水平式MOCVD腔體中使用氣體脈衝法生長AlxGa1-xN多層結構之數值模擬分析;Numerical analysis of pulsed injection MOCVD method to grow AlxGa1-xN multi-layer structure in horizontal reactor

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Title:	水平式MOCVD腔體中使用氣體脈衝法生長AlxGa1-xN多層結構之數值模擬分析;Numerical analysis of pulsed injection MOCVD method to grow AlxGa1-xN multi-layer structure in horizontal reactor
Authors:	孫正勳;SUN, CHENG-HSUN
Contributors:	機械工程學系
Keywords:	金屬有機化學氣相沉積;含鋁氮化鎵;MOCVD;AlGaN
Date:	2018-08-13
Issue Date:	2018-08-31 15:04:29 (UTC+8)
Publisher:	國立中央大學
Abstract:	金屬有機化學氣相沉積法(MOCVD)技術具有外延層(epitaxial layer)均勻性好、材料純度高等特性，因此為今LED磊晶產業中重要技術，而本研究將探討MOCVD製程中生長AlxGa1-xN薄膜的化學機制和傳輸現象。研究發現生長AlxGa1-xN薄膜會因不同的製程參數產生不同的固態薄膜比例x，而不同的x值也具有不同的能隙，因而產生不同的發光表現。當生長不同層AlxGa1-xN薄膜時，在兩層不同固態比例薄膜交接處(過度區)會產生Al原子比例不均勻的現象，此現象會造成能隙與預期有落差。為了探討在生長AlxGa1-xN薄膜時影響固態薄膜比例的因素，本研究先建立在入口處反應氣體TMGa、TMAl、NH3及載氣H2同時混合之穩態模型，並探討在不同溫度及反應前驅物流量對固態薄膜比例的影響，發現主要貢獻GaN沉積速率的物種為MMGa，而主要貢獻AlN沉積速率物種為DMA:NH2及[DMA:NH2] 2兩種。接著，本研究透過暫態數值模型模擬使用氣體脈衝方法(Pulsed Injection, PI Method)之MOCVD，在持續供應載氣H2的情況下控制反應源氣體TMGa、TMAl及NH3通入腔體之脈衝時間。模擬結果顯示，使用PI法能改變AlxGa1-xN反應路徑，TMAl主要反應路徑由聚合熱裂解反應轉變為TMAl自身熱裂解反應，此路徑的改變可以減少Particles的形成，並有效增加薄膜沉積速率。另外，隨著不同層AlxGa1-xN中間隔載氣的脈衝時間增加，可以有效減少兩層之間DMA_NH2及其聚合物的產生，並減少不同層AlxGa1-xN薄膜間Al原子比例不穩定的問題。 ;Metal Organic Chemical Vapor Deposition (MOCVD) is an important process for LED manufacture because of the unique advantages including uniform epitaxial layer and high purity of the material. In this study, a complicated chemical mechanism and mass transport phenomena of growing AlxGa1-xN films in MOCVD process were discussed. It is found that the solid fraction (x) of AlxGa1-xN layer will be changed by different process parameters, different solid fraction of AlxGa1-xN layer have different energy gap and different luminous performance. When growing different AlxGa1-xN layer structures, the phenomenon of non-uniform Al atoms would be observed in the junction, and it will cause different energy gap. In order to study the factor which affect the solid fraction of growing AlxGa1-xN films, the steady state model of TMGa, TMAl, NH3 and H2 mixed gas at the inlet was established, and the effects of temperature and precursor flow rate were discussed. The result shows that the main species which contributes the deposition rate of GaN is MMGa, and for AlN is DMA:NH2 and [DMA:NH2] 2. This study control the duration of TMGa, TMAl and NH3 supply while the carrier gas H2 was continuously supplied to the reactor chamber by using pulsed injection, (PI) method. The result shows that the reaction pathway of AlxGa1-xN will be changed by using PI method. TMAl polymer pathway replace the pyrolysis pathway, therefore particle formation can be reduced and increase the deposition rate effectively. In addition, as increasing the duration of the carrier gas between two different AlxGa1-xN layers, the mole fraction of DMA_NH2 and other polymers can be reduced and enhance the uniformity of AlxGa1-xN films effectively.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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