Photoluminescence study of porous p-type silicon: Identification of radiative transitions

The research discussed in this paper focused on a systematic methodology to elucidate the controversy about transitions responsible for the photoluminescence (PL) spectrum from porous silicon (PSi) layers etched on a p-type Si wafer, to understand the nature of light emitting mechanisms from PSi. The PL spectrum of PSi, as a function of temperature, shows the existence of broad peaks, initially associated with stable surface states. However, the PL studies as a function of time, under continuous laser fluency, shows the presence of electronic states due to silicon columns (quantum confinement) and the metastable surface states. Finally, the PL studies, during which the laser was cut off for several hours, confirm that the surface states are metastable. Based on the information provided by these studies, the interpretation of the results indicates that the PL spectrum of PSi is a superposition of porous surface states and states originated in the porous layer considered as a pseudo lattice of the Si bulk.