我們主要探討分子束磊晶所成長氮化鎵/氮化鋁鎵異質結構的特性。為了減少晶格不匹配，加入氮化鋁當緩衝層。我們改變緩衝層的參數，像氮和鋁的比例，緩衝層的厚度。在X-ray繞射的分析下，可以大約判定晶格不匹配的情形，以厚度為例，成長時間為20分鐘晶格不匹配最為嚴重。從掃描式電子顯微鏡和反射電子繞射來觀看表面形貌，我們發現N/Al=40的表面有明顯的氮終結而N/Al=26為鎵終結，對於厚度而言，成長時間為1分鐘和5分鐘有理想的鎵終結。在光致螢光分析下，我們可求得氮化鎵能隙為3.42ev。此外，藉著改變摻雜矽的溫度來改變載子濃度，可由霍爾量測發現1250度有較好的電子遷移率，對於改變緩衝層的參數，成長時間為1分鐘和成長時間5分鐘(N/Al=26)有較好的電子遷移率。我們試著尋找出成長品質最好的參數。

We mainly studied the characterization of GaN/AlGaN heterostructures which were grown by molecular beam epitaxy. For reduced lattice mismatch, we inserted AlN as buffer layer. We varied the parameters of buffer layer, such as the ratio of nitrogen and aluminum and the thickness. By the analysis of X-ray diffraction, we could determine the state of mismatch. For the thickness of buffer layer, lattice mismatch is most serious at 20 minute growth. Under the observation of field emission scan electron microscopy and reflection high energy electron diffraction, we found N/Al=40 is N-face and N/Al=26 is Ga-face. For the thickness of buffer layer, the samples of 1-minute and 5-minute growth had the optimal Ga-face. For the investigation of photoluminescence, we could obtain the energy gap of AlGaN is 3.42ev. Furthermore, the doping silicon was used to vary carrier concentration, and we could show that a good Hall mobility was achieved at the doping temperature 1250℃. We also could show good Hall mobility at 1 minute growth and 5 minute growth (N/Al=26). We tried to find the best parameters for the growth of GaN/AlGaN heterostructures.

目錄

中文摘要………………………………………………………1

英文摘要………………………………………………………2

第一章 前言…………………………………………………3

第二章 實驗基本原理………………………………………6
2-1 X-ray繞射光譜儀………………………………………6
2-2 霍爾效應基本原理…………………………………… 8
2-3 低溫霍爾量測………………………………………… 11
2-4 光致螢光光譜儀……………………………………… 13
2-5 掃描式電子顯微鏡…………………………………… 15
2-6 polarization……………………………………………16

第三章 實驗儀器與步驟……………………………………17
3-1 室溫霍爾實驗………………………………………… 17
3-1-1 樣品處理……………………………………………… 17
3-1-2 量測儀器……………………………………………… 18
3-1-3 量測方法……………………………………………… 19
3-1-4 計算方法……………………………………………… 21
3-2 PL實驗系統與步驟……………………………………23

第四章 實驗分析與結果………………………………………25
4-1 實驗樣品系列………………………………………………25
4-2 X-ray繞射分析……………………………………………27
4-3 掃描式電子顯微鏡與反射式電子繞射圖…………………37
4-4 微光致螢光…………………………………………………44
4-5 霍爾電性量測分析…………………………………………46

第五章 結論…………………………………………………… 51
參考資料…………………………………………………53

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