Light emission from porous silicon prepared using metal-dissolved hydrofluoric solution

In this work we report on the photoluminescence (PL) characteristics of porous silicon (PS) prepared by electrochemical anodization of a p-type Si wafer using chemically metal-dissolved hydrofluoric solutions. Various solid metals, oxidative (Al, Fe, Sn, Ni, Cr) and reductive (Cu), were used for this work. The effects of metals on the PL properties in as-grown, illuminated, and aged states have been studied. It is found that for the as-grown state the PL intensity is reduced by the addition of metal. In particular, the Cu-doped PS reveals a PL intensity lower by one order of magnitude as compared to that of normal PS. The improvement of stability in the PL intensity under illumination was only observed for the Cu-doped PS sample, which is more stable by a factor of 2 as compared to that of normal PS. On the other hand, the improved stability of the PL intensity in the aged state was observed for metal-doped PS samples other than for the Cu-doped sample. From the results, it is suggested that reductive metals are more effective in reducing the PL degradation caused by illumination while oxidative metals are more effective in reducing the PL degradation caused by ageing.