Enhanced Light Output of GaN-Based LEDs with Roughened Surface and Graded Refractive Index Nanostructures

• Main Authors: Yi-WenLo, 羅翊文
• Other Authors: Shui-Jinn Wang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/52516123208651906052

碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 101 === The present thesis is devoted to further improve the light output of light emitting diodes (LEDs). The use of SiO2/ZnO nanotube arrays (NTAs) which provides an efficient surface roughening scheme with the graded refractive index to effectively maximize light extraction efficiency through releasing total internal reflection (TIR) and minimize Fresnel loss was proposed and demonstrated. There are two parts comprised in this work. The first part focuses on the simulation and design of SiO2/ZnO NT As for LEDs. The optical simulation software, TracePro, was used to simulate the structures effects of SiO2/ZnO NT As (with different ZnO nanostructures and SiO2 coating thickness) on the light output efficiency of LEDs. An optimum design for SiO2/ZnO NT As with ZnO nanotube arrays and a deposited thickness of 60 nm has been obtained. The second part of the present study aims at the preparation of LEDs with SiO2/ZnO NT As. The hydrothermal growth method (HTG) was conducted to the p-GaN surface with ZnO NT As. A 60-nm-thick SiO2 layer with a typical refractive index of around 1.5 was coated on the ZnO NTs using a plasma-enhanced CVD system. Material analysis including surface morphology, components, transmittance, and photoelectrical properties of the prepared LEDs are examined and results are presented and discussed. A considerable improvement in Lop of proposed LEDs by 30.13% at 350 mA, as compared with that of the regular LEDs, has been achieved, which could be attributed to the SiO2/ZnO NT As structure can effectively release TIR and minimize the Fresnel loss. It is expected that the proposed SiO2/ZnO NTAs graded refractive index surface roughening could enhance the light output of GaN-based LEDs for application of solid state lighting.