Defects in He+ irradiated 6H-SiC probed by DLTS and LTPL measurements

Deep-Level Transient Spectroscopy (DLTS) and Low Temperature Photholuminescence (LTPL) were used to characterize the defects introduced in 6H-SiC epitaxial layer by 2.5 MeV He+ irradiation and their behaviour with thermal annealing in the temperature range 200 - 900 degreesC. The DLTS spectra of as irradiated sample show different levels at an energy of 0.40 eV (E-1/E-2), 0.51 eV (RD5) and 0.71 eV (Z(1)/Z(2)) from the bottom of the conduction band. The concentration of the E-1/E-2 level increases with annealing temperature, while the concentration of the remaining peaks decreases. The LTPL of the irradiated sample shows a series of sharp peaks and broad bands in the region 470-500 nm. A set of peaks (473-479 nm) related to carbon vacancies anneals at 600 degreesC, a second set (470 nm) is stable up to 900 degreesC and a third set (L-1-473 nm. and L-2-480 nm) anneals starting from 400 degreesC. The comparison of both measurements suggests that the Z(1)/Z(2) (0.71 eV) DLTS level and the L-1 (L-2) luminescence peaks can be related to the same defect center.