FAST AND SLOW VISIBLE LUMINESCENCE BANDS OF OXIDIZED POROUS SI

The visible luminescence of porous Si is known to contain at least two spectrally distinct emission bands with widely different response times. The orange-red luminescence component (1.5-1.9 eV) decays in times being of the order of 10 mu s at room temperature. The blue-green band (2.3-2.6 eV) is very much faster with response time in the 10-ns range. It is shown that with increasing degree of oxidation the fraction of the fast luminescence intensity rises from similar to 1% of the total in the as-prepared porous Si to become the dominant spectral component in strongly oxidized material. For the rapid-thermal-oxidized material excited with 337-nm radiation, the intensity of the fast luminescence is comparable to that in the as-prepared state.