Mechanism of conversion and propagation of dislocations in 4H-SiC epilayer

The elastic energies of four kinds of dislocations per unit growth length have been calculated. We propose that threading screw dislocations(TSDs) along <0001> can propagate into epilayer but can not convert to TEDs. We suggest that both basal plane mix dislocations(B_MDs) and threading screw dislocations (B_TSDs) can convert to TEDs, and B_MDs convert to TEDs much easier than B_TSDs in epilayer because of the higher elastic energy. Based on the experimental results, the relationship between the dislocation density and the conversion and propagation of dislocations is discussed.