## 1 Introduction  
Besides bulk processing, the physicochemical properties of silicon can be customized for specific applications by altering its surface [1]. Porous silicon (PSi) is a highly adaptable material with diverse applications, especially in the biomedical and photonics fields [2, 3]. Its utility stems from its ability to be easily adjusted to meet specific electrical, optical, and thermal requirements [4, 5]. For instance, several sensing devices leverage the optical and electrical properties of PSi to detect variations in chemical and biological samples [6], including even minute changes in gas molecules through surface modifications [7]. In photonics, PSi is incorporated into gamma ray detectors [8], photonic crystals [9, 10], and waveguides [11]. The characteristic photoluminescence and efficient light trapping capabilities of PSi make it ideal for use in next-generation solar cells and photodetectors [12, 13, 14, 15]. There are several effective techniques for creating porous silicon, including metal-assisted chemical etching [16], reactive ion etching [17], the sulfur-template method [18], metal-assisted electrochemical etching [19], and electroless chemical etching [20]. Most of these methods rely on dry etching or electrochemical processing [1]. Dry etching requires a hard mask to define the pore structure, whereas electrochemical methods use hydrofluoric solutions and an external power source to drive the reaction [21]. Since the first discovery of PSi in 1950s [22], there is an intensive research efforts to investigate the effect of each parameter of the electrochemical process of silicon surface [23; 24; 25]. The electrochemical process can be fine-tuned by adjusting the etching current density (J), etching time (t), temperature, and electrolyte composition [3; 23]. The main advantage of this process is the ability to produce porous silicon using a diluted electrolyte of hydrofluoric acid (HF) [23]. The parameters of the electrochemical process can be divided into two main categories, the electrical and chemical parameters [26]. The chemical part of the process include the mix of hydrofluoric acid (HF) with other solvents such as ethanol (ETOH) and dimethylformamide (DMF). The concentration and percent of each solvent are the main parameters for this mixture [27]. Focusing on the electrical parameters, we found that the anode and cathode type and their shapes greatly affect the current distribution on the substrate surface and result in diverse nano/micro structures [28; 29]. In this aspect, the conventional electrochemical reaction setup has the following design: counter electrode (metal)/electrolyte/working electrode (substrate). If the substrate is from a poor conductive material, such as silicon, we apply an ohmic contact to enhance the electrochemical reaction. Then, the final setup becomes as follow: metal/electrolyte/substrate/metal. When applying this configuration to silicon substrates, the electrolyte typically consists of an HF solution. As a result, the cathode material must be an inert metal that can withstand this corrosive acid. This resulted in limited options for the cathode material, with platinum (Pt) as conventional choice [24; 30]. Consequently, the fabrication on large scale is limited because of the high cost of Pt electrodes. Exploring alternatives for this crucial component of the electrochemical cell could enable scalable and cost-effective fabrication of these layers. Moreover, it could result in variations in the characteristics of the fabricated layers. Scaleable fabrication, cost-efficiency, and structural variations all have an impact on the physical properties of PSi and its potential applications. Current work presents a cost-effective modification in the electrochemical etching process that can produce a large area nanostructured PSi layer with better uniformity. The main idea is to employ heavily doped silicon wafers as a counter electrode instead of expensive Pt wires to have a symmetric anode/cathode setup in the form: Al/Si/electrolyte/Si/Al.