Study On Microstructure Of Moth-eye For Improving The External Quantum Efficiency Of LED

High-efficiency blue GaN-based LEDs have brought dramatic changes to human life,and solid-state lighting has great potential.LED to further replace the traditional lighting methods and the goal of more efficient LED,the external quantum efficiency must be further improved.To improve the external quantum efficiency,including two major aspects: the internal quantum efficiency and light extraction efficiency.Because the internal quantum efficiency is closely related to the properties of the semiconductor material and the epitaxial structure,the improvement of the internal quantum efficiency is mainly realized by the quality and structure of the semiconductor material.The internal quantum efficiency of GaN-based blue LED has exceeded 70% and tends to the theoretical limit with the continuous improvement of technology level and the continuous improvement of material quality.Therefore,the more effective way to improve the external quantum efficiency of the LED is to improve the light extraction efficiency.In order to improve the external quantum efficiency of LED,especially the efficiency of optical extraction,according to the equivalent medium theory in the LED passivation layer(SiNx)surface design and fabrication of frustum of a cone microstructure array.Through the simulation analyzes the micro structure of the fill factor of the bottom surface,bottom diameter,height and angle to improve light extraction efficiency of LED.The results show that when the microstructure of the fill factor of the bottom surface is 0.55,the radius of bottom surface is 220 nm the height is 245 nm,and the side slope angle is 70 degrees,the light extraction efficiency of the device is optimized.Which is 4.85 times as much as the device without surface microstructure.The sub-wavelength nanostructure is prepared on the surface of LED passivation layer by nanosphere lithography technology and the comparison test of electroluminescent between the proposed structure and LED chip without surface microstructure is carried out.The results show that the luminous efficiency of the samples with microstructure at 20 mA and 150 mA working current are 4.41 times and 4.36 times of the reference samples without microstructure.The calculated results and the experimental results are consistent,in the production of the LED passivation layer structure can effectively improve the light extraction efficiency,the external quantum efficiency is also improved accordingly.