Thermal conductivity of GaN crystals in 4.2–300 K range

Results of measurements of thermal conductivity of bulk GaN crystals in the temperature interval 4.2–300 K are reported. Experiments were performed on two types of single GaN crystals grown under high-pressure: highly conducting n-type sample and on a highly resistive sample compensated by magnesium doping. For n-GaN crystals, the highest thermal conductivity κmax is equal to 1600 W/m K at Tmax=45 K, and κ≃220 W/m K at 300 K. Our analysis indicates that for the best n-GaN crystal and for T≥Tmax, the contribution of Umklapp phonon scattering processes dominate whereas for other samples scattering of phonons by point mass defects represents the main contribution. The dependence of κ(T) is used to reveal possible mechanisms of thermal resistance of GaN crystals at temperatures Tmax. Our thermal conductivity measurements yields Debye's temperature θD≈400K.