We have measured high spatial/depth resolution (similar to 2-3 mu m) therma
l conductivity (kappa) at 300 K of both fully and partially coalesced GaN/s
apphire (0001) samples fabricated by lateral epitaxial overgrowth. On the f
ully coalesced sample we found 1.86W/cm K < kappa < 2.05 W/cm K over a dist
ance of approximately 50 mu m. One of the partially coalesced samples had 2
.00 W/cm K < kappa < 2.10 W/cm K on the overgrown regions, as identified by
atomic force microscopy imaging. These latter results are the highest ther
mal conductivity values reported on GaN material. A correlation between low
threading dislocation density and high thermal conductivity values was est
ablished. (C) 2000 American Institute of Physics. [S0003-6951(00)04336-9].