On the saturation mechanism in the Ge nanocrystals-based non-volatile memory

The hole charging mechanism in Germanium nanocrystals (nc-Ge) embedded in SiO2 fabricated by low pressure chemical vapour deposition is investigated by means of capacitance–voltage (C–V) analysis. The charging kinetics shows a logarithmic behaviour and a saturation phenomenon for various gate voltage stresses. For low gate bias stresses, the saturation of the carrier number in the nc-Ge seems to depend on the electric field in the oxide. On the other hand, we have demonstrated that for high gate voltage stresses, the number of holes per dot at saturation becomes constant and depends only on the diameter of the nc-Ge. Finally we propose a model to explain the saturation mechanism. This model is then used to extract the nanocrystals size.