Design of 'Chess-board' like Photonic Crystal Structure for Enhancement of LED Light Extraction

摘要

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/SiO_2 layer in conventional LED and on top surface of n-GaN layer in vertical LED. The results are compared with the LED structureswith 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 of0.6μm 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 SiO_2-on-p-GaN to avoid etching of p-GaN and it gives ~2.2 times enhancement in comparison to that of conventional LED.