Ambient erbium luminescence in silicon and silicon-germanium films

Prior studies have shown that photoluminescence from Er³⁺ impurities in silicon is severely limited at room temperature by non-radiative relaxation and solid solubility, and room temperature emission from Er³⁺ in oxide-based hosts becomes diminished at high erbium concentrations. This work presents studies of thin films (0·2 µm thick) prepared by vacuum co-evaporation from elemental sources (erbium, silicon and silicon/germanium) followed by vacuum annealing (600°C); materials of this type, which are produced with high Er³⁺ concentrations, are shown to be capable of yielding strong room temperature photoluminescence. Alloy films of Si–Er–O and Si–Ge–Er–O, containing (20 ± 2) at.% erbium and incorporating (16 ± 2) at.% oxygen (introduced by way of vacuum scavenging reactions), exhibit emission bands with dominant components at 1·51 and 1·54 µm (~0·04-µm overall spectral widths). Results are discussed in terms of erbium–oxygen complex formation and the effects of local randomness on cooperative inter-Er3+ energy transfer among thermal-broadened and local-field Stark-split ⁴I_13/2→⁴I_15/2 transitions. This paper discusses the advantages of scalability and low costs associated with producing optically active silicon-based materials.