Complex defects in Al0.5Ga0.5N by first principles calculations

The complex native point defects in Al0.5Ga0.5N are studied by density functional theory (DFT) and Heyd, Scuseria and Ernzerhof (HSE) hybrid functional. The lower formation energy as well as the donor and acceptor properties of Al0.5Ga0.5N with different complex native point defects are obtained. It is found that VGa-GaN exhibits donor property under p-type conditions while VAl-VN and VGa-VN exhibit acceptor properties under n-type conditions. Then, the density of states studies indicate that the defect peaks in the Al0.5Ga0.5N bandgap are all contributed by the defect atoms or atoms near the defects. Moreover, the charge distribution and bonding states analyses show that the Ali atom in VAl-Ali forms ionic bonds with the N atoms in Al0.5Ga0.5N and the antisite Ga atom in VGa-GaN forms ionic bonds with the N atoms in Al0.5Ga0.5N. Furthermore, the thermodynamic transition energy levels exploration reveals that VGa-GaN is most likely to undergo thermodynamic transitions. Meanwhile, the binding energies analyses elucidate that VGa-GaN is the most stable in Al0.5Ga0.5N. The formation mechanism of complex native point defects in Al0.5Ga0.5N has been revealed, which helps to get a deeper insight to the growth and doping of AlGaN and expands its application in high-power and high-frequency optoelectronic devices.