This disclosure enables high-productivity fabrication of semiconductor-based separation layers (made of single layer or multi-layer porous semiconductors such as porous silicon, comprising single porosity or multi-porosity layers), optical reflectors (made of multi-layer/multi-porosity porous semiconductors such as porous silicon), formation of porous semiconductor (such as porous silicon) for anti-reflection coatings, passivation layers, and multi-junction, multi-band-gap solar cells (for instance, by forming a variable band gap porous silicon emitter on a crystalline silicon thin film or wafer-based solar cell). Other applications include fabrication of MEMS separation and sacrificial layers for die detachment and MEMS device fabrication, membrane formation and shallow trench isolation (STI) porous silicon (using porous silicon formation with an optimal porosity and its subsequent oxidation). Further the disclosure is applicable to the general fields of Photovoltaics, MEMS, including sensors and actuators, stand-alone, or integrated with integrated semiconductor microelectronics, semiconductor microelectronics chips and optoelectronics.