Photoluminescence measurement of InGaN and GaN grown by a gas-source molecular-beam epitaxy method

GaN and ${\mathrm{In}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ were grown using a gas-source molecular-beam epitaxy method. Sapphire substrates were used for GaN growth. Ammonia $({\mathrm{NH}}_3)$ gas was used as the nitrogen source gas. As a result, GaN and ${\mathrm{In}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ crystals with mirror surfaces were obtained using uncracked ammonia gas. Photoluminescence measurements of ${\mathrm{In}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ and GaN were investigated. No deep-level emission was observed and only the band-edge emission spectra of ${\mathrm{In}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ 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.