Enhancement of the photoluminescence properties of porous silicon by silica gel coating

We have spin coated silica gel films of ∼10 μm onto porous silicon (PS) substrates with photoluminescence (PL) emissions peaks in the 600-700 nm spectral range, producing a 20-fold enhancement of the original intensity in the shorter wavelength end. We attribute this enhancement to the reduced nonradiative recombination that follows the interface passivation of the PS surfaces by an oxygen enriched Si Ox (x→2) layer of silica gel. The PL stability of enhanced substrates was significantly improved by sputtering the samples with Si O2 after the silica gel spin coating, which resulted in a final blueshift of the PL. The technique described herein is a cost effective method for producing passivated photoluminescent enhanced silicon structures that can be used for optoelectronic applications.