臺灣博碩士論文加值系統

本論文研究對於氮化物系列之發光二極體(light-emitting diodes ，LEDs)實驗製出不同最後一層位障厚度。結果發現最後一層位障厚度為12奈米的元件，可以增加光輸出的功率。在操作電流100毫安培下12奈米之元件其光輸出功率是37.6毫瓦，比最後一層位障厚度為2奈米之元件其光輸出功率是34.2毫瓦還佳。而在效率下滑方面上，最後一層位障厚度12奈米和最後一層厚度為2奈米的相比，從41 %改善到37 %。最後一層位障為12奈米之元件能改善效率下滑的原因，歸因於增加了電子侷限之能力以及減少了電子漏電流。
因此主動層中的電子與電洞輻射復合率獲得改善，此外我們改變最後一層位障厚度。發現其順向電壓都是相近的，可以說明最後一層位障厚度變化對發光二極體的串聯電阻並不敏感。

In this research, nitride-based light-emitting diodes (LEDs) with different last barrier thickness were fabricated. It was found that the LEDs with 12-nm thick GaN last barrier can improve the light output power from 34.2 to 37.6 mW at 100 mA comparing to the LED with 2-nm thick last barrier. And the efficiency droop is improved from 41% to 37%. The improvement in efficiency droop of LEDs with 12-nm thick GaN last barrier can be attributed to the enhancement the electron confinement and reduction of electron leakage current. Therefore, the recombination rate of electrons and holes in the active regain is enhanced. Besides, the forward voltages of these fabricated LEDs are similar. It implies that the series resistance of the LED is not sensitive to the variation in last barrier thickness.

摘要………………………………………………………………………I
ABSTRACT...............................................I
致謝……………………………………………………………………III
目次……………………………………………………………………IV
圖目錄………………………………………………………………………………V
第一章 前言………………………………………………………1
1-1 論文組織架構……………………………...…………………………………..2
1-2 III-V氮化物介紹……………………………………………………………3
1-3 發光二極體工作原理……………………………………………………….…5
1-3.1 發光二極體內部與外部量子效率………………………………………7
第二章 效率下滑探討………………………………………………………………10
2-1 發光二極體效率下滑原因及探討……………………………………………10
2-2 抑制效率下滑方法概述………………………………………………………12
2-3 結論…………………………………………………………………………….19
第三章 發光二極體實驗製程與機台介紹………………………………23
3-1 金屬有機物化學氣相沉積(MOCVD)………………………………23
3-2 元件製作步驟………………………………………………………23
第四章 氮化鎵發光二極體光電特性量測與分析………………………27
4-1. 電流-電壓特性分析…………………………………………………27
4-1.1抗靜電測試…………………………………………………………29
4-2.光特性量測與分析…………………………………………………31
4-2.1電流發光波長特性……………………………………………31
4-2.2電流與半高寬的關係…………………………………………32
4-2.3 光輸出功率……………………………………………………34
4-2.4 外部量子效率…………………………………………………35
4-2.5造成元件亮度飽和之探討……………………………………37
4-3.改變環境溫度對發光二極體帶來的影響…………………………39
4-3.2 改變溫度對藍移的探討………………………………………43
4-3.3最後一層位障厚度對低溫環境之探討…….………………45
參考資料…………………………………………………………………48
第五章 總結………………………………………………………………52

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