Robust Type‐II Band Alignment and Stacking‐Controlling Second Harmonic Generation in GaN/ZnO vdW Heterostructure

Abstract

AbstractMost traditional 2D materials have small bandgaps, resulting in low laser damage thresholds and limiting their applications in the ultraviolet region. Recently experimentally synthesized 2D GaN and ZnO can be such candidates due to their wide bandgaps, high charge mobilities, and optical transparency. Here, the van der Waals heterostructure GaN/ZnO is predicted that can exhibit both wide bandgap and strong second harmonic generation (SHG) response by compelling simulations. The results show the heterostructure always exhibits type‐II band alignment under all probable stacking configurations. The out‐of‐plane SHG coefficients are up to 90 pm V−1 at 400 nm, comparable to those of MoS2 and MoSe2 and higher than most 3D crystals. Interestingly, the positions are enhanced with localized, symmetric, and stacking‐dependent features in the Brillouin zone. This peculiar momentum space behavior is originated from the relative strength of two distinct mechanisms contributing to the second‐order nonlinear optical (NLO) response, that is, a purely interband transition part and a mixed interband‐intraband contribution. Thus, this study proposes that GaN/ZnO heterostructure may be an efficient and high laser damage thresholds (LDTs) NLO material and an interesting platform for studying NLO optical properties.