Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/11312
標題: 以MOCVD成長氮化鎵模板及其應用於LED之研究
Epitaxial Growth of GaN Templates by MOCVD for LED Applications
作者: 蔡宗晏
Tsai, Tsung-Yen
關鍵字: 氮化鎵
GaN
模板
圖案化藍寶石
缺陷
蝕刻
量子效率
濕蝕刻
光取出率
氧化鎵
templates
patterned sapphire
defects
etching
quantum efficiency
wet etching
light extraction efficiency
Ga2O3
出版社: 材料科學與工程學系所
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Narayan “Raman studies of GaN/sapphire thin film heterostructures” J. Appl. Phys., vol. 106, pp. 054317-054321 (2009).
摘要: 氮化鎵為III/V 族直接能隙半導體,自從1990年開始常被應用於發光二極體元件中。此化合物的硬度很高其晶體結構類似纖鋅礦,氮化鎵的能隙為3.4電子伏特因此也常被應用於高功率與高速元件當中。在本論文中我們利用有機金屬化學氣相沉積法將氮化鎵薄膜成長於三種不同的模板上。前兩種為選擇性蝕刻氮化鎵模板(型態I)以及條狀圖案化藍寶石模板(型態II),我們希望此兩種模板可以有效的降低貫穿式差排密度與增加內部量子效率。最後一種為氧化鎵模板(型態III),此模板具有可利用化學蝕刻分離藍寶石基板的功能,因此希望日後可取代雷射分離技術並且達到降低磊晶成本的目的。 在型態I之選擇性蝕刻氮化鎵模板是結合選擇性蝕刻缺陷與圖案化藍寶石技術,使其在成長氮化鎵時可以有阻擋貫穿式差排的延伸與缺陷集中的效果。此模板所成長出來的氮化鎵缺陷密度約為 1.6 × 105 cm-2。在350 mA電流注入下,其光輸出功率比傳統藍寶石基板效率提高約46%。而型態II之條狀圖案化模板是利用黃光微影技術與濕式蝕刻所製作出來的圖案化藍寶石模板,利用蝕刻技術我們希望可以將藍寶石基板的面積最大化,而此蝕刻後的圖形將能增加光萃取率與降低差排密度。此模板所成長出來的氮化鎵缺陷密度約為 5.3 × 106 cm-2。在350 mA電流注入下,其光輸出功率比傳統藍寶石基板效率提高約40%。 在型態III的氧化鎵模板則是使用脈衝雷射沉積系統於藍寶石基板上成長一層氧化鎵薄膜,然後再成長氮化鎵薄膜。此模板因氧化鎵的緣故因此必須於氮化環境下成長氮化鎵以克服在高溫下氫氣對於氧化鎵薄膜的破壞。也因氧化鎵易於被氫氟酸蝕刻因此我們利用此特性成功的分離氮化鎵與藍寶石基板,最後也在此模板上成長出發光二極體。
Gallium nitride (GaN) is a binary III/V direct bandgap semiconductor that has been widely used in light-emitting diodes (LEDs) since the 1990s. The compound is a hard material with a Wurtzite crystal structure. The wide band gap of 3.4 eV provides the material with special properties that facilitate its application in high-power and high-frequency devices. In this dissertation, GaN was grown on three different templates by metal organic chemical vapor deposition. The first two templates were selectively-etched GaN (SE-GaN, type I) and strip-patterned sapphire (SPS, type II) template, created with the aim of effectively reducing threading dislocation (TD) densities and increasing the internal quantum efficiency. The final template was a Ga2O3 template (type III), which could separate the sapphire substrate via a chemical etching process. We aim to enhance the effectiveness of this process as an alternative to laser lift-off technology, and to reduce the epitaxial cost. The type I SE-GaN templates were created using selective etching of GaN defects and the patterned sapphire substrate (PSS) technique. These templates acted as a TD growth mask in the GaN epitaxial layers, and achieved defect centralization. The etching pit density (EPD) of GaN grown on the SE-GaN template can reduce to 1.6 � 105 cm-2, and the output power of the SE-GaN LED sample under a 350 mA injection current can be enhanced by 46% as compared with that of the conventional GaN/sapphire LED one. The type II SPS templates were fabricated using photolithographic and wet-etching processes. The etching maximized the sapphire substrate area and graphics, which increased the light extraction efficiency and reduced TDs. The EPD of GaN grown on SPS templates can reduce to 5.3 � 106 cm-2. The output power of the SPS LED sample under a 350 mA injection current was enhanced by 40% as compared with that of the conventional GaN/sapphire LED one. The type III Ga2O3 templates, deposited using pulsed laser deposition on sapphire substrates, were used for the epitaxial growth of crystalline GaN on the Ga2O3 templates. An N2 ambient atmosphere was adopted because a severe degradation of the oxide material occurred under a H2 ambient atmosphere at high temperatures. Finally, the GaN LED structures were successfully grown on the.Ga2O3 template. A thin film LED was demonstrated, where the sacrificial Ga2O3 was easily achieved using a HF etchant; and the GaN and sapphire substrate can be successfully separated.
URI: http://hdl.handle.net/11455/11312
其他識別: U0005-2808201215101800
文章連結: http://www.airitilibrary.com/Publication/alDetailedMesh1?DocID=U0005-2808201215101800
Appears in Collections:材料科學與工程學系

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