Polarized Raman spectra in GaN

This is the authors' abstract. We don't add key points for this paper.

We have measured polarized Raman spectra in a 2.0 mu m GaN epitaxial layer of high quality, grown on a sapphire substrate. All symmetry-allowed optical phonons in GaN have been assigned as follows: A 1 (LO), 735 cm -1 ; A 1 (TO), 533 cm -1 ; E 1 (LO), 743 cm -1 ; E 1 (TO), 561 cm -1 ; E 2 , 144 and 569 cm -1 . Using the Lyddane-Sachs-Teller relation, the static dielectric constants of GaN for the ordinary and extraordinary directions have been estimated as epsilon perpendicular to 0 =9.28 and E/sub //0/=10.1. We have also observed quasi-LO phonons in GaN. A brief discussion on these will be given.