The porosity-modulation technique has been applied to improve the emission properties of the previously reported surface-emitting cold cathodes based on electroluminescent porous silicon (PS) diodes. It is demonstrated here that by introducing a modified structure into the PS layer, the emission efficiency is significantly improved. An extremely high efficiency of 12% has been obtained. A significant decrease in the emission current fluctuation and a consequent increase in the durability of the emission are also observed. These results are due to a regulated electric field distribution near the outer surface of the PS layer.