Investigation of Threading Screw Dislocation Evolution in 4H-SiC Single Crystals

doi:10.15541/jim20250509

Abstract

Abstract:

Threading screw dislocation (TSD) is a critical defect in silicon carbide (SiC) single crystals and have a strong impact on epitaxial quality and device performance. With the increasing diameter of SiC substrates, understanding the evolution behavior of TSD during bulk growth is of growing importance. This study aims to investigate the evolution characteristics of TSD in 6-inch 4H-SiC single crystals and to clarify the influence of crystal growth front convexity on TSD generation. Four 6-inch 4H-SiC single crystals with different growth convexities ranging from 0.36 to 2.58 mm were grown by the physical vapor transport (PVT) method through thermal field regulation. Longitudinal cross-sectional samples were characterized using X-ray topography (XRT) to trace the evolution behavior of individual TSD. Thermal field simulations were performed to analyze the relationship between temperature gradient and local C/Si ratio. XRT results reveal multiple TSD evolution behaviors, including inheritance from the seed, newly generated dislocations, merging and annihilation, and bending. The density of newly generated TSD during the initial growth stage increases monotonically with crystal convexity. When the convexity increases from 0.36 to 2.58 mm, the initial newly generated TSD density rises and reaches 126 cm^-2. Thermal field simulations indicate that larger convexity leads to steeper temperature gradients and a reduced C/Si ratio, promoting silicon droplet formation and TSD nucleation. In contrast, the influence of convexity on TSD generation during the final growth stage is weak, with densities remaining at 0-3 cm^-2. The results indicate that the initial growth stage is the dominant period for TSD formation, mainly governed by thermal field-induced C/Si imbalance. Optimizing the thermal field to maintain a low growth front convexity is essential for suppressing TSD formation in large-diameter 4H-SiC single crystals.

Key words: 4H-SiC single crystal, threading screw dislocation, C/Si ratio, temperature gradient

CLC Number:

TN304

ZHAO Ning, WEI Fuyuan, WANG Ping, SHI Tingting, WANG Bo, YANG Jian, LIU Chunjun. Investigation of Threading Screw Dislocation Evolution in 4H-SiC Single Crystals[J]. Journal of Inorganic Materials, 2026, 41(8): 1133-1140.

Figures/Tables 8

Fig. 1 Diagram describing the definition of crystal convexity

Fig. 2 Relative positions between the crucible and the induction coil corresponding to the four silicon carbide crystals with different convexities (a) 0.36 mm; (b) 1.62 mm; (c) 2.21 mm; (d) 2.58 mm

Fig. 3 Profiles of silicon carbide crystals with different convexities (a) Digital photos of four crystals showing region D to F; (b) Method for height measurement and convexity calculation

Fig. 4 Longitudinal cross-section of the crystal

Fig. 5 Longitudinal cross-section XRT of crystals with different convexities (a) 0.36 mm; (b) 1.62 mm; (c) 2.21 mm; (d) 2.58 mm; (e-h) Magnified view (inset)

Fig. 6 Variation of TSD density with crystal convexity (a) TSD density in the seed inheritance, initial growth, and final growth stages;(b) TSD density in the initially generated and finally generated growth stages

Fig. 7 Simulated C/Si ratio maps under various early stage thermal-field configurations (a) Minimum convexity; (b) Moderate convexity; (c) Maximum convexity. Colorful figures are available on website

Fig. 8 Silicon droplets at the seed-crystal interface under an optical microscope

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