GaN andInxGa1−xNwere grown using a gas-source molecular-beam epitaxy method. Sapphire substrates were used for GaN growth. Ammonia(NH3)gas was used as the nitrogen source gas. As a result, GaN andInxGa1−xNcrystals with mirror surfaces were obtained using uncracked ammonia gas. Photoluminescence measurements ofInxGa1−xNand GaN were investigated. No deep-level emission was observed and only the band-edge emission spectra ofInxGa1−xNand Si-doped GaN crystals were observed. It was confirmed that, in the case of undoped GaN growth, the yellow luminescence disappeared upon increasing the V/III flux ratio. ©1997 American Institute of Physics.