Ge nanoparticle formation and photoluminescence in Er doped SiO2 films: influence of sputter gas and annealing

The Er3+ luminescence at 1.54 μm is of current interest as silica-based optical fibers have low loss at that wavelength. The effect of placing Er in matrixes that are compatible with Si-integrated circuit technology has been explored and Er-doped Si-rich Si oxide has created much interest recently. In this work, we report on photoluminescence (PL) from Er-doped Ge-rich SiO2 films deposited on Si substrates and the effect of Ar+O2 vs. Ar as sputtering ambience is compared. The most intense PL is reached after annealing at 700 °C for the Ar sputtering ambience. These films contain Ge rich amorphous clusters observed by transmission electron microscopy. Higher annealing temperatures yield Ge nanocrystals while lower the PL intensity. For films sputtered in an Ar+O2 gas the PL intensity increases with annealing temperature up to 1000 °C while no Ge nanocrystals form.