Raman scattering of coherently strained GaNxAs1-x alloys grown on GaAs (001) substrates by molecular beam epitaxy has been investigated in the temperature range of 80-150 K. The intensity of GaAs-like longitudinal optical (LOGaAs) phonon and nitrogen-localized vibration mode (NLVM) decrease with temperature and the line width of both these modes show substantial broadening at higher temperatures. Temperature dependence of phonon line width and peak frequency of LOGaAs modes were analyzed in terms of anharmonic damping effect induced by thermal and compositional disorder. It is found that the anharmonicity is higher for GaNAs than that for GaAs, and increases with N concentration in GaNAs alloys. Both thermal- and disorder-induced anharmonicities can change the line width, line frequency, and lifetime of LOG As mode in GaNAs alloys. These results obtained from Raman investigation would lead to a better understanding of the anharmonic effects in dilute nitrides. (c) 2005 Elsevier B.V. All rights reserved.