Site of the Er³⁺ optical centers of the 1.54 μm room-temperature emission in Er-doped porous silicon and the excitation mechanism

Sites of the Er³⁺ luminescent centers in Er-doped porous silicon (PS:Er) formed by immersion are studied in order to make clear the cause of the strong room temperature luminescence at 1.54 μm due to the 4f intra-transition of Er³⁺ ions. The luminescence spectra and the temperature quenching of the intensity and the fluorescence lifetime are compared between PS:Er samples formed by immersion in an ErCl₃/alcohol solution and Er-implanted PS, using the same PS hosts. PS:Er samples formed by immersion show a small temperature quenching in the intensity and the fluorescence lifetime, resulting in a strong luminescence at RT. On the other hand, PS:Er samples formed by Er ion implantation into PS shows almost the same strong temperature quenching as the Er-implanted crystalline Si. These results indicate that the sites of Er ions responsible for the strong RT 1.54 μm luminescence in PS:Er formed by immersion is not inside Si nanocrystals but on the surface of Si nanocrystals.