臺灣博碩士論文加值系統

本論文主要在研製垂直導通型氮化鎵藍光發光二極體，並探討此元件之特性。我們使用雷射剝離技術來剝離氮化鎵磊晶片的藍寶石基板，搭配精密電鍍技術，將剝離下來的氮化鎵薄膜轉移到金屬銅基板上，製作p型在下的氮化鎵/鏡面/銅結構發光二極體元件。將這種大面積垂直導通型之氮化鎵/鏡面/銅的發光二極體與傳統氮化鎵/藍寶石基板結構比較起來，其在20 mA之正向電壓分別為2.87及2.76 V，而在350 mA則分別為4.5及4.4 V，顯示出其操作電壓相差不大，意味串聯電阻並不會因為垂直導通的元件設計而變大。至於其在‐5 V反向偏壓時之漏電流則分別為33.8及77.6 nA，這顯示出藉由這樣的製程設計之可行性。另外，在20 mA時氮化鎵/鏡面/銅顯示比氮化鎵/藍寶石基板發光二極體高出2.7倍的發光強度，而輸出功率也隨著注入的電流至500 mA仍持續線性增加，並高於傳統結構有2倍之多，其中，傳統的氮化鎵/藍寶石基板結構發光二極體呈現先達到飽和的狀態，在並經由不同電流注入之激發光譜圖，得到大面積垂直導通型氮化鎵/鏡面/銅基板結構的發光二極體於大電流操作下，仍維持波長持續藍移之現象，顯示其在大電流操作下的穩定性，這也顯示經由置換銅基板結構後的氮化鎵發光二極體將有較佳的散熱效應，此即歸因於銅基板有良好的熱傳導係數。

A vertical conducting GaN/mirror/Cu LED fabricated using the laser lift-off and electroplating techniques is demonstrated. The selective p-GaN top area was first electroplated by a thick copper film, and then a UV laser was employed to separate the GaN thin film from the sapphire substrate. The forward voltages (@ 20 mA) of the original GaN/sapphire and p-side-down GaN/mirror/Cu LED samples were 2.76 and 2.87 V, respectively. These results indicated that the series resistance of the GaN/mirror/Cu LEDs does not arise greatly with the present vertical conducting structure. The leakage currents (@ -5 V) of the original GaN/sapphire and p-side-down GaN/mirror/Cu LED samples were 77.6 and 33.8 nA, respectively. This suggests that the present device structure will not result in additional leakage current in the GaN/mirror/Cu LED device. The luminance intensity of the vertical conducting p-side-down GaN/mirror/Cu LED presented about 2.7 times in magnitude as compared with that of the original GaN/sapphire LED (@ 20 mA). The light output power for the GaN/mirror/Cu LED was about twofold stronger (@ 500 mA). A more stable peak wavelength shift under high current injection was also observed. These results indicated that large-area copper substrate LEDs have better thermal management and good heat sink.

第一章 緒論 1
1-1 前言 1
1-2 發光二極體之歷史回顧及發展 1
1-3 研究背景與動機 4
1-4 本論文之研究方向及架構 8

第二章 發光二極體理論模型簡介 17
2-1 光電特性 17
2-2 金屬與半導體接面之影響 19
2-2-1 金屬/半導體接觸之原理 19
2-2-2 歐姆接觸之原理 20
2-3 發光二極體之發光機制 22
2-4 熱效應對發光二極體之影響 24

第三章 雷射剝離氮化鎵薄膜 33
3-1 前言 33
3-2 雷射剝離技術之原理及方法 33
3-3 雷射剝離氮化鎵薄膜之試片製備 34
3-4 雷射剝離氮化鎵薄膜試片之分析 35
3-4-1 掃描式電子顯微鏡對雷射剝離氮化鎵薄膜之分析 35
3-4-2 原子力顯微鏡對雷射剝離氮化鎵薄膜之分析 36
3-4-3 雷射剝離氮化鎵薄膜之光激發光譜特性量測 37
3-4-4 穿透式電子顯微鏡對雷射剝離氮化鎵薄膜之分析 38

第四章 垂直導通型氮化鎵發光二極體之研製 49
4-1 前言 49
4-2 元件製程 49
4-2-1 氮化鎵試片之磊晶結構 49
4-2-2 試片之清洗 49
4-2-3 平台蝕刻 50
4-2-4 平台側壁之保護 51
4-2-5 電鍍銅基板 51
4-2-6 雷射剝離藍寶石基板 52
4-2-7 電極製作 52
4-2-8 氮化鎵/藍寶石結構發光二極體元件之製作 53
4-3 製程結果與討論 53
4-3-1 p型氮化鎵歐姆接觸 53
4-3-2 氮化鎵薄膜基板轉移之附著問題 54
4-3-3 GaN/mirror/Cu發光二極體側壁保護層之失效 56
4-3-4 GaN/mirror/Cu發光二極體製程之改善 56
4-4元件特性探討 57
4-4-1 電流-電壓特性 57
4-4-2 發光強度分析 58
4-4-3 發光光場圖形分析 60
4-4-4 光輸出功率 60
4-4-5 熱效應之影響 61
4-4-6 元件表面溫度之量測 62
4-4-7 GaN/mirror/Cu元件可靠度測試 62
第五章 結論 82

參 考 文 獻 84

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