Doping dependence of the thermal conductivity of hydride vapor phase epitaxy grown n-GaN/sapphire (0001) using a scanning thermal microscope

We have measured the doping concentration dependence of the room temperatur e thermal conductivity (kappa) of two series of n-GaN/sapphire (0001) fabri cated by hydride vapor phase epitaxy (HVPE). In both sets kappa deaeased li nearly with log n, the variation being about a factor two decrease in kappa for every decade increase in n. kappa approximate to 1.95 W/cm-K was obtai ned for one of the most Lightly doped samples (n = 6.9x10(16) cm(-3)), high er than the previously reported kappa = 1.7-1.8 W/cm-K on lateral epitaxial overgrown material [V.A. Asnin et al, Appl. Phys. Lett. 75, 1240 (1999)] a nd kappa approximate to 1.3 W/cm-K on a thick HVPE sample [E.K. Sichel and J.I. Pankove, J. Phys. Chem. Solids 38, 330(1977)]. The decrease in the lat tice component of kappa due to increased phonon scattering from both the im purities and free electrons outweighs the increase in the electronic contri bution to kappa.