POSSIBLE EXPLANATION OF THE CONTRADICTORY RESULTS ON THE POROUS SILICON PHOTOLUMINESCENCE EVOLUTION AFTER LOW-TEMPERATURE TREATMENTS

The modification of the porous silicon photoluminescence (PL) after a low level thermal oxidation at 300 degrees C is studied by analyzing t he surface chemical composition using infra-red spectroscopy. The amou nt of oxide is determined quantitatively. Two different porosities of porous silicon are studied: 70% and 80%. In the case of the 70% porosi ty porous layer, this thermal process leads to an important PL enhance ment in the early stages of oxygen incorporation followed by a degrada tion at higher oxidation levels whereas the photoluminescence of the 8 0% porosity porous layer only decreases. It is shown how this new anal ysis can account for the different and often contradictory results on the PL behavior under various low-temperature oxidation processes.