Gradual Ge1−xSix/Si heteronanocrystals based non-volatile floating gate memory device with asymmetric tunnel barriers

The gradual Ge1-xSix/Si heteronanocrystals on ultra thin SiO2 were fabricated to form the metal-oxide-semiconductor (MOS) memory structure with asymmetric tunnel barriers through combining self-assembled growth and selective chemical etching technique. Charge storage characteristics in such memory structure have been investigated by using capacitance-voltage measurements. The observations demonstrate that the holes reach a longer retention time even with an ultra thin tunnel oxide, owing to the high band offset at the valence band between Ge and Si.