PHOTOLUMINESCENCE OF HIGH POROSITY AND OF ELECTROCHEMICALLY OXIDIZED POROUS SILICON LAYERS

It is shown that strong visible photoluminescence can be obtained directly from as-formed high-porosity porous silicon samples, without need for subsequent chemical dissolution. Light emission at wavelengths as short as 560 nm can be observed after further thinning of the silicon pore walls, but this emission vanishes quite rapidly upon oxidation in air. Much more stable luminescence characteristics have been found for porous layers with silicon walls thinned by an electrochemical oxidation process. With this method, the wavelength of the maximum light emission is determined by the anodic current density used, thus allowing a good control of the luminescence characteristics.