Thermal characterization of GaN-on-diamond substrates for HEMT applications

• Published in: 13th InterSociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems pp. 435 - 439
• Main Authors: Jungwan Cho, Zijian Li, Bozorg-Grayeli, E., Kodama, T., Francis, D., Ejeckam, F., Faili, F., Asheghi, M., Goodson, K. E.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.05.2012
• Subjects: Aluminum nitride; diamond; Diamond-like carbon; Gallium nitride; High Electron Mobility Transistors (HEMT); Substrates; Temperature measurement; Thermal Boundary Resistance (TBR); Thermal conductivity; Thermal resistance; Time-Domain Thermoreflectance (TDTR)
• ISBN: 9781424495337; 1424495334
• ISSN: 1087-9870; 2577-0799
• DOI: 10.1109/ITHERM.2012.6231463

High-power operation of AlGaN/GaN high-electron-mobility transistors (HEMTs) requires efficient heat removal through the substrate. GaN composite substrates including high-thermal-conductivity diamond are promising, but high thermal resistances at the interfaces between the GaN and diamond can offset the benefit of a diamond substrate. We report on measurements of the thermal resistances at the GaN-diamond interfaces for two generations (1 st and 2 nd ) of GaN-on-diamond substrates using a combination of picosecond time-domain thermoreflectance (TDTR) and nanosecond transient thermoreflectance (TTR) techniques. Two flipped-epitaxial samples are presented to determine the thermal resistances of the AlGaN/AlN transition layer. For the 2 nd generation samples, electrical heating and thermometry in nanopatterned metal bridges confirms the TDTR results. This paper demonstrates that the latter generation samples, which reduce the AlGaN thickness by 75%, result in a strongly-reduced thermal resistance between the GaN and diamond. Further optimization of the GaN-diamond interfaces should provide an opportunity for improved cooling of HEMT devices.