Effects of symmetry, shape, and structural parameters of two-dimensional SiNx photonic crystal on the extracted light from Y2O3:Eu3+ film

This study examined the effects of the triangular- and square-lattice symmetries as well as the nanorod and airhole shapes of two-dimensional (2D) SiNx photonic crystal layers (PCLs) on the light extraction efficiency of thin-film phosphors (TFPs) in an attempt to improve the light extraction efficiency from the phosphor side of an Y2O3:Eu3+ thin film. Triangular-lattice and square-lattice 2D SiNx nanorods/airholes were fabricated as PCLs on sol-gel derived Y2O3:Eu3+ TFPs using different combinations of the following processes: nanosphere lithography or laser interfering lithography, mask fabrication, and reactive ion etching. The integrated light efficiency of the triangular lattice was approximately 1.33 and 1.64 times as high as that of the square lattice for the nanorods and airholes. The greatest improvement in the phosphor-side extraction efficiency of the Y2O3:Eu3+ TFPs was obtained by adding triangular-lattice 2D SiNx airhole PCL arrays. The angular distribution of the light emitted from the various types of 2D SiNx PCL-coated Y2O3:Eu3+ TFPs was also investigated to better understand the effects of the symmetry and shape of the 2D PCLs on the viewing angle of the light emitted from the Y2O3:Eu3+ thin films. Moreover, the effects of structural parameters, including the dielectric-areal fill factor and lattice parameter (below cutoff size and above 1.0 mu m size, as well as the optimum size of triangular lattice) of the 2D SiNx PC arrays, on the extraction efficiency of the Y2O3:Eu3+ TFPs were investigated to improve the scattering capability of the leaky modes as a function of the structural parameters. This enhanced extraction efficiency was attributed to the scattering of the forward emission excited directly by inward UV and the scattering of re-excited forward emission by backscattered UV through the leaky and/or Bragg scattering produced by the 2D periodic array.