The growth of high quality AlN and GaN thin films on basal plane sapphire, (100), and (111) silicon substrates is reported using low pressure metalorganic chemical vapor deposition. X-ray rocking curve linewidths of about 100 and 30 arcsec were obtained for AlN and GaN on sapphire, respectively. Room-temperature optical transmission and photoluminescence (of GaN) measurements confirmed the high quality of the films. The luminescence at 300 and 77 K of the GaN films grown on basal plane sapphire, (100), and (111) silicon was compared.

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.

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