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 (κ) measurements at room temperature on different patterned sections of GaN/sapphire (0001) fabricated by lateral epitaxial overgrowth using a scanning thermal microscope. In a number of regions we find κ≈1.7–1.8 W/cm K, values that are substantially higher than κ≈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 of 1.7 W/cm K deduced by Slack [J. Phys. Chem. Solids 34, 321 (1973)]. The implications of these findings for device applications will be discussed.