Thermal and electrical properties of high‐quality freestanding GaN wafers with high carrier concentration

Abstract

The thermal and electrical properties of GaN were investigated using high-quality freestanding crystals in the high carrier concentration region between 1.0x1018 and 1.24x1019 cm-3. The carrier concentration n increased almost linearly with increasing Si doping concentration. A very low electrical resistivity of 2.5 mΩcm was obtained at n = 1.24x1019 cm-3, combined with its high electron mobility. Thermal expansion coefficients along 〈110〉 and 〈100〉 were confirmed to be approximately constant at 5.1x10-6 K-1 (298-573 K) in the measured doping concentration range. Thermal conductivity remained high in the measured carrier concentration range at approximately 2.0 Wcm-1K-1 for n = 1.0x1018 cm-3, and 1.87 Wcm-1K-1 for n = 1.24x1019 cm-3. The compatibility of low electrical resistivity and high thermal conductivity has potential to contribute significantly to the realization of high-performance high-power nitride devices. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)