THE ORIGIN OF EFFICIENT LUMINESCENCE IN HIGHLY POROUS SILICON

The efficient visible luminescence of highly porous silicon is identif ied using photoluminescence spectroscopy. The observation of momentum- conserving phonon satellites of crystalline silicon shows beyond doubt that crystalline silicon is the luminescent material. We report a wea k three-phonon satellite in photoluminescence excitation spectra of po rous silicon. This is a manifestation of the weak two-phonon momentum- conserving transitions of crystalline silicon. The exchange splitting of the luminescent exciton is dramatically enhanced by quantum confine ment, in agreement with theoretical predictions.