Atomic-level simulations of epitaxial recrystallization and amorphous-to-crystalline transition in 4H-SiC

The amorphous-to-crystalline transition in 4H-SiC has been studied using molecular dynamics (MD) methods, with simulation times of up to a few hundred ns and at temperatures ranging from 1000 to 2000 K. Two nanosized amorphous layers, one with the normal of the a-c interfaces along the [-12-10] direction and the other along the [-1010] direction, were created within a crystalline cell to study epitaxial recrystallization and the formation of secondary phases. The recovery of bond defects at the interfaces is an important process driving the epitaxial recrystallization of the amorphous layers. The amorphous layer with the a-c interface normal along the [-12-10] direction can be completely recrystallized at temperatures of 1500 and 2000 K, but the recrystallized region is defected with dislocations and stacking faults. On the other hand, the recrystallization process for the a-c interface normal along the [-1010] direction is hindered by the nucleation of polycrystalline phases, and these secondary phases are stable for longer simulation times. A general method to calculate activation energy spectra is employed to analyze the MD annealing simulations, and the recrystallization mechanism in SiC consists of multiple stages with activation energies ranging from 0.8 to 1.7 eV.