On the origin of the visible luminescence from porous silicon

A correlation between the photoluminescence, chemical bonds and structure of c-Si subjected to electrochemical and laser induced chemical etching has been obtained by X-ray photoelectron spectroscopy, IR spectroscopy and Raman scattering. Photoluminescence is very strongly related to the chemical bonding and depends on the Si, O and C content and the presence of different oxidized states of Si which are different for porous silicon prepared on Si substrates of different electrical resistivity. Porous silicon having Si oxidized states typical for Si suboxides exhibits very intensive photoluminescence. The influence of the doping level of c-Si on the process of electrochemical etching as well as the influence of the laser power on the process of stain etching are discussed.