Role of Native Defects in Fe-Doped β-Ga₂O₃

Area of Science:

• Materials Science
• Solid State Physics
• Computational Materials Science

Background:

• Iron (Fe) impurities are known to compensate for n-type conductivity in Gallium Oxide (Ga2O3).
• Key scientific questions remain regarding Fe site occupation and its complexes with native defects in Fe-doped β-Ga2O3.

Purpose of the Study:

• To resolve the controversy over the preferential site occupation of Fe dopants in β-Ga2O3.
• To investigate the formation energies, transition levels, and optical properties of Fe-related defect complexes.
• To provide guidance for synthesizing and designing properties of Fe-doped β-Ga2O3 materials.

Main Methods:

• First-principle density functional theory (DFT) calculations using the generalized gradient approximation (GGA).
• Analysis of formation energies, phonon dispersion relationships, and strain-dependent stability.
• Investigation of defect formation energies, charge transitional levels, and optical properties of defect complexes.

Main Results:

• Fe dopants are energetically favored at the octahedrally coordinated Ga site in β-Ga2O3.
• The calculated Fe3+/Fe2+ transition level is 0.52 eV below the conduction band minimum.
• Under oxygen-rich conditions, Fe-doped Ga2O3 favors the formation of VGa and Oi defects, leading to energetically favorable FeGaGai and FeGaOi complexes.
• FeGaGai and FeGaVGa complexes enhance optical absorption in the visible-infrared region.

Conclusions:

• The study confirms the preferential occupation of Fe at the octahedral Ga site in β-Ga2O3.
• Calculated defect properties provide insights into Fe-doped Ga2O3 behavior and optical characteristics.
• The findings offer direct guidance for the synthesis and property design of Fe-doped β-Ga2O3 for specific applications.