Impact of dislocations on the thermal conductivity of gallium nitride studied by time-domain thermoreflectance

Abstract

GaN thermal conductivity (κGaN) of hydride vapor phase epitaxy grown GaN (HVPE GaN), high nitride pressure grown GaN (HNP GaN), and metal-organic chemical vapor deposition grown GaN on sapphire (GaN/sapphire) and on Si(111) (GaN/Si) are measured as 204.7 (±4.6), 206.6 (±6.8), 191.5 (±10.5), and 164.4 (±3.2) W/m K, respectively, using the time-domain thermoreflectance technique. Dislocation densities (σD) of HVPE GaN, HNP GaN, GaN/sapphire, and GaN/Si are measured as 4.80 (±0.42) × 105, 3.81 (±0.08) × 106, 2.43 (±0.20) × 108, and 1.10 (±0.10) × 109 cm−2, respectively, using cathodoluminescence and X-ray diffraction studies. Impurity concentrations of Si, H, C, and O are measured by secondary ion mass spectroscopy studies. The relationship between κGaN and σD is modeled through a new empirical model κGaN = 210 tanh0.12(1.5 × 108/σD). A modified Klemens's model, where dislocation induced scattering strength is increased, is proposed to explain the experimental rate of decrease in κGaN with increasing σD. Overall, this work reports how κGaN of heteroepitaxially-grown GaN can be estimated based on σD, providing key design guidelines for thermal management in GaN semiconductor devices.