ENHANCED PHOTOEMISSION FROM SHORT-WAVELENGTH PHOTOCHEMICALLY ETCHED POROUS SILICON

The visible photoluminescence (PL) from p-type porous Si is up to 100 times brighter if the p-Si substrate is irradiated with blue (450 nm) light during electrochemical preparation. The PL spectrum is also shifted to the blue by ca. 80 nm relative to a sample etched under comparable conditions in the dark. Red (700 nm) illumination during the etch has no effect on the subsequent PL spectrum. The surfaces of all these samples are much smoother and the PL is brighter than luminescent porous Si prepared via an initial electrochemical etch and subsequent chemical etch. Atomic force microscope images indicate that the surface of the short-wavelength photochemically etched porous Si is significantly stronger than Si etched in the dark. The increased PL intensity is attributed to photocorrosion of electrically isolated Si regions close to the surface of the porous Si layer.