Phenomenological Properties of the Fast (Blue) and Slow (Red) Components in the Photoluminescence of Porous Silicon

Abstract

Various observations concerning the blue-fast component of the photoluminescence of porous silicon are summarised and compared to the "normal" luminescence. It is now well known that porous silicon is able to emit light in the visible range and the bright yellow-red emission has been reported many times, but the dynamical aspect is not encouraging for application in fast electronics because the decay times are in the range of microseconds to milliseconds depending on temperature. But it has been shown that further processing such as rapid thermal oxidation I or the boiling water teclmique2 for example, are able to transform the layer in such a manner as it can become a bright emitter in the blue. In addition this blue component (always present in normal porous layers but hidden by the high energy wing of the "red" component) is more rapid. In order to help the researchers in the understanding of these new spectral and temporal structures we will draw some tables where different aspects of the two components are compared. Some of these observations have already been published by different groups but others are brand new and will be published soon. Concerning the words fast (F)and slow (S), they are perfectly adapted when we are concerned by the temporal properties of the luminescence, but in the case of the spectral behaviour this words have to be changed in blue (B) and red (R) lines. Indeed this is the first interesting observation, the fast decay concerns mainly a well resolved line peaking at ~ 500 nm while the slow decay is attached to the well known "normal" luminescence band which peaks in the yellow red or deep red region depending on the porosity of the material. In the following tables we will focus on the temporal aspect and on the spectral one, then we will make some suggestions.