於本論文中，我們利用氮化鋁鎵/氮化鎵成長在矽基板上，製作大電流高電子遷移率氮化鎵電晶體。由於兩者形成之異質結構擁有高電子濃度及高電子遷移率的特性，能夠提升操作電流並大幅降低元件的導通電阻，減少多餘功率損耗。
首先在製作大電流高電子遷移率氮化鎵電晶體前，針對Schottky gate HEMT與MIS gate HEMT 作探討，並且得到再順偏特性上，MIS gate HEMT相較於Schottky gate HEMT具有提升飽和電流以及增加閘極工作範圍(gate swing)。並且利用氧化矽作為鈍化層，來得到較佳的遲滯特性以及不錯的動態特性。因此基於上述討論的結果，在大電流高電子遷移率氮化鎵電晶體的製作上會使用MIS gate HEMT以及SiO2作為鈍化層的結構作為基礎。
在元件布局上首先是尋找最佳化尺寸設計，發現元件在閘極寬度(WG)為2000μm時具有最大的飽和電流(0.8A)左右，在基於這個單顆元件的尺寸下在採用多根指叉型結構，此目的是用來提升元件電流，使得電流能夠達到數十安培的等級，此外，在多根指叉型結構中，我們也設計了不同閘極寬度(WG)，分別20mm、40mm、60mm以及80mm。而當閘極寬度(WG)為80mm時，在順偏特性上能夠達到飽和電流(IDS)26.5A、導通電阻Ron為0.22Ω、閘極漏電流2.5*10-8mA/mm、臨界電壓(VTH)為-9V，而逆偏特性上能夠達到212V的崩潰電壓。


最後我們也成功利用gate recess 的技術製作出增強型的高電子遷移率氮化鎵電晶體，順偏特性上能夠達到飽和電流密度(JDS)414mA/mm、導通電阻Ron為8.4mΩ-mm、閘極漏電流2.8*10-7mA/mm、臨界電壓(VTH)為2.65V，而逆偏特性上能夠達到610V的崩潰電壓。

In this thesis, we use AlGaN/GaN grown on the silicon substrate to fabricate the high power high electron mobility transistors. Due to the high electron concentration and high electron mobility, the heterostructure formed by AlGaN/GaN can increase the current and reduce the on-resistance(Ron) of the device and reduce the excess power loss.
First, before the fabrication of high current HENT, the Schottky gate HEMT and MIS gate HEMT are discussed, the MIS gate HEMT has a higher saturation current and increase the gate swing ,compare with the Schottky gate HEMT, And SiO2 is used as a passivation layer to obtain better hysteresis characteristics and good dynamic characteristics. Therefore, based on the above discussed results, the MIS gate HEMT and SiO2 passivation are used as a basis for the structure in the fabrication of a high-current HEMT.
In the layout of the device, the first is to find the optimal size design. It is found that the device has the maximum saturation current (0.8A) when the gate width (WG) is 2000 μm . Based on the size of this single device(2000μm), the multi-finger structure is used. This purpose is to increase the device current. so that the current can reach the tens of amps. In addition, in the multi-finger structure, we also designed different gate widths (WG) of 20mm, 40mm, 60mm, and 80mm, respectively. When the gate width (WG) is 80 mm, in the forward characteristic, can achieved the saturation current (IDS) 26.5 A, the on-resistance (Ron) 0.22 Ω, the gate leakage current 2.5*10-8 mA/mm, and the threshold voltage (VTH) is -9V, and in the reverse bias characteristic, breakdown voltage can be reach 212V.
Finally, we have also succeeded in using gate recess technology to fabricate the enhancement mode HEMT with a saturation current density (JDS) of 414mA/mm and an on-resistance (Ron) of 8.4mΩ-mm. The leakage current is 2.8*10-7mA/mm, and the critical voltage (VTH) is 2.65V. The reverse bias characteristic can achieve a breakdown voltage of 610V.

摘要 I
ABSTRACT III
致謝 V
TABLE OF CONTENTS VI
LIST OF FIGURES VIII
LIST OF TABLES XII
CHAPTER 1 INTRODUCTION 1
1.1 Research background 1
1.2 Material properties of gallium nitride (GaN) 2
1.3 Spontaneous polarization effect 3
1.4 Piezoelectric polarization effect 4
1.5 2DEG formation mechansim 6
1.6 The 2DEG density of AlGaN/GaN heterostructure 8
1.7 Motivation 9
1.8 Thesis Organization 11
CHAPTER 2 GaN-BASED HIGH ELECTRON MOBILITY TRANSISTORs 16
2.1 Epitaxial growth 16
2.1.1 Basic structure 16
2.1.2 Substrate 16
2.1.3 Nucleation buffer layers 17
2.1.4 GaN channel and AlGaN barrier layer 18
2.1.5 GaN cap layer 20
2.2 Theoretical information about HEMT operation 21
CHAPTER 3 DESIGN AND FABRICAITON OF AlGaN/GaN HEMTs 29
3.1 Epitaxial structure 29
3.2 Device layout design 30
3.2.1 Schottky gate HEMT 30
3.2.2 MIS gate HEMT 30
3.2.3 MIS gate high current HEMT 31
3.2.4 MIS gate enhancement mode HEMT 31
3.3 Process flow for HEMT 32
3.3.1 Schottky gate HEMT 32
3.3.2 MIS gate high current HEMT 35
3.3.3 MIS gate enhancement mode HEMT 40
CHAPTER 4 RESULT AND DISCUSSION 51
4.1 Investigations on electrical performance of AlGaN/GaN structure before fabrication 52
4.1.1 Hall measurement 52
4.1.2 Transmission line model (TLM) measurement 53
4.2 Schottky gate HEMTs vs MIS gate HEMTs 55
4.2.1 Current-Voltage characteristics 55
4.2.2 Off-state characteristics 57
4.2.3 Passivation 59
4.2.4 Dynamic characteristic analysis 62
4.3 High current AlGaN/GaN HEMTs on Si substrate 64
4.3.1 Different gate width (WG) single HEMT characteristics analysis 64
4.3.2 Different gate width(WG) multi finger characteristics analysis 65
4.4 AlGaN/GaN enhancement mode HEMTs on silicon substrate 69
CHAPTER 5 CONSLUSIONS 97
REFERENCE 99

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