Damage accumulation in nitrogen implanted 6H-SiC: Dependence on the direction of ion incidence and on the ion fluence

The influence of crystallographic orientation and ion fluence on the shape of damage distributions induced by 500keV N+ implantation at room temperature into 6H-SiC is investigated. The irradiation was performed at different tilt angles between 0° and 4° with respect to the ⟨0001⟩ crystallographic axis in order to consider the whole range of beam alignment from channeling to random conditions. The applied implantation fluence range was 2.5×1014–3×1015cm−2. A special analytical method, 3.55MeV He+4 ion backscattering analysis in combination with channeling technique (BS∕C), was employed to measure the disorder accumulation simultaneously in the Si and C sublattices of SiC with good depth resolution. For correct energy to depth conversion in the BS∕C spectra, the average electronic energy loss per analyzing He ion for the ⟨0001⟩ axial channeling direction was determined. It was found that the tilt angle of nitrogen implantation has strong influence on the shape of the induced disorder profiles. Significantly lower disorder was found for channeling than for random irradiation. Computer simulation of the measured BS∕C spectra showed the presence of a simple defect structure in weakly damaged samples and suggested the formation of a complex disorder state for higher disorder levels. Full-cascade atomistic computer simulation of the ion implantation process was performed to explain the differences in disorder accumulation on the Si and C sublattices. The damage buildup mechanism was interpreted with the direct-impact, defect-stimulated amorphization model in order to understand damage formation and to describe the composition of structural disorder versus the ion fluence and the implantation tilt angle.