The Luminescence Mechanism of Porous Silicon

ABSTRACTWe report resonantly excited photoluminescence (PL) spectroscopy of highly porous silicon. In the PL spectra we observe satellite structure due to the participation of momentum-conserving phonons in the optical transitions. The momentum-conserving role of these phonons, together with their energies and relative coupling strengths, demonstrate beyond doubt that crystalline silicon, which has already been shown to be the dominant constituent of unoxidised porous silicon, also forms the luminescent material. We show that the theory of quantum confinement in crystalline silicon wires can explain our results and those of other experiments, if the electron-hole interaction, andthe localisation of carriers by fluctuations in wire width, are taken into account.