Based on density functional theory, the electronic structure, electron-localization characteristics, and dielectric response of pristine and Fe-doped GaN are comparatively investigated. The projected density of states (PDOS) shows that the states near the valence-band maximum of pristine GaN are dominated by N-2p states. After Fe doping, pronounced Fe-3d localized states appear near the Fermi level, accompanied by a reconstruction of the neighboring N-p states, indicating coupling between the Fe-3d and N-2p orbitals. The electron localization function (ELF) further reveals that substitutional Fe breaks the original symmetry of the local electron distribution and redistributes electron localization in the Fe–N neighborhood. The calculated dielectric functions show that the low-energy-limit real parts remain of a similar magnitude before and after doping, whereas Fe incorporation markedly modifies the peak shapes, intensities, and spectral-weight distribution of both the real and imaginary parts in the low- and intermediate-energy regions. These results indicate that Fe-3d-related localized electronic states play an important role in regulating the microscopic bonding environment and dielectric response of GaN. The calculated results provide a strong theoretical basis and experimental support for further studies of Fe-doped GaN materials and devices for high-voltage photoconductive switches.

GaN; Fe doping; first-principles calculations