以第三丁基聯胺/三甲基鎵有機金屬化學氣相沉積系統在不同基材上成長氮化鎵一維奈米線之研究 ; Synthesis of GaN Nanowires on Different Substrates by TMGa-TBHy MOCVD System

國立臺灣科技大學化學工程系 ; 學位：碩士 ; 指導教授：洪儒生 ; 本研究利用有機金屬化學氣相沉積(MOCVD)系統，將氮源由傳統MOCVD製程中所使用的氨氣(NH3)改為第三丁基聯胺(i-butylhydrazine, TBHy)，來與三甲基鎵(trimethyl gallium, TMGa)成長一維奈米結構之氮化鎵奈米線，以有效地降低MOCVD製程的反應溫度。由實驗結果發現，當反應溫度為700℃、V/III供給比為31.4時，藉由掃描式電子顯微鏡(scanning electron microscope, SEM)的量測，可得到一較佳的氮化鎵奈米線之表面形態，長度約為3.0 μm、直徑約為27 nm。第三丁基聯胺除了可以有效降低製程溫度到 700℃外，經由 X光電子能譜(X-ray photoelectron spectrometer, XPS)分析，所成長出的奈米線會有較低的碳汙染量。接著利用六種不同的基材來成長氮化鎵奈米線，分別為：Si(100)、Si(111)、Sapphire、MgO、LiAlO2和GaN，欲藉由降低基材和氮化鎵的晶格常數不匹配度與熱膨脹係數差異，來成長出傾向特定方向的氮化鎵奈米線。在GaN基材上，成長出的氮化鎵奈米線其光激發螢光光譜(photoluminescence, PL)比二維的GaN薄膜強約26.6%，邊際放射峰半高寬為86 meV，顯示特定方向成長出的氮化鎵奈米線，的確有較高的發光量子效率。 Gallium nitride (GaN) nanowires have been synthesized successfully by metalorganic chemical vapor deposition (MOCVD) technique using trimethygallium (TMGa) and i-butylhydrazine (TBHy) as reactants in the first time. Emphasis of this study is placed on evaluating the possibility of using TBHy, a new nitrogen precursor with lower decomposition temperature than ammonia. By using the new nitrogen precursor can decrease process temperature in traditional MOCVD system and the carbon concentration in GaN nanowires. The best morphology and the crystal quality can be obtained in the following experimental conditions : 700℃ and V/III=31.4. The diameter and length of GaN nanowires are about 27nm and 3 μm. Then, we use six different substrates : Si(100), Si(111), Sapphire, MgO, LiAlO2 and GaN to reduce effects of the difference between lattice mismatch and thermal expansion. In the experimental results, GaN nanowires have the specific direction and the better optical quality on GaN substrate. The photoluminescence (PL) intensity which grown GaN nanowires on GaN substrate is stronger 26.6% than GaN substrate and the FWHM (full width at half maximum) of band edge emission is 86 meV. Hence, this propose makes possible further investigation of increasing the brightness of LED in TMGa-TBHy MOCVD system.