Absorption enhancement in ultra-thin film Si slabs using novel photonic crystal textures

We perform rigorous coupled wave analysis (RCWA) and finite-difference time-domain (FDTD) calculations on thin (<; 200 nm) slabs of Si with various wavelength scale texturing. Traditional photonic crystal patterning is investigated and compared to a flat Si slab with a double layer anti-reflection coating. These traditional photonic crystal lattices are then modified with superlattice which further improve the absorption. We also investigate the angular spectra of select lattices and show how resonant absorption peaks shift with incident angle. It is concluded that alternate photonic crystal texturing can lead to significantly enhanced absorption over planar slabs with optimized anti-reflection coatings.