Positron annihilation study of 4H-SiC by Ge+ implantation and subsequent thermal annealing

Positron annihilation in 800 key Ge+ implanted hexagonal SiC was studied by thermal annealing at temperatures ranging from 800 to 1400 degrees C. The variation in Doppler broadening S values as a function of the incident positron energy suggests a broad distribution in the depth of vacancy defects in the implanted samples. Increasing the annealing temperature triggers the accumulation of vacancies into vacancy clusters. After annealing at 1400 degrees C, defects in the deep region of SiC are eliminated, and Ge precipitation is believed to appear in the sample at the same time. Though Ge has a much more negative positron affinity than SiC, positron annihilation coincidence Doppler broadening measurement reveals that a preferential trapping of positrons in Ge seems impossible. (C) 2011 Elsevier B.V. All rights reserved.