Photothermal spectroscopy of mesoporous layers on heavily doped n-type silicon substrates

Photothermal spectroscopy experiments have been used for the first time to study non-radiative processes in mesoporous silicon layers of varying porosity. Data on low porosity material can be explained by a model which involves interference between thermal waves reflected at the porous silicon film-silicon substrate interface. High porosity material, which exhibits strong red photoluminescence, cannot be fitted to this model. These materials seem to indicate the existence of another critically damped wave-like excitation in addition to the thermal waves.