Time-resolved photoluminescence techniques, involving a dye laser pumped by an N2 laser, was used to clarify the recombination of carriers that were selectively excited, to energy levels which ranged from 3.68 to 1.94eV, in oxidized porous material. It was found that the selective excitation of carriers to energy levels of around 2.7eV significantly increased the radiative recombination probability. The decay time of this enhanced photoluminescence was estimated to be about 4ns. The photoluminescence enhancement was attributed to the creation of O-induced defect states which were located at the oxidized surface layer and/or at the interface between the bulk Si and the SiOx layer.

S.Komuro, T.Kato, T.Morikawa, P.O’Keeffe, Y.Aoyagi: Applied Physics Letters, 1996, 68[7], 949-51