Enhancement Of Light Extracting Energy From LED By Using2D Photonic Crystal

Photonic crystals (PCs) has received increasing attention because of their rich physics as well as extensive applications. The remarkable feature of such artificial composites is their photonic band gaps, in which electromagnetic wave are prohibited. Based on this feature, photonic crystals have many applications in reality. For example, we can design laser diode and optical waveguide devices, but also optical filters and light switch. In recent years, PCs based on photonic band gaps, when used in light emitting devoid (LED), the light efficiency improved greatly, it become hot spot once again. Therefore, it is very significant to research the theory of photonic crystal band.We have studied the following two aspects in this paper. They are:(1) The complete band gap of2D photonic crystal;(2) Enhancement of light extracting from GaN based blue light emitting diodes by using Photonic crystal.To begin with, we put forward a kind of PC structure with elliptic air in2D square lattice. We can obtained optimized complete bandgap by adjusting the position of elliptic, the ratio of axial length, and the filling rate, when the filling rate F=0.608, the optimized complete band gap value is0.0332. This arrangement does not change C4v of the lattice symmetric structures. Compared with that of the low lattice symmetry, this is a new method to obtain completely band gap, we could obtain a complete band gap value in the situation of high lattice symmetry. Providing theoretical guidance for the design of photonic crystals and the application of photonic devices.Furthermore,3D-FDTD method based on the Yee algorithm with a perfectly-matched layer (PML)boundary condition is employed to simulate the light extracting energy (LEE) of three different structures of GaN based blue LEDs. The first one is a GaN based ordinary blue LED structure, the second one is a GaN based blue LED with prefect area photonic crystal (PPC) structure, the third one is a GaN based blue LED with defect area photonic crystal (DPC) structure. We find that the light extracting energy of LEDs with PPC structure enhanced little compared to that of without PC structure. In addition, the light extracting energy of blue LED with DPC structure was remarkably improved. Our results also give the parameters design principle of GaN based photonic crystal light emitting devoid (PC-LED) in theory.This study help us to understand the PC band structure further, and used better in LEDs to improve LEE.