Imaging ultra-weak UV light below 100 pW cm−2 using a 4H–SiC photodetector with an Al2O3 interfacial layer

Abstract

Weak light detection is crucial in various practical applications such as night vision systems, flame monitoring, and underwater operations. Decreasing the dark current of a photodetector can effectively mitigate noises, consequently enhancing the signal-to-noise ratio and overall weak light detection performance. Herein, we demonstrate a 4H–SiC UV photodetector capable of detecting extremely weak UV light. This device comprises a photosensitive layer of 4H–SiC, two TiN electrodes and an atomically thin Al₂O₃ interfacial layer between TiN and the C surface of 4H–SiC. Under 360 nm UV light illumination, the proposed Al₂O₃ device demonstrates an ultra-low dark current of 18 fA, possibly benefiting from the effective passivation of interfacial carriers, and a boosted photo-to-dark current ratio of 6.7 × 10⁷. Consequently, it achieves a weak-light detection limit as low as 31.8 pW cm⁻², significantly outperforming the control device lacking Al₂O₃. When compared to previously reported SiC photodetectors, our Al₂O₃ device boasts an exceptional large linear dynamic range of 172 dB. Leveraging this, we construct a photodetector array capable of clearly imaging an object under ultra-weak light illumination below the 100 pW cm⁻² level. The proposed photodetector represents a significant advancement in the development of highly sensitive image sensors for weak light detection.