本論文旨在開發以矽(111)為基底的氮化物多接面太陽能電池。利用電漿輔助分子束磊晶成長氮化物薄膜/奈米柱於矽(111)基板上，形成疊層太陽能電池的結構。對於矽基氮化物薄膜而言，由於矽與氮化鎵的晶格不匹配，我們先成長一層薄的氮化鋁作為緩衝層，成長氮化鋁同時，鋁擴散進矽的表面形成p型矽，與n型矽基板形成p-n接面，而後依序成長矽摻雜氮化鎵、本質氮化銦鎵與鎂摻雜氮化鎵。對於矽基氮化物奈米柱而言，藉由調高五三比及成長溫度，成長矽摻雜氮化鎵、本質氮化銦鎵與鎂摻雜氮化鎵奈米柱於矽(111)基板上。
在分析方面，利用掃描式電子顯微鏡來瞭解樣品表面形貌、透過XRD觀察氮化銦鎵樣品的成長品質和銦摻雜進氮化鎵的含量，以及利用穿透式電子顯微鏡分析奈米柱的微結構。在元件製程方面，透過黃光微影、濕式蝕刻以及感應式耦合電漿蝕刻定義出元件大小，利用電子束蒸鍍系統及濺鍍系統，蒸鍍透明導電層、正電極以及背電極，完成元件製作。在電性量測上，利用太陽光譜模擬器模擬AM 1.5G的光源，對元件進行照光之J-V量測，觀察其開路電壓、短路電流、填充因子以及轉換效率，並且利用入射光轉換效率系統進行外部量子效率量測，觀察各波長的光對元件的光電轉換效率。
同時，為了理解本論文中的氮化物薄膜/奈米柱太陽能電池之開路電壓下降效應。
我們準備三種不同成長方式的p-n接面氮化鎵太陽能電池，包含有機金屬氣相沉積成長的p-n接面氮化鎵、電漿輔助分子束磊晶成長p型氮化鎵於有機金屬氣相沉積成長的n型氮化鎵模板，以及電漿輔助分子束磊晶成長的p-n接面氮化鎵。分析其光伏效應，並提出開路電壓下降解釋。此外，無p型氮化鎵的本質氮化鎵肖特基太陽能電池亦被提出分析。
最後，提出了提高轉換效率的三個選擇作為未來展望，包括在MOCVD成長之p型氮化鎵模板成長高結晶品質的規則氮化銦鎵奈米柱、四個電極端點的矽基氮化物串聯太陽能電池結構和無p型氮化銦鎵肖特基太陽能電池。希望這些新設計的三族氮化物器件，可以帶來高轉換效率的乾淨再生能源。

The purpose of this dissertation is developing the Si (111) based nitride multi-junction solar cells. Nitride thin films/ nanorods are grown on Si (111) wafer, formed tandem solar cell structures, by plasma-assisted molecular beam epitaxy. For Si-based nitride thin film, a thin AlN layer was grown as buffer layer due to the lattice mismatch between Si and GaN. Al atoms will diffuse in the top of Si wafer during high-temperature AlN growth, and n-type Si substrate will form a p-n junction. Then, Si:GaN, u-InGaN, and Mg:GaN are grown in sequence. For Si-based nitride nanorods, Si:GaN, u-InGaN, and Mg:GaN nanorods are grown on Si (111) by raising the V-III ratio and growth temperature.
For structural characterization, the sample morphologies are observed by scanning electron microscope; the crystal quality and In concentration are inspected and calculated by X-ray diffraction; the fine structures of nanorods are analyzed by transmission electron microscope. For device process, the size of the mesa are defined by photolithography, wet etching and inductive coupled plasma etching; transparency conductive layers and electrodes are deposited by sputtering and e-beam evaporator. For electrical characterization, open circuit voltage (VOC), short circuit current (JSC), fill factor and conversion efficiency are obtained under AM 1.5 G solar spectrum illumination. The conversion ratio of the incident photon to electron for each wavelength is measured by external quantum efficiency system.
Meanwhile, three different growth methods samples, p-GaN/n-GaN grown by MOCVD, p-GaN grew by PA-MBE on MOCVD n-GaN template and p-GaN/n-GaN grown by PA-MBE, are prepared and analyzed for understanding Voc droop effect. Also, the u-GaN Schottky solar cell will be integrated into free p-GaN layer.
Finally, we propose three options for improving conversion efficiency, includes high crystalline quality of regular InGaN nanorods grown on p-GaN template, four terminal nitride//Si tandem solar cell structure and InGaN Schottky solar cells. Hope these new III-nitride device designs can bring high conversion efficiencies and clean renewable energy.

