Mixed-size diamond seeding for low-thermal-barrier growth of CVD diamond onto GaN and AlN

E.J.W. Smith, A.H. Piracha, D. Fields, J.W. Pomeroy, G.R. Mackenzie, Z. Abdallah, F. C-P. Massabuau, A.M. Hinz, D.J. Wallis, R.A. Oliver, M. Kuball, P.W. May

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11 Citations (Scopus)
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We report a method of growing a diamond layer via chemical vapour deposition (CVD) utilizing a mixture of microdiamond and nanodiamond seeding to give a low effective thermal boundary resistance (TBR eff) for heat-spreading applications in high-frequency, high-power electronic devices. CVD diamond was deposited onto thin layers of both GaN and AlN on Si substrates, comparing conventional nanodiamond seeding with a two-step process involving sequential seeding with microdiamond then nanodiamond. Thermal properties were determined using transient thermoreflectance (TTR), and the samples were also analysed with SEM and X-ray tomography. While diamond growth directly onto GaN proved to be unsuccessful due to poor adhesion, films grown on AlN were adherent and robust. The two-step mixed-seeding method gave TBR eff values < 6 m 2 K GW −1 that were 30 times smaller than for films grown under identical conditions but using nanodiamond seeding alone. Such remarkably low thermal barriers obtained with the mixed-seeding process offer a promising route for fabrication of high-power GaN HEMTs using diamond as a heat spreader with an AlN interlayer.

Original languageEnglish
Pages (from-to)620-626
Number of pages7
Early online date27 May 2020
Publication statusPublished - 15 Oct 2020


  • chemical vapour deposition (CVD)
  • thermal boundary resistance
  • transient thermoreflectance (TTR)
  • diamond seeding


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