Improved Thermal Interfaces of GaN-Diamond Composite Substrates for HEMT Applications

• Published in: IEEE transactions on components, packaging, and manufacturing technology (2011) Vol. 3; no. 1; pp. 79 - 85
• Main Authors: Jungwan Cho, Zijian Li, Bozorg-Grayeli, E., Kodama, T., Francis, D., Ejeckam, F., Faili, F., Asheghi, M., Goodson, K. E.
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.01.2013; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: AlGaN/GaN high-electron-mobility transistors (HEMTs); Aluminum gallium nitrides; Aluminum nitride; Conductivity; Electrical resistance measurement; Gallium nitride; Gallium nitrides; High electron mobility transistors; Nanomaterials; Nanostructure; Semiconductor devices; Studies; Substrates; Temperature measurement; thermal boundary resistance (TBR); Thermal conductivity; Thermal resistance; time-domain thermoreflectance (TDTR); Transition layers
• ISSN: 2156-3950; 2156-3985
• DOI: 10.1109/TCPMT.2012.2223818

High-power operation of AlGaN/GaN high-electron-mobility transistors (HEMTs) requires efficient heat removal through the substrate. GaN composite substrates, including the 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 thermal resistances at GaN-diamond interfaces for two generations (first and second) of GaN-on-diamond substrates, using a combination of picosecond time-domain thermoreflectance (TDTR) and nanosecond transient thermoreflectance techniques. Two flipped-epitaxial samples are presented to determine the thermal resistances of the AlGaN/AlN transition layer. For the second 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/AlN transition layer thickness, 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.