Interface defect-assisted single electron charging (and discharging) dynamics in Ge nanocrystals memories

The charging and discharging dynamics of Ge nanocrystal memories is measured and compared with a realistic quantum mechanical model that is able to reproduce qualitatively the overall device behavior. Quantitatively, the charging (discharging) dynamics is faster (slower) than predicted by calculations. To explain the discrepancies, we propose the quantum confined nanocrystal states are responsible for collecting the incoming electrons, but some of them are captured by defects in the nanocrystal surface. The potential created by the filled defects modify the spatial distribution of the nanocrystal wave functions, enhancing their penetration in the tunneling oxide and increasing the incoming transition rates. In the discharging process, the electrons confined in the nanocrystal states escape initially, while the ones in the defects have to be thermally excited to the nanocrystals states in order to tunnel out, slowing down the escape of the last few electrons.