Bowing parameter of the band-gap energy of GaNxAs1-x

We report a study of nitrogen incorporation in GaAs using a N rf plasma source. The N composition can be increased by lowering the growth temperature. X-ray diffraction shows no phase separation. Optical absorption measurements indicate that GaNxAs1-x is a direct band-gap material in the N composition range studied (x less than or equal to 14.8%), rather than a semimetal, contrary to theoretical predictions based on Van Vechten's model. Analyzing the N composition dependence of the band-gap energy of the alloy indicates a composition-dependent bowing parameter, consistent with the first-principles supercell calculations [L. Bellaiche, S. H. Wei, and A. Zunger, Phys. Rev, B 54, 17 568 (1996)]. (C) 1997 American Institute of Physics.