Thermal conductivity of fully and partially coalesced lateral epitaxial overgrown GaN/sapphire (0001) by scanning thermal microscopy

Florescu, D. I.; Asnin, V. M.; Pollak, Fred H.; Jones, Andrew M.; Ramer, J.; Schurman, M.; Ferguson, Ian T.

doi:10.1063/1.1308057

Cited by 112 publications

(51 citation statements)

References 12 publications

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“…Concerning devices based on Group-III nitrides, sapphire, SiC, Si, and bulk GaN are used as substrates. In terms of thermal conductivity (at room temperature) SiC (6H-SiC-490 W/m × K) has a considerable advantage over the sapphire (46 W/m × K), Si (130 W/m K), and GaN (~130-200 W/m × K) substrates [1][2][3]. However, using the SiC, Si or sapphire leads to high concentration of misfit dislocations in nitride heterostructures, which can achieve magnitude of 10 8 cm -2 .…”

Section: Introductionmentioning

confidence: 99%

Thermal conductivity of GaN crystals grown by high pressure method

Jeżowski

Stachowiak

Plackowski

et al. 2003

Physica Status Solidi (b)

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Results of measurements of thermal conductivity κ of bulk GaN crystals in the temperature interval 4.2-300 K are reported. Experiments were performed on three types of GaN material: (i) single, highpressure grown GaN crystals showing highly n-type conductivity, (ii) on bulk Mg doped GaN crystals with slightly p-type conductivity, (iii) on homoepitaxial GaN layer grown by hydride vapour phase epitaxy (HVPE) on bulk GaN crystal. For the n-GaN crystals, the record thermal conductivity value κ max is equal to 1600 W/m × K at T max = 45 K, and κ ≅ 230 W/m K at 300 K. It is suggested that for this crystal and for T ≥ T max the contribution of Umklapp phonon scattering processes dominate in the heat transport processes. A heavily Mg doped crystal and HVPE GaN layer on bulk GaN show much lower thermal conductivity in the whole applied temperature region. The temperature dependence of κ shows the importance of point defects (impurities, vacancies) in determination of the thermal resistance of GaN bulk crystals.

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Section: Introductionmentioning

confidence: 99%

Thermal conductivity of GaN crystals grown by high pressure method

Jeżowski

Stachowiak

Plackowski

et al. 2003

Physica Status Solidi (b)

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“…The experimental thermal conductivity values of GaN obtained at room temperature, using a scanning thermal microscope, are scattered in the range of 50 to 210 W/mK. 5,6) This is attributed to the effects of impurities and dislocations on the thermal properties. Luo et al 7) reported the thermal conductivity value of 155 W/mK using a third-harmonic electrical technique.…”

Section: Introductionmentioning

confidence: 99%

High Thermal Conductivity of Gallium Nitride (GaN) Crystals Grown by HVPE Process

et al. 2007

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A relatively large sample of gallium nitride (GaN) was grown as a single crystal using the hydride vapor phase epitaxy (HVPE) process. The thermal diffusivity of the single crystal has been measured using a vertical-type laser flash method. The thermal expansion was measured using a dilatometer in order to estimate the thermal diffusivity with sufficient reliability. The effect of sample thickness and temperature on thermal diffusivity was evaluated. The specific heat capacity of GaN was also measured by using a differential scanning calorimeter. The thermal properties of single-crystal GaN have been compared with the measured thermal properties of single-crystal silicon carbide (SiC). The thermal conductivity of single-crystal GaN at room temperature is found to be 253 AE 8:8% W/mK, which is approximately 60% of the value obtained for SiC. The excellent thermal property that is obtained in this study clearly indicates that GaN crystals are one of the promising materials for use in high-power-switching devices.

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“…For instance, its band gap energy is 3.4 eV at 300 K [25]. K [27]. Its breakdown field is also relatively high.…”

Section: Gallium Nitridementioning

confidence: 99%

CVD solutions for new directions in SiC and GaN epitaxy

Li¹

2015

Linköping Studies in Science and Technology. Dissertations

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This thesis aims to develop a chemical vapor deposition (CVD) process for the new directions in both silicon carbon (SiC) and gallium nitride (GaN) epitaxial growth. The properties of the grown epitaxial layers are investigated in detail in order to have a deep understanding. SiC is a promising wide band gap semiconductor material which could be utilized for fabricating high-power and high-frequency devices. 3C-SiC is the only polytype with a cubic structure and has superior physical properties over other common SiC polytypes, such as high hole/electron mobility and low interface trap density with oxide. Due to lack of commercial native substrates, 3C-SiC is mainly grown on the cheap silicon (Si) substrates. However, there’s a large mismatch in both lattice constants and thermal expansion coefficients leading to a high density of defects in the epitaxial layers. In paper 1, the new CVD solution for growing high quality double-position-boundaries free 3C-SiC using on-axis 4H-SiC substrates is presented. Reproducible growth parameters, including temperature, C/Si ratio, ramp-up condition, Si/H2 ratio, N2 addition and pressure, are covered in this study. GaN is another attractive wide band gap semiconductor for power devices and optoelectronic applications. In the GaN-based transistors, carbon is often exploited to dope the buffer layer to be semi-insulating in order to isolate the device active region from the substrate. The conventional way is to use the carbon atoms on the gallium precursor and control the incorporation by tuning the process parameters, e.g. temperature, pressure. However, there’s a risk of obtaining bad morphology and thickness uniformity if the CVD process is not operated in an optimal condition. In addition, carbon source from the graphite insulation and improper coated graphite susceptor may also contribute to the doping in a CVD reactor, which is very difficult to be controlled in a reproducible way. Therefore, in paper 2, intentional carbon doping of (0001) GaN using six hydrocarbon precursors, i.e. methane (CH4), ethylene (C2H4), acetylene (C2H2), propane (C3H8), iso-butane (i-C4H10) and trimethylamine (N(CH3)3), have been explored. In paper 3, propane is chosen for carbon doping when growing the high electron mobility transistor (HEMT) structure on a quarter of 3-inch 4H-SiC wafer. The quality of epitaxial layer and fabricated devices is evaluated. In paper 4, the behaviour of carbon doping using carbon atoms from the gallium precursor, trimethylgallium (Ga(CH3)3), is explained by thermochemical and quantum chemical modelling and compared with the experimental results. GaN is commonly grown on foreign substrates, such as sapphire (Al2O3), Si and SiC, resulting in high stress and high threading dislocation densities. Hence, bulk GaN substrates are preferred for epitaxy. In paper 5, the morphological, structural and luminescence properties of GaN epitaxial layers grown on N-face free-standing GaN substrates are studied since the N-face GaN has advantageous characteristics compared to the Ga...

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Thermal conductivity of fully and partially coalesced lateral epitaxial overgrown GaN/sapphire (0001) by scanning thermal microscopy

Cited by 112 publications

References 12 publications

Thermal conductivity of GaN crystals grown by high pressure method

Thermal conductivity of GaN crystals grown by high pressure method

High Thermal Conductivity of Gallium Nitride (GaN) Crystals Grown by HVPE Process

CVD solutions for new directions in SiC and GaN epitaxy

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