Broadband control of the optical properties of semiconductors through site-controlled self-assembly of microcrystals

We investigate light-matter interactions in periodic silicon microcrystals fabricated combining top-down and bottom-up strategies. The morphology of the microcrystals, their periodic arrangement, and their high refractive index allow the exploration of photonic effects in microstructured architectures. We observe a notable decrease in reflectivity above the silicon bandgap from the ultraviolet to the near-infrared. Finite-difference time-domain simulations show that this phenomenon is accompanied by a ∼2-fold absorption enhancement with respect to a flat sample. Finally, we demonstrate that ordered silicon microstructures enable a fine tuning of the light absorption by changing experimentally accessible knobs as pattern and growth parameters. This work will facilitate the implementation of optoelectronic devices based on high-density microcrystals arrays with optimized light-matter interactions.