Phonon heat conduction in Al _xGa _1-xN film

We report on theoretical investigation of the thermal conductivity of Al _xGa _1-xN (0≤x≤1) films over a wide range of temperature by using both Debye's and Callaway's model. Our calculated results agree well with most of the available experimental results of films grown by Hidride Vapor Phase Epitaxy (HVPE) and Metal Oxide Chemical Vapor Deposition (MOCVD) techniques. We find that the large contribution of alloy mass disorder and point impurity scattering is the primary reason for the increase in thermal conductivity of Al _xGa _1-xN alloy film beyond room temperature. Above room temperature, MOCVD films have lower thermal conductivity compared to HVPE grown films due to the presence of a larger amount of defects in MOCVD films as compared to HVPE films. Variation of thermal resistivity with x in Al _xGa _1-xN shows a peak at x=0.7 due to the highest contribution of mass disorder.