Sensltizen Luminescence Of Erbium-doped Silicon-rich Oxynitride

The silicon optoelectronic monolithic integration can provide a rapid, large bandwidth and low crosstalk optical interconnects. These advantages make the silicon optoelectronics one of the hotspots of the international semiconductor research. However, the lack of COMS compatible silicon-based light sources has been the primary roadblock for silicon optoelectronics. The erbium-doped Si-based material is a promising candidate for Si-based light sources since its fabrication is compatible with CMOS technology. Moreover, the luminescence of Er3+ coincides with the low-loss window in silica optical fibers and has hence attracted much attention. However, the excitation cross section of Er3+ is rather small and needs to be improved.In this dissertation, the sensitization mechanisms of Er3+ in silicon rich oxynitride have been systematically investigated. Based on the study of the optical properties, we have succeeded in fabricating light emitting devices based on erbium doped silicon rich oxynitride with turn-on voltages as low as 5 V. In the following, the primary achievements in this work are described.(1) The effect of silicon excess concentration on the 1540 nm Er3+ luminescence has been clarified and the silicon excess concentration has been optimized. The density of silicon nanoclusters would initially increase with silicon excess concentration until 6.4%. Then coalescence of silicon nanoclusters would take place and their density would decrease with the increase of silicon excess concentration. The density of optically active Er3+ ions is found to decrease with silicon excess concentration. We also demonstrate that the high temperature annealing process could efficiently remove the nonradiative channels and the lifetime of Er3+ would not decrease with silicon excess concentration. Thus the optimized Er3+ luminescence is observed in the sample with a medium silicon excess concentration.(2) The sensitization mechanism of Er3T is found to evolve with the annealing temperature:excess Si related localized states play the essential role in samples when the annealing temperature is below 700 ℃, while silicon nanoclusters (Si-NCs) become the dominate sensitizers when the annealing temperature exceeds 800 ℃. Our results show that higher density of sensitized Er3+ could be acquired via energy transfer from localized states, and thus provide an alternative way for the engineering of light sources based on Er:SRON. The main limitation of Er3+ PL in low temperature (700 ℃≤) annealed samples seems to lie in the relatively short lifetime, which could be solved by passivation of defects.(3) The temperature dependence of sensitized Er3+ emission via localized states and silicon nanoclusters has been studied to get insight into the excitation and de-excitation processes in silicon rich oxynitride films. The thermal quenching of Er3+ luminescence is elucidated by terms of decay time and effective excitation cross section. The temperature quenching of Er3+ decay time demonstrates the presence of non-radiative trap states, whose density and energy gap between Er3+ 4I13/2 excited level is reduced by high temperature annealing. The effective excitation cross section initially increases and eventually decreases with temperature, indicating that the energy transfer process is phonon-assisted in both samples.(4) We have succeeded in fabricating light emitting devices based on erbium doped silicon rich oxynitride with turn-on voltages as low as 5 V. We demonstrate that thermal treatments would change the defect states in the films and subsequently the electrical conduction mechanisms. The electroluminescence of Er3+ is carrier mediated and depends on the density of localized states in the films.