Theoretical design of SnTe/GeS lateral heterostructures: A first-principles study

Abstract

Using first-principles calculations, we theoretically designed new (SnTe)m/(GeS)n LHSs with the armchair interface connected by covalent bonds. We verified (SnTe)m/(GeS)n LHSs can be synthesized experimentally due to their small heat of formation. In contrast to the indirect bandgaps of pristine SnTe and GeS monolayers, the (SnTe)2/(GeS)2 LHS is a direct gap semiconductor with type-II alignment. The (SnTe)m/(GeS)n LHSs can achieve a transition from type-II to type-I alignment and from direct to indirect bandgap by increasing component units of (SnTe)m/(GeS)n LHSs. Meanwhile, the bandgaps of (SnTe)m/(GeS)n LHSs decrease monotonously as the component units increases. The conduction band minimum (CBM) and the valence band maximum (VBM) of (SnTe)2/(GeS)2 LHS are mainly distributed on SnTe and GeS, respectively. However, the CBM and VBM of (SnTe)4/(GeS)4 and (SnTe)6/(GeS)6 LHSs are dominated by SnTe. Furthermore, we found that the bandgap of (SnTe)2/(GeS)2 LHS can be effectively tuned by applying external strain.