Design of “Chess-board” like photonic crystal structure for enhancement of LED light extraction

In this paper, we use Finite-Difference Time-Domain(FDTD) method to study light extraction enhancement in GaN-based LEDs. We have proposed a novel Chess-board like photonic crystal structure on top surface of p-GaN/SiO₂ layer in conventional LED and on top surface of n-GaN layer in vertical LED. The results are compared with the LED structures with conventional 2-D photonic crystal (PhC) structures and conventional LEDs. Results from these simulations show that the maximum light extraction for conventional LED with the Chess-board like structure occurs for a grating period of 0.6μm with a grating-depth of 0.18 μm, which gives ~ 4 times enhancement compared to that of conventional LED and 1.2-1.4 times compared to that of LED with conventional2-D photonic crystal. For vertical LED, the maximum enhancement in light extraction occurs for the same grating-period with a depth of 0.5 μm, which is ~ 3.5 times compared to that of the conventional vertical LEDs. We have also simulated our proposed structure on top of SiO₂-on-p-GaN to avoid etching of p-GaN and it gives ~2.2 times enhancement in comparison to that of conventional LED.