Optical properties of porous silicon surface

The optical characteristics (transmission and reflection, absorption and scattering coefficients) of the Si nanowires obtained by electrochemical treatment of Si wafers were studied experimentally in spectral range 350-750 nm, using the different angles of incidence and measuring the angular distribution of the reflected (scattered) light. Theoretical treatment made on the basis of the Mie theory and some original modelling explains the characteristics determined and gives a simple method of estimation of refractive index of porous semiconductor layer created above the bulk specimen. The main conclusion is that the integrated light reflection from the P-Si surface is essentially smaller than the reflection from the bulk crystalline Si. Both theory and experiment show that the porous surface layer, although non-homogeneous and thus possessing the light scattering, acts as antireflection coating for Si, and could be used, in particular, in solar cells made from Si as well as from the other semiconducting materials.