Charging/discharging induced premature breakdown/recovery in Si nanocrystals embedded in SiO 2 matrix

Abstract

In this work, we have found that the charging of nc-Si in a thin gate oxide can induce a reduction in the total gate oxide capacitance. The capacitance can approach zero value if all the nanocrystals are charged up. The reduction of the gate oxide capacitance is attributed to the premature breakdown in the gate oxide due to the charging up in the nanocrystals, as the reduction of the gate oxide capacitance corresponds to a large decrease in the gate oxide leakage current. Here the breakdown caused by the charging in the nanocrystals is somewhat similar to the soft or hard breakdown in pure SiO 2 thin films that are related to the charge trapping in the oxide film. The breakdown caused by the charging in the nanocrystals is found to be fully recoverable under ultra-violet (UV) light illumination for 5 minutes and a thermal annealing at temperature of 100°C for 10 minutes. The reduction and recovery of the capacitance due to the charging and discharging in the nanocrystals is explained with an equivalent circuit model.