We have developed a nanophotonic platform with microdisks using epitaxial III-nitride materials on silicon. The two-dimensional platform consists of suspended waveguides and mushroom-type microdisks as resonators side-coupled with a bus waveguide. Loaded quality factors up to 80000 have been obtained in the near-infrared spectral range for microdisk diameters between 8 and 15 μm. We analyze the dependence of the quality factors as a function of coupling efficiency. We have performed continuous-wave second harmonic generation experiments in resonance with the whispering gallery modes supported by the microdisks.