Bismuth doping of silicon compatible thin films for telecommunications and visible light emitting devices

In the last decades, in the field of silicon microphotonics many efforts have been made to find strategies in order to obtain efficient luminescence from silicon or from Si compatible materials that could be totally integrated on Si microchips. Among the several approaches, mixed rare earth silicates and oxides have received great attention as active media, owing to their compatibility with the standard Si technology and the possibility to dissolve inside high concentrations of luminescent centers. In this paper we will review the last achievements on the investigation of the structural and optical properties of erbium doped yttrium silicates and oxides. We will further show the advantages of using bismuth as Er co-dopant, as strategy to improve optical efficiency at 1540 nm, wavelength of interest for telecommunications. The stabilization and the role of the Bi3+ oxidation state will be evidenced along the paper by comparing the results of the Bi influence on the Er emission in the two hosts. Photoluminescence in excitation measurements will permit to demonstrate that Bi ions act as efficient sensitizers to transfer energy to Er ions. Hence, through mediated excitation the Er excitation cross section is increased up to two or three orders of magnitude in silicates and oxide, respectively, if compared to the Er resonant condition at 488 nm. In the second part of the paper we will focus on the investigation of Bi doped yttrium oxide as efficient visible emitter. In particular, the peculiar dependence of the Bi emission on the excitation wavelength, which makes the Bi-doped oxide a tunable light source, together with the estimation of its optical efficiency, permits to clearly evidence its potentiality for application in visible light emitting devices.