Effective index approximation for ordered silicon nanowire arrays

A semi-analytical model for the optical properties of silicon nanowires (SiNWs) is presented. Results from the model offer a good physical understanding of the optical behavior of SiNWs. It is shown that light trapping within ordered nanowires only happens over a small wavelength band (20–75 nm) that is dependent on the diameter of the nanowires, not length. Furthermore, wavelength tunable absorption peaks can be achieved in ordered SiNWs by adjusting the geometrical parameters. A good match between the model and experimental results confirms the validity of the proposed effective index model.