在此論文中我們探討了在藍寶石基板上以射頻電漿輔助分子束磊晶成長第三族氮化物半導體。藍寶石基板的氮化和低溫緩衝層被用來克服基板與氮化鎵之間的晶格不匹配以形成良好品質之氮化鎵。低溫長時間的氮化對氮化鎵薄膜的光學性質與磊晶品質有明顯的改善；而以基板溫度522℃，鎵略多餘氮的比例下成長兩分鐘緩衝層可得到較佳之氮化鎵薄膜。較高的基板溫度與足夠的氮對鎵比例則是控制氮化鎵薄膜品質的兩個重要因素。而三族氮化物的極性常以化學蝕刻以及觀察表面重建來檢驗，鎵極性的氮化鎵薄膜表現出2x表面重建和良好抵抗化學蝕刻而氮極性則表現出3x表面重建和無法抵抗化學蝕刻。成長溫度對銦在氮化銦鎵中的比例佔了很重要的影響，銦的成分隨著基板溫度的增加而減少同時亦隨著薄膜成長方向而遞減。

以銦輔助成長技術來成長氮極性之氮化鎵薄膜也在此論文中探討，隨著增加摻入銦的量，氮化鎵薄膜之光致激光強度和電子遷移率分別增加15倍和6倍，而載子濃度也增加幾個等級。從拉曼量測上也發現氮化鎵薄膜的應力從0.6729減少到0.5044GPa。相對應所有螺旋差排密度之(10-12) X光繞射半高寬從593增加到744 arcsec；而對應伯格向量c不為零的螺旋差排量測之 (0002)X光繞射半高寬則從528減少至276 arcsec。 氮化鎵薄膜之光學性質的增益主要導因為伯格向量之c不為零的螺旋差排減少，而此差排密度的減少也經由穿透式電子顯微鏡得到進一步的驗證 。

The group III nitride semiconductor grown on c-plane sapphire by radio frequency plasma assisted molecular beam epitaxy has been studied. To archive good quality GaN film, nitridation and low temperature buffer layer were applied to overcome the issue of lattice mismatch. Low temperature and long period nitridation process shows better improved of optical properties and crystal quality of GaN film. Buffer layer grown with slightly Ga-rich, substrate temperature at 522℃, for 2 minutes leads to better GaN film. High substrate temperature and sufficient nitrogen to gallium ratio are two important factors to control the growth of the good quality GaN epilayer. Chemical etching and observation of surface reconstructions were used to characterize the polarity of group III nitrides. The Ga-polarity GaN film shows 2x surface reconstruction with high chemical resistance while the N-polarity is sensitive to chemical and displays the 3x reconstruction pattern. The process of indium incorporated with GaN is very sensitive to growth temperature. The indium content decreased with increasing the substrate temperature and also decreased along the growth direction.

The N-polar GaN with an indium-facilitated growth technique was also studied. Upon the incorporation of indium during growth, the photoluminescence intensity and electron mobility of GaN has been enhanced by a factor of 15 and 6 respectively. The electron concentration drastically increases by several orders of magnitude. The biaxial strain of GaN film estimated with Micro-Raman technique reduces from 0.6729 to 0.5044GPa. The full-widths at half maximum of asymmetric (10-12) x-ray reflection which related to the density of overall threading dislocations increases from 593 to744 arcsec. In contrast, the symmetric (0002) reflection related only to threading dislocations having a non-zero c-component Burgers vectors reduces from 528 to 276 arcsec. The enhancement of GaN optical property is generally attributed to the reduction of non-zero c-component dislocations. The reduction in density is confirmed by cross-sectional transmission electron microscopy.

Abstract i
摘要 iii
Chapter 1 Introduction 1
Reference 10
Figures 16
Chapter 2 Growth and Characteristics 25
2.1 Radio frequency plasma assisted molecular beam epitaxy 25
2.2 Growth procedure 27
2.2.1 Sapphire preparation 27
2.2.2 Nitridation 27
2.2.3 Buffer layer 28
2.2.4 GaN epilayer 28
2.2.5 InGaN bulk 28
2.3 Characteristic measurements 28
2.3.1 Reflective high energy electron diffraction 28
2.3.2 Alpha step surface profiler 29
2.3.3 X-ray diffraction 29
2.3.4 Field emission scanning electron microscopy 30
2.3.5 Transmission electron microscopy 30
2.3.6 Raman spectroscopy 31
2.3.7 Electron probe microanalyzer 31
2.3.8 Secondary ion mass spectrometry 31
2.3.9 Photoluminescence 32
2.3.10 Hall effect measurement 32
2.3.11 Quantitative dislocation density from TEM
image 33
2.3.11.1 Plane view TEM 33
2.3.11.2 Cross sectional TEM 34
Reference 39
Figures 40
Chapter 3 Result and Discussion 49
3.1 Nitridation 49
3.2 Low temperature GaN buffer layer 51
3.3 GaN Epilayer 53
3.4 Polarity of GaN epilayer 57
3.5 InGaN bulk 58
Reference 60
Figures 62
Chapter 4 Indium-facilitated Growth 88
Reference 95
Figures 97
Chapter 5 Conclusions 105
Chapter 6 Future Works 108
Reference 111

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Chapter 2
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Chapter 3
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[16]A.R. Smith, R.M. Feenstra, D.W. Greve, M.-S. Shin, M. Skowronski, J. Neugebauer, and J.E. Northrup, Determination of wurtzite GaN lattice polarity based on surface reconstruction. Applied Physics Letters, 72(2114) (1998).
[17]D.C. Reynolds, D.C. Look, W. Kim, O. Aktas, A. Botchkarev, A. Salvador, H. Morkoc, and D.N. Talwar, Ground and excited state exciton spectra from GaN grown by molecular-beam epitaxy. Journal of Applied Physics, 80 (1996) 594.
[18]I. Vurgaftman, J.R. Meyer, and L.R. Ram-Mohan, Band parameters for III-V compound semiconductors and their alloys. Applied Physics Review, 89 (2001) 5815.
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Chapter 4
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Chapter 6
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