Structural properties of Si/SiO₂ nanostructures grown by decomposition of substoichiometric SiO_xN_y layers for photovoltaic applications

Abstract

The structural properties of crystalline Si nanodots embedded in a SiO 2 matrix are investigated with respect to the exploitation of quantum confinement effects (QCE) 3. Photoluminescence (PL) spectra are blue-shifted relative to the Si bulk PL, which is in good agreement with theoretical QCE models. It is found that for observing the PL signal the nanodots must be covered by a SiO 2 shell to reduce charge carrier recombination via defects at the nanodot surface. This requires an [O]/[Si] ratio >0.5 for which the inter-dot distance becomes too large for charge carrier transport between the nanodots. It is concluded that a better control over the nanodot formation at high [O]/[Si] ratios has to be achieved before QCE can be successfully applied in Si solar cell devices.