Red light emission properties of porous silicon

The discovery of visible luminescence from porous silicon has generated significant interest, in view of the fact that bulk silicon does not emit light in the visible part of the spectrum. This material differs from bulk silicon in one important way, that is, it consists of interconnected silicon structures, which in some cases are on the order of several nanometers, having a very large surface to volume ratios, Thus, in a material such as this, both the effect of particle size and surfaces must be examined in order to determine the optical behavior of this system. The mechanism leading to intense room temperature visible photoluminescence (PL) exhibited by porous silicon (PoSi) is still a source of controversy. Although significant data on PoSi exist, no single model has been able to consistently explain all the results. The authors discuss the competing models for the source of the luminescence.