Extended X-ray absorption fine structure measurements showed 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 provided new insight into the origin of this very different Er-doping behavior.

Erbium in Si and GaN - Extended versus Point Defects. P.H.Citrin, D.R.Hamann, P.A.Northrup: Physica B, 2001, 308-310, 369-73