Study On Enhancement In Extraction Efficiency Of Led By Photonic Crystal Technology

Semiconductor light-emitting diodes(LEDs) are new solid-state light sources which have been broadly used in different fields, causing the technological revolution to the lighting history. But in the application, the efficiency is much lower than traditional light sources, it has become the bottleneck which influence the extensive uses. So much attention has been paid to enhancing the efficiency of LED. Based on this background, one dimensional phtonic crystals and two dimensional photonic crystal are investigated to enhance the efficiency of LED, the influence of photonic crystal structure parameters on extraction efficiency is investigated to obtain the optimizing structure, and superiority of the PC LED is proved by optical simulation.First, the luminescence principle of LED base on the band theory is analyzed and introduce the performance index of LED. The mathematic model of electronic-optic efficiency is established, and then, the influence of internal quantum efficiency and extraction efficiency on electronic-optic efficiency is investigated. The photonic crystal is employed to increase the extraction efficiency of LED and the factors of influence extraction efficiency are analyzed.Second, the narrowband reflection characteristic of one dimensional photonic crystal is used to reflect the light which incident from active layer to the substrate to reduce the light absorption of substrate and electrode. The reflection characteristic of one dimensional photonic crystal is investigated using transmission matrix, on that basis, the structure of one dimensional defect photonic crystal is designed and the reflection of the light which incident at any angle is achieved by parameter optimizing. Third, the light of guiding mode is diffracted off the chip by the diffraction properties of two dimensional photonic crystal. The diffraction efficiency is analyzed based on rigorous couple-wave theory and equivalent medium theory. The PC structure is fabricated on the surface of normal LED, by choosing the proper lattice constant and depth of air hole to obtain the maxium diffraction efficiency.At last, the structure of LED with one dimensional defect PC and two dimensional PC is designed, and meanwhile, simulate the optical property by Tracepro. Compared with noramal LED, the superiority of the PC LED is obviously.