We present a nanometer-scale correlation of the structural, optical, and chemical properties of InGaN/GaN core-shell microrods. The core-shell microrods have been fabricated by metal organic vapor phase epitaxy (MOVPE) on c-plane GaN/sapphire templates covered with a SiO2-mask. The MOVPE process results in a homogeneous selective area growth of n-doped GaN microrods out of the mask openings. Surrounding the n-GaN core, a nominal 5 nm thick GaN shell and 30 nm thick InGaN layer were deposited.
Highly spatially resolved cathodoluminescence (CL) directly performed in a scanning transmission electron microscope (STEM) was applied to analyze the selective Indium incorporation in the thick InGaN shell and the luminescence properties of the individual layers. Cross-sectional STEM analysis reveal a hexagonal geometry of the GaN-core with m-plane side-walls. Directly at the corners of the hexagon a-plane nano-facets with a length of 45 nm are formed. The overgrowth of the GaN core with InGaN leads to a selective formation of Indium-rich domains with triangular cross-section exactly at these nano-facets as evidenced by Z-contrast imaging. Probing the local luminescence properties, the most intense CL emission appears at the m-plane side-facets with 392 nm peak wavelength. As expected, the Indium-rich triangles emit a red-shifted luminescence around 500 nm.
Frank Bertram, Marcus Mueller, Gordon Schmidt, Sebastian Metzner, Peter Veit, Juergen H. Christen, Jana Hartmann, Hao Zhou, H.H. Wehmann, and Andreas Waag, "Nanoscopic insights into the structural and optical properties of a thick InGaN shell grown coaxially on GaN microrod
(Conference Presentation)," Proc. SPIE 10532, Gallium Nitride Materials and Devices XIII, 105321E (Presented at SPIE OPTO: January 31, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2288262.5751516187001.
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