Highly Luminescent $a\hbox {-SiO}_{\rm x} \langle \hbox {Er} \rangle /\hbox {SiO}_{2}/\hbox {Si}$ Multilayer Structure

We have fabricated highly luminescent samples with erbium-doped amorphous silicon suboxide $(a\hbox {-SiO}_{x} \langle \hbox {Er}\rangle )$ layers on $\hbox {SiO}_{2}/\hbox {Si}$ substrates. The layers are designed to provide a resonance with large modal overlap with the active material and with low quality factor (Q-factor) at 1540 nm. Also, the structure has higher Q-factor resonances in the wavelength range between 800 and 1000 nm. Within this range, strong light emission from $a\hbox {-SiO}_{x}$ defect-related radiative centers and emission from the $\hbox {Er}^{3+},{}^{4}{ \rm I}_{11/2} - ^{4}{\rm I}_{15/2}$ optical transition (980 nm) are observed. A twofold and fourfold improvement in photoluminescence (PL) intensity are achieved in the wavelength ranges between 800 and 1000 nm and between 1500 and 1600 nm (region of $\hbox {Er}^{3+},{}^{4}{\rm I}_{13/2} - {}^{4}{\rm I}_{15/2}$ transition), respectively, when compared to the $a\hbox {-SiO}_{x} \langle \hbox {Er} \rangle$ active material deposited directly on Si substrate. The latter higher PL intensity enhancement is apparently caused by optical pumping at 980 nm (higher Q-factor) with subsequent emission from the ${}^{4}{\rm I}_{15/2}$ level in the low Q-factor resonance at 1540 nm. Further, five times increase of this emission at 1540 nm is obtained after optimized temperature annealing. The temperature-induced quenching in the PL intensity indicates distinct deactivation energies related to different types of Er centers which are more or less coupled to defec- s depending on the thermal treatment temperature