Heat capacity and phonon mean free path of wurtzite GaN

Abstract

The authors report lattice specific heat of bulk hexagonal GaN measured by the heat flow method in the temperature range of 20–300K and by the adiabatic method in the range of 5–70K. The best fit with the accuracy of 3% was obtained for the temperature-independent Debye temperature ΘD=365K and Einstein temperature ΘE=880K. The authors relate these temperatures to the function of density of states. Using their results for heat conduction coefficient, they established in the temperature range of 10–100K the explicit dependence of the phonon mean free path on temperature ℓph∝T−2. Above 100K, there is an evidence of contribution of the Umklapp processes, which limits phonon free path at high temperatures.