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研究生: 吳嘉益
Jia-Yi Wu
論文名稱: 高功率氮化鎵高電子遷移率場效電晶體在藍寶石及矽基板之研究
High power GaN-Based HEMTs on Sapphire and Silicon Substrates
指導教授: 徐碩鴻
Shuo-Hung Hsu
口試委員:
學位類別: 碩士
Master
系所名稱: 電機資訊學院 - 電子工程研究所
Institute of Electronics Engineering
論文出版年: 2008
畢業學年度: 96
語文別: 英文
論文頁數: 70
中文關鍵詞: 氮化鎵異質結構場效電晶體
外文關鍵詞: GaN, HEMT, high electron mobility transistor
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  • 本論文主要研究氮化鎵異質結構場效電晶體在矽基板及藍寶石基板上對於高功率與微波方面的應用。這些具有400 □m閘極寬度的功率元件展現了300 mA/mm高的最大電流密度,以及80 mS/mm 的轉導係數。這些結果也指出元件在矽基板上亦可獲得較佳的特性,並且不同形狀的元件結構被採用來觀察不同的幾何形狀對崩潰耐壓及其他的非理性效應的影響,包含了閘極漏電流與低頻雜訊,而這些形狀則為指叉狀、矩形及圓形結構。如預期中的結果,這些封閉式結構的矩形和圓形電晶體在藍寶石基板中展現了高達650伏特的崩潰耐壓,這同樣也驗證了擁有較多根的指叉狀閘極會展現出較嚴重的缺陷影響,這些缺陷是來自於蝕刻平臺隔離時所伴隨產生的破壞。基於這個現象,封閉式結構的元件有效的避免了這些缺陷並提高了部分元件特性,從實驗的結果觀察到封閉式結構比指叉狀結構擁有較少的低頻雜訊和較好的崩潰耐壓。最後,元件的微波特性也是研究的目標之一,量測閘極長度為2 □m及寬度為2 mm元件,可求得達3.4 GHz的截止頻率及8.0 GHz的震盪最大頻率,倘若閘極長度縮小至可和業界元件相比的長度時,其結果和業界的成果可說是相近的。


    ABSTRACT............. I 摘要.................II ACKNOWLEDGEMENT.....III CONTENTS.............IV CHAPTER 1 1 1.1 RESEARCH BACKGROUND 1 1.2 THESIS ORGANIZATION 2 CHAPTER 2 3 2.1 POWER DEVICE AND WIDE BANDGAP MATERIALS 3 2.1.1 Wide bandgap materials 4 2.1.2 Saturation electron velocity 5 2.1.3 Breakdown voltage versus on - resistance 6 2.2 ALGAN/GAN HIGH ELECTRON MOBILITY TRANSISTORS (HEMTS) 7 2.2.1 Polarization and 2DEG mechanism 9 2.3 LAYER STRUCTURE 11 2.3.1 Buffer and GaN layer 11 2.3.2 Considerations of AlGaN layer 11 2.3.3 SiNX passivation after forming Schottky and Ohmic contacts 12 CHAPTER 3 13 3.1 FIELD PLATE ENGINEERING 13 3.1.1 Designs with field plate engineering 14 3.2 LAYOUT OPTIMIZATIONS 15 3.2.1 Closed-gate structure with a field plate 16 3.3 DESIGN OF RF DEVICE 18 3.4 MEASUREMENT METHOD 20 3.4.1 Drain lag and gate lag measurements 20 3.4.2 Capacitor – voltage measurement 21 3.4.3 Flicker noise measurement 21 CHAPTER 4 23 4.1 MESA ISOLATION 26 4.1.1 Lithography 27 4.1.2 Mesa isolation etch 28 4.2 OHMIC CONTACT 28 4.2.1 Surface treatment 29 4.2.2 Metal Evaporation 29 4.2.3 Lift-off 30 4.3 SCHOTTKY GATE 31 4.4 PASSIVATION 31 4.5 FIELD PLATE ENGINEERING 32 CHAPTER 5 33 5.1 ON-STATE CHARACTERISTICS 33 5.1.1 ID-VD characteristics 33 5.1.2 ID-VG characteristics 34 5.1.3 Results and discussions of on-state characteristics 34 5.2 OFF-STATE CHARACTERISTICS 41 5.2.1 Leakage current 42 5.2.2 Breakdown voltage 42 5.2.3 Results and discussions of off-state characteristics 42 5.3 AC AND RF CHARACTERISTICS 46 5.3.1 Drain lag and gate lag measurements 46 5.3.2 RF measurement results 49 5.3.3 CV measurement results 52 5.4 GAN-BASED SCHOTTKY VARACTORS 54 5.4.1 Varactor layouts 54 5.4.2 Varactor measurement results 55 5.4.3 Conclusion 56 CHAPTER 6 FUTURE WORK 59 REFERENCES 60

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