Understanding the physics of unintentional doping and defect formation during epitaxial growth of III-nitride semiconductors is crucial to develop optical and electronic devices. Herein, the impact of magnesium doping on unintentional oxygen incorporation into GaN and AlN during metal-organic vapor-phase epitaxy is investigated by first-principles calculations. It is found that the presence of Mg substituting group-III atoms (Ga or Al) in subsurface layers energetically promotes unintentional oxygen incorporation. The calculation results also suggest that even when Mg + H complex defects exist in subsurface layers, they promote unintentional oxygen incorporation in a similar manner. The mechanism of unintentional oxygen incorporation enhanced by magnesium doping and complex defect structures is discussed in terms of charge neutrality or electron-counting model in the growth surface.
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