Memory characteristics of MOS capacitors with Ge nanocrystal-embedded Al₂O₃ gate layers

Ge nanocrystals (NCs) embedded in Al₂O₃ gate oxide layers used as the floating gate layers were prepared by the thermal annealing of Ge ions implanted in the gate oxide layers. Capacitance versus voltage (C - V) curves of the Ge NC-embedded metal-oxide-semiconductor (MOS) capacitors were characterized in this work. The C - V curves of the NC-embedded MOS capacitor show counterclockwise hysteresis loops at various sweep voltages, which indicates the presence of charge storage in the Ge NCs caused by the Fowler-Nordheim tunneling of electrons between the p-type Si substrate and the Ge NCs. In addition, capacitance versus time measurements were made for the Ge NC-embedded MOS capacitor to investigate its retention characteristics.