Mechanism Reveal of Threading Edge Dislocation Multiplication during the Initial Stage of 4H-SiC Growth

4H silicon carbide (4H-SiC), renowned for its exceptional performance, has opened promising vistas for contemporary high-performance power devices. Nevertheless, the high-density threading edge dislocations (TEDs) in the 4H-SiC substrate can seriously restrict the performance of the device, which poses an urgent problem that needs to be addressed. Here, the mechanism of TED multiplication during the initial stage of 4H-SiC single-crystal growth by the physical vapor transport technology is systematically investigated. The research reveals that the TED multiplication occurs specifically at the interface where nitrogen starts to incorporate, which is precisely the seed-grown crystal interface. The morphology of dislocation etch pits in the transformation process from basal plane dislocations (BPDs) to TEDs was observed on the 4H-SiC wafers after etching with molten KOH and was explained by theoretical calculations. Facilitated by X-ray topography, the origins of the multiplied TEDs were directly observed, including those inherited from the seed crystal and those converted from BPDs in the seed crystal. Additionally, TEDs nucleate at the seed-growth crystal interface. This work offers insights into the formation and propagation of dislocations during the growth of 4H-SiC single crystals and provides a favorable guide for growing 4H-SiC single crystals with low-density TEDs.