Luminescence of thulium in III-V semiconductors and silicon

Thulium (Tm) emissions were investigated in 390 keV, Tm-implanted AlGaAs, GaAs, InP, and Si using photoluminescence spectroscopy. The emissions in the different semiconductors were observed in the 1.20 to 1.35-μm region and are attributed to transitions between the crystal-field-split spin–orbit levels 3H5– 3H6 of Tm3+ (4f12). The main emission in GaAs is located at 1.233 μm and shows doublet structure with a width for each component of better than 0.15 meV at 6 K. Anneal temperature dependent studies identify multiple sites as the source of the Tm3+ emissions. The optimum anneal temperatures of Tm-implanted GaAs and AlGaAs are between 725 and 750 °C, for 10- or 15-min anneals, whereas InP:Tm appears to have the strongest emissions in the 575 to 625 °C temperature range. The intracenter Tm3+ emissions for Si:Tm were observed at 850 °C. Sample temperature dependent studies of Tm3+ emissions show that the sharp emissions can be seen to as high a temperature as 240 K for specific samples. Luminescence intensity studies as a function of excitation laser power in GaAs:Tm and AlGaAs:Tm exhibit a sublinear relationship. Lifetime measurements at 10 K of the main 1.233-μm line found two decay components with times of 0.5±0.3 μs and 2.6±0.3 μs. Selective excitation studies indicate that free carriers and/or excitons are involved in the excitation of the Tm centers.