Auger Processes in the Ensemble of Si Nanocrystals

Abstract

We review some of our recent works on the porous Si luminescence and emphasize the importance of the nonradiative Auger-process in the description of the Si nanocrystal photoluminescence (PL) properties. Due to a very long radiative time already at moderate levels of optical excitation a double occupation of crystallites by e-h pairs is achieved. This results in an efficient photoluminescence suppresion by a resonant pump beam and persistent hole burning phenomena. The hole burnt in the luminescence spectrum in a pump-to-probe or persistent mode has two well defined onsets related to the TO momentum conserving phonons of Si. An increase of the temperature heals the spectral hole and this is accompanied by a thermoluminescence signal. These results allow us to conclude that most of the luminescence of porous Si arises from radiative recombination between states confined inside the nanocrystals.