EFFECT OF IRRADIANT WAVELENGTH DURING POROUS SILICON FORMATION

Photoelectrochemical etching of silicon using light assistance of vari ous wavelengths has been studied. As the etching process proceeds, a b lueshift is noted in the photoluminescence spectra. However, after a c ertain period of etching, under a fixed current density, a saturation point is reached, below which no further shift to higher energies is d etected. This cutoff point occurs at approximately 2 eV, even if a muc h higher energy irradiant light source is used during the formation pr ocess. These results provide strong evidence for the surface-state mec hanism of luminescence and render the pure quantum confinement model u nlikely. (C) 1997 American Institute of Physics.