Effect of illumination on the electron transport mechanisms in Silicon nanocrystal-based nanopixels

In this paper, we present an analysis of conduction in silicon nanocrystals (nc-Si) of small area nanopixels in dark conditions and under illumination. The photosensitive layer of the analyzed devices is mad up a small number of (nc-Si) embedded in SiO₂. The interface between the oxide and the silicon substrate is shown to play a significant role in the conduction process: we observed that the presence of (nc-Si) situated inside the oxide, at some angstroms from the interface with the active region, induced discrete variations in the current. In dark conditions the transport of electrons is dominated by trap-assisted mechanisms (Poole-Frenkel, Hopping) at low electric fields and a Fowler-Nordheim mechanism at high electric fields. Under illumination, a new generation-recombination contribution is observed. This mechanism has been carefully studied by Random Telegraph Signal (RTS) measurements. This work shows that the photo-induced current fluctuations (RTS) could be related to the interaction between single photogenerated charges.