以氮化鎵為基底的材料已成功應用於短波長雷射二極體，發光二極體及紫外光光檢測器。在本實驗中，我們以成功使用有機金屬化學氣相沈積法將氮化鎵磊晶膜生長於藍寶石基板上，並且對生長氮化鎵磊晶膜前之氮化鎵非晶結核層之生長溫度、時間以及氮化鎵磊晶膜之生長溫度等參數進行研究。根據77K的光激發光譜、X光散射測量、掃瞄式電子顯微鏡的結果，瞭解氮化鎵的基本特性，並且利用上述方式，生長更好的氮化鎵磊晶膜。在本實驗中，發現非晶結核層在升高溫時會有再結晶現象，此現象在不同條件下的結核層會有不同的結晶程度，成為影響單晶品質與表面平整度的重要參數。根據實驗的結果，我們亦針對黃光區及施體受體對的成因做更深入的研究與探討。

The materials based on GaN have successfully developed on short-wavelength laser diodes (LDs), light-emitting diodes (LEDs) and ultraviolet photodetector. In this study, GaN epitaxial layers have been successfully grown on sapphire substrates. We used several methods including the growth temperature and time of amorphous nucleation layer before growing epilayer and the growth temperature of GaN epilayer to study it. From the results of the photoluminescence (PL) measured at 77K, the X-Ray diffraction measurement, SEM cross sectional views to realize the characteristic and we get a better qualities of GaN epilayers after using the foregoing methods. In this study, the re-crystallization of the amorphous nucleation layer would occur while temperature re-rise to high temperature, and the phenomenon have different crystallinity under the different growth conditions of nucleation layer, which influence the quality and morphology of GaN epilayers seriously. According to the results of the experiments, we study the mechanisms of yellows luminescence and donor-acceptor pair.

CONTENTS.....................................I
LIST OF FIGURES..............................IV
ABSTRACT.....................................VII

1.INTRODUCTION............................................1
1.1 Evilutions and Applications of Group-III Nitrides.....1
1.2 Blue LEDs Materials...................................5
1.3 Crucial Role of GaN Nucleation Layer..................7

2.EXPERIMENTS.............................................8
2.1 MOCVD Growth System...................................8
2.1.1 Flexibility, Simplicity and Versatility.............8
2.1.2 Halide Free.........................................9
2.1.3 Single Hot Zone and Cold Wall System................9
2.1.4 Capability of Multiple Heterostructure.............10
2.1.5 High Temperature and Low Pressure..................10
2.2 Chemical Reactions in MOCVD Process..................11
2.2.1 Advantage of Using TEGa in our System..............12
2.3 Growth System Design.................................13
2.3.1 Equipment Apparatus................................13
2.3.2 Gas Handling System................................13
2.3.3 Reaction Chamber Design............................14
2.3.4 Heating System.....................................15
2.3.5 Exhausted System...................................15
2.3.6 Safety Equipment Considerations....................16
2.4 Substrate Preparation................................17
2.5 Growth Processes.....................................18
2.6 Evaluation of GaN Epilayers..........................19

3. RESULTS AND DISCUSSION................................20
3.1 Photoluminescence Properties of GaN..................20
3.2 Study of GaN Epilayer by Modulating the Growth Temperature of GaN Nucleation Layer......................22
3.2.1 PL Properties......................................24
3.2.2 SEM Analysis.......................................26
3.2.3 X-Ray Measurements.................................27
3.3 Study of GaN Epilayers by Modulating the Growth Time of GaN Nucleation Layer..................................27
3.3.1 PL Properties......................................29
3.3.2 SEM Analysis.......................................30
3.3.3 Raman Spectroscopy and X-ray Diffraction Measurements of Various Nucleation Layer Thicknesses after Recrysallization.........................................33
3.3.4 X-Ray Measurements.................................33
3.4 Study of GaN Epilayers by Modulating the Growth Temperature..............................................34
3.4.1 PL Properties......................................35
3.4.2 SEM Analysis.......................................36
3.4.3 X-Ray Measurements.................................37
3.5 Study of GaN Epilayers by Modulating the Flow Rate of TEGa.....................................................37
3.5.1 PL Properties......................................38
3.5.2 SEM Analysis.......................................38
3.5.3 X-Ray Measurements.................................39
3.5.4 XPS Analysis.......................................40
3.6 Study of GaN Epilayers by Modulating the Flow Rate of NH3......................................................41
3.6.1 PL Properties......................................42
3.6.2 SEM Analysis.......................................42
3.7 Other Analyses in Our Experiment.....................43
3.7.1 X-ray Measurements.................................43
3.7.2 Fourier Transform Infrared (FTIR) Analysis.........44
3.7.2 EDX Analysis.......................................45
3.8 Mechanism of DAP and YL in Our Experiment............45
3.9 Effect on GaN Epilayers with Adding SiN Layer before Nucleation Layer.........................................46
3.9.1 PL Properties......................................47
3.9.2 DCXD Rocking Curves Measurements...................48

4. CONCLUSIONS...........................................50

FIGURES..................................................52
REFERENCE ................................................93

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