Enhanced Light-trapping with Conformal ALD Coating of Black Silicon by High-k Metal Oxides

We present investigations of optical properties of black silicon (b-Si) nanostructures passivated with several high-k metal oxides (Al2 O3, TiO2, HfO2 and Sc2 O3), obtained by atomic layer deposition (ALD) method. The reflectivity was studied using the finite difference time domain (FDTD) method as well as experimentally, where Si wafers was structured by reactive ion etching method for b-Si fabrication. Modeling and measurements show improvements in the antireflection properties of thin-film/b-Si nanostructures over a wide range of light wavelengths. TiO2, HfO2 and Sc2 O3 films provide a good alternative to Al2 O3 as passivating materials and antireflection coatings.