Exhaustive characterization of modified Si vacancies in 4H-SiC

TL;DR

This study combines computational and experimental methods to identify and characterize silicon vacancy-related defects in 4H-SiC, revealing new defect configurations relevant for quantum technologies.

Contribution

It introduces a high-throughput defect database approach to identify defect structures that explain observed magneto-optical signals in 4H-SiC, specifically focusing on silicon vacancies and nearby antisite defects.

Findings

Identification of C_Si as a perturbing defect near V_Si^-

Reported zero phonon lines and zero field splitting for defect complexes

High agreement between computational predictions and experimental photoluminescence data

Abstract

The negatively charged silicon vacancy ($\mathrm{V_{Si}^-}$) in silicon carbide is a well-studied point defect for quantum applications. At the same time, a closer inspection of ensemble photoluminescence and electron paramagnetic resonance measurements reveals an abundance of related but so far unidentified signals. In this study, we search for defects in 4H-SiC that explain the above magneto-optical signals in a defect database generated by Automatic Defect Analysis and Qualification (ADAQ) workflows. This search reveals only one class of atomic structures that exhibit silicon-vacancy-like properties in the data: a carbon antisite ($\mathrm{C_{Si}}$) within sub-nanometer distances from the silicon vacancy only slightly alters the latter without affecting the charge or spin state. Such a perturbation is energetically bound. We consider the formation of $\mathrm{V_{Si}^-+C_{Si}}$ up to 2 nm distance and report their zero phonon lines and zero field splitting values. In addition, we perform high-resolution photoluminescence experiments in the silicon vacancy region and find an abundance of lines. Comparing our computational and experimental results, several configurations show great agreement. Our work demonstrates the effectiveness of a database with high-throughput results in the search for defects in quantum applications.