The Investigation on GaN Growth byEpitaxial Lateral Overgrowth

• Main Authors: ching-i chang, 張靜宜
• Other Authors: Chuan-Pu Liu
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/95774979747453593523

碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 93 === 　The optical performance of a GaN blue-light emitting diode is greatly influenced by the density and distribution of threading dislocations, which in turn strongly depend on the ratio of mask to window width during Epitaxial Lateral Overgrowth (ELOG). Thus we study the dependence of microstructure and optical property evolution on the spatial distribution of the defects in the ELOG GaN films by varying mask to window width ratio. The window width is maintained at 5μm and the ratio is varied from one to five. We employ a two-step ELOG method to fabrication GaN by Metalorganic chemical vapor deposition (MOCVD), where SiO2 as the mask was grown on low-temperature GaN as the buffer and seed layer. The patterns were square dot array and developed by conventional photolithography method, where the ELOG GaN stripes on SiO2 were arranged along the directions of the underlying GaN. X-ray rocking curves show that all the resulting films are of excellent epitaxial quality with non-uniform strain distribution, which was a function of the mask ratio and determines the spatial distribution of threading dislocations. The detailed GaN island evolution was also revealed by scanning electron microscopy. Photoluminescence and cathodoluminescence examine the origins of UV and yellow emissions, which can be explained by defect generation as examined by transmission electron microscopy. The mechanism for impeding threading dislocations is discussed.