Nitrogen-induced localized level observed by photoreflectance in GaAsN thin films grown by chemical beam epitaxy

•GaAsN with high-nitrogen-homogeneity were grown by CBE.•The nitrogen-induced localized level (EN) was investigated by photoreflectance.•EN value decreased with increase in N content.•The change of microstructure of nitrogen atom and their cluster were discussed.

Dilute nitride films of GaAsN with high nitrogen homogeneity were grown by using the chemical beam epitaxy technique. This allowed us to investigate the electronic structure of the nitrogen-induced localized level (EN) in GaAsN by photoreflectance measurements. We found that the EN value decreased as the nitrogen content increased. Consideration of the energy levels of isolated nitrogen (Nx); pairs of nitrogen atoms (NNi) where i=1, 2, and so on in order of increasing pair separation; and nitrogen clusters may help explain the changes in the estimated EN value.