Thermal conductivity of GaN crystals grown by high pressure method

Abstract

Abstract Results of measurements of thermal conductivity κ of bulk GaN crystals in the temperature interval4.2–300 K are reported. Experiments were performed on three types of GaN material: (i) single, high‐pressure 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. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)