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http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/68120
Title: | 綠光二極體銦含量及量子井厚度波動之分析 Analyzing the Source of Excess Voltage in Green LEDs |
Authors: | Shuan Wang 王瑄 |
Advisor: | 吳育任 |
Keyword: | 氮化鎵,量子井,發光二極體,三維模擬,量子井厚度波動, Light-emitting diodes,quantum well,Gallium Nitride,3-D model,alloy fluctuation,thickness fluctuation, |
Publication Year : | 2017 |
Degree: | 碩士 |
Abstract: | To complete a better simulation for GaN-based MQW LEDs, we developed 3-D model considering alloy fluctuation and thickness fluctuation. The model is based on 3D-DDCC solver and combined with localization landscape equation. The equation is a Schrodinger-like equation and is used to deal with carrier localization in quantum wells. The solver solves Poisson’s equation, landscape equation and
drift-diffusion equation iteratively to obtain results. The simulation results include the distribution of potential, carrier, current, recombination, etc. The indium atoms in InGaN QW layers are not uniformly distributed, which is called alloy fluctuation. To consider this phenomenon in simulation, we developed a random alloy generation program and combined it with the model. Along with Gmsh, 3D FEM strain solver and 3D landscape Poisson drift-diffusion self-consistent solver, the model is constructed to solve GaN-based MQW LED problem. In chapter 3, we ran simulations for 5QWs green LED and discussed the simulation results. The effect of alloy fluctuation can be observed in the distribution of potential and carrier. However, the voltage is still too high compared to experiment reports. We further considered quantum well thickness fluctuation in the model and studied the effect to carrier transport. We designed two types of thickness fluctuation and extended the period from 30 nm to 70nm. The electron transport is greatly improved in the case with large period of thickness fluctuation. Better electron transport increases the overlap of electrons and holes and the voltage drops obviously. On the other side, the quantum efficiency decreases due to the shrink of radiative recombination volume. Carrier densities increase in the volume and cause stronger Auger recombination. With alloy fluctuation and thickness fluctuation considered, the simulation of GaN-based 5QW green LED is completed. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/68120 |
DOI: | 10.6342/NTU201704401 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 光電工程學研究所 |
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ntu-106-1.pdf Restricted Access | 2.35 MB | Adobe PDF |
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