Lanthanide-based graded barrier structure for enhanced nanocrystal memory properties

A memory structure comprising Ge nanocrystals and lanthanide-based charge trapping dielectric stack was fabricated to realize a self-aligned graded barrier structure. By exploiting efficient charge trapping of the nanocrystals embedded in the heterogeneous high- k dielectric, strong memory effect was manifested by a large counterclockwise capacitance-voltage hysteresis of 2.7 V under a low voltage operation of ±4 V. The high- k barrier with graded composition provides a favorable confinement barrier for improved hole retention with simultaneous enlargement of the memory window.