Blue Luminescence from Photochemically Etched Silicon

Light-emitting layers are formed by the photochemical etching of Si in HF with H2O2 as an oxidant under the irradiation of a He–Ne laser (633 nm, 18.4 W/cm2). Photoluminescence (PL) using a He–Cd laser (325 nm) from the etched layer has a peak wavelength at 640 nm and a wide full-width at half maximum (FWHM) of approximately 0.3 eV. The peak position and the wide FWHM from the etched layer are considered to be similar to those from porous silicon. The PL peak wavelength can be varied from 700 nm to 640 nm by increasing the etching time, so that red or yellow luminescence can be observed in daylight. The etched layer formed with H2O2 emits blue photoluminescence at 440 nm after being dipped in an ethanol for 17 h, and the blue light emission can be seen in air. The visible luminescence of the photochemically etched layers can be explained by the well-known quantum size effect of nanocrystalline Si.