Investigation on bandgap, diffraction, interference, and refraction effects of photonic crystal structure in...

In this paper, we have made a clear differentiation among bandgap, diffraction, interference, and refraction effects in photonic crystal structures (PhCs). For observing bandgap, diffraction, and refraction effects, PhCs are considered on the top p-GaN surface of light emitting diodes (LEDs), whereas for interference effect, hole type PhCs are considered to be embedded within n-GaN layer of LED. From analysis, it is observed that at a particular lattice periodicity, for which bandgap lies within the wavelength of interest shows a significant light extraction due to inhibition of guided mode. Beyond a certain periodicity, diffraction effect starts dominating and light extraction improves further. The interference effect is observed in embedded photonic crystal LEDs, where depth of etching supports constructive interference of outward light waves. We have also shed light on refraction effects exhibited by the PhCs and whether negative refraction properties of PhCs may be useful in case of LED light extraction.