Damage and recovery behavior of 4H-SiC implanted with He ions

Abstract

Multiple-energy He ions were used to produce thicker damage layers with 3000 appm/0.17 dpa (by low dose implantation) and 6000 appm/0.34 dpa (by high dose implantation), respectively, in mono-crystalline 4H-SiC at room temperature (RT). Results from XRD and nano-indentation tests indicated that the low dose implanted sample contained larger numbers of defects, but still sustained crystalline state. However, amorphization occurred in the sample with high implantation dose. Subsequently, both implanted samples were annealed in vacuum condition at 300, 500, 700, 900 and 1100 °C for 0.5 h, successively. After each step of annealing, the samples were characterized by Raman spectroscopy. Raman spectra indicated that graphite was formed in the implanted samples. From RT to 500 °C, the concentration of graphite in both implanted samples increased with temperature, which was considered to be related with the release of He atoms from the Si tetrahedral interstitial sites. However, the graphite showed different annealing behavior for the low dose and high dose implanted samples at the temperature from 500 to 1100 °C. For the sample with low implantation dose, the graphite concentration decreased with increase of temperature, which was due to the decomposition of the distorted graphite. However, for the sample with high implantation dose, the graphite completely vanished after annealing at 700 °C, which could be caused by the occurrence of recrystallization in SiC.