Photoionization current spectroscopy of individual silicon vacancies in silicon carbide

TL;DR

This study uses photocurrent spectroscopy to analyze the ionization behavior of silicon vacancies in silicon carbide, revealing their excitation properties and optimizing conditions for quantum device applications.

Contribution

It introduces photocurrent spectroscopy as a new method to analyze defect charge states in silicon carbide, providing insights into their ionization dynamics and robustness.

Findings

V1 and V2 vacancies have similar ionization cross-sections increasing at shorter wavelengths.

Carbon vacancies dominate the background photocurrent with a steeper wavelength dependence.

Optimal wavelength regimes for defect photocurrent enhance quantum device performance.

Abstract

Defect charge-state dynamics are central to both spin-photon interfaces and photoelectrical spin readout. Despite the significance of silicon vacancies (V1/V2) in silicon carbide (4H-SiC) for both applications, their ionization behavior has remained unclear because their lack of optical blinking prevents conventional charge-state analysis. Here, we employ photocurrent spectroscopy of individual defects to measure the wavelength dependence of their excitation and ionization cross-sections. We reveal that V1 and V2 exhibit similar ionization cross-sections that increase toward shorter wavelengths, while carbon vacancies dominate the more steeply increasing background photocurrent. These results indicate that V2 and its surrounding environment appear more robust than V1 under resonant excitation. We also identify wavelength regimes that optimize defect-origin photocurrent for photoelectrical spin readout relative to background contributions, which differ between single-defect and ensemble measurements. Our results establish photocurrent spectroscopy as a powerful complement to optical methods, advancing the development of defect-based quantum devices.