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

Research output: Contribution to journalArticle

Abstract

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 (TBReff) 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 twostep mixed-seeding method gave TBReff values <6 m2 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
JournalCarbon
Publication statusAccepted/In press - 19 May 2020

Keywords

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

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    Smith, E. J. W., Piracha, A. H., Fields, D., Pomeroy, J. W., Mackenzie, G. R., Abdallah, Z., ... May, P. W. (Accepted/In press). Mixed-size diamond seeding for low-thermal-barrier growth of CVD diamond onto GaN and AlN. Carbon.