Phase separation growth of Er2SiO5 thin film in Si-rich ErSiO preform

ErSiO crystalline compounds such as erbium silicates (Er2Si2O7 and Er2SiO5) and Er2O3 have been attracting attention as the new light source material for silicon photonics. In our previous reports, several results indicated that the ErSiO crystalline compound was non-stoichiometry (Er:Si:O=1:2:2.4) and showed carrier mediated excitation. In our later study, however, it has been found the ErSiO crystalline compound contains Er2SiO5 (PDF#52-1809) crystalline matrix. ErSiO compounds made from the sol-gel solution of Er:Si=1:2 and Er:Si=2:1 show that the X-ray diffraction (XRD) peak patterns are in good agreement with the Er2SiO5. Rutherford back scattering (RBS) and secondary ion mass spectrometry (SIMS) results for the ErSiO compounds also show phase separation of Er2SiO5 and SiO2. SiO2-rich Er2O3-SiO2 systems usually show phase separation of Er2Si2O7 and SiO2 but this system behaves in a different manner. Furthermore, bulk Er2SiO5 emits light only by direct excitation of Er. From PL excitation (PLE) measurements, the indirect excitation emission observed in the Si-rich non-stoichiometric ErSiO compound is considered due to Er2SiO5 crystallites embedded in SiOx, which can be formed by the phase separation.