Pulsed anodic etching: An effective method of preparing light-emitting porous silicon

A pulsed anodic etching method is developed to prepare light-emitting porous silicon. Under the same equivalent etching condition, pulsed etching can yield a more uniform porous silicon film with stronger photoluminescence intensity than the film prepared by ordinary dc etching. The atomic force microscopic observation shows that the porous silicon surface prepared by pulsed etching contains more widely separated Si columns but with steeper sidewalls, which are believed to result in the improvement of quantum confinement. The thickness of pulse etched porous silicon film is found to be much larger than that of a dc etched sample.