Erbium in Si and GaN: Extended versus point defects

Extended X-ray absorption fine structure measurements show that Er defects in O-poor Si closely resemble bulk Er₃Si₅ with long Er-Si bonds, while in GaN, regardless of O content, Er substitutes for Ga sites as point defects with unusually short Er-N bonds. The structure and energetics of these two systems were examined in a series of density functional theory calculations. The detailed findings and excellent agreement with the data provide new insight into the origin of this very different Er-doping behavior.