Electronic and optical properties ofSi∕SiO2nanostructures. II. Electron-hole recombination at theSi∕SiO2quantum-well–quantum-dot transition

Abstract

A photoluminescence (PL) study of crystalline $\mathrm{Si}∕\mathrm{Si}{\mathrm{O}}_{2}$ quantum wells has been carried out for thicknesses in the $3.9\char21{}0.6\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ 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 $1.60\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ 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 $\mathrm{Si}{\mathrm{O}}_{2}$. A strong increase in the photoluminescence efficiency is measured for wells pertaining to the very-low-thickness domain.