近年來，由於氮化鎵元件有低導通電阻、高電流密度、高切換速度、高臨界崩潰電場及良好的熱穩定性，使其在高功率、高頻率及高溫操作的應用受到極大的注目。且隨著磊晶技術的進步，氮化鎵不僅能用較低的成本成長於大面積的矽基板上，在未來還很有機會可以整合進CMOS的電路中。因此，矽基氮化鎵對我們高功率應用的研究來說再適合也不過。
在本篇論文中，我們在矽基氮化銦鋁/氮化鎵高電子遷移率電晶體中提出了混和式汲極和混和式源/汲極的架構。此兩種架構跟傳統的高電子遷移率電晶體相比皆能在相同的導通電阻之下達到更高的崩潰電壓，且同時其高頻特性不會受太大的影響。更值得注意的是採用混和式源/汲極的高電子遷移率電晶體在同樣導通電阻的情況下可達到最好的崩潰電壓。這是因為混和式蕭特基-歐姆接觸的架構可以改變電場的分布且降低最大峰值電場因而抑制源極載子的注入及減緩在靠近汲極端的閘極邊緣之下的衝擊電離效應。由量測結果可得知，跟傳統的高電子遷移率電晶體相比，使用混和式源/汲極的崩潰電壓可提升高達120% (從50V到110V)。
另一方面，我們也在矽基氮化鋁鎵/氮化鎵蕭特基二極體中提出了用感應耦合電漿蝕刻及中性原子蝕刻兩種不同的技術來做出掘入式蕭特基陽極的架構。不論使用哪種蝕刻方式，此掘入式陽極的蕭特基二極體與傳統的蕭特基二極體相比，在一樣的導通電阻下能夠擁有更高的崩潰電壓且同時能有效地降低導通電壓。最重要的是，由於中性原子蝕刻的技術可以實現近乎無傷害的蝕刻表面，因此使用中性原子蝕刻的掘入式陽極蕭特基二極體能比用感應耦合電漿蝕刻的蕭特基二極體有較好的表現。最後，使用中性原子蝕刻的蕭特基二極體與傳統的蕭特基二極體相比，可以有效地降低導通電壓從1.1 V到0.55 V且同時大大地提升崩潰電壓高達369% (從130 V到610 V)。

Recently, GaN-based power devices have received significant attention for high power, high frequency and high temperature applications due to their superior electrical characteristics including low on-resistance, high current density, high switch speed, high critical breakdown electric field, and good thermal stability. With the gradually advanced epitaxy technology, GaN not only can be grown on the large size Si substrate at low price but also may be integrated with CMOS in the future. Therefore, GaN-on-Si substrate is a very promising choice for high power applications.
In this thesis, we demonstrated the InAlN/GaN High Electron Mobility Transistors (HEMTs) on a Si substrate with hybrid drain and hybrid source/drain structures. Both structures can achieve higher VBK than conventional HEMTs at the same Ron and meanwhile will not degrade the high frequency characteristics. More importantly, the hybrid source/drain HEMTs have the increased breakdown voltage (VBK) at the same Ron because the hybrid Schottky-ohmic structures can manipulate the electric field distribution and reduce the peak electric field leading to suppression of source-carrier-injection and impact ionization underneath the drain-side gate edge. The VBK of hybrid source/drain HEMTs can be improved up to 120% (from 50 V to 110 V) compared with conventional HEMTs. On the other hand, we also demonstrated the AlGaN/GaN Schottky Barrier Diodes (SBDs) on a Si substrate with Schottky recessed anode by neutral beam etching (NBE) and inductive coupled plasma (ICP). The recessed anode SBDs can effectively reduce Von and simultaneously realize higher VBK than non- recessed anode SBDs at the same Ron no matter which etching method is used (NBE or ICP). Most importantly, due to nearly damage-free etching by NBE technology, the anode-recessed SBDs by NBE achieve a better performance than the SBDs etching by ICP. Finally, the NBE technology compared with conventional SBDs can reduce Von from 1.1 V to 0.55 V with an enhanced VBK up to 369% (from 130 V to 610 V).

摘要 i
ABSTRACT ii
TABLE OF CONTENTS iii
LIST OF FIGURES vi
LIST OF TABLES xii
Chapter 1 Introduction 1
1.1 Motivation 1
1.2 Thesis Organization 2
Chapter 2 Basic Concepts of GaN Material 3
2.1 Pros and Cons of GaN-on-Si Substrate 3
2.1.1 Wide bandgap materials 3
2.1.2 Saturation electron velocity 5
2.1.3 Breakdown voltage versus on-resistance 6
2.1.4 Substrate issue 8
2.2 Heterojuction Structure 10
2.2.1 Comparison of different barrier layers 10
2.2.2.1 Comparison of lattice constant with different barrier layer 10
2.2.2.2 Comparison of 2DEG density with different barrier layers 11
2.2.2 AlN interlayer 14
2.2.3 Buffer and GaN channel layer 15
2.3 Summary 17
Chapter 3 Design and Fabrication of InAlN/GaN High Electron Mobility Transistors for Power Applications 18
3.1 InAlN/GaN HEMTs 18
3.2 Schottky Source/Drain Technology 20
3.3 Device Design and Layout 21
3.4 Process Flow 24
3.4.1 Mesa isolation 24
3.4.2 Ohmic contact 25
3.4.2.1 Ohmic recess 26
3.4.2.2 Metal deposition 27
3.4.2.3 Rapid thermal annealing (RTA) 28
3.4.2.4 Transfer length method (TLM) 29
3.4.3 Schottky contact 31
3.4.4 Passivation 33
3.4.5 Via window and top metal 35
3.5 Results and Discussion 37
3.5.1 I-V characteristic 37
3.5.2 High frequency characteristic 49
3.5.3 Off-state characteristic 53
3.6 Summary 61
Chapter 4 Design and Fabrication of AlGaN/GaN Schottky Barrier Diodes with Schottky Recessed Anode by Different Etching Methods 62
4.1 AlGaN/GaN SBDs 62
4.2 Neutral Beam Etching 63
4.3 Device Design and Layout 64
4.4 Process Flow 66
4.4.1 Mesa isolation 66
4.4.2 Ohmic contact 67
4.4.3 Schottky recess 68
4.4.4 Schottky contact 70
4.4.5 Passivation 70
4.4.6 Via window and top metal 71
4.5 Results and Discussion 72
4.5.1 I-V characteristic 72
4.5.2 Off-state characteristic 77
4.6 Summary 84
Chapter 5 Conclusion and Future Work 85
References 86

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