Local structure of erbium-oxygen complexes in erbium-doped silicon and its correlation with the optical activity of erbium

It is well-known that the sharp luminescence emission at 1.54 μm from erbium-doped silicon has set off a great interest for this material in view of its applications in the third window of optical telecommunications. It is also known that the erbium luminescence is very poor in the absence of impurities like oxygen, carbon and nitrogen, but in spite of the large amount of research work devoted to this material, it is not yet completely clear what is the local structure of the optically active Er centre in oxygen-doped Er-Si alloys. The aim of this paper is to present and discuss the results of the analysis of the EXAFS spectra of two sets of Er-doped silicon samples, of which one was obtained by erbium and oxygen co-implantation and the other was grown by LPE (liquid phase epitaxy). The EXAFS spectra of these samples were satisfactorily fitted by assuming that Er sits in three different configurations, depending on the presence or the absence of oxygen and dislocations in the epi-layer. The relevance of these results in terms of optical and electrical activity of erbium is discussed in details.