Samples of P+-implanted 6H-SiC were studied by using a variable-energy slow positron beam. In as-grown samples a slow fall of the annihilation S-parameter from the surface to the bulk value was observed, indicating a long diffusion length, i.e. an absence of positron-trapping defects. This result was also confirmed by positron-lifetime measurements yielding essentially a single-component lifetime of 148ps. In the implanted samples, a wide flat region of slightly increased defectiveness was detected. However, it was noted that, in order to reproduce reasonably well the depth of the damaged layer, it had to be assumed that strong electric fields were present in the implanted region. Upon annealing, S-curves revealed a rising maximum, moving towards the surface. It was thought to be probable, in as-implanted samples, that the defects were decorated with P+ ions and did not trap positrons in an effective manner. After annealing at the highest temperature, a highly defected region extended to a depth of 50nm. Atomic force microscopy was also used to monitor the evolution of surface defects.

Defect Dynamics in P+ Implanted 6H-SiC Studied by Positron Annihilation Spectroscopy. G.P.Karwasz, R.Rurali, G.Consolati, P.Godignon: Physica Status Solidi C, 2004, 1[2], 257-60