On the upper limit of thermal conductivity GaN crystals

The maximal value of thermal conductivity κmaxκmax of the perfect wurtzite GaN crystal containing isotopes of natural abundance is estimated. Our upper limit of κ=4800W/K m at Tmax=32K is smaller than that calculated by Liu and Balandin κ=6000W/K m and higher than that obtained by Slack et al. κ=3750W/K m. The phenomenological dependence κ∝T−1.43κ∝T−1.43 obtained by Mion et al. for the temperature interval 300–450 K is extended to 200–300 K. For temperatures higher than TmaxTmax the best fitting of our experimental data to Callaway’s formula is obtained for Grueneisen’s constant equal to γ=1.35γ=1.35.