Tunable electronic properties and band alignments of MoSi₂N₄/GaN and MoSi₂N₄/ZnO van der Waals heterostructures

Van de Waals heterostructure (VDWH) is an emerging strategy to engineer the electronic properties of two-dimensional (2D) material systems. Motivated by the recent discovery of MoSi₂N₄-a synthetic septuple-layered 2D semiconductor with exceptional mechanical and electronic properties, we investigate the synergy of MoSi₂N₄ with wide-bandgap (WBG) 2D monolayers of GaN and ZnO using first-principle calculations. We find that MoSi₂N₄/GaN is a direct bandgap type-I VDWH, while MoSi₂N₄/ZnO is an indirect bandgap type-II VDWH. Intriguingly, by applying an electric field or mechanical strain along the out-of-plane direction, the band structures of MoSi₂N₄/GaN and MoSi₂N₄/ZnO can be substantially modified, exhibiting rich transitional behaviors, such as the type-I-to-type-II band alignment and the direct-to-indirect bandgap transitions. These findings reveal the potentials of MoSi₂N₄-based WBG VDWH as a tunable hybrid materials with enormous design flexibility in ultracompact optoelectronic applications.