Hybrid absorption/interference wide-angle filter using PECVD Si-Rich Si_xN_y and SiO_x for LED lighting

We propose a method to fabricate interference filters using Plasma Enhanced Chemical Vapor Deposition (PECVD) to reduce blue and near-infrared wavelengths that are inherent to LED lighting, but that have a negative impact on human health and the environment respectively. We developed a Si-rich silicon nitride (Si-rich Si_xN_y) material, with a very high refractive index, a high extinction coefficient in the blue range and a very low extinction coefficient in the rest of the spectrum. We combined this Si-rich Si_xN_y with silicon oxide (SiO_x) to realize an LED interference filter. The use of a material with a selective absorbance and high refractive index allows a simple fabrication process of the filter composed of six layers only, even for a complex spectral response. Moreover, the filter response is uniform and tolerant to incidence angle variation. With this work, we demonstrate the high potential of PECVD technique for the fabrication of low cost and reproducible interference filters that could be used in various applications.