Study On Electronic Structure And Optical Properties Of Fe-Doped GaN

In this paper,the first-principles method was used to study the electronic structure and optical properties of iron-doped GaN materials.The photo-electric properties of intrinsic GaN materials and 6.25%of Fe-doped GaN systems were calculated by using a density functional theory system.The effect of doping on the photoelectric properties of the system is theoretically discussed.The calculated forbidden band width of intrinsic GaN is 3.41 eV,and the heavily doped system of Fe is obviously narrowed to 3.06 eV,but it remains to be a direct bandgap semiconductor.The incorporation of Fe leads to different levels of spin polarization in the GaN material.The source of this spin polarization is the Fe 3d state.The static dielectric constants of intrinsic GaN materials and Fe-doped GaN systems are 3.13,4.41,and the static refractive indexes are 1.77,2.10,the maximum energy loss is 16.22eV,22.43eV respectively.The calculation results provide strong theoretical basis and experimental support for further research on Fe-doped GaN high voltage photoconductive switch materials and devices.This paper also calculated the electronic structure and optical properties of intrinsic GaN and Fe-doped GaN systems containing N-vacancy and Ga-vacancy systems,respectively.The calculation results show that the N-vacancy is a kind of donor defect,but its introduction causes the position of the bottom of the material conduction band to deviate from the center point of the Brillouin region,that is to say,the material changes from the direct bandgap semiconductor to the indirect bandgap semiconductor.And the introduction of N vacancies raises the Fermi energy level of the material,and in Chapter 3 it has been calculated that the incorporation of Fe will increase the Fermi energy level of the material.Its Fermi level should be higher after co-doped following the normal reasoning,but our simulation results are not.This result indicates that the co-doping of N vacancies with Fe leads to a new combination of materials,Fe-VN conjugates.The introduction of Ga vacancies as acceptor defects does not change the position of the conduction band and the valence band,but introducing other impurity levels in the material will cause the material to spin polarization near the forbidden band.The addition of vacancies to the intrinsic material causes large changes in the optical properties of the low-energy region.The results of calculation demonstrate that the further introduction of Fe will suppress this phenomenon,which means that the introduction of Fe will increase the insulation of the material and thus achieves Semi-insulated..Finally,the electronic structure and optical properties of Mg-doped GaN system and Mg-Fe co-doped system were also studied.The optical properties are similar to those of the calculations in Chapter 4.A single Mg-doped material will cause the material's optical properties to change significantly in the low energy region,but the introduction of Fe will inhibit this phenomenon,further verifying that the introduction of Fe will make the insulation of the material is enhanced to achieve semi-insulation of the material.