PHOTOLUMINESCENCE STUDY OF RADIATIVE RECOMBINATION IN POROUS SILICON

Photoluminescence in porous Si films has been studied in the temperatu re range from 15 to 250 K. The luminescence peak is found to shift to higher frequency with increasing temperature. Above 100 K the luminesc ence intensity shows strong thermal quenching with an activation energ y of 60 meV. Below 100 K photoluminescence decay data obtained using q uadrature frequency resolved spectroscopy are characterized by a singl e lifetime of about 300 mus. At 250 K several time constants are seen to contribute to the luminescence decay. We attribute the very intense low-temperature photoluminescence to recombination at localized extri nsic centers.