本論文主要是探討常閉型P型氮化鎵高電子遷移率電晶體的設計與製作。本研究主要分成兩部分，第一部分是應用於高功率元件，第二部分是應用於高頻微波元件。
在高功率元件的應用中，我們探討利用增長閘極與汲極的距離以增加崩潰電壓。我們選擇利用閘極與汲極的距離為15μm時，能兼具電流密度與崩潰電壓的最佳值。此元件的臨界電壓為0.6V，最大汲極飽和電流密度約378mA/mm，並達到崩潰電壓615V。另外在閘極與汲極的距離為20μm時，能達到約1390V的崩潰電壓。我們也對元件進行動態以及變溫的可靠度量測，以驗證製程與磊晶片緩衝層的特性。
在高頻微波元件的應用中，我們分別探討MS gate與MIS gate兩種閘極結構的特性分析。另外在MIS gate的研究中，我們引進新的元件結構。與傳統結構相比，元件的操作特性大幅提升。我們使元件的臨界電壓達到1.5V，最大汲極飽和電流密度約412mA/mm，最大轉導值101.3mS/mm，改善在元件開啟狀態時的閘極漏電流。在閘極偏壓5V時，閘極漏電流僅7.3*10-9mA/mm。而在頻率表現方面，經小訊號的分析，在截止頻率與最大震盪頻率分別達到6.0與9.8GHz。

In this thesis, our research is mainly about design and fabrication of enhancement mode P-GaN HEMT. We have two topics. The one is for high power device, the other one is about high frequency RF device.
In the first section, we increase gate to drain spacing (Lgd) to increase breakdown voltage. When Lgd is 15μm, the deivce can have high performance both in current density and breakdown voltage. The deivce with threshold voltage (Vth) 0.6V, saturated drain current density 378mA/mm and breakdown voltage 615V. We also let the device reaches breakdown voltage 1390V when Lgd enlarges to 20μm. On the other hand, we let the device under temperature variation and pulse I-V dynamic measurement to ensure process and epitaxy buffer layer characteristics.
The second part is about RF application device. We compare MS gate and MIS gate structure device characteristics. Also, We introduce new structure for MIS gate device. Comparing to conventional structure, the device performance improves greatly. The deivce Vth is 1.5V, satrurated current density 412mA/mm, maximum transconductance (gm) 101.3mS/mm and we improves gate leakage current in on-state. The gate leakage current is 7.3*10-9mA/mm when gate bias is 5V. And cut-off frequency and maximum oscillation frequency are 6.0 and 9.8 GHz, respectively.

摘要 I
Abstract II
致謝 III
Table of Contents V
List of Figures Ⅷ
List of Tables XII
Chap 1 Introduction 1
1-1 Background research of Gallium Nitride (GaN) 1
1-2 GaN HEMT development and application 3
1-3 AlGaN/GaN heterojunction and how two-dimensional electron gas(2DEG) induced 5
1-4 Enhancement mode HEMT (E-mode HEMT) 7
1-5 Motivation 9
1-6 Thesis organization 10
Chap 2 Fundamental principles of HEMT and device analysis 11
2-1 HEMT working principle and mechanism 11
2-1-1 Conventional D-mode HEMT working principle 11
2-1-2 P-GaN HEMT working principle 14
2-2 Transmission Line measurement (TLM) 16
2-3 Pulse I-V measurement 20
2-4 Small signal characteristics 22
2-4-1 Scattering parameters (S parameters) 22
2-4-2 RF performance figures of merit 23
Chap 3 Design and Fabrication of P-GaN HEMT 25
3-1 Process flow 25
3-1-1 Process flow of MS POWER HEMT 25
3-1-2 Process flow of MS/MIS RF HEMT 31
3-2 Epitaxy structure 40
3-3 Experiment design 41
3-3-1 Schottky gate P-GaN power HEMT 41
3-3-2 MS/MIS gate P-GaN RF HEMT 43
3-4 Measurement system 46
3-4-1 DC characteristics 46
3-4-2 Small signal measurement 48
Chap 4 Results and discussion 49
4-1 MS P-GaN Power HEMT 49
4-1-1 Etching depth and TLM measurement 50
4-1-2 DC characteristics 52
4-1-3 Pulse I-V dynamic characteristics 57
4-1-4 Thermal stability characteristics 60
4-2 P-GaN RF HEMT 62
4-2-1 Etching depth and TLM measurement 63
4-2-2 MS P-GaN RF HEMT characteristics 65
4-2-3 MIS P-GaN RF HEMT DC characteristics 67
4-2-4 Comparison with MIS and MS RF P-GaN HEMT 70
Chap 5 Conclusions 76
References 78

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