臺灣博碩士論文加值系統

本論文探討紅光覆晶發光二極體(FCLED)；9 mil×6 mil之製備，元件完成後針對電流均勻性不佳之問題，以模擬軟體SpecLED探討不同n-GaAs分佈與電流均勻性的關係，並以實際元件證實藉由將n-GaAs蝕刻為特定圖案，有助於改善電流均勻性及光電特性，再將高反射率之Ag金屬取代原AuGe反射鏡提升光輸出功率，希望藉由模擬與實驗改善FCLED光電特性。製程探討方面，p型電極金屬的歐姆接觸若以傳統的AuBe/GaP達成，由於退火溫度過高，貼合晶片之高分子膠材將會產生氣泡，導致磊晶層破裂，因此採用Au/Cr/ITO鍍膜於p型GaP視窗層的方式達成歐姆接觸。 Mesa平台蝕刻若選用ICP(Inductively Coupled Plasma)雖然能減少底切現象，但無法精確的控制蝕刻深度，而溴水及甲醇混合溶液對磊晶層及ITO蝕刻選擇比高，進行蝕刻時可精確地停在ITO表面，因此Mesa平台蝕刻將選用濕蝕刻進行，但由於濕蝕刻會導致底切現象而減少發光區面積的，mesa蝕刻也分兩段式完成。本論文探討的 n-GaAs面積包含未蝕刻100%、面積蝕刻至17.7%、9.8%等三種情況，在操作電流為5mA時，不論是AuGe或Ag反射鏡，光輸出功率以n-GaAs面積降至17.7%為最佳，此情況下歐姆接觸面積足夠，且減少了吸光n-GaAs層之面積。於n-GaAs蝕刻面積為17.7%下，也對n-GaAs圖案進行電流均勻性討論，包含9個直徑為20 um圓以及25顆直徑為16 um圓，模擬軟體SpecLED分析結果以9個直徑為20 um圓有較佳的電流均勻性。n-GaAs面積100%光輸出功率為2.08 mW，蝕刻至17.7%，搭配電流均勻性較佳的n-GaAs圖案9顆直徑為20 um圓，光輸出功率為2.20 mW，而後將AuGe反射鏡置換為Ag光輸出功率為2.38 mW，藉由環氧樹脂減少全反射光輸出功率可進一步提升為2.69 mW，與最原始未蝕刻n-GaAs搭配 AuGe反射鏡之LED相比，光輸出功率由2.08 mW提升至2.69 mW提升率為29.3%，此外光電轉換效率也可由22.1%提升至28.0%。

In this thesis, the manufacturing processes of FCLED；9 mil×6 mil are discussed. The current spreading ability of different shapes of n-GaAs is analyzed by SpecLED and the real chip is manufactured. The real chip and simulation both proved that the current spreading ability can be improved by etching n-GaAs. The mirror is changed from AuGe to Ag which has higher reflectivity than AuGe in order to improve the output power. The ohmic contact of p-electrode can be accomplished by AuBe/GaP, but the annealing temperature would make bonding glue produce bubbles. In this thesis, Au/Cr/ITO is deposited on p-GaP to accomplished ohmic contact. Mesa etching process is accomplished by wet etching and etching solution is Bromine-methanol solution which provides high etch selectivity of epilayer and ITO. The dry etching process with ICP(Inductively Coupled Plasma) do not have high etch selectivity of epilayer and ITO, so it can not control etch depth. In this thesis, FCLEDs with three types of n-GaAs area including 100%、17.7%、9.8% are discussed. FCLEDs with17.7% n-GaAs area have lower current density compared with FCLEDs with 9.8% n-GaAs area and have lower n-GaAs area which can absorb output power compared with FCLEDs with 100% n-GaAs area. With the same 17.7% n-GaAs area, two types of arrangement of n-GaAs including 9 circles with a diameter of 20 um and 25 circles with a diameter of 16 um are discussed. The result of SpecLED simulation shows that arrangement of n-GaAs of 9 circles has better current spreading ability than 25 circles. While the injection current is 5 mA, the output power of FCLED with 100% n-GaAs area is 2.08 mW. The output power of FCLED with17.7% n-GaAs area and 9 circles n-GaAs arrangement is 2.20 mW. The output power of FCLED with Ag mirror and 17.7% n-GaAs area 9 circles n-GaA pattern is 2.38 mW and is 2.69 mW after packaged. The FCLED output power can be improved from 2.08 mW to 2.69 mW and WPE can be improved from 22.1% to 28.0% by n-GaAs etching and changing mirror.

致謝 i
摘要 ii
Abstract iii
目錄 iv
表目錄 vii
圖目錄 viii
第一章 緒論 1
1-1 前言與研究動機 1
1-2 論文架構 2
第二章 LED文獻回顧與理論基礎簡介 3
2-1 ITO透明導電膜 3
2-2 晶圓接合技術 4
2-2-1直接晶圓接合 4
2-2-2間接晶圓接合 5
2-3 平台濕蝕刻製程 5
2-4 金屬與半導體接面之影響 7
2-4-1金屬/半導體接觸之原理 7
2-4-2歐姆接觸之原理 8
2-5 傳輸線模型原理 9
2-6 LED之光取出原理及影響 10
2-6-1輻射發光效率 11
2-6-2內部量子效率 11
2-6-3外部量子效率 11
2-6-4光取出效率 12
第三章 實驗步驟及量測原理 14
3-1 紅光覆晶LED製備流程 14
3-1-1 AlGaInP之磊晶結構 15
3-1-2元件之清洗 16
3-1-3磊晶片黏合於Sapphire製作 16
3-1-4濕蝕刻GaAs基板與磷化銦鎵蝕刻停止層 16
3-1-5製作n-GaAs的歐姆接觸層與熱處理 17
3-1-6平台(MESA)之製作 17
3-1-7 P型電極製作 18
3-1-8元件切割與封裝 18
3-2 圖案化蝕刻n-GaAs改善結構 18
3-3 Ag反射鏡改善結構 19
3-3-1點狀AuGe 20
3-3-2 Ag/Au/Ti蒸鍍 21
3-3-3 SiO2及Ti蝕刻 21
3-4 量測元件特性 21
3-4-1光電量測特性 21
3-4-2積分球 21
3-4-3 N&K光學量測系統 23
3-4-4 IS量測系統 23
3-4-5掃描式電子顯微鏡 24
第四章　結果與討論 26
4-1 高分子膠穿透率評估 28
4-2 貼合壓力選擇 29
4-3 P極金屬歐姆接觸 29
4-4 N極金屬歐姆接觸 30
4-5 發光外觀 31
4-5-1 REF-LED發光外觀 31
4-5-2 n-GaAs蝕刻與電流均勻性 33
4-5-3 n-GaAs點電流集中現象 34
4-5-4電流密度與電流擁擠現象 35
4-6 圖案化n-GaAs蝕刻LED光電特性 36
4-6-1電流-電壓特性曲 36
4-6-2光輸出功率 37
4-6-3光電轉換效比較 38
4-6-4發散角 39
4-7 導入Ag反射鏡之光電特性 40
4-7-1電流-電壓特性曲 40
4-7-2光輸出功率 41
4-7-3光電轉換效比較 41
4-7-4 SpeCLED模擬軟體分析 42
4-8 封裝效益 44
4-9 兩反射鏡討論 45
第五章 結論 47
第六章 未來展望 48
參考文獻 50

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