Evidence for negatively charged vacancy defects in 6H-SiC after low-energyproton implantation

We have used pulsed-slow-positron-beam-based positron lifetime spectroscopy to investigate the nature of acceptors and charge states of vacancy-type d efects in low-energy proton-implanted 6H-SiC(H). We can infer from the temp erature dependence of the lifetime spectra that neutral and negatively char ged vacancy clusters exist in the track region. Depending on annealing, the y give rise to positron lifetimes of 257 +/-2, 281 +/-4, and 345 +/-2 ps, r espectively. The 281 ps cluster likely has an ionization level near the mid dle of the band gap. By comparison with theory, the 257 and 280 ps are iden tified as (V-C-V-Si)(2) and (V-C-V-Si)(3) clusters, respectively. In additi on, other acceptors of ionic type act as strong trapping centers at low tem perature (T < 150 K). Neutral monovacancy-like complexes are also detected with a lifetime of 160 +/-2 after 900 degreesC annealing. (C) 2001 American Institute of Physics.