Thermal conductivity of GaN crystals grown by high pressure method

Abstract

Results of measurements of thermal conductivity κ of bulk GaN crystals in the temperature interval 4.2-300 K are reported. Experiments were performed on three types of GaN material: (i) single, highpressure grown GaN crystals showing highly n-type conductivity, (ii) on bulk Mg doped GaN crystals with slightly p-type conductivity, (iii) on homoepitaxial GaN layer grown by hydride vapour phase epitaxy (HVPE) on bulk GaN crystal. For the n-GaN crystals, the record thermal conductivity value κ max is equal to 1600 W/m × K at T max = 45 K, and κ ≅ 230 W/m K at 300 K. It is suggested that for this crystal and for T ≥ T max the contribution of Umklapp phonon scattering processes dominate in the heat transport processes. A heavily Mg doped crystal and HVPE GaN layer on bulk GaN show much lower thermal conductivity in the whole applied temperature region. The temperature dependence of κ shows the importance of point defects (impurities, vacancies) in determination of the thermal resistance of GaN bulk crystals.

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Characterisation of the electrical properties of solution‐grown GaN crystals by reflectivity and Hall measurements

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Thermal conductivity of crystalline AlN and the influence of atomic-scale defects

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