H-ion Irradiation-induced Annealing in He-ion Implanted 4H-SiC

Radiation-induced defect annealing in He^+ ion-implanted 4H-SiC via H^+ ion irradiation is investigated by Raman spectroscopy. There are 4H-SiC wafers irradiated with 230 keV He^+ ions with fluences ranging from 5.0\times10^15 cm^-2 to 2.0\times10^16 cm^-2 at room temperature. The post-implantation samples are irradiated by 260 keV H^+ ions at a fluence of 5.0\times10^15 cm^-2 at room temperature. The intensities of Raman lines decrease after He implantation, while they increase after H irradiation. The experimental results present that the magnitude of Raman line increment is related to the concentration of pre-existing defects formed by He implantation. A strong new peak located near 966 cm^-1, which is assigned to 3C-SiC LO (\it \Gamma) phonon, is found in the He-implanted sample with a fluence of 5.0\times10^15 cm^-2 followed by H irradiation. However, for the He-implanted sample with a fluence of 2.0\times10^16 cm^-2 followed by H irradiation, no 3C-SiC phonon vibrations are found. The detailed reason for H irradiation-induced phase transformation in the He-implanted 4H-SiC is discussed.