Optical control of charge number in single floating quantum-dot gate in field-effect transistor structure

The optical characteristics of a single floating quantum-dot (QD) gate field-effect transistor memory cell were investigated at 77 K. The channel current, which can detect sensitively the charging of the QD, was saturated via some discrete levels after illuminations by light pulses, and the saturation value increased with the stronger illumination power. It was also found, by comparing the optical writing characteristics for different illumination powers at 77 K with retention characteristics at 120 K, that the discrete current levels observed in the optical characteristics corresponded to the hole number variation in the single QD. These results show that the number of holes stored in a single QD was controlled by changing the illumination power.