Stimulated emission in porous silicon quantum dots:the role of trap states

Stimulated emission has been observed from porous silicon formed by irradiation and annealing when optically excited by a 514 nm laser. When the excitation intensity exceeded a threshold, very sharp peaks emerged in the emission spectra from 650～750 nm. The full width at half maximum(FWHM) of the emission park with Lorentzian shape is less than 0.5 nm. The sample has a special oxide structure which was fabricated by laser irradiation and annealing treatment on silicon. In the Fourier transform infrared spectroscopy(FTIR), some peaks emerge due to Si=O bonds and Si－O－Si bonds in the oxidation porous structure.Calculation shows that trap electronic states appear in the band gap of the smaller nanocrystal when double bonds or bridge bonds are formed between silicon and oxygen. The stimulat