Verification letter from the oral examination committee i
Power of Attorney ii
致謝 iii
摘要 iv
Abstract vi
Chapter 1 Introduction and research objectives 1
1.1 Harnessing the power of the Sun 1
1.2 Operation of a solar cell 5
1.3 III-nitride material system 10
1.4 Objectives and organization of the thesis 19
Chapter 2 A brief review of epitaxy and characterization techniques 21
2.1 Plasma-assisted molecular beam epitaxy 21
2.2 Material characterization techniques 24
2.2.1 Structural characterization 24
2.2.1.1 Scanning electron microscopy (SEM) 24
2.2.1.2 Transmission electron microscopy (TEM) 25
2.2.1.3 High-resolution X-ray diffraction (HRXRD) 26
2.2.2 Optical characterization 27
2.2.2.1 Photoluminescence measurements (PL) 27
2.2.2.2 Cathodoluminescence measurements (CL) 27
2.2.3 Electrical characterization 28
2.2.3.1 Solar simulators 28
2.2.3.2 External quantum efficiency (EQE) or Incident photon-to-current efficiency (IPCE) 29
2.3 Process system 31
2.3.1 Mask aligner and exposure system 31
2.3.2 Dual e-beam evaporator (e-beam) 31
2.3.3 Rapid thermal annealing system (RTA) 32
2.3.4 Inductively coupled plasma etch (ICP) 33
2.3.5 Sputter 33
Chapter 3 Si-based nitride thin film sample growth, device process, structural, optical and electrical properties discussion 34
3.1 Background and literature review 34
3.2 Si-based nitride thin film sample growth 36
3.3 Structural characterization 38
3.3.1 SEM image 38
3.3.2 HR-XRD analyses 39
3.4 Si-based nitride thin film solar cell process 43
3.4.1 First mask process 43
3.4.2 Second mask process 46
3.4.3 Third mask process 47
3.5 Electrical characterization 47
3.5.1 Controlling thickness of substrate and enhancing the ECE 47
3.5.2 Discussion of J-V curves under the thermal and light power effects 50
3.5.3 Si-based InGaN and GaN (Sample A and Sample B) solar cell comparison 53
3.6 Summary 55
Chapter 4 Si-based nitride nanorods sample growth, devise process, structural, optical and electrical properties discussion 56
4.1 Background and literature review 56
4.2 Si-based nitride nanorods sample growth 58
4.3 Structural characterization 60
4.3.1 SEM image 60
4.3.2 HR-XRD analyses 62
4.3.3 TEM 64
4.4 Si-based nitride nanorods sample devise process 68
4.4.1 First mask process 68
4.4.2 Second mask process 69
4.4.3 Third and fourth mask process 70
4.5 Electrical characterization 72
4.5.1 Band diagram simulation 72
4.5.2 The J-V curve analyses 73
4.5.3 EQE analyses 76
4.6 Summary 78
Chapter 5 P-GaN/n-GaN template sample growth, devise process, and electrical properties discussion 79
5.1 Background and literature review 79
5.2 The structures of different growth method combination p-n nitride sample 80
5.2.1 Mg:GaN/Si:GaN grown by PA-MBE 80
5.2.2 Mg:GaN grown on MOCVD n-GaN template by PA-MBE 81
5.2.3 P-GaN/n-GaN grown by MOCVD 82
5.3 The p-n GaN solar cell process 83
5.4 Electrical characterization 85
5.4.1 Mg:GaN/Si:GaN grown by PA-MBE 85
5.4.2 Mg:GaN grown on MOCVD n-GaN template by PA-MBE 86
5.4.3 P-GaN/n-GaN grown by MOCVD 89
5.5 Summary 91
Chapter 6 Schottky junction III-nitride solar cell 92
6.1 Background and literature review 92
6.2 The simulation of Schottky junction GaN solar cell with different doping level 93
6.3 The u-GaN Schottky junction solar cell process 94
6.4 Electrical characterization 96
6.5 Summary 96
Chapter 7 Conclusions and Perspectives 97
Reference 99
Appendix - 1 -
Appendix I: MBE procedure - 1 -
A-I.1 MBE substrate preparation procedure - 1 -
A-I.1.1 Substrate: sapphire (Al2O3) (c-plane, m-plane) - 1 -
A-I.1.2 Substrate: silicon (Si) - 1 -
A-I.1.3 Substrate: silicon carbide (SiC) - 3 -
A-I.1.4 Substrate: GaN template - 4 -
A-I.2 MBE substrate load/unload procedure - 5 -
A-I.2.1 Load - 5 -
A-I.2.2 Unload - 6 -
A-I.3 MBE venting procedure - 8 -
A-I.3.1 For buffer chamber (general growth mode used) - 8 -
A-I.3.2 For whole MBE system including buffer and growth chamber (open chamber) - 9 -
A-I.4 MBE pump-down procedure - 10 -
AI.4.1.1 For pumping down buffer chamber (general growth mode used) - 10 -
AI.4.1.2 After venting the whole MBE system (for back to the ultra-high vacuum) - 10 -
A-I.5 MBE growth procedure - 11 -
A-I.6 MBE baking procedure - 14 -
A-I.7 MBE outgassing procedure - 15 -
A-I.8 RGA procedure - 15 -
A-I.9 RHEED procedure - 17 -
A-I.10 MBE shutter blade repair - 18 -
A-I.11 Shutter control interface - 21 -
A-I.12 Effusion cell information - 23 -
Appendix II: Metal modulated epitaxy (MME) - 26 -
Appendix III: Four-terminal InGaN//Si dual-junction solar cell - 27 -
Appendix IV: Fabrication of nitride nanorods array by nanosphere lithography - 29 -
Appendix V: Controlling surface morphology and circumventing secondary phase formation in non-polar m-GaN by tuning nitrogen activity - 31 -
Appendix VI: Fast detection of tumor marker CA19-9 using AlGaN/GaN high electron mobility transistors - 54 -

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