臺灣博碩士論文加值系統

本論文利用有機金屬化學氣相沉積系統成長氧化鋅鎵(ZnGa2O4)薄膜於銦錫氧化物(ITO)薄膜上，作為深紫外發光二極體(Deep UV-LEDs)之歐姆接觸層與透明導電膜，藉以改善深紫外發光二極體之光電特性。
ZnGa2O4薄膜選擇流量部分，本實驗嘗試了五種DEZn的流量，分別為10、30、40、50、60 sccm。隨著DEZn流量的增加，其X光繞射峰逐漸由氧化鎵之晶相逐漸轉變為ZnGa2O4，在流量為10 sccm時以形成鋅摻雜的氧化鎵為主，當流量提升至30 sccm時開始轉變為氧化鎵鋅，而晶粒大小則隨著流量增加從146Å變大至233Å。此外，在波長為280 nm時，ZnGa2O4薄膜具有相當良好的穿透率約93.2%。
本論文設計3種不同形貌的歐姆接觸層結構(Dot、Hole、Whole)之水平Deep UV-LEDs (Dot-LED、Hole-LED及Whole-LED)，以及ZnGa2O4薄膜之水平Deep UV-LED (Z-LED)和ITO薄膜之水平Deep UV-LED (C-LED)進行探討與比較。其中，ZnGa2O4薄膜無法直接與p+-GaN形成歐姆接觸，使Z-LED無元件特性。另一方面，Hole-LED則因為ZnGa2O4薄膜延伸至p-AlGaN，造成元件阻抗較高，使得光電特性較差。此外，分別製作半徑為25 µm (R25)和50 µm (R50)不同尺寸的Dot-ITO之Dot-LED進行比較，可發現R50Dot-LED的外部量子效率較R25Dot-LED提升43.4%。在注入電流200 mA下，Dot-LED與Whole-LED之光輸出功率較C-LED提升33.7%和12.3%。在外部量子效率方面，Dot-LED與Whole-LED較C-LED分別提升34.2%和12.9%。這些結果清楚地表明，ZnGa2O4/ITO-Dot和ZnGa2O4/ITO-whole接觸層結構可以作為Deep UV-LEDs的透明導電膜，進而增加發光亮度。

In this thesis, the ZnGa2O4 films were grown on ITO layer by metalorganic chemical vapor deposition using Diethylzinc (DEZn), Triethylgallium (TEGa), and oxygen sources. The ZnGa2O4/ITO films were employed as an ohmic contact layer and a transparent conductive layer for the deep-ultraviolet light-emitting diodes (DUV-LEDs) to improve optoelectronic characteristics of LEDs.
Based on the ZnGa2O4 films experiment results, the X-ray diffraction peak shifts to the lower angle with increasing DEZn flow rate, which indicated that the film transferred from β-Ga2O3 into ZnGa2O4. From the transmittance spectra, the ZnGa2O4 films exhibited high transparency above 92% at wavelength of 280 nm.
Three kinds of different ohmic-contact-layer shapes (Dot, Hole and Whole) of the DUV-LEDs (dot-LED, hole-LED and whole-LED), and the ZnGa2O4/DUV-LED (Z-LED), and the ITO/DUV-LED (C-LED) were fabricated and discussed. In addition, Z-LED has no device characteristics because of the ZnGa2O4 film cannot form ohmic contact to p+-GaN layer. For Hole-LEDs, since the ZnGa2O4 film extends to p-AlGaN layer, resulting in high resistance and poor optoelectronic properties. In addition, Dot-ITO film with different radiuses of 25 μm (R25) and 50 μm (R50) were prepared. It can be find that the R50Dot-LED exhibited a 43.4% enhancement in external quantum efficiency (EQE) compared with the R25Dot-LED. At an injection current of 200 mA, the Dot-LED and Whole-LED exhibited 33.7% and 12.3% enhancement in light output power, respectively, as compared with that of the C-LED. The EQEs of the Dot-LED and Whole-LED had 34.2% and 12.9% improvement compared to that of the C-LED. These results clearly indicate that the ZnGa2O4/ITO-Dot and ZnGa2O4/ITO-whole- contact-layer structure can be used as a TCL for DUV-LEDs to increase the light output.

