Device engineering for photocurrent detected magnetic resonance and scanning probes using solid-state spin defects

Solid-state spin defects provide a versatile platform for quantum sensing with nanoscale spatial resolution and room-temperature operation. Spin defects in diamond have enabled mature scanning-probe devices, while related defects in silicon carbide and hexagonal boron nitride are being actively explored for scalable sensing platforms. However, the sensitivity of practical and scanning-probe devices remains below that of optimized bulk systems. Although optical fluorescence detection is widely used, practical performance is often constrained by limitations in signal acquisition and readout efficiency, motivating continued efforts to improve readout technologies. This review surveys material platforms and optical and photoelectrical readout technologies for solid-state spin defects. We compare fluorescence- and photoelectric-based detection schemes in terms of readout fidelity, sensitivity, and scalability, and discuss how materials properties and carrier transport influence practical performance. These perspectives provide guidelines for improving readout efficiency and advancing high-sensitivity quantum sensors and scanning probes.