Thermal conductivity of bulk GaN grown by HVPE: Effect of Si doping

The thermal conductivity of bulk GaN grown by Hydride Phase Vapor Epitaxy with intentional Si doping was measured using the 3ω method. The effect of Si concentration ranging from 1.6 × 10 16 to 7 × 10 18 cm −3 on the thermal conductivity was studied over the temperature range of 295–470 K. The room temperature thermal conductivity was found to decrease with increasing Si doping from 245 to 210 W/m · K. Also, for each Si doped sample the thermal conductivity decreases with increasing temperature. The experimental data were analysed by a modified Callaway model and the contribution of different resistive phonon scattering process was examined. It was found that in n ‐type GaN the phonon‐free‐electron scattering became an important resistive process that leads to a reduction of the thermal conductivity at high temperatures. At the highest free electron concentrations, electronic thermal conduction was found to play a role in addition to lattice thermal conduction and compete with the effects of phonon‐free‐electron scattering.