Luminescence mechanisms in porous silicon

The recent discovery of light emission in porous silicon has attracted intense, worldwide interest in this material because of its potential use in a new family of Si-based optoelectronic devices. However, before the device applications of porous Si are fully exploited, a basic understanding of the processes which cause luminescence is required. In this work, the different models that have tried to explain the light emission in porous Si are analyzed using a variety of surface analytical techniques such as Atomic Force Microscopy (AFM), X-Ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectrometry (SIMS). These experiments have established that photoluminescence (PL) in this material can be explained by radiative recombination processes induced by the quantum confinement of charge carriers in Si quantum wires formed by electrochemical etching. These radiative processes involve: (a) bulk states which define the bandgap through the size and geometry of the porous Si nanostructure and (b) surface states within the bandgap which are dependent on surface chemistry.