為了滿足未來互補式金氧半場效電晶體效能表現的需求，更高電子遷移率通道半導體：如三五族砷化鎵，搭配高介電常數氧化物是必需發展的趨勢。然而其中一個最富挑戰性的問題是：如何保護三五族半導體與高介電常數氧化物的界面
，使界面缺陷降低，進而讓半導體表面位能做有效率的移動。
本實驗藉著有力的原位成長半導體及氧化物技術，將原子層沉積法的氧化鋁以及分子束磊晶法的氧化鋁/氧化鎵(氧化釓)原位成長在乾淨的砷化鎵半導體通道層上，並成功地成長出非常明顯且無界面化合物形成的氧化物半導體界面，過程全在超高真空系統中進行。並由一連串的高頻與低頻電容電壓曲線量測以及低頻介穩態電容電壓曲線的計算，做界面特性與金氧半二極體的電性分析。
金屬/原子層沉積氧化鋁/砷化鎵半導體的金氧半二極體在砷化鎵能隙的中間帶中存在一界面能帶密度的鋒值約8x1012 eV-1cm-2，經過850oC快速高溫氦氣退火10s後，界面能帶密度的鋒值變得更寬更大約2x1013 eV-1cm-2。然而，金屬/分子束磊晶氧化鋁/氧化鎵(氧化釓)/砷化鎵半導體的金氧半二極體在整個砷化鎵能隙中展現出較低的界面能帶密度，即使經過850oC快速高溫氦氣退火10s的熱處理，其界面能帶密度仍小於1012 eV-1cm-2。
為了活化場效電晶體的源極與汲極區，800oC以上快速高溫退火是必需以符合未來三五族互補式金氧半場效電晶體的應用。因此，即使經過高溫處理仍擁有較低界面能帶密度的金屬/分子束磊晶氧化鋁/氧化鎵(氧化釓)/砷化鎵半導體的異質金氧半二極體結構具有高發展潛力，做為未來場效電晶體的設計。

In order to fulfill the performance requirements of future CMOS technologies beyond the 15 nm node, it is adamant to employ higher carrier mobility channel semiconductors such as III-V compound semiconductor GaAs plus high-k dielectrics. Nevertheless, a robust high-k oxide/GaAs interface with a low interfacial density of states (Dit) is needed to realize the inversion-channel III-V MOSFETs.
In this work, a powerful technique of in-situ ALD-Al2O3 and MBE-GGO on GaAs approach without using interfacial passivation layers and chemical treatments between oxide/III-V interfaces were performed in a multi-chamber UHV system. By using in-situ process, both oxide/semiconductor hetero-structures showed very abrupt interface without interfacial layer was revealed by HR-TEM.
The interfacial properties are investigated by high frequency (1kHz-1MHz), quasi-static (QS) capacitance-voltage (C-V) measurements and QS-CV calculations. By QS-CV calculations, the Dit distribution versus energy within the band gap can be extracted and is consistent with aforementioned high frequency C-V results between these two systems. The Dit distribution of ALD-Al2O3/GaAs has exhibited a peak around midgap with a value of ~8x1012 eV-1cm-2 and is much broaden and larger with a value ~2x1013 eV-1cm-2 after additional rapid thermal annealing at 850oC in He for 10s. On the other hand, a low Dit value of less than 1012 eV-1cm-2 is attained for the entire band gap for MBE-GGO/GaAs even with RTA at 850oC in He for 10s. Consequently, MBE-GGO is proper dielectric oxide for MOSFETs design due to effective passivation of GaAs surface without Dit peak around mid-gap and excellent thermodynamic stability after RTA to 850oC for S/D activation.

Chapter 1 Introduction 1
1.1 Background 1
1.2 Alternative High-岂 dielectrics 3
1.3 Motivation and Challenges of III-V Channel Materials Beyond Si CMOS 3
1.4 High-岂 Dielectrics on III-V InGaAs 5
Chapter 2 Theory and Instrumentations 8
2.1 Principles of Atomic Layer Deposition 8
2.1.1 Basic characteristic of ALD 8
2.1.2 General characteristics of the surface chemistry of ALD 10
2.2 Ultra-High Vacuum Multi-Chamber MBE System 14
2.2.1 Molecular beam epitaxy 14
2.2.2 In-situ reflection high energy electron diffraction 16
2.3 X-ray Photoelectron Spectroscopy 17
2.4 Scanning Tunneling Microscopy 19
2.5 X-ray Reflectivity 20
2.6 High-Resolution Transmission Electron Microscope 21
2.7 Fundamental of The Metal-Oxide-Semiconductor 22
2.7.1 The ideal MOS capacitor 22
2.7.2 Non-ideal effects in MOS capacitors 25
2.7.3 MOS capacitance-voltage measurements 26
Chapter 3 Experimental Procedures 35
3.1 In-situ ALD Oxide Deposition Process in Ultra-high Vacuum Multi-chamber MBE System 35
3.2 MBE-Al2O3/G2O3(Gd2O3) Oxide Deposition Process in Ultra-high Vacuum Multi-chamber MBE System 40
3.3 In-situ Angle-resolved X-ray Photoelectron Spectroscopy 42
3.4 High resolution transmission electron microscopy 42
3.5 Electrical Properties Measurement 42
Chapter 4 Results and Discussions 43
4.1 HR-TEM Micrograph of Interface 43
4.2 In-situ ALD-Al2O3 on GaAs 44
4.2.1 ALD-Al2O3 on (2x4) and (4x6) surface reconstruction GaAs 44
4.2.2 Thermodynamic stability of in-situ ALD Al2O3 on GaAs 50
4.3 In-situ MBE-Al2O3/GGO on GaAs 57
4.4 Interfacial characteristics of high-岂 dielectric on GaAs 59
4.4.1 Steady state requirement for QSCV measurement 60
4.4.2 Interfacial characteristics of in-situ ALD Al2O3 on (4x6) GaAs(001) with different annealing conditions 67
4.4.3 Interfacial characteristic of MBE-Al2O3/GGO on (4x6) GaAs(001) 72
Chapter 5 Conclusion 75
References 77

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