Tunable electronic properties and band alignments of MoSi$_2$N$_4$/GaN and MoSi$_2$N$_4$/ZnO van der Waals heterostructures

TL;DR

This study explores the electronic properties and tunability of MoSi₂N₄-based van der Waals heterostructures with GaN and ZnO, revealing their potential for customizable optoelectronic devices through external stimuli.

Contribution

It provides the first first-principles analysis of MoSi₂N₄ combined with GaN and ZnO, demonstrating tunable band alignments and transitions under electric fields and strain.

Findings

MoSi₂N₄/GaN is a direct band gap Type-I heterostructure.

MoSi₂N₄/ZnO is an indirect band gap Type-II heterostructure.

External electric fields and strain can induce band structure transitions.

Abstract

Van de Waals heterostructures (VDWH) is an emerging strategy to engineer the electronic properties of two-dimensional (2D) material systems. Motivated by the recent discovery of MoSi$_2$N$_4$ - a synthetic septuple-layered 2D semiconductor with exceptional mechanical and electronic properties, we investigate the synergy of \ce{MoSi2N4} with wide band gap (WBG) 2D monolayers of GaN and ZnO using first-principle calculations. We find that MoSi$_2$N$_4$/GaN is a direct band gap Type-I VDWH while MoSi$_2$N$_4$/ZnO is an indirect band gap Type-II VDWH. Intriguingly, by applying an electric field or mechanical strain along the out-of-plane direction, the band structures of MoSi$_2$N$_4$/GaN and MoSi$_2$N$_4$/ZnO can be substantially modified, exhibiting rich transitional behaviors, such as the Type-I-to-Type-II band alignment and the direct-to-indirect band gap transitions. These findings reveal the potentials of MoSi$_2$N$_4$-based WBG VDWH as a tunable hybrid materials with enormous design flexibility in ultracompact optoelectronic applications.