Thermal Properties of AlGaN/GaN HFETs on Bulk GaN Substrates

Killat, N.; Montes, M.; Pomeroy, James W.; Paskova, T.; Evans, K. R.; Leach, J. H.; Li, X.; Özgür, Ü.; Morkoç̌, H.; Chabak, Kelson D.; Crespo, A.; Gillespie, J.; Kossler, Mauricio; Walker, Dennis E.; Trejo, M.; Via, G. D.; Blevins, J. D.; Kuball, Martin

doi:10.1109/led.2011.2179972

Cited by 54 publications

(24 citation statements)

References 19 publications

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“…The Callaway model, with some approximations, has been successfully used to fit thermal conductivity data for various GaN samples. 6,19,30,31,41 However, the extracted values for the scattering rate coefficients, which in principle only depend on the material parameters, are quite different.…”

Section: Resultsmentioning

confidence: 99%

Effect of Si doping on the thermal conductivity of bulk GaN at elevated temperatures – theory and experiment

et al. 2017

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The effect of Si doping on the thermal conductivity of bulk GaN was studied both theoretically and experimentally. The thermal conductivity of samples grown by Hydride Phase Vapor Epitaxy (HVPE) with Si concentration ranging from 1.6×1016 to 7×1018 cm-3 was measured at room temperature and above using the 3ω method. The room temperature thermal conductivity was found to decrease with increasing Si concentration. The highest value of 245±5 W/m.K measured for the undoped sample was consistent with the previously reported data for free-standing HVPE grown GaN. In all samples, the thermal conductivity decreased with increasing temperature. In our previous study, we found that the slope of the temperature dependence of the thermal conductivity gradually decreased with increasing Si doping. Additionally, at temperatures above 350 K the thermal conductivity in the highest doped sample (7×1018 cm-3) was higher than that of lower doped samples. In this work, a modified Callaway model adopted for n-type GaN at high temperatures was developed in order to explain such unusual behavior. The experimental data was analyzed with examination of the contributions of all relevant phonon scattering processes. A reasonable match between the measured and theoretically predicted thermal conductivity was obtained. It was found that in n-type GaN with low dislocation densities the phonon-free-electron scattering becomes an important resistive process at higher temperatures. At the highest free electron concentrations, the electronic thermal conductivity was suggested to play a role in addition to the lattice thermal conductivity and compete with the effect of the phonon-point-defect and phonon-free-electron scattering.

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Section: Resultsmentioning

confidence: 99%

Effect of Si doping on the thermal conductivity of bulk GaN at elevated temperatures – theory and experiment

et al. 2017

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“…8 Since it is widely believed that the generated Joule heat mainly dissipates through the substrate, the obvious solution is to use low thermal resistivity but expensive substrates such as SiC, 9 and GaN. 10 Recently, Hirama and co-workers have reported a thermal resistance record value of 4.1 K-mm/W for an AlGaN/GaN HEMT fabricated on single-crystal diamond. 11 Riedel et al were able to further reduce the thermal resistance of AlGaN/GaN HEMTs on SiC using a hot-wall metal organic chemical vapor deposition (MOCVD) grown aluminum nitride (AlN) nucleation layer, which lowers the thermal-boundary resistance between GaN and SiC.…”

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confidence: 99%

“…Also, as schematically illustrated in Fig. 6, the proximity of the "cold" GaN regions below the trenches, which serve as the heat spreader, to the "hot" GaN regions below the current carrying mesa channel structures and to the "hotspots" localized at the G-D edge 4,10,26 gives high heat spreading ability to the MMC device. Particularly, the "hot" GaN regions are directly adjacent to "cold" GaN regions creating a large temperature gradient which drives heat to flow laterally.…”

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Reduced thermal resistance in AlGaN/GaN multi-mesa-channel high electron mobility transistors

Asubar

Yatabe

Hashizume

2014

Applied Physics Letters

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Dramatic reduction of thermal resistance was achieved in AlGaN/GaN Multi-Mesa-Channel (MMC) high electron mobility transistors (HEMTs) on sapphire substrates. Compared with the conventional planar device, the MMC HEMT exhibits much less negative slope of the I-D-V-DS curves at high V-DS regime, indicating less self-heating. Using a method proposed by Menozzi and co-workers, we obtained a thermal resistance of 4.8 K-mm/W at ambient temperature of similar to 350K and power dissipation of similar to 9W/mm. This value compares well to 4.1 K-mm/W, which is the thermal resistance of AlGaN/GaN HEMTs on expensive single crystal diamond substrates and the lowest reported value in literature

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“…Those main reliability issues can be traced directly to the quality of the epitaxial material [12], [13], exhibited in the dislocation density, and can be reduced or eliminated with a near dislocation free material, such as GaN/GaN substrates. The increase in R on occurs due to charge trapping, mainly in the bulk of the material in the case of DC power switching [11].…”

Section: Introductionmentioning

confidence: 99%

Low-Dispersion, High-Voltage, Low-Leakage GaN HEMTs on Native GaN Substrates

Alshahed

Heuken

Alomari

et al. 2018

IEEE Trans. Electron Devices

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Abstract-In this work the advantages of GaN HEMTs grown on native GaN substrates over GaN/Si or GaN/Sapphire substrates are investigated, and correlated with epitaxial quality. TEM plane view and cross section analysis of GaN/GaN revealed dislocation density lower than 1 × 10 6 cm −2 , which is at least 3 orders of magnitude lower than the case of GaN/Si or GaN/Sapphire. In the case of GaN/Si, the dislocations did not necessarily originate from the substrate/nucleation layer interface, but the strain relief and isolation buffer stacks were main contributors to the dislocation density. GaN/GaN HEMTs demonstrated superior electrical and thermal performance. GaN/GaN demonstrated 3 orders of magnitude lower off-state leakage, current collapse (Ron increase) after stress bias less than 15% compared to 50% in the case of GaN/Si, and 2% drop of the onstate current due to self-heating in DC operation as compared to 13% and 16% for GaN/Si and GaN/Sapphire respectively. The GaN/Si thermal performance approached GaN/GaN only by substrate removal. Therefore GaN/GaN can allow high on-state current, low off-state leakage current, minimal current collapse, and enhanced thermal dissipation capability at the same time, which can be directly correlated to the absence of high dislocation densities.

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Thermal Properties of AlGaN/GaN HFETs on Bulk GaN Substrates

Cited by 54 publications

References 19 publications

Effect of Si doping on the thermal conductivity of bulk GaN at elevated temperatures – theory and experiment

Effect of Si doping on the thermal conductivity of bulk GaN at elevated temperatures – theory and experiment

Reduced thermal resistance in AlGaN/GaN multi-mesa-channel high electron mobility transistors

Low-Dispersion, High-Voltage, Low-Leakage GaN HEMTs on Native GaN Substrates

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