Defect study of light-emitting HCl-treated porous silicon

Electrochemically etched porous silicon (PSi) samples have been exposed to a $3M\mathrm{HCl}$ solution for set time intervals, resulting in a stable and enhanced luminescence from this material. These samples were examined using photoluminescence (PL), electron spin resonance (ESR), and Raman spectroscopy. The Raman chemical disorder component is found to increase significantly with increased HCl exposure, tracking also with the increased PL intensity. In contrast, a significant drop in the nanocrystalline Raman component is monitored, suggesting that the number of silicon nanocrystallites decreases with increasing exposure to HCl. ESR spectra of these treated PSi samples indicate the presence of an NL8 type of oxygen shallow donor, which tracks extremely well with the increasing PL emission and the amount of chemical disorder induced with increasing HCl exposure.