First-principles Study On Electronic Properties Of The BlueP/C₂n And Sb/InSe Van Der Waals Heterojunctions

In recent years,a multitude of two-dimensional（2D）semiconductor materials have been attracting widespread interest attributed to their outstanding physical properties and fascinating applications,which becomes a hotspot in the semiconductor field.However,an individual 2D material system cannot sufficient to meet the demand for actual applications.The van der Waals（vd W）heterojunction is a structure formed by stacking two or more 2D materials vertically through the van der Waals force.Due to the low-dimensional structure,special interface morphology and easy adjustment of electronic properties,a vd W heterojunction can provide an ideal material platform for obtaining novel nanoelectronic devices and optoelectronic devices with excellent photoelectric properties.In our paper,the structures and related properties of the Blue phosphorus/C₂N vd W heterojunction and Antimonene/InSe vd W heterojunction are explored by using first principle method based on density functional theory（DFT）.The interfacial interaction and electronic properties of the Blue phosphorus/C₂N（Blue P/C₂N）heterojunction are investigated via DFT calculations.The results show that 2D Blue P and 2D C₂N can form a stable heterojunction through vd W interaction.This heterojunction has a natural type-II band alignment with a direct band gap value of 1.514 e V,which gives the enormous potential for solar cell applications.When the heterojunction is under solar illumination,the photogenerated electron-hole pairs can separate out on the disparate monolayers effectively.It induces the formation of spatially indirect excitons.Simutaneously,the charge density difference and work function calculations can prove the formation of the interfacial built-in electric field,which facilitates the directional separation of photogenerated carriers.Furthermore,it is found that the band gap of this heterojunction exhibits approximate linear variation with respect to the perpendicular external electric field,even leading to an intriguing semiconductor-metal transition at a strong electric field.Very interestingly,band alignment change from type-II to type-I occurs at an applied external electric field of-0.2 V?^-1.This characteristic provides an attractive possibility to obtain novel multifunctional devices.2D semiconductor materials Antimonene（Sb）and InSe are used to construct the Sb/InSe vd W heterojunction and an external electric field is applied along Z direction to tune the electrical properties.It is demonstrated that the heterojunction is a direct band gap semiconductor with the gap value of 0.650 e V.And,a type-II staggered-gap band alignment is achieved from the Sb/InSe interface with which Sb layer dominated the lowest energy holes as well as the lowest energy electrons are separated in InSe layer,facilitating the spatial effective separation of photogenerated electron-hole pairs.Additionally,an indirect-direct band gap transition can be triggered via varying the interlayer distance.Compared with the monolayer Sb and monolayer InSe,the carrier mobility of the heterojunction can be significant improved.More fascinatingly,the characteristic of type-II band alignment is robust,while the band gap values are tunable with respect to a moderate external electric field,even leading to an intriguing semiconductor-metal transition at a strong electric field.Moreover,the number of transferring charges increases with the enhanced strength of the applied external electric fields.These results are expected to provide meaningful guidelines for the design of novel nanoelectronic and optoelectronic devices based on Sb/InSe vd W heterojunction.