Thermal conductivity of GaN films: Effects of impurities and dislocations

We report details of the calculation of the lattice thermal conductivity κ in wurtzite GaN. Numerical simulations are performed for n-type wurtzite GaN with different density of silicon dopants, point defects and threading dislocations. Using the material specific model we verified the experimentally observed linear decrease of the room-temperature thermal conductivity with the logarithm of the carrier density n. The decrease was attributed mostly to the increased phonon relaxation on dopants. Our calculations show that the increase in the doping density from 1017 to 1018 cm−3 leads to about a factor of 2 decrease in thermal conductivity from 1.77 W/cm K to 0.86 W/cm K. We have also established that the room-temperature thermal conductivity in GaN can be limited by dislocations when their density is high, e.g., ND>1010 cm−2. The obtained results are in good agreement with experimental data. The developed calculation procedure can be used for accurate simulation of self-heating effects in GaN-based devices.