Minimum in the bandgap and luminescence peak energy of red-luminescent Si nanoparticles in porous silicon

Abstract

The evolution of the red luminescence spectrum of porous Si with the excitation energy has been investigated for samples prepared in different conditions. The results have suggested that Si nanoparticles in porous Si are divided into red-luminescent Si nanoparticles with bandgaps larger than 1.5 eV and red-nonluminescent ones with the smaller bandgaps. It is estimated that the luminescence peak energy of the Si nanoparticle with the critical bandgap is 1.4 eV and the particle size is about 5 nm. The critical bandgap is explained from the energy correlation between a red luminescence center in the Si nanoparticle and the bandgap.