Formation of antireflection structures for silicon in near-infrared region using AlOx/TiOx bilayer and SiNx single-layer

Abstract Antireflection (AR) layers for Si were investigated for applications in optical communication in the wavelength range of 1270–1330 nm. The Essential Macleod software was used to find the optimal thicknesses of the AR coatings with two different structures of AlOx/TiOx bilayer and SiNx single-layer. The simulations revealed reflectances lower than 0.5% for both AlOx/TiOx and SiNx AR structures. Furthermore, atomic layer deposition and plasma-enhanced chemical vapor deposition were used to grow the AlOx/TiOx and SiNx layers, respectively. For the fabricated structures, average reflectances of 0.2% (AlOx/TiOx) and 0.3% (SiNx) were achieved in the wavelength range of 1270–1330 nm. For the AlOx/TiOx bilayer, a lower transmittance of ~88% was obtained, compared with that of the SiNx single-layer of ~99%. An additional air annealing at 300 °C for 2 h led to a crystallization of the amorphous TiOx into anatase phase, which yielded an improved transmittance of ~99%, comparable with that of the SiNx single-layer structure. X-ray photoelectron spectroscopy revealed that the oxidation state of Ti in TiOx influenced the absorption in the near-infrared region.