Reexamination of N composition dependence of coherently grown GaNAs band gap energy with high-resolution x-ray diffraction mapping measurements

GaNAs films grown on GaAs(001) substrates by metalorganic molecular beam epitaxy were studied by high-resolution x-ray diffraction (XRD) mapping measurements. The lattice constants of epitaxial films are usually estimated from symmetric and asymmetric XRD 2θ–θ measurements. In this study, it is pointed out that the consideration of the tilt angle between the GaAs(115) and GaNAs(115) planes caused by elastic deformation of the films is crucial to determine the lattice constants of the GaNAs films coherently grown on GaAs substrates. Mapping measurements of (115) XRD (2θ–θ ) –Δω were performed for this purpose. The band gap energy of the films was determined by Fourier transform absorption spectroscopy measurements. The band gap energy bowing measured up to the N composition of 4.5% will be discussed by comparing with other measurements and theoretical calculations