Mixed-Size Diamond Seeding for Low-Thermal-Barrier Growth of CVD Diamond onto GaN and AlN

Ed Smith, A.H Piracha, Daniel E Field, James W Pomeroy, G R Mackenzie, Zeina Abdallah, Fabien C P Massabuau, A Hinz, DJ Wallis, Rachel A. Oliver, Martin H H Kuball, Paul W May*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review


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

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