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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/7083


    Title: 氮化鎵薄膜成長於奈米級圖樣化氮化鎵基板之研究Investigation;of GaN grown on nano-scale patterned GaN template
    Authors: 張力權;Li-chuan Chang
    Contributors: 光電科學研究所
    Keywords: 圖樣化基板;發光二極體;氮化鎵;LED;patterned template;GaN
    Date: 2009-06-03
    Issue Date: 2009-09-22 10:36:54 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 在本論文中,我們利用有機金屬氣相沉積機台(Organometallic Vapor Phase Epitaxy, OMVPE)成長氮化鎵薄膜於奈米級圖樣化氮化鎵基板(Nano-scale patterned GaN template, NPGaN )。在不成長低溫緩衝層(Low temperature buffer layer )下,未摻雜氮化鎵薄膜可成功直接成長於奈米級圖樣化氮化鎵基板。透過高解析度X-光繞射儀(X-ray)以及原子力顯微鏡(AFM)量測顯示出氮化鎵薄膜成長於奈米級圖樣化氮化鎵基板上,其氮化鎵薄膜的品質比起傳統成長在藍寶石基板上是有效地改善,其氮化鎵薄膜之X-ray半高寬可減少100 arcsescs以及缺陷密度可降低約1/3倍。此外,在不成長低溫緩衝層(Low temperature buffer layer )下,n型氮化鎵薄膜可以直接成長於奈米級圖樣化氮化鎵基板,應用此不需成長低溫緩衝層及未摻雜的氮化鎵薄膜的優點,我們進而直接成長氮化鎵發光二極體(Light Emitting Diodes, LED)於奈米級圖樣化氮化鎵基板,同時成長傳統氮化鎵發光二極體結構於藍寶石基板做為比較的試片,從變溫(20K-300K)光激螢光光譜分析(PL)量測顯示出氮化鎵發光二極體於奈米級圖樣化氮化鎵基板之相對內部量子效應比傳統氮化鎵發光二極體結構於藍寶石基板提昇13.4%;而且從12 mil × 12 mil尺寸的LED元件量測結果顯示出,LED元件在20 mA操作電流下,其電壓皆為3.31V,而光輸出功率分別為2.92 mW和2.25 mW,提昇了30%。 此外成長厚度為4.3 μm n型氮化鎵薄膜於奈米級圖樣化氮化鎵基板,同時成長低溫緩衝層、1.8 μm未摻雜氮化鎵、2.5 μm n型氮化鎵薄膜於藍寶石基板樣品做為比較的試片,將樣品製作雷射剝離(Laser lift off)製程和移除未摻雜的氮化鎵製程,以鈦/鋁/鈦/金(Ti/Al/Ti/Au)做金屬電極,進而量測N-face n型氮化鎵成長於奈米級圖樣化氮化鎵基板、N-face 未摻雜氮化鎵成長於藍寶石基板及N-face n型氮化鎵成長於藍寶石基板的特徵電阻(specific contact resistance),在未做熱處理下的特徵電阻分別為5.8 × 10-5 Ω-cm2、non-ohmic 及1.3 × 10-4 Ω-cm2,因此,透過n型氮化鎵薄膜成長於奈米級圖樣化氮化鎵基板之技術,可獲得最低之N-face n型氮化鎵之特徵電阻並可省略垂直型結構製程中的移除未摻雜氮化鎵的製程步驟。The characteristics of GaN-based materials grown on nano-scale patterned GaN template (NPGaN) using self-assemble nickel (Ni) nano-mask by Organometallic Vapor Phase Epitaxy (OMVPE) have been studied. The 3.3-µm-thick un-doped GaN (u-GaN) layer and 4.3-µm-thick n-typed GaN (n-GaN) layer were directly grown on NPGaN without low temperature (LT) buffer layer, respectively. GaN-based MQWs LED structure were also successfully grown on NPGaN without LT buffer layer and u-GaN layer. For comparison, the u-GaN and GaN-based MQWs LED structure grown on sapphire with conventional LT GaN buffer layer were also prepared, respectively. The primary measurement results obtained in this study are summarized as follows: It was found that the u-GaN directly grown on NPGaN without LT buffer layer reduced dislocation density by AFM measurements and full width at half maximum (FWHM) of X-ray ω-rocking curve of GaN (102). The output power of the fabricated LED were enhanced by 30%, compared to that of a conventional LED. The improvement originated from both the enhanced light extraction efficiency assisted by the NPGaN and the relatively internal quantum efficiency by reducing dislocation densities. The ohmic behaviors of as-deposited Ti/Al/Ti/Au contact to N-face n-GaN directly grown on NPGaN were investigated. For comparison, N-face u-GaN and N-face n-GaN by u-GaN removal process grown on sapphire with conventional LT GaN buffer layer were also prepared, respectively. It was found that the specific contact resistance of N-face n-GaN directly grown on NPGaN, N-face u-GaN and N-face n-GaN by u-GaN removal process grown on sapphire with conventional LT GaN buffer layer were 5.8 × 10-5 Ω-cm2, non-ohmic behavior and 1.3 × 10-4 Ω-cm2, respectively. The technique offers a potential template for vertical structure GaN-based LEDs.
    Appears in Collections:[光電科學研究所] 博碩士論文

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