Illumination effects in irradiated 6H n-type SiC observed by positron annihilation spectroscopy

摘要

In the present study, we used positron annihilation spectroscopy to investigate defects after electron irradiation in 6H n-type SiC. The density of vacancy-type defects strongly increased during this treatment. An isochronal annealing experiment was performed, and the main recovery stage was found to be between 1000℃ and 1400℃. This corresponds to the annealing range of the E_1/E_2 defect, which was also found by a correlated positron and DLTS study in 6H―SiC epilayers after electron irradiation (J. Appl. Phys. 80 (1996) 5639). Optical excitation experiments during the positron experiment show that the observed defect has an ionization level at about E_c― 0.47eV, which is similar to the level E_c―0.44eV obtained by DLTS for the E_1/E_2 defect (Appl. Phys. Lett. 74 (1999) 839). Doppler-coincidence experiments suggest that the observed vacancy is surrounded by C atoms, so that most probably the Si vacancy (isolated or bound to an impurity or another defect) is the dominating defect after electron irradiation.