Growth of bulk AlN single crystals with low oxygen content taking into account thermal and kinetic effects of oxygen-related gaseous species

Guguschev, Christo; Dittmar, A.; Moukhina, Elena; Hartmann, C.; Golka, S.; Wollweber, J.; Bickermann, Matthias; Fornari, R.

doi:10.1016/j.jcrysgro.2012.02.019

Cited by 16 publications

(9 citation statements)

References 22 publications

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“…of silicon . As they can form volatile compounds such as Al 2 O, CO, SiO, and Si and easily escape the semi‐closed crucible , therefore their concentrations in the gas phase should be considerably higher. In contrast, tungsten nitrides are unstable at temperatures beyond 700 °C.…”

Section: Resultsmentioning

confidence: 99%

“…However, even they cannot be considered inert: Gradual chemical attack and reaction with the gaseous growth species (in particular Al) and volatile impurities (e.g. species containing oxygen, silicon and carbon) present in the setup and the starting materials are inevitable . As a consequence, the chemistry in the hot zone at temperatures exceeding 2000 °C can become quite complex.…”

Section: Introductionmentioning

confidence: 99%

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Precipitates originating from tungsten crucible parts in AlN bulk crystals grown by the PVT method

Langhans

Kiefer

Hartmann

et al. 2015

Crystal Research and Technology

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In order to evaluate the possible involvement of crucible materials in the growth of AlN bulk crystals grown by physical vapor transport, we applied growth conditions with a high vertical thermal gradient and hence high supersaturation of aluminum vapor. Under these conditions, precipitates formed causing diffuse grayish substructures at the initial growth interface and in the crystal body, decorating dislocations. Electron microscopy studies revealed that the precipitates are elongated, single‐phase particles with sizes of 50–500 nm of commensurate structure, oriented along the <11true2¯0> direction. Chemical analysis of the precipitates showed tungsten as well as carbon and oxygen. The lattice parameters of the precipitates are in close agreement to hexagonal tungsten hemicarbide (W2C). The possible transport from the tungsten parts and its conversion into tungsten hemicarbide precipitates is discussed. We thus conclude that the W2C precipitates may contribute to the decoration of dislocations, even in growth with moderate thermal gradients.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Precipitates originating from tungsten crucible parts in AlN bulk crystals grown by the PVT method

Langhans

Kiefer

Hartmann

et al. 2015

Crystal Research and Technology

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“…An AlN single crystal is grown by PVT on a seed that is prepared from a spontaneously nucleated crystal which has a typical dislocation density of about 1 × 10 3 cm –2 . , The surface of N-polar (0001̅) seed is polished by a chemical-mechanical polishing process . The growth setup and the details of the seeded growth process are described in Hartmann et al , For the present investigations, we used a comparably high seed temperature (2251 °C) and low temperature difference between source and seed surface (37 K) combined with a heat up ramping at an inverted temperature gradient .…”

Section: Methodsmentioning

confidence: 99%

Dislocation Climb in AlN Crystals Grown at Low-Temperature Gradients Revealed by 3D X-ray Diffraction Imaging

Straubinger

Hartmann

Kabukcuoglu

et al. 2023

Crystal Growth & Design

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The dislocation evolution in a cross-section a-plane cut through a sublimation-grown aluminum nitride (AlN) crystal grown with low-temperature gradients and subsequent low thermal stress is investigated with different X-ray diffraction imaging methods. Exploiting the so-called weak-beam contrast using monochromatic X-rays in combination with suitable three-dimensional (3D) interpretation and reconstruction allows the identification of individual dislocations as well as tracing their progression in the crystal volume, even in the considerably strained interface region. It is particularly striking that the laterally grown crystal volume is dislocation-free. The dislocation densities in the seed and the bulk volume are similar (1 × 103 cm–2), but while the dislocations in the seed are randomly arranged, the dislocations in the bulk volume show a uniform line shape, indicating a common mechanism of dislocation movement. Since the dislocation slings in the bulk do not lie in slip planes, it can be concluded that the lateral movement does not result from dislocation glide, but from impurity-driven climb of dislocations during growth. The absence of slip can be explained by the low-temperature gradients and the subsequent low thermal stress below the critical resolved shear stress (CRSS).

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“…Homoepitaxial seeding on native 2H-AlN (for simplicity, hereinafter referred to as AlN) and heteroepitaxial seeding on 6H-SiC (hereinafter referred to as SiC) are two typical techniques employed to grow AlN bulk crystals. For the former, grain selection , and a spontaneous nucleation approach − are generally adopted to obtain the first generation of AlN seeds . High-quality and large-size AlN bulk crystals can be grown iteratively through homoepitaxial growth. ,,, The prominent advantage of homoepitaxial seeding is that AlN bulk single crystals with high structural quality can be grown using high-quality AlN seeds obtained by the spontaneous nucleation approach at near-equilibrium growth conditions .…”

Section: Introductionmentioning

confidence: 99%

Comparison of the Thermal Stress Behavior of AlN Single Crystal Growth on AlN and SiC Seeds via the Physical Vapor Transport Method through Three-Dimensional Numerical Modeling and Simulation

Zhao

Wang²,

Zhang

et al. 2021

Crystal Growth & Design

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We extend a thermal-elastic stress model by the finite element method to evaluate anisotropic three-dimensional thermal stress in AlN bulk crystals grown on on-axis 2H-AlN and 6H-SiC seeds. The distribution of stresses in the growing AlN crystals at various crystal thicknesses is simulated based on the developed model. The simulation results show that a high von Mises stress layer with strong fluctuations at the 6H-SiC/2H-AlN interface is observed for the heteroepitaxial growth, and a critical crystal thickness of 1 mm for the stress relaxation is required to avoid cracking. On the contrary, a smooth evolution of the von Mises stress is observed for the homoepitaxial growth on the 2H-AlN seed. The maximum total resolved shear stress inside the crystal when using SiC seeds is slightly higher than that of using AlN seeds at the initial growth stage, while this phenomenon reverses after the crystal thickness exceeds approximately 3 mm. Whether using AlN or SiC seeds, the magnitude of the total resolved shear stress increases steadily, and the difference between the homoepitaxial and heteroepitaxial growth is quite small during the whole bulk AlN growth by the physical vapor transport process.

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Growth of bulk AlN single crystals with low oxygen content taking into account thermal and kinetic effects of oxygen-related gaseous species

Cited by 16 publications

References 22 publications

Precipitates originating from tungsten crucible parts in AlN bulk crystals grown by the PVT method

Precipitates originating from tungsten crucible parts in AlN bulk crystals grown by the PVT method

Dislocation Climb in AlN Crystals Grown at Low-Temperature Gradients Revealed by 3D X-ray Diffraction Imaging

Comparison of the Thermal Stress Behavior of AlN Single Crystal Growth on AlN and SiC Seeds via the Physical Vapor Transport Method through Three-Dimensional Numerical Modeling and Simulation

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