Origin of Electron and Hole Charging Current Peaks in Nanocrystal-Si Quantum Dot Floating Gate MOS Structure

The nanocrystal-Si quantum dot (nc-Si QD) floating gate MOS structure is fabricated by using plasma-enhanced chemical vapour deposition (PECVD) and furnace oxidation technology. The capacitance hysteresis in capacitance-voltage (C-V) measurements confirm the charging effect of nc-Si QDs. Asymmetric charging current peaks both for electrons and holes have been observed in current-voltage (I-V) measurements at room temperature for the first time. The characteristic and the origin of these current peaks in this nc-Si QD MOS structure is investigated systematically. Moreover, the charge density (10^-7C/cm²) calculated from the charging current peaks in the I-V measurements at different sweep rates shows that each quantum dot is charged by one carrier. The difference of charging threshold voltages between the electrons and holes charging peaks, ΔV_G, can be explained by the quantum confinement effect of the nc-Si dots in size of about 3.5nm.