Investigation of electrical and optical measurements of silicon nanocrystals embedded in SiO2 matrix

Samples containing silicon nanocrystals (Si-nc) with radius of approximately 3 nm embedded in SiO2 exhibit a strong PL emission around 750 nm because of the quantum confinement of the exciton inside the Si-nc. To characterize the contribution of absorption by Si-nc to the photo-electric efficiency of silicon, metal–oxide–semiconductor structures were fabricated, without and with Si-nc embedded in silicon oxide and electrically characterized in the dark and under illumination. Samples containing Si-nc show a relatively large photocurrent compared to samples without Si-nc. Electron trapping and de-trapping in Si-nc was also observed by capacitance–frequency measurements showing a decrease of photo-generated electrons under illumination at high frequency. The efficiency of the photo-generated electrons from Si-nc was evaluated and shows a high EQE below 650 nm suggesting that Si-nc could be an interesting candidate for an the third generation photovoltaic solar cells.