Fabrication of ErSiO self-organized superlattice thin films and evaluation of the 1.54μm optical waveguide amplification characteristics

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This study deals with the ErSiO new materials with a self-organized superlattice structure and its possibility for the 1.54μm optical waveguide amplification.In the fiscal year 2003, fabrication of ErSiO new thin films were developed using MOMBE, nano-structured porous silicon and sol-gel methods. ErSiO crystalline materials could be successfully formed by every method. They all show crystalline structures characteristics of ErSiO superlattice and also sharp and fine-structured 1.54μm luminescence spectra at room temperature due to Stark splittings in the Er 4f-4f transitions.In the fiscal year 2004, developments of a new fabrication method and the process improvements for ErSiO films thicker than 100 nm were studied. Using these improved ErSiO thin films, the self-organization mechanisms of ErSiO superlattice, detailed crystalline structures, electrical properties, and the origins of the peculiar luminescence spectra and the short fluorescence lifetime were investigated. First, contro … More l of the ratio of Er, Si and O at 1:2:2.4, especially control of O, was found to be most important for the growth of ErSiO crystalline superlattices with their peculiar luminescence spectra and fast fluorescence lifetime. A laser ablation method was also attempted to obtained improved ErSiO superlattice at lower process temperature together with process improvements of sol-gel and MOMBE methods. ErSiO crystalline thin films were obtained at 900-1000℃, about 200℃ lower than before. Possibility of epitaxial growth on tilted Si(100) by MOMBE was shown.In the fiscal year 2005, origins of very fast fluorescence lifetimes, 10-20μs compared to several ms in Er-doped Si-related materials, were studied in detail. By varying the optical density in ErSiO thin films, it was found that the fast fluorescence lifetime was the radiative lifetime itself of ErSiO, which may be due to very uniform and strong crystalline fields on Er^<3+> ions. ErSiO optical waveguides were formed and the transmission properties and up-conversion characteristics were studied.In conclusion, ErSiO with the Er concentration higher than 10^<20>/cm^3 and the radiative lifetime of 10-20μs is a very promising materials for the stimulated emission and light amplification at 1.54μm. Less