Evolution and recrystallization of buried amorphous layers in Al 22+ implanted 4H-SiC

Abstract

Epitaxial 4H-SiC has been irradiated at 150 K with 1.1 MeV Al 2 2+ molecular ions to fluences ranging from 1.5×10 13 to 8.00×10 14 Al + cm −2. The evolution and isochronal recovery of the buried amorphous layers at higher fluences were investigated by in situ Rutherford backscattering spectrometry using a 2.0 MeV He + beam along the 〈0 0 0 1〉 channeling direction. The damage accumulation at the damage peak in the as-implanted samples indicates a sigmoidal dependence on ion fluence, and a buried amorphous layer is formed at 2.00×10 14 Al + cm −2. The buried amorphous thickness increased rapidly at 2.00×10 14 Al + cm −2 and eventually saturated at a thickness of ∼500 nm at the highest fluence. The relative amount of recovery at any depth decreased with increasing ion fluence for temperatures up to 870 K, and once a thick buried amorphous layer is produced, recovery is only observed at the crystalline–amorphous interface. Defect annihilation processes are responsible for the slight recrystallization and sharpening of the damage profiles that are observed at these low annealing temperatures.