III-nitride semiconductors are compound semiconductors having direct band gap and are used for materials of optoelectronic devices. GaN-based rod structure enhances efficiency in the optoelectronic devices. However, there is inhomogeneity in luminescence and doping properties along the rod structure due to the three-dimensional structure different with film case. Because this inhomogeneity affects the performance of the optoelectronic devices, understanding of this property is an important issue. In this dissertation, we systematically studied inhomogeneous emission properties in active layers and doping variation by Mg-doping in the GaN rod. As a result, we confirmed the wavelength, efficiency and polarization change at a different position in the active layers. In addition, composition and electrical properties change by Mg-doping were comprehensively studied by componential, electrical, and optical analyses. Furthermore, we proposed a new designed photonic crystal laser based on a single nanorod. It is expected that this analyses results of inhomogeneity in the GaN rod will contribute to enhance the efficiency of the optoelectronic devices and the new designed nanorod-based laser will be used for a variety of applications.