GaN and InxGa1-xN were 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 and InxGa1-xN crystals with mirror surfaces were obtained using uncracked ammonia gas. Photoluminescence measurements of InxGa1-xN and GaN were investigated. No deep-level emission was observed and only the band-edge emission spectra of InxGa1-xN and 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.