RAMAN INVESTIGATION OF LIGHT-EMITTING POROUS SILICON LAYERS - ESTIMATE OF CHARACTERISTIC CRYSTALLITE DIMENSIONS

Light-emitting porous silicon layers prepared on two types of boron-do ped p and p+-Si substrates were studied by Raman spectroscopy in a bro ad frequency range (0-1100 cm-1). Standard phonon confinement model su pported by new results from low-frequency scattering permit us to esti mate consistently the characteristic dimensions of nanometric crystall ites in porous silicon, without invoking complex size distribution. A sizable fraction of a highly disordered (a-Si) phase in the p-type sam ples is detected, and there is no clear spectral evidence of other Si- based compounds.