ABSORPTION AND PHOTOLUMINESCENCE OF FREE POROUS SILICON

The total absorption in the spectral ranges 0.5-1.2 mu m and 2.5-25 mu m, the photoactive absorption in the range 0.5-1.2 mu m, and the phot oluminescence in porous silicon films separated from the substrate wer e investigated. It is shown that for most of the experimental samples the absorption edge is described by a relation that is characteristic of indirect interband transitions. The observed absence of any correla tion between the energy position of the absorption edge and the photol uminescence band is explained by the fact that absorption of radiation occurs within nanocrystals of porous silicon, whereas the photolumine scence emerges from a thin chemical film on the surface of the porous silicon. (C) 1995 American Institute of Physics.