The total energy of Er point defects, and the coupling of Er with native defects, were calculated by using the  ab initio  pseudopotential method. The results of the total energy calculations suggested that an Er atom coupled easily with the native defects. It was suggested that this was why the Er intra-4f shell luminescence spectrum was complicated, and depended strongly upon the sample preparation method and growth conditions.

A.Taguchi, T.Ohno: Materials Science Forum, 1995, 196-201, 627-32