Improved performance of SiGe nanocrystal memory with VARIOT tunnel barrier

The authors have fabricated a nonvolatile flash-memory device using SiGe nanocrystal floating gate with new variable oxide thickness (VARIOT) tunnel barrier. It is found that the writing speed of VARIOT sample is almost hundred times faster at a low programming voltage of 5-8 V compared to the traditional flash memory with single-layer tunnel barrier. The results have shown that a long-charge retention time of up to 10⁶ s and a good endurance characteristics of up to 10⁶ write/erase cycles can be achieved at 85 degC