Computational study of anisotropic epitaxial recrystallization in 4H-SiC

Two nano-sized amorphous layers were created within a crystalline cell to study anisotropic expitaxial recrystallization using molecular dynamics (MD) methods in 4H-SiC. Both amorphous layers were created with the normal of the amorphous-crystalline (a-c) interfaces along the [0001] direction, but one had a microscopic extension along the [(1) over bar2 (1) over bar0] direction, i.e. the dimension along the [(1) over bar2 (1) over bar0] direction is much larger than that along the [(1) over bar 010] direction (I-x model), and the other had a microscopic extension along the [(1) over bar 010] direction (I-y model). The amorphous layer within the I-x model can be completely recrystallized at 2000 K within an achievable simulation time, and the recrystallization is driven by a step-regrowth mechanism. On the other hand, the nucleation and growth of secondary ordered phases are observed at high temperatures in the I-y model. The temperature for recrystallization of the amorphous!
layer into high-quality 4H-SiC is estimated to be below 1500 K. Compared with other models, it is found that the regrowth rates and recrystallization mechanisms depend strongly on the orientation of 4H-SiC, whereas the activation energy spectra for recrystallization processes are independent of any specific polytypic structure, with activation energies ranging from 0.8 to 1.7 eV.