Clustering of vacancy defects in high-purity semi-insulating SiC

TL;DR

This study uses positron lifetime spectroscopy to analyze native vacancy defects in semi-insulating silicon carbide, revealing vacancy clusters and Si vacancy related defects that influence electrical resistivity and change during annealing.

Contribution

It identifies specific vacancy defects and their evolution during annealing, linking defect structures to electrical properties in high-purity SiC.

Findings

Vacancy clusters consist of 4-5 missing atoms.

Si vacancy related defects are negatively charged.

Open volume correlates with resistivity.

Abstract

Positron lifetime spectroscopy was used to study native vacancy defects in semi-insulating silicon carbide. The material is shown to contain (i) vacancy clusters consisting of 4--5 missing atoms and (ii) Si vacancy related negatively charged defects. The total open volume bound to the clusters anticorrelates with the electrical resistivity both in as-grown and annealed material. Our results suggest that Si vacancy related complexes compensate electrically the as-grown material, but migrate to increase the size of the clusters during annealing, leading to loss of resistivity.