Photoluminescence identification of the VSi and NC–VSi defects in 4H-SiC generated by keV Si ion irradiation

Abstract

The quantum properties of the silicon vacancy (VSi) and nitrogen-vacancy complex (NC–VSi) defects in 4H-SiC are a subject of ongoing research due to applications in quantum metrologies. While MeV proton irradiation has been widely used for NC–VSi generation, the intermediate VSi–H complex is detrimental. This study uses Si ions of keV energies conveniently achievable from a modest ion implanter to generate both VSi and NC–VSi. Their signatures and densities are determined by photoluminescence (PL) spectroscopy and the intensities compare well with previous studies using MeV ions. Two types of 4H-SiC, high purity semi-insulating and n-type, are investigated. In the pristine semi-insulating sample, VSi is already present, and the intensity increases with a fluence up to 1 × 1014 cm−2 and decreases thereafter for 1 × 1015 and 1 × 1016 cm−2. A post-implantation thermal annealing further modulates the VSi PL emission. On the other hand, in the pristine n-type wafer, the VSi defect is absent due to its high dopant concentration, but is created after an implantation at a fluence of 1 × 1012 cm−2. The NC–VSi defect in n-type is not activated even up to an ion fluence of 1 × 1016 cm−2 but emerges after a post-implantation annealing. Thus, a judicious choice of ion fluence and annealing controls the formation and the density of VSi and its conversion to NC–VSi defects in SiC. Wavelength dependent photoluminescence spectroscopy gives further insights into the defects. The defect densities are correlated to the ion-induced structural disorder and thermally induced recrystallization monitored by Raman spectroscopy.