We have examined photoluminescence spectra of porous
substrates as a function of treatments. The PL investiga-tions of the porous GaAs layer show visible and infrared
photoluminescence bands.
The infrared PL peak is associated
with the Eg of the bulk GaAs and the visible one is due
to the quantum confinement in the GaAs crystallites
formed by electrochemical etching. For the porous InP
we must study the photoluminescence spectra in more details
in order to clarify the precise nature of the different
transitions.