Multiple mechanism model for photoluminescence from oxidized porous Si

In order to explain experimental results for photoluminescence (PL) from po rous silicon (PS), a novel multiple mechanism model is suggested. There are three types of competitive photoexcitation-photoemission processes in PS; and which of them dominates, is usually determined by the oxidation degree of the PS. For a PS sample free from oxidation, the process that both photo excitation and photoemission of electron-hole pails occur within nanometer silicon particles (NSPs) is dominating. For most oxidized PS samples, the p rocess with the photoexcitation occuring in NSPs, but photoemission occurin g in luminescence centers in the SiOx layers surrounding the NSPs, dominate s. When NSPs in oxidized PS samples have very small density or very small o r large sizes, the process that both photoexcitation and photoemission occu r in Si oxide layers is dominating.