We report on the polarized IR reflectance study of wurtzite GaN thin film grown on 6H-SiC substrate measured at various angles of incidence, namely, from 15 degrees to 75 degrees. Attention is focused on the effects of incident angles on the Brillouin zone center optical phonon modes of She GaN thin film. The reflection spectra are compared to the calculated spectra generated with a damped single harmonic oscillator model. Good agreement between the measured and calculated spectra has been obtained. Overall, the results revealed that the optical phonon modes of the GaN thin film and 6H-SiC substrates are independent of the angle of the incidence beam. (c) 2007 American Vacuum Society.