Thermal Boundary Resistance Reduction by Interfacial Nanopatterning for GaN-on-Diamond Electronics Applications

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Abstract
GaN high electron mobility transistors (HEMTs) on SiC substrates are the highest performing commercially available transistors for high-power, high-frequency applications. However, Joule self-heating limits the maximum areal power density, i.e., operating power is derated to ensure the lifetime of GaN-based devices. Diamond is attractive as a heat sink due to its record-high thermal conductivity combined with its high electrical resistivity. GaN-on-diamond devices have been demonstrated, bringing the diamond as close as possible to the active device area. The GaN/diamond interface, close to the channel heat source, needs to efficiently conduct high heat fluxes, but it can present a significant thermal boundary resistance (TBR). In this work, we implement nanoscale trenches between GaN and diamond to explore new strategies for reducing the effective GaN/diamond TBR (TBReff). A 3× reduction in GaN/diamond TBReff was achieved using this approach, which is consistent with the increased contact area; thermal properties were measured using nanosecond transient thermoreflectance (ns-TTR). In addition, the SiN x dielectric interlayer between the GaN and diamond increased its thermal conductivity by 2× through annealing, further reducing the TBR. This work demonstrates that the thermal resistance of heterogeneous interfaces can be optimized by nanostructured patterning and high-temperature annealing, which paves the way for enhanced thermal management in future device applications.
Funding Information
  • Engineering and Physical Sciences Research Council (EP/P00945X/1, EP/V057626/1, EP/Z531091/1)

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