Bias- and photo-induced charging effects in SiO2 films containing Si nanocrystals

Bias- and photo-induced charging effects are reported for metal-insulator-semiconductor (MIS) structures containing nanocrystals produced by ion-implantation and annealing. UV illumination or constant voltage stress is shown to induce reversible shifts in the current-voltage (I-V) characteristics in a similar manner, and the shape of the shifted I-V curves almost does not change with time. The phenomenon of negative photoconductivity observed under forward bias persists even after a 60 min illumination. The current-voltage (C-V) curves, as well as the I-V curves, are reversibly shifted by a short-time illumination under a positive or a negative bias. No such behaviors are observed in structures that have not been ion-implanted. These and other effects are explained by nanocrystal charging and charge movement in the insulator layer of the MIS structures.