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標題: | 利用雙空缺模型分析鍺的外部擴散效應與自動摻雜對於磷化銦鎵長在鍺基板有序排列之影響 Using the di-vacancy hopping model to analyse Ge out-diffusion and its effect on ordering phase in InGaP grown on Ge substrate |
作者: | Hong-Ming Wu 吳宏明 |
指導教授: | 楊英杰(Ying-Jay Yang) |
關鍵字: | 雙空缺跳動模型,外部擴散,相互擴散,有序排列, Di-vacancy hopping model,out-diffusion,inter-diffusion,ordering, |
出版年 : | 2016 |
學位: | 博士 |
摘要: | 我們分析磷化銦鎵直接成長於4吋鍺基板的有序排列特性,利用TEM的繞射圖形指出,在我們的樣品為Cu-Pt B的有序排列,並且有序排列方向為[1-11],這個方向垂直於Ge基板斜切方向,並且只有單一有序排列方向,而TEM高解析影像中的InGaP/Ge介面處,沒有發現到antiphase domain的存在。另外,室溫PL量測下,計算晶圓中心樣品有序排列係數為0.47,而在晶圓邊緣樣品發現雙波峰的現象,利用蝕刻的方式來研究雙波峰分別的來源,實驗顯示在低能量為上層磷化銦鎵的貢獻,而高能量的波峰來自下層,這樣的結果我們推測雙波峰現象為高與低的磷化銦鎵有序排列放光造成,其原因是鍺外部擴散,使得鍺原子擴散到磷化銦鎵磊晶層中,破壞了原有的三族有序排列。最後由拉曼頻譜分析中,利用固定雷射偏振方向,旋轉樣品來觀察354cm-1有序排列之相關波峰,驗證在我們的樣品中Cu-Pt B有序排列方向確實在[1-11]。
接著我們研究鍺的自動摻雜與外部擴散現象,並且利用二次離子質譜儀,量測出在磷化銦鎵磊晶層中鍺原子的分佈。分析指出,鍺的外部擴散範圍約為100 nm,然而在晶圓邊緣的樣品比晶圓中心樣品有著更嚴重的鍺原子自動摻雜現象,使得磷化銦鎵有序排列退化。在晶圓邊緣樣品中,我們觀察到Cu-Pt有序排列殘留於磊晶表層,推測有序排列退化是發生在沉積之後,藉由鍺原子移動使得In/Ga原子同樣進行相互擴散,而不是經由鍺氣相態的自動摻雜,增加In/Ga原子相互擴散造成的退化。另外,我們提出了雙空缺模型來說明鍺的外部擴散現象以及擴散對磷化銦鎵有序排列的影響。在雙空缺模型中,鍺原子的雙性特性將增加雙空缺的密度,而這樣的結果指出鍺濃度和擴散現象是相依的。另一方面,In/Ga原子相互擴散和鍺外部擴散現象是藉由In/Ga原子跳動行為與鍺原子經由雙空缺移動,兩者進行才能實現。基於此模型下,我們模擬鍺外部擴散現象,其完美的擬合鍺在二次離子質譜的曲線。由擬合結果獲得鍺的擴散係數,並由殘餘有序排列層厚度,估計出磷化銦鎵有序排列退化中的時間常數。我們推演出鍺原子和In/Ga原子的跳動率是在同一個數量級,而這樣的結果指出雙空缺易於鍺原子附近結合。 最後我們比較鍺氣相自動摻雜和外部擴散效應在有和沒有Si3N4覆蓋於鍺基板背面,在晶圓邊緣的樣品比中心樣品有著較強的鍺氣相自動摻雜現象,這增加了鍺原子併入初始的GeIII和GeV,使外部擴散效應增加。在SIMS的自動摻雜區指出覆蓋Si3N4的樣品大量減少了自動摻雜的濃度,但在晶圓的邊緣中並沒有被覆蓋到,這樣的結果導致SIMS圖中自動摻雜區呈現了指數型衰減曲線。在有和沒有覆蓋Si3N4的邊緣樣品中,我們觀察到殘留Cu-Pt有序排列層存在於樣品的表面,推測在沉積之後有序排列將被破壞。我們使用了雙空缺擴散模型並加上指數型摔減的自動摻雜初始值,其中有兩性特性的鍺增加了GeIII/GeV補償比例,增加了雙空缺密度促進In/Ga交互擴散。模擬擬合了中心和邊緣樣品外部擴散曲線並擬合的很好。在邊緣的樣品中有覆蓋Si3N4樣品在室溫下的PL雙峰能量差比沒有覆蓋的來的接近,這是因為大量減少了氣相的自動摻雜,增加了磊晶層中有序排列的均勻度,這樣的結果和雙空缺模型所推測的一致。 We report on the structural properties of ordering InGaP directly deposited on (001) Ge substrate by organometallic vapor phase epitaxy. The Ge substrate is 6° miscut towards (110). Results from transmission electron diffraction indicate the existence of CuPt-B ordering phase in the sample. The ordering direction is assigned to be [1-11], which is perpendicular to the miscut direction of the Ge substrate. Because only one ordering phase is observed, no anti-phase domain exists in the sample. The order parameter determined from photoluminescence at room temperature is 0.47. Raman scattering was also used to analyze the ordering effect. A mode at 354 cm-1 relevant to the ordering phase confirms that the CuPt-B ordering is along [111]. We study Ge auto-doping and out-diffusion in InGaP epilayer with Cu-Pt ordering grown on 4-inch. Ge substrate. Ge profiles determined from secondary ion mass spectrometry indicate that the Ge out-diffusion depth is within 100 nm. However, the edge of the wafer suffers from stronger Ge