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We report the selective-area growth of a gallium nitride (GaN)-nanorod-based InGaN/GaN multiple-quantum-well (MQW) core-shell structure embedded in a three-dimensional (3D) light-emitting diode (LED) grown by metalorganic chemical vapor deposition (MOCVD) and its optical analysis. High-resolution transmission electron microscopy (HR-TEM) observation revealed the high quality of the GaN nanorods and the position dependence of the structural properties of the InGaN/GaN MQWs on multiple facets. The excitation and temperature dependences of photoluminescence (PL) revealed the m-plane emission behaviors of the InGaN/GaN core-shell nanorods. The electroluminescence (EL) of the InGaN/GaN core-shell-nanorod-embedded 3D LED changed color from green to blue with increasing injection current. This phenomenon was mainly due to the energy gradient and deep localization of the indium in the selectively grown InGaN/GaN core-shell MQWs on the 3D architecture.

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The correlation between luminescence and defects was investigated by the structural and optical analyses of semipolar InGaN/GaN quantum wells (QWs) grown on a planar m-plane sapphire substrate and patterned m-plane sapphire substrate using metal organic chemical vapor deposition. Scanning electron microscopy images indicated that the semipolar InGaN/GaN QWs grown on the planar substrate had high density of small arrowhead-like features on the surface, while those grown on the patterned sapphire substrate (PSS) had low density of large arrowhead-like features. Moreover, for the PSS sample, low defect regions were formed by periodically aligned patterns that reduced defect density, as verified by transmission electron microscopy. The monochromatic cathodolumine-scence images revealed that the luminescence of the planar sample was affected by the arrowhead-like features and high internal defect density, whereas that of the PSS sample was more influenced by the regions with reduced defects, as indicated by bright spotty features. Furthermore, the microphotoluminescence mapping images showed increased In incorporation where the arrowhead-like features were present. In particular, for the PSS sample, the wavelength of the luminescence from the reduced defect region was approximately 5 nm shorter than that from the region with a high density of internal defects. This result suggests that In incorporation was also increased in the high defect region.

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