Improved Thermal Interfaces of GaN–Diamond Composite Substrates for HEMT Applications
نویسندگان
چکیده
High-power operation of AlGaN/GaN high-electronmobility 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-ondiamond substrates, using a combination of picosecond timedomain 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.
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