Thermometric quantum sensor using excited state of silicon vacancy centers in 4H-SiC devices

We characterized the excited state (ES) and the ground state (GS) of negatively charged silicon vacancy (⁠$VSi−$⁠) centers in hexagonal silicon carbide (4H-SiC) using optically detected magnetic resonance (ODMR) to realize thermometric quantum sensors. We report the observation of inverted contrast between ODMR signals of the ES and the GS and clarify the effect of energy sublevels of spin states in 4H-SiC. We confirm that ES ODMR signals of $VSi−$ centers are dependent on the temperature with a thermal shift of 2 MHz/K on zero-field splitting (ZFS). Thus, we fabricated microscale dots of $VSi−$ centers in a 4H-SiC p–n diode using proton beam writing and demonstrated the operation of thermometric quantum sensors by measuring the temperature change induced by an injected current. Our demonstration paves the way for the development of atomic-size thermometers inside SiC power devices for future applications.