Luminescent chemically-etched porous poly-crystalline silicon on insulating substrates

Polycrystalline silicon deposited on insulating substrates has been chemically-etched to form thin films of porous material exhibiting room temperature visible photoluminescence with emission wavelengths of around 650 nm. Material of 4000 Å thickness was quickly converted to porous silicon within 15 s of etching, with an etch rate of 1–1.5 µm/h. In contrast to anodization, chemical-etching parameters have little effect on modulating the resultant peak wavelength. Peak photoluminescence intensity was achieved 8–12 s of etching in 1:3:5 parts HF:HNO3:H2O at room temperature with ambient lighting. The chemical etching process and its etch characteristics have been discussed in relation to its suitability for large area thin film devices.