Further enhancement of light extraction efficiency of light-emitting diode with Ag film grown on photonic crystals

Photonic bandgap of photonic crystals (PCs) and the effect of grating diffraction can be used to improve the extraction efficiency of the light from a light-emitting diode (LED). The transmission of light at certain wavelength through periodic sub-wavelength hole arrays in metal films is extraordinary, because the surface plasmon acts effectively. In this letter, PCs with the square lattice of cylinder unit cells are placed in GaN layer of GaN-based blue LED, and the silver film is plated on PCs. The finite-difference time-domain (FDTD) method is used to investigate the optical transmission; the results show that the extraction efficiency of the PC-assisted LED (PC-LED) is enhanced when the silver film is plated on the PCs under certain conditions. Finally, we use the surface plasmon dispersion relation to analyze the mechanism of antireflection.