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

Abstract

6-inch 4° off-axis 4H-SiC crystals were grown by the physical vapor transport (PVT) method on the seeds processed by hydrogen (H2) etching. The seed surface morphology after H2 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 H2 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 H2 etching was dramatically reduced compared with the seeds. It is believed that H2 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.