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

Abstract

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 (10−7 C/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, ΔVG, can be explained by the quantum confinement effect of the nc-Si dots in size of about 3.5 nm.