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 ep itaxy were studied by high-resolution x-ray diffraction (XRD) mapping measu rements. The lattice constants of epitaxial films are usually estimated fro m symmetric and asymmetric XRD 2 theta-theta measurements. In this study, i t 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 cr ucial to determine the lattice constants of the GaNAs films coherently grow n on GaAs substrates. Mapping measurements of (115) XRD (2 theta-theta)-Del ta omega were performed for this purpose. The band gap energy of the films was determined by Fourier transform absorption spectroscopy measurements. T he band gap energy bowing measured up to the N composition of 4.5% will be discussed by comparing with other measurements and theoretical calculations . (C) 1999 American Institute of Physics. [S0003-6951(99)00809-8].