Self-organized Ge nanocrystals embedded in HfAlO fabricated by pulsed-laser deposition and application to floating gate memory

A trilayer metal-oxide-semiconductor structure containing a HfAlO tunnel layer, isolated Ge nanocrystals, and a HfAlO control layer, was obtained using pulsed-laser deposition (PLD). Self-organized Ge nanocrystals were formed by PLD at 600 °C, suggesting a useful low-temperature process for fabricating Ge nanocrystals embedded in dielectric materials. The self-organized Ge nanocrystals so formed were uniform in size and distribution with a density approaching 1012 cm-2. The effects of deposition temperature and growth rate in forming Ge nanocrystals were investigated and it was revealed that a relatively low temperature and growth rate are favorable for the formation of Ge nanocrystals. The memory effect of the Ge nanocrystals with storage charge density of up to 1012 cm-2 has been demonstrated by the presence of hysteresis in the capacitance-voltage curves.