Optoelectronic applications of porous polycrystalline silicon

We report visible light emission from porous structures formed in bulk and thin-film polycrystalline silicon materials by anodic etching in an HF:ethanol solution. Our results indicate photoluminescence (PL) peaks at wavelengths between 650 and 655 nm and with intensities comparable to those typically obtained from porous samples of single-crystal silicon. The analyses of the surface morphology of porous polycrystalline silicon (PPSI) layers suggest that the etch rate could be preferentially greater at the grain boundaries. We have illuminated PPSI films formed on quartz substrates from both the front and rear of the samples and have measured PL emission from the same corresponding sides. Luminescent polycrystalline silicon films offer the possibility of integrating a novel Si-based flat-panel display along with the recently developed thin-film transistor (TFT) driver circuitry on a glass substrate. In addition, nanostructures originating from polycrystalline silicon substrates may enable low-cost fabrication of highly efficient photovoltaic cells.