Theoretical Study On The Optoelectric Transport Properties Of Several Two-dimensional Wide Bandgap Semiconductors And Black Phosphorus

Two dimensional semiconductors have attracted extensive research interest in photodetection because of their extraordinary performances including ultrafast response,high responsivity and low dark current.But they are usually difficult to have many excellent photoelectric properties at the same time.In this paper,The electronic and optical properties and photogalvanic effects(PGEs)of Black phosphorus and sixteen Two-dimensional wide bandgap(2D-WBG)semiconductors and their heterojunctions are studied by using Non-equilibrium Green' Function(NEGF)method combined with first-principles calculation.At the same time,a variety of outstanding photodetection performances are obtained.The specific research contents are as follow:Firstly,the electronic and optical properties of 16 kinds of 2D-WBG materials and their heterojunctions are systematically studied by using the first principles methods.The HSE06 band gaps of these 2D-WBG semiconductors range from 3.0 to 7.41 e V,and the first optical absorption peaks are located at 4 e V to 8 e V,which is suitable for a variety of application fields in Ultraviolet(UV)photodetection.Besides,we designed the 2D Mg Br2/Cd Cl2 van der Waals heterostructure(vd Wh),which has the type-II energy band alignment with a direct bandgap of 4.38 e V.We further studied the PGEs in the Ultraviolet photodetectors(UV-PDs)composed of monolayer Zr NY(Y =Cl and Br)and in the Mg Br2/Cd Cl2 vd Wh using quantum transport methods.Robust PGEs canbe induced in the photodetectors based on this vd Wh and also on monolayer Zr NY(Y=Cl and Br)due to the C3 v symmetry under the illumination of polarized light,which then leads to a persistent photocurrent without Built-in electric field or the need to apply an external bias voltage.The photocurrent has either a sine or cosine dependence on the polarization.Moreover,a high polarization sensitivity was achieved with a remarkable extinction ratio of up to 280.In comparison,the proposed Mg Br2/ Cd Cl2 vd Wh UV-PD is superior to all these reported UV-PDs in polarization detection.We also studied the behavior of spin-polarized photocurrent in a nickel–phosphorene–nickel(Ni–Ph–Ni)photodetector by using quantum transport calculations.PGEs can be generated in the photodetector under illumination with linearly or elliptically polarized light,which makes the photodetector self-powered.A remarkably large magnetoresistance ratio(MR)of up to 360% and fully spin-polarized photocurrent can be obtained by modulating the light polarization and photon energy,which indicates outstanding spin-valve and spin-filtering effects.The results of this paper can offer theoretical reference for the design of photodetectors based on Zr NY and the Mg Br2/Cd Cl2 vd Wh with self-powered,visible-blind and polarization sensitive UV-PDs,and also provide a theoretical reference for the design of excellent self-powered spin electronic devices based on black phosphorus.