Room temperature visible light emission from Si/SiO2 multilayers: Roles of interface electronic states and silicon phase

We have studied luminescence properties and microstructure of 20 patterns Si/SiO₂ multilayers. The photoluminescence spectra consist of two gaussian bands in the visible-infrared spectral region. It has been demonstrated that the strong PL band is caused by the radiative recombination in the Si/SiO₂ interfaces states, whereas the weaker band originates from radiative recombination in the nanosized Si layers. The peak shift of this latter band shows a discontinuity that corresponds to a crystalline-to-amorphous phase change when the Si layers are thinner than 30 Å. The peak energy as a function of the layer thickness is interpreted using a quantum confinement model in the case of amorphous Si layers.