First-Principles Study On ZnO/BP And AlN/InSe Van Der Waals Heterostructures

The successful preparation of graphene has opened the door to exploring two-dimensional（2D）semiconductor materials.Their excellent physical properties,successful preparation in the laboratory,wide application in the fields of nanoelectronics and optoelectronics have made them the focus of material research.However,a single 2D material inevitably has some defects.The emergence of van der Waals heterostructures formed by two or more 2D materials stacked together vertically through van der Waals forces between layers makes up for the shortcomings of a single 2D material and obtains diverse excellent characteristics.Van der Waals heterostructure possesses plenty of advantages,for example,the selection of material is diverse and simple,special interface state,convenient control of the electronic structure,making it has unlimited potential in the application of novel nanoelectronics and optoelectronic devices in the future.In this paper,we focus on twoⅢ-Ⅴ 2D semiconductor material BP and AlN,and design two novel van der Waals heterostructures in Materials Studio.There are ZnO/BP and AlN/InSe heterostructures.First-principles calculations are utilized to explore the geometric structure and optoelectronic properties of the two heterostructures.We have obtained some valuable research results.2D semiconductor material zinc oxide（ZnO）single layer was vertically stacked on boron phosphide（BP）to form the ZnO/BP van der Waals heterostructure.The geometric structure,electronic and optical properties of the two single layers and the heterostructure were studied.Results show that the 2D semiconductor ZnO and BP form a stable heterostructure with a negative binding energy of-20.15 me V（?）^-2.ZnO/BP displays an indirect characteristic with0.40 e V.The valence band and conduction band are provided by ZnO monolayer and BP monolayer,respectively,showing a typical type-Ⅱ band arrangement.Thereupon,photo-generated electrons and holes are effectively separated.In addition,compared with the two monolayers,the effective masses of electrons and holes in the ZnO/BP heterostructure are reduced,the carrier mobility is correspondingly improved.The optical absorption spectrum shows that the construction of ZnO/BP heterostructure is valuable for increasing the light absorption range and the absorption coefficient of ZnO in the visible light region.The band gap approximately linear changes at the effect of external perpendicular electric field.When the reverse electric field strength increases to 0.4 V（?）^-1,the ZnO/BP heterostructure realizes the transition from indirect to direct.And with increasing electric field intensity,the heterostructure undergos a semiconductor-metal transition.In addition,the heterostructure exhibits mechanical stability under 2%compression and tensile strain due to the absence of imaginary frequency in the phonon spectrum and retains the type-Ⅱ band arrangement.Aforementioned results indicate that the ZnO/BP heterostructure provides considerable value for the application of novel multifunctional devices in the future.The structural stability,energy band characteristics,carrier mobility,optical absorptionspectrum and the regulation effect of external electric field of AlN/InSe van der Waals heterostructure are calculated and analyzed.Results show that the AlN/InSe heterostructure exhibits dynamic stability,an indirect band gap of 0.78 e V,and staggered type-Ⅱ band alignment characteristic.This feature promotes the separation of photo-generated electron-hole pairs.At the same time,the AlN/InSe heterostructure exhibits excellent carrier mobility(10³cm²V^-1s^-1).In addition,compared with AlN single layer,the formation of the AlN/InSe system broadens the light absorption range,and the absorption coefficient magnitude can reach up to 10⁵cm^-1.When electric fields in different directions are applied,the band gap of the AlN/InSe heterostructure changes differently,and under a specific electric field,the heterostructure undergoes a change from semiconductor to metal.More fascinatingly,the total of transferring electrons is constantly increasing under a more powerful electric field,whatever the electric field direction is.Results show that AlN/InSe heterostructure can provide guidance for the manufacture of photodetectors and photovoltaic devices.