Size-Dependent Photoluminescence of Self-Trapped Excitons and Charge Retention of Si Nanocrystals in SiO[sub x] Films

Temperature-dependent μ-photoluminescence of self-trapped exciton (STE)-based radiation in Si nanocrystals (Si-nc's) with sizes enlarging from 2.3 to 4.5 nm is demonstrated, while the monotonically decreasing trend of the STE activation energy (from 1.75 to 1.2 meV) with Si-nc size-dependent dielectric permittivity is elucidated by a Bohr hydrogen-like atom model. Charge accumulation induced capacitance hysteresis accompanied by lengthened retention is observed when the Si-nc size exceeds 2.3 nm. A modified flatband voltage shift model corroborates the proportionality of the charge density with the third power of the Si-nc size, supporting the fact that the Si-nc volume is more pronounced than the Si-nc density for charge retention.