誌謝 i
摘要 ii
Abstract iii
目錄 iv
表目錄 vii
圖目錄 viii
第一章 緒論 1
1-1前言 1
1-2研究動機 3
1-3 論文架構 4
第二章 理論基礎 5
2-1發光二極體發光理論 5
2-2金屬-半導體接面理論 5
2-2-1蕭特基接觸原理 6
2-2-2 歐姆接觸之原理 6
2-3薄膜材料性質及應用 7
2-3-1 氧化鎵 7
2-3-2 氧化鎵鋅 9
2-4光電特性 10
2-5發光二極體發光效率原理 11
2-5-1 內部量子效率Internal quantum efficiency(IQE) 12
2-5-2 光萃取效率(Extraction efficiency)及外部量子效率External Quantum Efficiency (EQE) 12
2-6 發光二極體的基本特性參數 15
2-6-1 正向偏壓 (forward voltage，Vf) 15
2-6-2 漏電流 (leakage current，Ir) 15
2-6-3 光強度(Luminance Intensity, I) 15
2-6-4 輸出光功率 (output power) 16
2-6-5 光電轉換效率 wall plug efficiency (WPE) 16
第三章 實驗步驟 17
3-1前言 17
3-2深紫外光氮化鎵試片之磊晶結構 17
3-3 薄膜備製 18
3-3-1試片清洗 18
3-3-2沉積氧化銦錫 18
3-3-3氧化鎵鋅薄膜成長 20
3-4 ZnGa2O4 DUV LED元件製作 21
3-4-1 試片清洗 21
3-4-2定義元件範圍 21
3-4-3 電極製作 22
3-4-4 元件切割 22
3-3 量測元件特性 24
3-3-1 光電特性量測 24
3-3-2 積分球量測系統 24
3-3-3 Alpha-Step量測系統 25
3-3-6 N&K光學量測系統 25
3-3-4 IR紅外熱像分析儀簡介 26
3-3-4輝光放電分光儀(GDS) 27
3-3-5掃描式顯微鏡原理簡介 27
3-3-6 CL分析技術原理 28
3-3-7原子力顯微鏡原理 28
3-3-8光致螢光光譜儀量測系統 29
3-3-9X射線繞射分析儀 (XRD) 30
3-3-10霍爾效應分析儀(Hall Effect Analyzer) 32
3-3-11 X射線光電子能譜學（XPS） 33
第四章結果與討論 35
4-1 Zn摻雜濃度對氧化鎵磊晶薄膜特性之探討 35
4-1-1 不同Zn摻雜濃度對磊晶薄膜結晶特性及元素組成 35
4-1-2不同Zn摻雜濃度電性之影響 41
4-2 ZnGa2O4(透明導電層)與ITO(歐姆接觸層)之薄膜分析 42
4-2-1 ZGO(透明導電層)/ITO(歐姆接觸層)對於深紫外光之穿透率 42
4-3-2 ITO與p+GaN之歐姆接觸 44
4-3-3 ZGO(透明導電層)/ITO(歐姆接觸層)電性之影響 46
4-2-4 不同結構的歐姆接觸層對於深紫外光之穿透率與樣貌 48
4-2-5不同構造歐姆接觸與氧化鋅鎵薄膜結晶特性 51
4-2-6 金屬與ZnGa2O4之歐姆接觸 52
4-3元件樣貌 53
4-4陰極發光與光致螢光分析量測 54
4-5不同樣貌之歐姆接觸層UVLEDs元件之光電特性 56
4-5-1元件之電流-電壓特性 56
4-5-2光輸出功率分析 57
4-5-3 元件之光電轉換效率及外部量子效率 60
4-5-4紅外線熱影像分析 62
4-6不同Dot-ITO尺寸之UVLEDs元件光電特性 64
4-6-1元件電流-電壓特性 64
4-6-2元件之光輸出功率及電光轉換效率 65
第五章 結論與未來展望 68
參考文獻 69

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