OBSERVATION OF PHONON STRUCTURES IN POROUS SI LUMINESCENCE

Steplike phonon structures arc observed in the luminescence spectrum o f porous Si under excitation within the luminescence band at liquid He temperature. The shape of the phonon structures are successfully inte rpreted in terms of a model based on phonon assisted indirect transiti ons. From the spacing of the structures, it is concluded that the lumi nescence occurs in an entity which has a phonon spectrum very similar to crystalline Si. The broad spectrum of luminescence is attributed to an inhomogeneous distribution of the indirect band gap energy of Si p articles.