Effects Of Point Defects And Dislocations On Spectral Phonon Transport Properties Of Wurtzite Gan

The spectral phonon transport properties of bulk wurtzite GaN are investigated with the Monte Carlo method on the basis of the first principle calculations. Contributions of different phonon modes to the thermal conductivity with respect to the phonon frequency, mean free path, and wavelength are studied and the effects of point defects and dislocations are discussed. It is found that the effects of the dislocations are negligible when the dislocation concentration is below 1 x 10(10) cm(-2). The mode analysis shows that the transverse acoustic phonons contribute to the major part of the thermal conductivity from 100 K to 500 K. The point defects and dislocations reduce the thermal conductivity mainly by restraining the transverse modes with little influence on the longitudinal mode. Above 20% thermal conductivity are contributed by phonons with a mean free path larger than 7 mu m in pure crystals at near room temperature. For natural crystals with point defects this length will become ever larger, indicating that the size effects should be taken into consideration when the sample characteristic dimension is less than 10 mu m. More than 90% thermal conductivity is contributed by phonons with wavelength less than 10 nm for GaN crystals with and without defects, implying that the quantum confinement effect is negligible when the sample characteristic size is larger than 10 nm. (C) 2013 AIP Publishing LLC.