their bulk-state counterparts. We performed a theoretical investigation of chalcogen atoms replacement in WS₂/WSe₂ heterostructure by isovalent Te atoms in order to reveal its effects on the band gap, electronic structure and density of states . The doped heterostructures were found to preserve semiconductor properties, whereas the gap changed its nature from direct to indirect in dependence on the position and the distance between substituting Te atoms. Te atoms in the S atom positions led preferably to an indirect gap and increased its value as compared to the pristine material; upon substitution of Se atoms, the direct gap of the heterostructure is preserved but with a small reduction, whereas the substitution of both S and Se atoms changed the gap in a different way depending on Te position. This information makes possible the creation of multilayered structures with tunable gap important for a novel generation of electronic and photonic devices.