Optical properties and internal quantum efficiency of InGaN/GaN core-shell microrods for solid state lighting

We investigate, via temperature and excitation density dependent quasi-resonant confocal micro-photoluminescence, the optical properties and internal quantum efficiency (IQE) of InGaN/GaN single quantum wells (QWs) on Ga-polar GaN microrods selectively grown by continuous flow metal organic vapor phase epitaxy on patterned SiO₂/n-GaN/sapphire template. Seven samples were grown with different growth parameters for the InGaN/GaN QW. The homogeneity of their optical properties is analyzed by mappings along the m-plane facet of the microrods in order to get insight on the growth mechanisms of the shell. Excitation density dependent measurements show that the IQE is affected by the high doping level of the core, which is required to grow such high aspect-ratio structures. Local IQEs between $15\pm 1\hspace{0.17em}\%$ near the tip and $44\pm 5\hspace{0.17em}\%$ near the base of microrods are estimated from measurements at room and low temperature. By comparison with results reported on planar c-plane QWs, we conclude that the radiative recombination rate is the main limitation for the emission efficiency.