Optimizing Optical and Electrical Properties of Porous Silicon by Enhancing Morphology through Substrate Type and Electro-Etching Control

Porous silicon films are heavily used in technology. Their optical and electrical characteristics should be manipulated based on their application. Such characteristics can be tailored by controlling their morphology and porosity. Various types of monocrystalline Si substrates, with (110) face and 500–550 μm thickness, with different doping concentrations and resistivity values, have been used here to prepare porous silicon films with various characteristics. Preparation conditions, such as etching time, current density, light exposure, and HF concentration in ethanol, have also been varied. Macro-, meso-, and nanoporous films were selectively prepared by controlling the preparation conditions. Measured optical and electrical characteristics for the film are affected by its morphology and porosity. The film morphology and porosity can in turn be varied depending on preparation conditions, despite the substrate resistivity and doping concentration. Among various prepared films, the nanoporous film exhibits best characteristics in terms of high uniformity, low reflectance, and low sheet resistance (28.76 Ω/sq), despite its high substrate resistivity. Porous silicon characteristics can thus be tailored as desired for optoelectronic applications, simply by controlling preparation conditions.