Electronic and optical properties of Si/SiO2 nanostructures.: II.: Electron-hole recombination at the Si/SiO2 quantum-well-quantum-dot transition -: art. no. 205325

A photoluminescence (PL) study of crystalline Si/SiO2 quantum wells has been carried out for thicknesses in the 3.9-0.6 nm range. We show that quantum confinement plays a great role on emission properties of these narrow quantum wells in term of PL line energy and quantum efficiency. In particular, for the very-low-thickness domain, a set of discrete and high-energy lines is observed between 1.20 and 1.60 eV and viewed as resulting from two phenomena: the thickness fluctuations of the silicon layer and the appearance of structural barriers in the plane of the thinnest wells due to the formation of a two-dimensional distribution of Si nanocrystals embedded in SiO2. A strong increase in the photoluminescence efficiency is measured for wells pertaining to the very-low-thickness domain.