In this article, we estimate hydrostatic stress developed in gallium ion-implanted gallium nitride epitaxial layers using Raman measurements. We have calculated deformation potential constants for E-2(high) mode in these epi-layers. The presence of a polar phonon-plasmon coupling in these systems has also been demonstrated. In as-implanted samples, with an increase in implantation fluence, we have observed disorder-activated Raman scattering. (c) 2006 Elsevier B.V. All rights reserved.