臺灣博碩士論文加值系統

本論文藉金屬有機化學氣相沉積法研製具有氮化銦鋁鎵障壁層及氮化鎵通道金屬-氧化物-半導體異質結構場效電晶體；為應用於功率開關和高功率放大器元件，選擇寬能隙、高電子遷移率和高臨界電場的GaN作為通道材料。四元化合物InAlGaN取代InAlN作為障壁層，改善晶格應力以及磊晶溫度差異導致的晶格缺陷，提升通道的電子遷移率。源極和汲極沉積摻雜矽離子的n型氮化鎵覆蓋層以降低接觸電阻。採用超音波霧化熱裂解沉積高k值氧化鋁、氧化鋯作為閘極介電層，減少閘極的漏電流並鈍化表面，提升元件直流特性。
本論文研製兩微米閘極長度具有不同閘極氧化層以及一微米閘極長度具有閘極場極板的金屬-氧化物-半導體異質結構場效電晶體；LG為1 μm、源極-閘極間距(LSG)為3 μm、閘極-汲極間距(LGD)為10 μm、閘極場板長度(LGFP)為2 μm時所量測直流特性為：最大飽和電流密度 (IDS,max) 1794 mA/mm，最大轉導 (gm,max) 為207 mS/mm，開關電流比(Ion/Ioff) 為1.8× 108，導通電阻(Ron) 為3.9 Ω·mm，閘極場極板有效降低閘極汲極間的峰值電場，量測三端關閉狀態崩潰電壓(BVDS)為504 V。
實驗結果表示In0.1Al0.8Ga0.1N/AlN/GaN 寬能隙通道金屬-氧化物-半導體異質結構場效電晶體降低磊晶過程中產生的缺陷，提升通道電子遷移率且提升最大飽和電流密度。採用低成本且非真空的超音波霧化熱裂解沉積法沉積閘極介電質，高k值的氧化鋯提供更高的氧化層電容，有效提升閘極對通道的控制能力，提高電流密度。採用閘極場極板可有效改善崩潰電壓特性。本論文之設計有利應用功率開關以及功率放大元件。

In this thesis, metal-oxide-semiconductor heterostructure field-effect transistors with InAlGaN barrier layer and GaN channels were fabricated using metal-organic chemical vapor deposition (MOCVD). GaN was chosen as the channel material for power switching and high power amplification due to its wide energy gap, high electron mobility, and high critical field. InAlGaN, was employed as the barrier layer instead of InAlN to improve the lattice stress and reduce lattice defects caused by epitaxial temperature difference, enhancing the electron mobility in the channel. At the source and drain electrodes, n-type GaN cap layer was deposited with silicon ions doping to reduce the contact resistance. High k-value Al2O3 and ZrO2 were deposited using ultrasonic spray pyrolysis deposition to reduce the leakage current and passivate the surface of the gate electrode.
In this work, metal-oxide-semiconductor heterostructured field-effect transistors with gate length of 2 μm and different gate oxide were fabricated. Additionally, a transistor with a gate length of 1 μm and a gate field-plate was also fabricated. The measured DC characteristics for LG = 1 μm, LSG = 3 μm, LGD = 10 μm, and LGFP = 2 μm include a maximum saturation current density (IDS,max) of 1794 mA/mm, a maximum extrinsic transconductance (gm,max) of 207 mS/mm, an on/off ratio (Ion/Ioff) of 1.8 × 108, and an on-resistance (Ron) of 3.9 Ω-mm. The gate field-plate mitigates the peak electric field in gate-drain region, resulting in a three-terminal off-state breakdown voltage (BVDS) of 504 V.
The experimental results demonstrate that the developed In0.1Al0.8Ga0.1N/AlN/GaN wide bandgap channel metal-oxide-semiconductor heterostructure field-effect transistors reduce epitaxial defects, improve electron mobility, and increase maximum saturation current density. Using low-cost and non-vacuum ultrasonic spray pyrolysis deposition technology, the gate dielectric layer was deposited, effectively reducing gate leakage current under high voltage. The high-k value ZrO2 results in a high oxide capacitance, enhancing gate control over the channel and increasing current density. Additionally, the gate field-plate effectively improves the breakdown voltage characteristics. The present design is advantageous for applications in power switching and power amplification.

誌謝 III
摘要 V
Abstract VII
Contents IX
Figure Captions XI
Table Captions XIII
Chapter 1 Introduction 1
Chapter 2 Device Structure and Fabrication 7
2-1 Device Structure 7
2-2 Device Fabrication 7
2-2-1 Mesa Isolation 7
2-2-2 n-GaN Cap Layer Etching 9
2-2-3 Source/Drain Ohmic Contacts 10
2-2-4 Gate Dielectric Deposition by USPD 12
2-2-5 Gate (Gate Field-Plate) Electrode Deposition 14
Chapter 3 Experimental Results and Discussion 16
3-1 Materials Analysis 16
3-1-1 Hall measurement 16
3-1-2 X-ray diffraction (XRD) 17
3-1-3 X-ray Photoelectron Spectrometer (XPS) 17
3-2 Electrical Analyses 18
3-2-1 Output Characteristics 19
3-2-2 Transfer Characteristics 20
3-2-3 Transfer Length Method (TLM) 22
3-2-4 Breakdown Characteristics 23
3-2-5 Power Characteristics and Overall Performance 23
3-4 Capacitance-Voltage Characteristics 27
3-4-1 Hysteresis Phenomenon 28
3-4-2 Interface State Density (Dit) 28
Chapter 4 Conclusions 30
References 31
Figures 40

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