The effect of macroscopic polarization on intrinsic and extrinsic thermal conductivities of AlN

• Macroscopic polarization contributes to phonon velocity and Debye temperature of AlN.
• Revised phonon scattering rates are calculated as a function of phonon frequency.
• Intrinsic and extrinsic thermal conductivities of AlN are computed.
• Extrinsic thermal conductivity at room temperature is enhanced from 286 to 344 W/m-K.

The effect of macroscopic polarization on thermal conductivity of bulk wurtzite AlN has been theoretically investigated. Our results show that macroscopic polarization modifies the phonon group velocity, Debye frequency and Debye temperature of the AlN. Using revised phonon velocity and Debye temperature, various phonon scattering rates and combined scattering rate are calculated as functions of the phonon frequency at room temperature. The intrinsic and extrinsic thermal conductivities of AlN have been estimated using these modified parameters. The theoretical analysis shows that up to a certain temperature the polarization effect acts as negative effect and reduces the intrinsic and extrinsic thermal conductivities. However, after this temperature both thermal conductivities are significantly enhanced. High phonon velocity and Debye temperature are the reason of this enhancement which happens due to the polarization effect. The revised thermal conductivities at room temperature are found to be increased by more than 20% in AlN due to macroscopic polarization phenomenon. The method we have developed can be taken into account during the simulation of heat transport in optoelectronic nitride devices to minimize the self heating processes.