Reduction of threading screw dislocations in 4H-SiC crystals by physical vapor transport growth

6-inch 4° off-axis 4H-SiC crystals were grown by the physical vapor transport (PVT) method on the seeds processed by hydrogen (H
2
) etching. The seed surface morphology after H
2
etching was characterized by atomic force microscopy (AFM). Large steps with a width of 4μm and a height of 7nm formed on the seed crystal surfaces after H
2
etching. The distribution and density of the dislocations were observed by the automatic microscope scanning. The results showed that the threading screw dislocations (TSD) density of wafers performed by H
2
etching was dramatically reduced compared with the seeds. It is believed that H
2
is conducive to the generation of macro-steps, and the macro-steps deflect the direction of the TSD and convert it into a Frank-type stacking fault on the basal plane. In addition, the density of TSD further reduced as the crystal grows owing to paired TSDs merged and annihilated.