Structural and optical characteristics of Er-doped SRSO layers deposited by the confocal sputtering technique

Er-doped silicon-rich silicon oxide layers have been grown at 600 °C by magnetron co-sputtering of three confocal cathodes (Si, SiO2 and Er2O3) in pure argon plasma. The structural and optical properties of the layers were examined in the function of deposition and annealing conditions. It was shown that the increase of the RF power density applied on the Si cathode from 0.74 to 2.07 W cm−2, while maintaining constant RF power on the two other cathodes, allows a fine engineering of the Si excess from 5 to 15 at%. The Er content was evaluated to 1×1021 at cm−3. A high Er3+ emission was observed under non-resonant (476 nm) excitation from as-deposited layers, which was significantly improved after annealing at 600 °C. The Er PL was found to be much more intense than the best samples reported so far, which was annealed at 900 °C and contains, however, lower Er content (5.4×1020 at cm−3) and Si excess (7 at% of Si). The Er emission lifetime was found to be about 6 ms for low Si excess (5 at%) and 1–2 ms for high Si excess. Upon reducing the Er content by a factor of three, the Er3+ PL intensity was further increased and the lifetime reached 5.5 ms, suggesting a notable increase of the fraction of coupled Er ions.