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Seminar | Institute for Molecular Engineering

Optical Charge Control of Defects in Silicon Carbide

IME Seminar

Abstract: Optically active defects in wide-bandgap host materials offer a diverse platform for quantum computing, sensing, and communication. Among those materials, silicon carbide (SiC) provides a technologically relevant solution amenable to wafer-scale fabrication and hosts defects with long coherence times, such as the divacancy and the silicon vacancy. Creating and using these defects, however, cannot be consistently achieved without adequate control of their charge properties.

I will begin by showing how the divacancy charge state, normally unstable under photoluminescence excitation, can be controlled by a combination of ultraviolet and infrared excitation. This control provides a tuning parameter to understand the charge dynamics in the system and the material properties required to obtain stable defects for quantum information. In this manner, the photoluminescence intensity of divacancy and silicon vacancies can be modulated by orders of magnitude, remains stable at cryogenic temperatures, and does not negatively affect the coherence times of the defect spin state. By combining photoluminescence measurements, electron paramagnetic resonance and annealing studies, a comprehensive model was developed to explain the charge behavior.

Next, I will present recent results showing how the charge conversion process is also sensitive to local high-frequency (MHz-GHz) electric fields and mechanical strains. The charge conversion rate and therefore the defect photoluminescence are modified in the presence of these fields, enabling the defects as electric field and strain sensors. Using this technique, the electric field from lithographically patterned capacitors is mapped out, as well as the mechanical modes in a surface acoustic wave resonator and in clamped membranes. Finally, this method is extended to provide full 3-D vector information, as well as phase and frequency resolution.

This demonstrates the potential of optically active defects for in situ electrical and micromechanical systems characterization in relevant commercial materials including SiC, and potentially in other wide-bandgap materials such as diamond or AlN.