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

Abstract

Positron annihilation in 800 keV Ge + implanted hexagonal SiC was studied by thermal annealing at temperatures ranging from 800 to 1400 °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 °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.