Electrical Characteristics of Ge-Nanocrystal Embedded MOS Capacitors for Non-Volatile-Memory Application

Germanium nanocrystals (NCs)-embedded silicon dioxide (SiO2) layers on top of Si substrates were prepared using the implantation of 74Ge+ ions into the SiO2 layers and the annealing of the implanted oxide layers. The distribution of Ge NCs embedded inside the SiO2 layers was examined by high resolution transmission electron microscopy, and optical properties of the embedded NCs were characterized by photoluminescence and micro-Raman spectroscopy. Capacitance versus voltage (C-V) measurements of Ge NCs-embedded MOS capacitors with single Al2O3 capping layers were performed in order to study memory characteristics of these MOS capacitors. The C-V curves exhibit large threshold voltage shifts originating from charging effect of the Ge NCs, revealing the possibility that the MOS structure is applicable to Nano Floating Gate Memory (NFGM) devices.