High spatial resolution thermal conductivity of lateral epitaxial overgrown GaN/sapphire (0001) using a scanning thermal microscope

We have performed high spatial resolution thermal conductivity (kappa) meas urements at room temperature on different patterned sections of GaN/sapphir e (0001) fabricated by lateral epitaxial overgrowth using a scanning therma l microscope. In a number of regions we find kappa approximate to 1.7-1.8 W /cm K, values that are substantially higher than kappa approximate to 1.3 W /cm K previously reported by Sichel and Pankove [J. Phys. Chem. Solids 38, 330 (1977)] on "bulk" material and comparable to the theoretical estimate o f 1.7 W/cm K deduced by Slack [J. Phys. Chem. Solids 34, 321 (1973)]. The i mplications of these findings for device applications will be discussed. (C ) 1999 American Institute of Physics. [S0003-6951(99)04335-1].