In this work, nanostructures porous silicon (PS) layer is fabricated by (PEC) using 650nm laser diode at different illumination power densities for n-type silicon substrate of resistivity (10Ω.cm) and HF of 48.5% and ethanol(99%)(1:1). The morphological and optical and electrical properties are studied. These characteristics are studied by using our mathematical model which represents the electrical properties. The electrical properties of porous silicon layer are classify according to the structure properties and we prove that the electrical properties depend on the relative permittivity...