Excitonic Contribution of Nanosilicon on Light Emitting Properties

Abstract

A phenomenological model is developed by integrating the effect of excitonic energy states, localized surface states and quantum confinement (QC) to obtain an analytical expression for the room temperature photoluminescence (PL) intensity. We calculate the binding energy of strongly confined excitons in silicon (Si) quantum dots (QD) having sizes 1 to 7.75 nm to examine its contribution on optical band gap and electronic properties. The band gap with excitonic contribution is found to decrease as much as 0.23 eV for the smallest dot. The effect of exciton states explains almost accurately the experimental PL data. Our model provides the mechanism for controlling the PL intensity through fitting parameters. Huge excitonic effects, which depend strongly on QD size and shape, characterize the optical spectra. The results for the size dependence of the optical band gap, the PL intensity, and oscillator strength are presented the role excitonic effects on optical and electronic properties are discussed.