A Low-Dark-Current 4H-SiC MOS UV Photodetector With a Charge-Trapping Gate Stack by Electric Field Modulation Operation

Abstract

A 4H-SiC metal–oxide–semiconductor ultraviolet photodetector featuring an Al₂O₃/AlO ${}_{x}$ /SiO₂ charge-trapping gate stack is demonstrated for highly sensitive ultraviolet intensity monitoring. A high-quality SiO₂/SiC interface formed by intermittent spray hydrated oxidation suppresses interface defects, resulting in an ultralow dark current density ( ${3}.{96} \times {10}^{-{10}}~\text {A}/ {cm}^{{2}}$ ) under a reverse bias of -5 V. Subsequently, the upper gate dielectric layers are fabricated using thermal evaporation followed by a multi-step anodic oxidation process. Under ultraviolet illumination, photogenerated holes tunnel through the ultrathin SiO₂ layer and are stored in the oxygen-deficient AlO ${}_{x}$ layer, where the accumulated positive charges redistribute the internal oxide electric field. The continuously increasing oxide field drives a carrier transport transition from Poole–Frenkel emission to Fowler–Nordheim tunneling. The device achieves a photo-to-dark current ratio of ${8}.{0} \times {10}^{{4}}$ at an ultraviolet power density of 400 W/m² and exhibits excellent linearity with a coefficient of determination (R²) exceeding 0.997. These results demonstrate a highly promising electric-field-modulation approach for robust charge-trapping-assisted ultraviolet sensing and precision intensity monitoring applications.