A new approach to the analysis of light collected by textured silicon surfaces

The light backscattered by different types of textured crystalline silicon samples was investigated with the aim to find a correlation between light collection and light backscattering properties. Different families of texture geometry were considered: inverted pyramids, hemispherical wells, and porous silicon. For each texture family, different samples were prepared with a different amount of texture surface coverage. Textured samples were analyzed by measuring the light intensity angular distribution, the total reflectance and the diffused component of reflectance, by using optical apparatus specifically devoted to these measurements. Unpolarized laser beams at 543 nm, 633 nm and 1064 nm, incident orthogonally to the silicon surface, were used in the experiments. In order to make a quantitative investigation of the light backscattering properties, simple models of scattered light angular distribution were considered, corresponding to ellipsoids of revolution characterized by a single parameter, the ratio between minor and major axes (aspect ratio). The total light collection, corresponding to each specific texture geometry, shows a simple linear behavior respect to a parameter obtained from the product of the aspect ratio with the diffused component of reflectance. The found correlation is considered an interesting empirical result even though a clear understanding of the optical phenomena underneath has not been achieved yet.