First-principles Studies Of Fe,Co Doped GaAs?110? And Perovskite CH₃NH₃Pb(I_1-xBr_x)₃

Magnetic atoms such as Mn,Fe and Co,dopants in the semiconductors are the socalled dilute magnetic semiconductors?DMS?and the atoms is called the magnetic impurities.The nature of the semiconductors would be changed by these magnetic atoms,and will show magnetic characteristics.As an important semiconductor material,GaAs has a mount of excellent properties,such as direct band gap,high carrier mobility.Moreover,high frequency,and temperature,good low-temperature performance and strong resistance to radiation are also shown in its semiconductor devices.Recent years,methylammonium lead halide perovskite CH3NH3PbX3(?X = halogen?and its mixed-halide crystals have attracted wide interests in the world due to their applications in optoelectronic devices and play an important role in solar cells.Especially,the power conversion efficiencies?PCEs?of solar cells have increased every year.From the theoretical view,studies on the micro-geometric,electronic structures and the other properties of these materials are meaningful in experiments.In this paper,using the first-principles method,we calculate the electronic structure and properties of single Fe and Co doped in GaAs?110?surface.We also calculate the electronic structure and optical properties of mixed orthorhombic perovskites CH₃NH₃Pb(I_1-xBr_x)₃.The main research contents are as follows:1.Using the first-principles method,we calculate the electronic structure and properties of single Fe dopant in GaAs?110?surface,such as the LDOS,PDOS,bond length and angle.We find that the calculation results are agree with the STS and STM in experiments and make a further discussion of the micro nature in theory.2.Using the first-principles method,we calculate the electronic structure and properties of single Co dopant in GaAs?110?surface,such as the LDOS,PDOS and charge density image,and can explain the experimental phenomena well in theory.3.Using the first-principles method,based on SR-DFT and SOC-DFT,we calculate the electronic structure and optical properties of different concentrations of Br dopant in CH₃NH₃Pb(I_1-xBr_x)₃?x=0;0.25;0.5;1?.Our results show that the concentrations of Br have significant effects on the geometry,electronic structures,and optical properties of CH₃NH₃Pb(I_1-xBr_x)₃.