We use Raman scattering to obtain a stress map of lateral epitaxy overgrown
GaN. Isolated hexagonal islands are grown by selective area overgrowth wit
hout a seed layer. Stress mapping is obtained from shifts in the E-2 phonon
. GaN in the aperture area has the greatest biaxial compressive stress, app
roximate to 0.18 GPa. The overgrowth region is under slightly smaller stres
s, about 0.15 GPa. We attribute marked variations in the A(1)(LO) phonon in
tensity to spatial variations in the free carrier concentration. This is fo
und to be small in the aperture region and high in the lateral overgrowth.
The position-dependent presence of the lower coupled plasmon-phonon band is
consistent with this interpretation. (C) 1999 American Institute of Physic
s. [S0003-6951(99)03338-0].