EVIDENCE OF HOMOGENEOUSLY BROADENED SPECTRA IN THE VISIBLE PHOTOLUMINESCENCE OF POROUS SILICON

The visible photoluminescence (PL) of porous silicon (PS) has been inv estigated in terms of the behavior of PL excitation and emission spect ra. It is shown that for appropriately prepared samples, the excitatio n and emission spectra become entirely independent of the emission and excitation wavelengths, respectively, while both their bandwidths and the large Stokes shift between them remain unchanged. The result indi cates that the broad PL bands of PS are due to homogeneous broadening, and that carrier localization accompanied by a strong electronphonon coupling plays an important role in the visible luminescence of PS.