Porous silicon passivation for applications in sensors and photovoltaics: Optical characterization

Porous silicon monolayers with different porosities were produced by etching p-type crystalline silicon (c-Si) in HF-based electrolytes. Mesoporous structures were achieved in heavily doped c-Si anodized into HF:ethanol, whereas for macroporous ones slightly doped c-Si was etched in HF and dimethylformamide solution. After electrochemical oxidation of them, it was found that depending on both the porosity and remaining cSi size, the thickness of them becomes contracted, while the reduction of the effective refractive index (ERI) is associated to the presence of silicon oxide within the structures. The optical reflectance of the as-etched, oxidized and polymer deposited macroporous silicon shows that they are excellent materials for sensor and photovoltaic application.