Design, Fabrication and Optical Characterization of Photonic Crystal Patterned Ultra-Thin Silicon

In this work, significant enhancement in absorption, especially in the near infra-red region, is achieved for ultra-thin crystalline silicon of various thicknesses using a photonic crystal structure. This is realized by patterning the silicon with close-packed inverted pyramid structuring, wherein the lattice spacing is comparable to the wavelength of the near infra-red light, which results in strong wave-interference-based light trapping. Absorption enhancement of more than a factor of two in the spectral range of 1000–1100 nm is achieved without any other optical enhancments. Details on the techniques used to realize the ultra-thin silicon, the fabrication of the inverted pyramids using standard photolithography and a complete optical analysis are reported in this work.