THE ORIGIN OF EFFICIENT LUMINESCENCE IN HIGHLY POROUS SILICON

The efficient visible luminescence of highly porous silicon is identified 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 weak three-phonon satellite in photoluminescence excitation spectra of porous 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 confinement, in agreement with theoretical predictions.