臺灣博碩士論文加值系統

本論文前面部份針對氮化鎵薄膜結構的特性受到不同條狀凹凸深度基板的影響作探討。後面部份則針對不同的圖案化基板對發光二極體光特性的影響作探討。我們的樣品為使用日酸SR-2000有機金屬化學氣相磊晶系統在不同條狀凹凸深度的藍寶石基板上成長氮化鎵薄膜結構，藉由不同深度的改變來研究其對差排密度的影響及其機制。其後，我們使用tracepro光學軟體，藉由近似發光二極體的模型來追蹤其光路路徑，並探討圖案化基板對光路路徑的改變及輸出光特性之影響。
我們使用高解析度X光繞射儀對樣品作搖擺圖形及倒異空間圖譜的量測。從(002)對稱面搖擺圖形的半高寬分析可以得知，當深度越深時和條形呈水平方向之磊晶品質越好。在(102)非對稱面搖擺圖形的半高寬分析亦可得到同樣結果。另外，由倒異空間圖譜可以發現當深度越深時，將會因為應力的增加而使晶格排列改變並使傾斜角變大，如此也加速了差排的偏折而降低了差排密度。故當凹凸深度越深時越能改善螺旋差排和刃差排密度。另外，我們使用光激致光光譜量測，在室溫時隨著使用越深的條形凹凸藍寶石成長之氮化鎵薄膜樣品，其能帶邊緣放射波峯之光激螢光強度越強。其表示當差排密度因凹凸越深而減少時，也減少了非輻射中心數量，因此提高了輻射中心結合的效率。在低溫時則發現二個峯值，經判斷強度較小的峯值為凹區，強度較大的峯值為凸區。而且當條狀凹凸深度越深時，二個波峯的位置及強度差異越大，此為應力的差異越大使得越多的差排位於凹區。
在後面部份，由光路的追蹤可以看出不同的圖案對散射效應的差異，在條狀凹凸深度越深時其散射效應越明顯。若是在有斜角度之條狀凹凸基板時則在斜面會增加光的反射，增加正面之出光。我們並藉由此基本架構模擬出最佳化組合的趨勢。
綜合以上所說，藉由圖案化基板來減少差排密度及改變光路在發光元件中之路徑皆能達到提高出光效率的目的。

In the front of the article, the optical characteristics of GaN epitaxial layer on the patterned sapphire substrate with different trench depth were discussed. To study the effects of dislocation density and mechanism, the samples(GaN epilyers) were grown by SR-2000 MOVPE system on patterned sapphire substrate. After that, the issue is the effect of light way of LED structure on the patterned sapphire substrate. Tracepro optical software was used to track to light way with the model similar to LED and figure out the effect of light way and trend on patterned sapphire substrate.
The high resolution X-ray diffraction was employed to measure the rocking curve and reciprocal space map (RSM). As the trench depth became deeper, GaN epilayers in the direction of parallel to the stripe had superior crystal quality according to the narrow full width at half maximum (FWHM) in symmetrical rocking curve of (002), and in asymmetry rocking curve of (102). The reciprocal space mapping (RSM) also revealed the differences of lattice constant and extend tile angle because of the strain extended. So the screw-type and edge-type dislocation density reduce as the trench became deeper. In addition, in room temperature the photoluminescence (PL) peak is larger as the trench became deeper by the dislocations decrease, and the nonradiative center decrease too. In low temperature we find out two peak, the weak peak was concave and strong peak was raised. As the trench became deeper, the photoluminescence peak positions showed a wider separation and a larger intensity difference owing to more dislocations in the concave area.
Tracking the light way helped us to find out the effects of different patterned sapphire substrate. The scattering effect was stronger for the deeper trench. In addition, as the stripe had side angle, the light was reflected by side face. And the trend of the best composition was simulated by software calculation.
In summary, the patterned sapphire substrate exhibited excellent characteristics to reduce the dislocation of GaN epilayers and to enhance the extraction of light way. It all achieved the goal of improving light efficiency.

第一章 緒論
1.1前言………………………………………………………… 1
1.2 研究動機………………………………………………… 2
1.3研究方法及步驟…………………………………………… 3

第二章 文獻回顧與背景知識
2.1 氮化鎵材料發展……………………………………………… 6
2.2 氮化鎵之基板選擇及結晶結構………………………… 7
2.3 錯位差排的形成………………………………………… 8
2.3.1 氮化鎵磊晶層之差排缺陷介紹…………………… 9
2.3.2 氮化鎵中差排的質量傳輸………………………… 10
2.4 橫向覆蓋生長法中生長參數對晶體外型之影響……… 11
2.4.1 開口位態的影響……………………………………… 12
2.4.2 溫度的影響………………………………………… 13
2.4.3 Ⅲ-Ⅴ反應源流量比………………………………… 13
2.5 圖案化基板成長法中之凹凸基板對光路之影響………… 14
2.5.1 光學散射效應……………………………………… 14
2.5.2 不同基板形狀對光路行進之影響………………… 15

第三章 樣品與量測系統介紹
3.1 樣品介紹………………………………………… 30
3.1.1 條狀凹凸藍寶石基板製作………………………… 30
3.1.2 晶圓清洗…………………………………………… 30
3.1.3 磊晶成長…………………………………………… 31
3.2 高解析度X光繞射量測………………………………… 32
3.2.1 X光繞射原理………………………………………… 32
3.2.2 高解析度X光繞射量測方式介紹…………………… 33
3.2.3 倒異空間圖譜介紹………………………………… 34
3.3 光激螢光光譜量測……………………………… 35
3.3.1 光激螢光光譜原理………………………………… 35
3.4 儀器架設………………………………………… 36

第四章 圖案化藍寶石石基板成長氮化鎵薄膜之特性研究
4.1 高解析度X光繞射特性分析……………………… 45
4.1.1 搖擺圖形量測結果分析…………………………… 45
4.1.2 倒異空間圖譜量測結果分析……………………… 47
4.2 光激螢光光譜分析……………………………………… 48
4.2.1 室溫光激螢光光譜分析…………………………… 48
4.2.2 變溫光激螢光光譜分析…………………………… 50
第五章 圖案化藍寶石基板對元件特性改善之模擬研究
5.1 光學模擬說明………………………………………… 66
5.1.1 模型結構說明……………………………………… 66
5.1.2 材料光學參數說明……………………………… 66
5.1.3 光路強度說明…………………………………… 66
5.2 模擬結果…………………………………………… 67
5.2.1 不同深度的條狀凹凸基板之光學模擬結果…… 67
5.2.2 不同斜面角度的條狀凹凸邊緣之光學模擬結果… 68
5.3 最佳化驅趨勢預測…………………………………… 69

第六章 結論……………………………………………… 81

參考文獻…………………………………………………… 84

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