臺灣博碩士論文加值系統

自從1993年日亞化學公司宣佈生產氮化鎵藍綠光發光二極體迄今，全世界掀起一陣研發氮化鎵材料及元件之熱潮。眾所皆知，氮化鎵為一寬能隙材料，因此製作其歐姆接觸是個很大的挑戰。本實驗利用電子束蒸鍍法製備氮化鎵的歐姆接觸，並且在石英爐管中進行活火處理。我們以Ti/Al（30nm/100nm）做為n型氮化鎵的接觸材料，而p型氮化鎵則是以Ni/Au（5nm/5nm）形成接觸。在實驗量測與分析部份，則是利用sourcemeter、歐傑電子能譜儀、原子力顯微鏡、低掠角X光繞射儀及光譜儀來探討金屬/氮化鎵接觸的電性和結構。
在n型氮化鎵歐姆接觸方面，試片經過550℃合金化10分鐘後形成良好的歐姆接觸，此時特徵接觸電阻為3.4×10-6 W-cm2，但是在此溫度合金化15分鐘後，其特徵接觸電阻卻增加至9.6×10-6 W-cm2。同時我們亦發現，氮化鎵的雜質摻雜濃度對於其歐姆接觸之電性表現有很大的影響。至於p型氮化鎵歐姆接觸方面，本實驗所得最佳活化條件為750℃退火60分鐘，此時雜質摻雜濃度和載子遷移率分別為2.2×1017 cm-3和9.39 cm2/V-s。試片在合金化之前的特徵接觸電阻為3.9×10-1 W-cm2，對光波長470nm的透光率為41﹪，而在500℃合金化10分鐘後其特徵接觸電阻降低為2.0×10-2 W-cm2，透光率亦增加至78﹪。Au/Ni/p-GaN接觸之接觸電阻的改善及透光率的增加與金屬/半導體界面的交互擴散及Ga4Ni3、Ga2Au7等金屬間化合物的形成密切相關。

Since the production of GaN blue/green LEDs was announced by Nichia in 1993, it has attracted a large amount of research on GaN materials and devices. As we know, it is difficult to form the ohmic contacts on GaN because it is a wide bandgap material. In this study, ohmic contacts on GaN were prepared by electron beam evaporation, and each sample was alloyed in N2 atmosphere using a tube furnace. Ti/Al(30nm/100nm) and Ni/Au(5nm/5nm) were chosen as the contact materials on n-type and p-type GaN, respectively. In the analysis, we use sourcemeter, Auger electron spectrometer, atomic force microscope, grazing incident x-ray diffractometer, and photospectrometer to study the electronic properties and crystalstructure of the metal/GaN contacts.
In the n-type contact, the sample alloyed at 550℃ for 10 minutes exhibited an excellent ohmic behavior with a lowest specific contact resistance of 3.4×10-6 W-cm2. However, the specific contact resistance of the sample alloyed for 15 minutes increased to 9.6×10-6 W-cm2. At the same time, it was found that the doping concentration of GaN had great influence on the electronic properties of ohmic contacts. For the p-type contact, the best condition of activation on p-GaN was annealed at 750℃ for 60 minutes, and the doping concentration and carrier mobility were 2.2×1017 cm-3 and 9.39 cm2/V-s, respectively. The as-deposited contact exhibited a specific contact resistance and transmittance of 3.9×10-1 W-cm2 and 41%, respectively. Then, after alloyed at 500℃ for 10 minutes they became 2.0×10-2 W-cm2 and 78%, respectively. The improvement in contact resistance and optical transmittance can be closely related to the interdiffusion in the metal/semiconductor interface and the formation o

第一章 緒論……………………………………………………………….1
1-1 前言……………………………………………………………….1
1-2 三族氮化物之發展歷史………………………………………….1
1-3 氮化鎵歐姆接觸之文獻回顧…………………………………….5
第二章 理論基礎………………………………………….………………9
2-1 金屬/半導體接觸之原理…………………………………………9
2-2 歐姆接觸之原理………………………………………….……..14
2-3 傳輸線模型之原理……………………………………….……..17
第三章 實驗方法………………………………………….……………..21
3-1 氮化鎵薄膜之製備………………………………………….…..21
3-1-1 藍寶石基板之清洗……………………………………..21
3-1-2 薄膜磊晶生長…………………………………………..21
3-1-3 p型氮化鎵之活化處理………………………………...22
3-2 歐姆接觸之製作………………………………………….……..25
3-2-1 晶片清洗………………………………………….……26
3-2-2 金屬沉積………………………………………….…….27
3-2-3 黃光製程………………………………………….…….27
3-2-4 合金化處理……………………………………………..28
3-3 實驗量測與分析………………………………………….……..30
3-3-1 氮化鎵薄膜之光電性質分析…………………….…….30
3-3-2 氮化鎵薄膜之磊晶品質分析…………………….…….30
3-3-3 歐姆接觸之電性量測…………………….…………….31
3-3-4 歐姆接觸之AES縱深分析…………………….……….31
3-3-5 歐姆接觸之AFM分析…...…………………….…….…31
3-3-6 歐姆接觸之X光繞射分析...……………….………….32
3-3-7 歐姆接觸之穿透率量測…………………….………….32
第四章 結果與討論…………………….………………………………..34
4-1 氮化鎵薄膜之磊晶生長結果…………………….……………..34
4-1-1 氮化鎵薄膜之光電特性…………………….………….34
4-1-2 氮化鎵薄膜之磊晶品質…………………….………….36
4-2 n型氮化鎵之歐姆接觸…………………….…………………...39
4-2-1 合金化溫度對Al/Ti/n-GaN接觸之影響………………39
4-2-2 合金化時間對Al/Ti/n-GaN接觸之影響………………52
4-2-3 雜質摻雜濃度對Al/Ti/n-GaN接觸之影響……………61
4-3 p型氮化鎵之歐姆接觸………………….……………………..64
4-3-1 p型氮化鎵之活化結果………………….……………..64
4-3-2 合金化溫度對Au/Ni/p-GaN接觸之影響……………...66
第五章 結論………………….…………………………………………..77
參考文獻………………….………………………………………………..80
誌謝………………….……………………………………………………..83
作者簡介………………….………………………………………………..84

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