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Home > Archive > IHTC-16 > Thermophysical Property Measurements > PROBING LOCAL THERMAL CONDUCTIVITY VARIATIONS IN CVD DIAMOND WITH LARGE GRAINS BY TIME-DOMAIN THERMOREFLECTANCE
International Heat Transfer Conference 16
2018, 10-15 August, Beijing, China
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PROBING LOCAL THERMAL CONDUCTIVITY VARIATIONS IN CVD DIAMOND WITH LARGE GRAINS BY TIME-DOMAIN THERMOREFLECTANCE

DOI: 10.1615/IHTC16.tpm.022782
pages 8694-8701
Zhe Cheng
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
Ramez Cheaito
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
Tingyu Bai
Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, 91355, USA
Luke Yates
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
Aditya Sood
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
Brian M. Foley
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
Thomas L. Bougher
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
Firooz Faili
Element Six Technologies, Santa Clara, CA 95054, USA
Mehdi Asheghi
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
Kenneth E. Goodson
Thermosciences Division, Mechanical Engineering Department, Stanford University Bldg. 530, 440 Escondido Mall, Stanford, CA 94305-3030, USA
Baratunde A. Cola
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA; School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
Mark Goorsky
Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, 91355, USA
Samuel Graham
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA; School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA

Abstrakt

Chemical vapor deposited (CVD) diamond, due to its high thermal conductivity, is an attractive candidate for thermal management of GaN-based high-electron mobility transistors (HEMTs). However, because of its heterogeneous grain structure, CVD diamond has a spatially inhomogeneous thermal conductivity at the microscale. To understand this inhomogeneity and the effect of structural imperfections on thermal conduction, time-domain thermoreflectance (TDTR) is used to study the local thermal conductivity of two samples: a heavily boron-doped ~534 μm-thick diamond sample with an average surface grain size of ~23 μm, and an undoped diamond sample that was cut from a bulk piece of CVD diamond. For the doped diamond, large thermal conductivity variations (of nearly 50 %) are observed across the surface of the sample. For the undoped sample, the large average grain size (several hundred ?m) results in a high local thermal conductivity (>2000 W/m-K, close to the conductivity of bulk diamond). The thermal conductivity is not seen to change significantly with grain size (127 - 260 μm), and we measure up to ~8 % variation in the local thermal conductivity. We speculate that grain boundary scattering affects phonon transport differently in the two samples, possibly due to varying amounts of near-boundary disorder. This work provides insights to understand the local thermal conductivity inhomogeneity and phonon transport across grain boundaries in CVD diamond with large grains, which is important for thermal management applications in high-power electronics.
SCHLÜSSELWÖRTER: Electronic equipment cooling, Nano/Micro scale measurement and simulation, GaN on diamond, anisotropic thermal conductivity, thermal conductivity mapping, TDTR