Photoluminescence from silicon nanocrystals initiated by Auger recombination

The mechanism of intense photoluminescence (PL) of silicon nanocrystals (nc-si), so interpreted as recombinative emission is reconsidered. Analysis of available theoretical and experimental data is presented to show that nc-si have an indirect band structure and, therefore, it is doubtful that electron–hole recombination is the only mechanism of intense emission. A model is proposed according to which a fraction of electrons reaches the second conduction sub-band by Auger recombination, a part of intense visible radiation being caused by direct electron transitions from the second conduction sub-band to the first one. Continuity equations are constructed in the first and the second conduction sub-bands. The system of equations with three adjustable parameters is solved numerically. At suitable parameter values the calculated PL decay curve coincides well with the experimental results. Some properties discovered experimentally are explained on the basis of this mechanism.