Tunable electronic and optical properties of two-dimensional ZnSe/AlAs van der Waals heterostructure

Heterostructure formed by combining a single material has outstanding electronic and optical properties, and therefore it has received great attention. In this work, we constructed a ZnSe/AlAs heterostructure. Moreover, based on first-principles calculations of density functional theory (DFT), its stacking orders, electronics, optical properties and the effects of Ge doping on the heterostructure were studied. The results show that the ABI (the Zn atoms of the ZnSe layer are above the As atoms of the AlAs layer) stacking with an interlayer spacing of 2.75 Å is thermodynamically stable. Additionally, it has a direct bandgap of 0.986 eV which is less than the bandgap of the ZnSe and AlAs monolayers. By changing the interlayer distance, the external electric field and the plane strain, the bandgap of the ZnSe/AlAs heterostructure exhibits tunability and is accompanied by a semiconductor–metal transition. Importantly, compared with the single layer, the light absorption capacity of the ZnSe/AlAs heterostructure is significantly enhanced, especially in the ultraviolet region. The addition of Ge will shrinks the bandgap of the ZnSe/AlAs heterostructure and caused a direct–indirect transition. The light absorption peak of the heterostructure was slightly red-shifted, which was helpful to improve its absorption in the visible light region. The above results indicate that the ZnSe/AlAs heterostructure is expected to be a good candidate for optoelectronic devices and nanoelectronics.