HfO2 with embedded Ge nanocrystals with memory effects

The charge storage properties of Ge nanocrystals-based MOS-like capacitors with tunnel and gate HfO₂ are studied. HfO₂/Ge/HfO₂/Si trilayer structures were prepared by magnetron sputtering (in Ar) and subsequent rapid thermal annealing (650 °C). HfO₂/Si structures were also prepared, some under similar conditions, while others were deposited in Ar:O₂. TEM investigations and C-V measurements were performed. TEM on annealed trilayers evidences the formation of ordered and precisely positioned array of Ge nanocrystals embedded in crystalline HfO₂. The annealed Al/HfO₂/Ge/HfO₂/p-Si/Al capacitors present counterclockwise C-V hysteresis (0.8 V memory window) mainly given by Ge nanocrystals, with negligible contribution from crystallized-HfO₂ traps.