Modelling and simulation of oxygen transport during AlN crystal growth by the PVT method

Fu, Dejun; Wang, Qikun; Zhang, Gang; Zhu, Ruzhong; Liu, Huan; Li, Zhe; Wu, Liang

doi:10.1016/j.jcrysgro.2020.125902

Cited by 7 publications

(14 citation statements)

References 40 publications

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“…A sufficiently high radial temperature gradient (ΔT r ) around the seed surface is necessary for reasonable crystal diameter expansion, although a large ΔT r can lead to additional defects, such as low-angle grain boundaries (LAGBs) or basal plane dislocations (BPDs). 29−31 Considering the abovementioned, we designed a proprietary hotzone setup and crucible system and optimized it using FEMAG software and a series of in-house finite element codes, including a mass transfer module, 28,32 an impurity transport module, 27 an anisotropic 3D stress module, 33−35 and a growth rate and supersaturation prediction module. 36 In particular, a seed holder that can sustain positive supersaturation only at the seed deposition surface was designed to prevent any parasitic nucleation adjacent to the growing AlN seed and therefore to completely eliminate parasitic polycrystalline growth on the periphery of AlN boules.…”

Section: Experimental Preparationmentioning

confidence: 99%

Toward Φ56 mm Al-Polar AlN Single Crystals Grown by the Homoepitaxial PVT Method

Lei²,

et al. 2022

Crystal Growth & Design

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Crack-free and parasitic-free Al-polar aluminum nitride (AlN) single crystals up to Φ56 mm were iteratively grown by the homoepitaxial physical vapor transport method. The detailed iterative growth processes from the spontaneous AlN boules to Φ56 mm single crystals were presented. Our growth experiments revealed that stable growth of large Al-polar crystals with good structural quality and UV transparency was possible using a pure tungsten setup. For each iteration, the initial expansion angle, which was dominated by the radial temperature gradient (ΔT r ), reached 50−60°under our specific growth system and growth conditions and then gradually decreased to 10−20°during the growth process. For all as-grown crystals, mirror-like facets with a step-flow growth mode could be observed. However, the {101̅ 0} side planes were strongly suppressed when using larger AlN seeds. Material characterization showed that the full width at half maximum of symmetric and asymmetric highresolution X-ray diffraction rocking curves was 84−144 arcsec and 45−70 arcsec, respectively. The average etch pit density evaluated by preferential chemical etching was approximately 8.5 × 10 4 cm −2 . The optical transmission spectra revealed that the entire wafer exhibited excellent ultraviolet (UV) transparency, with absorption coefficients of 19−29 cm −1 in the UV range of 4.43−4.77 eV (260−280 nm).

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Section: Experimental Preparationmentioning

confidence: 99%

Toward Φ56 mm Al-Polar AlN Single Crystals Grown by the Homoepitaxial PVT Method

Lei²,

et al. 2022

Crystal Growth & Design

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“…In this work, only two species (Al and N 2 ) in the growth chamber were considered, while impurities such as Al 2 O were neglected due to their low concentrations [10][11][12][13][14][15][16]. The powder source charged at the crucible bottom was considered a porous medium.…”

Section: Geometry Description and Numerical Modelingmentioning

confidence: 99%

“…The temperature distribution was obtained through global modeling technology [16] using the FEMAG two-dimensional axisymmetric model. Global simulation techniques include an analysis of heat transfer based on decoupled and global-local iterative strategies, taking into account all reactor components (or macroelements) [19].…”

Section: Geometry Description and Numerical Modelingmentioning

confidence: 99%

“…In Mode II, both heaters were used, and the bottom center of the powder source (T bc ) and seed center (T sc ) were chosen as the TCPs. Due to the presence of Knudsen layers at the source and seed surfaces [14][15][16], the vapor flux at the sublimation and deposition surfaces could be precisely determined by solving the Hertz-Knudsen equation. The deposition or sublimation molar flux is given by…”

Section: Geometry Description and Numerical Modelingmentioning

confidence: 99%

“…Wang et al [15] developed a mass transport model to study the rate limiting step in the crystal growth process, and the results showed the relationship between the Al partial pressure gradient and growth rate under different thermal fields. Fu et al [16] established mass transfer models considering three-phase (Al/N/Al 2 O) Stefan flow and investigated the influences of growth parameters on oxygen impurity transport in the AlN growth chamber. All above extensive efforts showed that the vapor diffusion and buoyancy have significant effects on mass transport during the AlN crystal growth using the PVT method.…”

Section: Introductionmentioning

confidence: 99%

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Influences of Powder Source Porosity on Mass Transport during AlN Crystal Growth Using Physical Vapor Transport Method

Wang²,

Zhang

et al. 2021

Crystals

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We developed a two-dimensional (2D) transport model to investigate mass transport during bulk AlN crystal growth via the physical vapor transport (PVT) process using the finite element method (FEM), taking the powder source porosity, buoyancy, and vapor diffusion into account. The porosity effects of the powder source on mass transport under various growth conditions were investigated in detail. The simulation results show that the porosity of the powder source significantly affects the mass transport process during AlN sublimation growth. When the porosity of the powder source decreases, the growth rate becomes more uniform along the seed deposition surface, although the sublimation rate and crystal growth rate decrease, which can be attributed to the reduced specific surface area of the powder source and the reduced flow rate of Al vapor in the powder source. A flat growth interface can be achieved at a porosity of 0.2 under our specific growth conditions, which in turn facilitate the growth of high-quality AlN crystals and better yield. The decomposition of the powder source and the transport of Al vapor in the growth chamber can be suppressed by increasing the pressure. In addition, the AlN growth rate variation along the deposition surface can be attributed to the Al vapor pressure gradient caused by the temperature difference in the growth chamber.

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Structural Design Optimization of Physical Vapor Transport Furnace for Aluminum Nitride Crystal Growth via Modeling and Simulation

Chen,

Ding,

et al. 2023

Ind. Eng. Chem. Res.

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The growth of high-quality aluminum nitride (AlN) crystals heavily relies on precision of high temperatures that the thermal gradient impacts their growth rate, size, and quality, especially when the physical vapor transport (PVT) method is used. In this paper, we proposed innovative mechanical and design improvements to the crystal growing furnace by optimizing the shape and height of the blind hole to achieve a uniform or better thermal distribution. We presented simulation results of the thermal field in the crystal growing device using COMSOL and found that the proposed modification effectively reduces the thermal gradient and minimizes the thermal stress. Additionally, the new structure promotes organized natural convection, which benefits species transport in the furnace.

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Modelling and simulation of oxygen transport during AlN crystal growth by the PVT method

Cited by 7 publications

References 40 publications

Toward Φ56 mm Al-Polar AlN Single Crystals Grown by the Homoepitaxial PVT Method

Toward Φ56 mm Al-Polar AlN Single Crystals Grown by the Homoepitaxial PVT Method

Influences of Powder Source Porosity on Mass Transport during AlN Crystal Growth Using Physical Vapor Transport Method

Structural Design Optimization of Physical Vapor Transport Furnace for Aluminum Nitride Crystal Growth via Modeling and Simulation

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