First-principles Study Of Two-dimensional PbSe And AsP Semiconductors

PbSe is a narrow band gap semiconductor with high carrier mobility.It has broad basic research and application prospects in solar cell materials,photosensitive sensor materials.In terms of experiments and theoretical calculations,the research on two-dimensional PbSe is still missing.Thus,performing insights on this kind of novel 2D material is crucial.Two-dimensional As P,as a member of the V-V family of binary compounds,has also quickly entered the field of vision of researchers.It has a direct band gap of 1.54 e V and an ultra-high carrier mobility.It is a substitute for solar cell materials.In this paper,based on a first-principles calculation method of density functional theory.First,we explored the band structure and stability of monolayer PbSe.The hybrid functional(HSE06)calculation shows that monolayer PbSe possess direct band gap of 1.85 e V,and the band gap of PBE calculation is 1.27 e V.The result of phonon dispersion spectrum show the dynamic stability of monolayer PbSe.Then,we investigated the strain effect of monolayer PbSe.Monolayer PbSe exhibits isotropic optical and electrical properties along x and y directions.By comparing the calculated results of PBE and hybrid functional(HSE06),it is found that the two methods give the same result of the influence of strain on band gap.Our results show that the direct energy gap of PbSe monolayer can be tuned by strain.The PBE calculations show that a semiconductor-metal transition is observed in the monolayer PbSe at a compression strain of-11%in the x direction.Besides,monolayer PbSe exhibit a broad optical absorption spectrum from the ultraviolet region to the infrared region.We find that the optical absorption coefficient of monolayer PbSe in the UV light is improved significantly under biaxial compression strain,the optical absorption coefficient can reach the order of 10⁶ cm^-1 when biaxial compression strain is-6%.We also find that the work function of monolayer PbSe is very sensitive to biaxial strain,it can be modulated from 3.60 e V to 5.31 e V within the strain range.Monolayer PbSe presented small electron and hole effective mass,the effective mass of electrons and holes can effectively decreased by biaxial compressive strain,which means that strain is an effective means to control carrier mobility.These results imply that monolayer PbSe has potential applications in nanoelectromechanical systems and optoelectronic devices.The moderate direct band gap of black As P monolayer is quite advantageous in optical applications.In this paper,the electronic properties of black As P monolayer was investigated by applying external strain.We found that black As P monolayer exhibits strong anisotropy and zigzag direction prefer to resist elastic deformation than armchair direction.It is found that both compressive and tensile strain induced the transition of band gap from direct-indirect-direct when strain is applied in zigzag direction,while a-3%strain in armchair direction induces the transition of band gap from direct to indirect,the transition of band gap from direct to indirect occurred at-3%and 3%for biaxial strain.The effective mass of electron and hole in armchair direction is an order of magnitude smaller than zigzag direction,suggests the electron and hole is inclined to transport in armchair direction.Besides,the effective mass of black As P monolayer can be tuned dramatically by strain.Therefore,we can take this approach to achieve the goal of modify carrier mobility.