The optical and electrical variation green and blue silicon quantum dot (Si-QD) based MOSLED with the different thickness of SiOx layer has been demonstrated. The turn-on voltage of the Si-QDs based MOSLED with the different RF plasma power is linearly enlarged by increasing the thickness of the SiOx layer. The turn-on electric field is still constant at 6.6x106 V/cm. The EL emission power of the blue Si-QD based MOSLED with increasing the thickness form 150 nm to 350 nm enhances from 55 nW to 470 nW due to the larger Si-QD amount from 1.5x1018 cm-3 to 4.3x1018 cm-3 in higher thickness. The blue Si-QDs based MOSLED with the SiOx thickness of 350 nm has the maximum EL power of 470 nW. The EL wavelength of the blue Si-QD based MOSLED red-shifts from 420 nm to 450 nm when the SiOx thickness increasing from 150 nm to 350 nm. The red-shifted phenomenon on EL spectra with increasing the thickness could be explained by means of the relationship between the varied Si-QD size and degraded electron conductivity. The EL wavelength of the Si-QD based MOSLED has a band filling effect phenomenon by the increment of the biased current and thickness. The distribution of Si-QD was uniform in whole SiOx layer although there existed different Si-QD size.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.