PL and EL features of p-type porous silicon prepared by electrochemical anodic etching

Porous silicon (PS) was fabricated by electrochemical etching of Si wafers in a HF solution. The surface of the PS exhibited an etched layer with a thickness of 30–40 nm; this layer appeared to consist of aggregates of nanocrystallites with a size range of 5– 10 nm. Electroluminescence (EL) and photoluminescence (PL) phenomena of the PS sample were examined. A prototype of ITO/PS/p-type Si/Al EL device was illustrated with its fundamental features. The PS exhibited PL spectra, in a wavelength range of 550–900 nm with the maximum intensity at 725 nm, which are attributed to quantum confinement effects (QCE) owing to the presence of the aggregates of the nanocrystalline Si. The EL device produced EL spectra with their maximum intensity at 700 nm, which are similar to the PL spectrum ( 725 nm). It seems likely that the red EL reflects the size of the Si crytallites. In addition a particular fraction of the generated carriers contribute to EL by radiative recombination via localized surface states of the nanocrystallites. # 2004 Elsevier B.V. All rights reserved.