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Near-junction cooling of GaN HEMT by capped diamond heat spreader and embedded microchannels
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Zhang, Hang. Near-junction cooling of GaN HEMT by capped diamond heat spreader and embedded microchannels. Retrieved from https://doi.org/doi:10.7282/t3-zdph-8723

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TitleNear-junction cooling of GaN HEMT by capped diamond heat spreader and embedded microchannels
NameZhang, Hang (author); Guo, Zhixiong (chair); Jaluria, Yogesh YJ (member); Mazzeo, Aaron AM (member); Lu, Yongfeng YL (member); Rutgers University; School of Graduate Studies
Date Created2022
Other Date2022-10 (degree)
SubjectMechanical engineering, Capped diamond heat spreader, Near-junction cooling methods, GaN HEMTs
Extent1 online resource (148 pages) : illustrations
DescriptionGallium nitride (GaN) high-electron-mobility-transistors (HEMTs) are designed to operate at increasing higher power density and frequency to suit specific applications in 5G communication and electric vehicles. Proper thermal management methods are required to ensure the power density output and long-term reliability of GaN HEMTs. The non-uniformly distributed high die-level heat flux (> 1 kW/cm²) coupled with microscale hotspots has imposed significant thermal management challenges, overshadowing traditional “remote” cooling methods. This dissertation aims to explore two novel “near-junction” cooling techniques. The first one is a capped diamond heat spreader used to facilitate the spreading of heat from hotspot to die. The second is embedded manifold microchannels which quickly remove the heat from the die to the ambient by convection. Firstly, the thermal impacts of capping a diamond layer on multi-finger GaN HEMTs have been investigated under steady-state operation conditions. The scale of temperature reduction highlighted the applicability of the capped diamond spreader as a promising cooling strategy. Secondly, a further study was carried out for diamond heat spreader on a commercial 380-gates GaN-based power amplifier with kW peak power-level under periodic pulse-operated conditions. A scale-down model has been built to enable practical modeling for pulse mode calculation, which can significantly reduce the computational time while maintaining dynamic peak temperature. To precisely evaluate the cooling performance, thickness dependence and anisotropy of micrometer-sized diamond thermal conductivity were considered through two proposed fitted formulas based on experimental data in the literature. The capped diamond cooling strategy is shown to be more effective under harsh thermal conditions, including smaller duty cycle, higher interfacial thermal resistance, and substrate of lower thermal conductivity. Thirdly, an embedded manifold microchannel cooling (EMMC) arrangement was presented, in which microchannels were directly etched in the GaN substrate in close proximity to hotspots. A unit-cell model is built in which a single transistor is coupled with a microchannel beneath, mimicking a recently reported GaN power converter with EMMC arrangement. The single-phase laminar flow of deionized water through near-junction microchannels has been extensively investigated in the unit-cell. The effects of geometrical parameters of the manifold and microchannel, heat flux and flow rate on the thermal-hydraulic performance of the unit-cell were thoroughly studied. Finally, the capped diamond heat spreader was combined with the EMMC to cool the GaN device for the first time.
NotePh.D.
NoteIncludes bibliographical references
Genretheses
Persistent URLhttps://doi.org/doi:10.7282/t3-zdph-8723
LanguageEnglish
CollectionSchool of Graduate Studies Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.
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