Crystallinity Evaluation and Dislocation Observation for an Aluminum Nitride Single-Crystal Substrate on a Wafer Scale

Yao, Yongzhao; Sugawara, Yoshihiro; Ishikawa, Yukari; Okada, Narihito; Tadatomo, Kazuyuki

doi:10.1007/s11664-020-08016-x

Cited by 10 publications

(7 citation statements)

References 44 publications

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“…Additionally, a gradual increase of Á2Â seems to appear along the x position of the wafer, possibly indicating a slight curvature of the whole wafer. As suggested in the literature (Yao et al, 2019(Yao et al, , 2020, AlN wafers may exhibit a curvature of the [0004] planes due to the strain caused by the thermal gradients during growth, as well as the anisotropic cooling post-growth. The resulting convex warp of the N-face basal plane may explain the Á2Â of the prism planes.…”

Section: Resultsmentioning

confidence: 93%

“…4(c), which can be explained in this special case because the diffraction vector is parallel to b Â l, for which edge dislocations are known to show some weak contrast even though g Á b is equal to zero. However, since the projected dislocation lines run parallel to the Burgers vectors, this may point to a small screw component of these TEDs, and due to the complex diffraction contrast a low fraction of threading mixed dislocations (TMDs) of a + c type cannot be excluded, these being frequently observed in wurtzitic structures (Nakamura et al, 2007;Yao et al, 2020). In addition, it is remarkable that the third, symmetrically equivalent Burgers vector of b ¼ 1 3 ½1120 is not observed in this specific region, which is potentially connected to the fact that this group of dislocations is related to a strain field induced by an outwardspointing thermal gradient, hence affecting only two of three potential Burgers vectors.…”

Section: Resultsmentioning

confidence: 99%

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X-ray characterization of physical-vapor-transport-grown bulk AlN single crystals

et al. 2020

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AlN slices from bulk crystals grown under low thermomechanical stress conditions via the physical vapor transport (PVT) method were analyzed by X-ray methods to study the influence of the growth mode on the crystal quality. Defect types and densities were analyzed along axial [0001] as well as lateral growth directions. X-ray diffraction (0110) rocking-curve mappings of representative wafer cuts reveal a low mean FWHM of 13.4 arcsec, indicating the generally high crystal quality. The total dislocation density of 2 × 103 cm−2 as determined by X-ray topography is low and dislocations are largely threading edge dislocations of b = 1/3〈1120〉 type. The absence of basal plane dislocations in homogeneous crystal regions void of macroscopic defects can be linked to the low-stress growth conditions. Under the investigated growth conditions this high crystal quality can be maintained both along the axial [0001] direction and within lateral growth directions. Exceptions to this are some locally confined, misoriented grains and defect clusters, most of which are directly inherited from the seed or are formed due to the employed seed fixation technique on the outer periphery of the crystals. Seed-shaping experiments indicate no apparent kinetic limitations for an enhanced lateral expansion rate and the resulting crystal quality, specifically with regard to the growth mode on a-face facets.

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Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

X-ray characterization of physical-vapor-transport-grown bulk AlN single crystals

et al. 2020

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“…In general, spatial distributions of dislocations in AlN crystals with densities below 10 6 cm −2 can be studied by defect-selective etching (DSE), 5,14,15 laser scattering tomography (LST), 16 and X-ray diffraction imaging techniques such as X-ray topography (XRT). 17−19 DSE only provides the distribution of intersection points in the form of pits caused by chemical etching along the dislocation lines.…”

Section: ■ Introductionmentioning

confidence: 99%

“…In general, spatial distributions of dislocations in AlN crystals with densities below 10 6 cm –2 can be studied by defect-selective etching (DSE), ,, laser scattering tomography (LST), and X-ray diffraction imaging techniques such as X-ray topography (XRT). − …”

Section: Introductionmentioning

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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“…One can investigate the motion of dislocations in a material by atomistic modeling, and various methods are employed to evaluate the Peierls stress and dislocation mobility in different crystals. Bulatov and Kaxiras used the Peierls–Nabarro (PN) model and density functional theory (DFT) to calculate the Peierls stress in silicon.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations of the Thermally and Stress-Activated Glide of a ⟨0001⟩{11̅00} Screw Dislocation in AlN

Zhao

Wang²,

et al. 2021

Crystal Growth & Design

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The low-temperature plasticity of aluminum nitride (AlN) is determined by the interaction between edge and screw dislocations. However, the motion of screw dislocations and their glide mechanisms have not been evaluated. In this study, the motion of a ⟨0001⟩{11̅ 00} screw dislocation in a single crystal of AlN is explored by molecular dynamics simulations using LAMMPS software with the Stillinger−Weber (SW) potential. Four modes of thermally activated motion are observed under different conditions of temperature and stress: double kinks, Shockley partials, self-pinning, and debris and dislocation loops. The mobilities of a ⟨0001⟩{11̅ 00} screw dislocation and a 1/3⟨112̅ 0⟩{11̅ 00} edge dislocation are compared under various conditions. Our results show that the mobilities of the ⟨0001⟩{11̅ 00} screw and 1/3⟨112̅ 0⟩{11̅ 00} edge dislocations are quite low at T < 600 K. The ⟨0001⟩{11̅ 00} screw dislocation moves faster at 900 < T < 1500 K and seems less dependent on the temperature than does the 1/3⟨112̅ 0⟩{11̅ 00} edge dislocation at 1200 < T < 2200 K. However, the opposite phenomenon is observed at higher temperatures. The mobility of the ⟨0001⟩{11̅ 00} screw dislocation is slightly lower than that of the 1/3⟨112̅ 0⟩{11̅ 00} edge dislocation at T > 1800 K, although the mobility difference can reach several orders of magnitude at 900 < T < 1200 K due to different Peierls barriers.

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Crystallinity Evaluation and Dislocation Observation for an Aluminum Nitride Single-Crystal Substrate on a Wafer Scale

Cited by 10 publications

References 44 publications

X-ray characterization of physical-vapor-transport-grown bulk AlN single crystals

X-ray characterization of physical-vapor-transport-grown bulk AlN single crystals

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

Molecular Dynamics Simulations of the Thermally and Stress-Activated Glide of a ⟨0001⟩{11̅00} Screw Dislocation in AlN

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