成長於(100)矽基板之P型倒置結構半極性氮化銦鎵奈米量子井應力分析;Strain analysis on semipolar nanopyramidal InGaN quantum wells grown on (100) Si substrates

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/79469

Title:	成長於(100)矽基板之P型倒置結構半極性氮化銦鎵奈米量子井應力分析;Strain analysis on semipolar nanopyramidal InGaN quantum wells grown on (100) Si substrates
Authors:	鄭羽翔;Zheng, Yu-Shiang
Contributors:	光電科學與工程學系
Keywords:	奈米異質磊晶術
Date:	2019-01-30
Issue Date:	2019-04-02 14:28:58 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究探討磊晶應力對氮化銦鎵奈米量子井的光電特性影響。我們利用奈米異質磊晶術，將此奈米量子井成長於(100)矽基板上。為了降低磊晶層與矽基板之間的磊晶應力，我們先在矽基板表面，成長一層均勻分佈的氧化鋅奈米柱陣列，之後以有機金屬化學氣象沉積法成長氮化銦鎵量子井，再將此奈米量子井轉移至銀基板上，並探討量子井在基板轉移前後因應力改變所產生的光譜變化。我們利用纖維鋅礦結構的氧化鋅材料與纖維鋅礦結構的氮化鎵材料之間較小的晶格差異，成功在(100)矽基板上成長出無裂痕的(10-11)面半極性氮化鎵六角椎金字塔型結構，並且利用氧化鋅奈米緩衝層在高溫磊晶時的擴散行為，產生自發性的P-型氮化鎵，以達成獨特的p-side down元件結構，希望能達到高發光效率的發光二極體。本研究以不同流量的二茂鎂(Bis(cyclopentadienyl)-magnesium, Mg(C5H5)2): 40、80、120 sccm，在p -型氮化鎵產生不同的電洞濃度，藉以分析電洞濃度對磊晶應力及量子井發光效率的影響。由於氮化物磊晶層與矽基板有極大的熱膨脹係數差異，在磊晶的過程中，會產生相當的晶格應力，此應力會降低量子井中的發光效率。此外，矽基板與氮化鎵磊晶層介面的反射率很低，也會降低發光二極體的外部量子效率。為了解決這兩大問題，我們將磊晶層轉移到銀基板上，再藉由移除矽基板，來釋放磊晶層中的應力。因為銀基板的具備高反射率，能有效提高量子井的光萃取效率。根據掃描式電子顯微鏡的觀察、模擬軟體的分析、X光繞射儀以及拉曼光譜的量測，我們發現: 鎂摻雜量較少的樣本，展現較小的伸張應力，以及較佳的晶格品質因此具備較高的內部量子效率。;In this study, the effect of lattice strain before and after substrate transfer on the optoelectrionic properties of nanostructured InGaN quantum wells (QWs) structures was investigated. The nanostructure QWs were grown on (100) Si substrates by metal-organic chemical vapor deposition (MOCVD), employing ZnO nanorods as the buffer layer to release the huge stratin between Si and the nitride epilayer. Using the small lattice mismatch between ZnO and GaN, we successfully grew the (10-11) semi-polar nanopyramidal QWs on the (100) Si substrate. The diffusion of Zn into GaN during the epitaxial growth also allows us to achieve the naturally formed p-type GaN, producing the desired p-side-down structure for QWs with enhanced interal quantum efficiency. During the growth, three different flow rates of Bis(cyclopentadienyl)-magnesium Mg(C5H5)2, i.e. 40, 80, and 120 sccm were adopted with the attempt to study the effect of p-type doping on the strain and the quantum efficiency of the QWs. Due to the large thermal mismatch between the GaN epilayer and the Si substrate, huge lattice strain is expected in the epilayer after the MOCVD growth. The strain decreased the internal quantum efficiency of the InGaN QWs via the quantum-confinement Stark effect. The semipolar nanostructured QWs produced in this study are expected to exhibit improved radiative recombination efficiency becoause of the alleived QCSE. In addition, we transferred the epitaxial layer from the Si substrate to a silver substrate using a wet-etching technique, releasing the stress on the samples and increasing reflectivity at the epilayer/substrate interface. The released stress and enhanced interface reflectivity should lead to improved external quantum efficiency of the nanopyramidal QWs. Scanning electron microscopy was used to observe the microstructure of the samples and a simulation software is used to analyze the relationship between the film thickness and the reflection wavelength. The samples were also characterized by x-ray diffraction (XRD) and Raman spectroscopy. According to these characterizations, it is found that the sample with less magnesium doping exhibits less tensile stress, and thus the higher internal quantum efficiency.
Appears in Collections:	[Graduate Institute of Optics and Photonics] Electronic Thesis & Dissertation

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