Comprehensive Analysis of Formation Mechanism of Vacancy Complexes in 4H-SiC

In recent years, much research has focused on optically addressable defect spins, such as the negatively charged nitrogen-vacancy center in diamond and neutral divacancy (VV⁰) complexes in silicon carbide (SiC), for quantum technology applications, including scalable quantum sensing and quantum networking. In particular, VV⁰ complexes in 4H-SiC are attracting widespread interest for their optical addressability, near-infrared emission, and long coherence times. Key to their development is the understanding the formation dynamics and how it relates to the structural and electrostatic properties of these defects. To address this, we report a systematic approach combining experiments, theory, and computation that leads to a thorough understanding of defect formation dynamics and control. Previous studies have focused on photoluminescence spectra to estimate the structure of color centers. However, alternate approaches are necessary to fully identify the structure of the novel color centers and clarify formation mechanisms as few techniques can provide a full quantitative picture of these complex vacancy structures.
In this study, we explore positron annihilation lifetime spectroscopy (PALS) and positron annihilation spectroscopy (PAS) as means to identify the structural and formation dynamics of vacancy complexes due to electron irradiation and subsequent annealing processes. The PAS and PALS techniques have strong advantages as they offer non-destructive analysis methods and can probe insulating host materials. Moreover, PALS analysis can provide insights into the vacancy volume and density, allowing a pathway to identify the vacancy complex type guided by theoretical calculations. We will compare the detailed results of the PL spectra, PAS, and PALS measurement, to provide a framework for future studies to assess the vacancy complexes in 4H-SiC as qubit candidates for quantum networks and quantum sensing.