Main purpose of this work is to measure and analyze different wavelength InGaN/GaN light emitting diode spectrum characteristics of spontaneous emission. We can extract density of states and junction temperature from light-emitting diode spontaneous emission spectrum.
Ideal quantum well structure of the spontaneous emission spectrum, by a step function and exponential decreasing function of u(hv-E)、e^(-hv/KT) multiplied by the composition. Spontaneous emission spectrum will be divided by the exponential decreasing function to e^(-hv/KT) analyze the distribution of low energy tail of the energy gap and blue shift. According to the result, we investigate the blue shift is caused by the piezoelectric effect (piezoelectric polarization) or the band filling effect (localized states). The experimental results reveal, InGaN/GaN LED's joint density of states will change with the increase of indium. And joint density of states can also cause changes in the blue LED shift will also change. Therefore may judge InGaN/GaN LED blue shift the phenomenon is the piezoelectric effect (piezoelectric polarization) creates.
目錄
指導教授推薦書
口試委員會審定書
授權書………………………………………………………………… iii
致謝……………………………………………………………………iv
中文摘要……………………………………………………………v
英文摘要………………………………………………………………vi
目錄……………………………………………………………………vii
圖目錄…………………………………………………………………viii
第一章 導論…………………………………………………………… 1
1-1前言………………………………………………… 1
1-2 背景簡介……………………………………………… 2
1-3 研究動機………………………………………… 6
1-4 InGaN材料特性…………………………………………………6
1-5研究儀器介紹…………………………………………………9
第二章 理論基礎………………………………………………………13
2-1光學性躍遷……………………………………………………13
2-1.1 光的能態密度………………………………………………15
viii
2-1.2 自發性輻射…………………………………………………21
2-1.3 吸收係………………………………………………………25
第三章 實驗量測與理論分析…………………………………………27
3-1 InGaN/GaN發光二極體變溫發光特性………………………28
3-2 InGaN/GaN發光二極體能態密度變電流特性………………29
第四章 結論…………………………………………………………43
4-1 結論……………………………………………………………43
參考文獻……………………………………………………………… 44
ix
圖目錄
第一章 導論
Fig1-1 電致螢光EL圖……………………………………………… 11
Fig1-2 (a)單色分光儀結構圖(b)單色分光儀工作原理………………12
第二章 理論基礎
Fig2-1 (a)自發輻射，(b)受激輻射，(c)受激吸收……………………15
Fig2-2 自發輻射E-k圖………………………………………………18
Fig2-3 二維能態密度圖形……………………………………………21
Fig2-4 理想二維量子井的自發輻射圖………………………………24
第三章 實驗量測與理論分析
Fig3-1 InGaN/GaN紫光LED變溫EL(nm)……………………………31
Fig3-2 InGaN/GaN紫光LED變溫EL(eV)……………………………32
Fig3-3 InGaN/GaN紫光LED變溫EL(eV)半對數座標圖……………32
Fig3-4 300K實驗值取高能量斜率範例圖…………………………33
Fig3-5接面溫度與環境溫度關係圖………………………………33
Fig3-6紫光(375nm)EL光譜圖……………………………………34
Fig3-7藍光(454nm)EL光譜圖……………………………………34
Fig3-8綠光(517nm)EL光譜圖…………………………………………35
Fig3-9 3紫光(375nm) optical joint density of stat圖……35
x
Fig3-10藍光(454nm) optical joint density of stat圖…………………36
Fig3-11綠光(517nm) optical joint density of stat圖…………………36
Fig3-12紫光(375nm) localized states + piezoelectric field……………37
Fig3-13藍光(454nm) localized states + piezoelectric field……………37
Fig3-14綠光(517nm) localized states + piezoelectric field……………38
Fig3-15紫光(375nm) piezoelectric field乘上波茲曼分布……………38
Fig3-16藍光(454nm) piezoelectric field乘上波茲曼分布…………39
Fig3-17綠光(517nm) piezoelectric field乘上波茲曼分布…………39
Fig3-18紫光(375nm) piezoelectric field乘上波茲曼分布光譜………40
Fig3-19藍光(454nm) piezoelectric field乘上波茲曼分布光譜…… 40
Fig3-20 綠光(517nm) piezoelectric field乘上波茲曼分布光譜………41
Fig3-21 紫光(375nm)實際SHIFT與piezoelectric field模擬SHIFT…41
Fig3-22藍光(454nm)實際SHIFT與piezoelectric field模擬SHIFT…42
Fig3-23綠光(517nm)實際SHIFT與piezoelectric field模擬SHIFT…42
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