The electroluminescence (EL) properties of Er-doped Si nanoclusters (NC) embedded in metal–oxide–semiconductor devices are investigated. Due to the presence of Si NC dispersed in the ${\mathrm{SiO}}_2$ matrix, an efficient carrier injection occurs and Er is excited, producing an intense 1.54 μm room temperature EL. The EL properties as a function of the current density, temperature, and time have been studied in detail. We have also estimated the excitation cross section for Er under electrical pumping, finding a value of ${\text{∼1×10}}^{\text{−14}}\hspace{0.17em}{\mathrm{cm}}^2.$ This value is two orders of magnitude higher than the effective excitation cross section of Er ions through Si NC under optical pumping. In fact, quantum efficiencies of ∼1% are obtained at room temperature in these devices.

The structural properties and the room temperature luminescence of ${\mathrm{Er}}_2{\mathrm{O}}_3$ thin films deposited by magnetron sputtering have been studied. In spite of the well-known high reactivity of rare earth oxides towards silicon, films characterized by good morphological properties have been obtained by using a $\mathrm{Si}{\mathrm{O}}_2$ interlayer between the film and the silicon substrate. The evolution of the properties of the ${\mathrm{Er}}_2{\mathrm{O}}_3$ films due to thermal annealing processes in oxygen ambient performed at temperatures in the range of $800–1200°\mathrm{C}$ has been investigated in detail. The existence of well defined annealing conditions (rapid treatments at a temperature of $1100°\mathrm{C}$ or higher) allowing to avoid the occurrence of extensive chemical reactions with the oxidized substrate has been demonstrated; under these conditions, the thermal process has a beneficial effect on both structural and optical properties of the film, and an increase of the photoluminescence (PL) intensity by about a factor of 40 with respect to the as-deposited material has been observed. The enhanced efficiency of the photon emission process has been correlated with the longer lifetime of the PL signal. Finally, the conditions leading to a reaction of ${\mathrm{Er}}_2{\mathrm{O}}_3$ with the substrate have been also identified, and evidences about the formation of silicate-like phases have been collected.

The photon absorption in Si quantum dots (QDs) embedded in SiO2 has been systematically investigated by varying several parameters of the QD synthesis. Plasma-enhanced chemical vapor deposition (PECVD) or magnetron cosputtering (MS) have been used to deposit, upon quartz substrates, single layer, or multilayer structures of Si-rich-SiO2 (SRO) with different Si content (43–46 at. %). SRO samples have been annealed for 1 h in the 450–1250 °C range and characterized by optical absorption measurements, photoluminescence analysis, Rutherford backscattering spectrometry and x-ray Photoelectron Spectroscopy. After annealing up to 900 °C SRO films grown by MS show a higher absorption coefficient and a lower optical bandgap (∼2.0 eV) in comparison with that of PECVD samples, due to the lower density of Si–Si bonds and to the presence of nitrogen in PECVD materials. By increasing the Si content a reduction in the optical bandgap has been recorded, pointing out the role of Si–Si bonds density in the absorption process in small amorphous Si QDs. Both the photon absorption probability and energy threshold in amorphous Si QDs are higher than in bulk amorphous Si, evidencing a quantum confinement effect. For temperatures higher than 900 °C both the materials show an increase in the optical bandgap due to the amorphous-crystalline transition of the Si QDs. Fixed the SRO stoichiometry, no difference in the optical bandgap trend of multilayer or single layer structures is evidenced. These data can be profitably used to better implement Si QDs for future PV technologies.