Impact of impurity-based phonon resonant scattering on thermal conductivity of single crystalline GaN

Abstract

The impact of impurities on the thermal conductivity of halide vapor phase epitaxy gallium nitride (GaN) was studied. Phonon resonances with impurities, modeled as Lorentz oscillators, were used to explain the much lower thermal conductivity than predicted by the Debye-Callaway model. The resonance energies for the oscillators were determined by Raman spectroscopy for Mn and by mass difference approximation for C and Fe. Employing the obtained resonance energies and proportionality factors extracted as fitting parameters, the modified model showed a good agreement with the experimental data. While the doping decreased thermal conductivity for all temperatures, the room temperature values started decreasing significantly once the doping levels approached ∼1019 cm-3. Consequently, required doping levels to achieve certain GaN-based devices may reduce the thermal conductivity of GaN by as much as 1/3.