Photo- and electroluminescence in porous silicon

When silicon is electrochemically etched in HF, a highly porous film, known as porous silicon, is generated. This material has very small silicon structures with sizes in the region of 3-5 nm, which are covered with hydrogen and oxygen. While bulk silicon as an indirect semiconductor, is not luminescent, the porous silicon shows bright photoluminescence. Since this was discovered in 1990, porous silicon has become one of the most intensely studied materials. The author discusses the photoluminescence and electroluminescence of porous silicon