The high-quality InxGa1−xN/GaN multiple quantum wells were grown on GaN microdisks with γ-LiAlO2 substrate by using low-temperature two-step technique of plasma-assisted molecular beam epitaxy. We demonstrated that the hexagonal GaN microdisk can be used as a strain-free substrate to grow the advanced InxGa1−xN/GaN quantum wells for the optoelectronic applications. We showed that the green light of 566-nm wavelength (2.192 eV) emitted from the InxGa1−xN/GaN quantum wells was tremendously enhanced in an order of amplitude higher than the UV light of 367-nm wavelength (3.383 eV) from GaN.