Electrical study of memory effects in InAs quantum dots embedded in SiO{sub}2 on silicon substrates

摘要

Memory structures based on InAs nanocrystals directly grown by molecular beam epitaxy (MBE) on SiO{sub}2 have been studied. The nanocrystals have a typical diameter of 5 nm and the density is about 2 × 10{sup}11 cm{sup}(-2). High resolution TEM measurements have shown high crystalline quality and low size dispersion. Using these 7 nm-quantum dots, a test structure with a 3.5 nm-thick SiO{sub}2 tunnel oxide and a 10 nm-thick control oxide has been processed for data retention measurements. We have observed that 80% of the initial injected electrons are still stored after three months. These results for the retention time of electrons in InAs nanocrystals are much better than comparable structures with silicon or germanium quantum dots. Finally, we demonstrate that an optimized structure with 3.5 nm-thick tunnel oxides, 10 nm-in diameter nc-InAs and 7 nm-thick control oxides could fill the industrial requirements for nonvolatile memories in terms of W/E time, W/E operating voltage and data retention.