gas-phase auto-doping than the center, leading to ordering deterioration in the InGaP epilayer. In the edge, we observed a residual Cu-Pt ordering layer left beneath the surface, suggesting that the ordering deterioration takes place after the deposition rather than during the deposition and In/Ga inter-diffusion enhanced by Ge vapor-phase auto-doping is responsible for the deterioration. We thus propose a di-vacancy diffusion model, in which the amphoteric Ge increases the divacancy density, resulting in a Ge density dependent diffusion. In the model, the In/Ga inter-diffusion and Ge out-diffusion are realized by the random hopping of In/Ga host atoms and Ge atoms to di-vacancies, respectively. Simulation based on this model well fits the Ge out-diffusion profiles, suggesting its validity. By comparing the Ge diffusion coefficient obtained from the fitting and the characteristic time constant of ordering deterioration estimated from the residual ordering layer, we found that the hopping rates of Ge and the host atoms are in the same order of magnitude, indicating that di-vacancies are bound in the vicinity of Ge atoms. Finally, we compare of the Ge gas phase auto-doping and out-diffusion in InGaP epilayers grown on 4-inch with and without Si3N4 coating on backside of Ge substrate by organometallic vapour phase epitaxy. The edge of the wafer suffers from stronger Ge gas-phase auto-doping than the centre, which increase Ge atoms incorporate of initial GeIII and GeV and leading enhancement of out-diffusion. In SIMS auto-doping region indicate the Si3N4 capping backside sample reduces the most of all gas phase auto-doping, but only substrate wafer side uncapping. This result leading to auto-doping region present exponent decay profile in SIMS. In the with and without edge sample, we observed a residual Cu-Pt ordering layer left beneath the surface, suggest that the deteriorating of the ordering takes place after the deposition. We used di-vacancy diffusion model and added exponent decay of gas-phase auto-doping, in which the amphoteric Ge increases GeV/GeIII compensation ratio and promotes In/Ga inter-diffusion with increasing the di-vacancy density. Simulation based on this model well fits the Ge out-diffusion profile in the both sample, suggesting its validity. In edge sample, with coating sample of PL energy different of two peak is close than without sample. It attribute decrease of gas-phase auto-doping and enhancement uniformity of degree of order in depth of epilayer. These findings are obviously in consistent with that obtained from the Di-vacancy model. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/49749 |
DOI: | 10.6342/NTU201602411 |
全文授權: | 有償授權 |
顯示於系所單位: | 電子工程學研究所 |
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