PL properties of porous Si anodized with various light illuminations

This paper deals with a possible origin of visible photoluminescence (PL) in porous Si (PS). Experiments to examine the dependence of PL on the Si crystalline size have been performed to support the model that the PL origin varies from the Si nanocrystalline core states to the surface states, depending on the difference between the band gap energy of the Si core and that of the surface layer. A method was employed to control the Si core size by anodizing n-type crystalline Si (c-Si) under various light illuminations. Consequently, the size dependence of PL was clearly obtained in PS not exposed to air. Furthermore, we observed a red shift of the PL just after the PS was exposed to air. These results indicate that the origin of visible PL in PS is reasonably explained by the model.