Strain effect on the N composition dependence of GaNAs bandgap energy grown on (001) GaAs by metalorganic molecular beam epitaxy

We study the N composition dependence of GaNAs bandgap energy up to 4.5%. T he lattice structures and lattice strain of GaNAs films were characterized by the high-resolution X-ray diffraction (XRD) mapping measurements. By the asymmetric (1 1 5) XRD mapping measurements, the precise elastic deformati on of the epitaxial films was determined. The measured bandgap of the coher ently strained GaNAs is very close to the theoretical bandgap based on the dielectric model for N composition less than 1.5%. Above this value, it dev iates considerably from the dielectric model calculation. The theoretical c alculations based on the first-principle supercell calculations cannot expl ain the measured bandgap properties with the increase of the N composition. The influence of inhomogeneity in GaNAs films on the bandgap bowing will b e also discussed. (C) 1999 Elsevier Science B.V. All rights reserved.