Enhancing Broadband 4H-SiC Photodetectors With Gold Nanoparticles: Expanding Sensitivity From UV to SWIR Spectrum

4H-silicon carbide (4H-SiC) is promising for photodetectors (PDs) capable of operating at high voltages and elevated temperatures. However, the wide bandgap of 4H-SiC (3.26 eV) restricts its applications to the ultraviolet (UV) range below 400 nm. It is essential to develop 4H-SiC PDs with a broadband response covering the UV to short-wavelength infrared (SWIR) spectrum. This study demonstrates a 4H-SiC broadband PD with sensitivity extending from UV to SWIR range up to 2200 nm. The superior performance is attributed to the presence of numerous defect centers forming deep energy levels within the 4H-SiC bandgap, which allows the absorption of visible (VIS) and SWIR photons with energies lower than the bandgap. Moreover, the incorporation of thermally annealed gold nanoparticles (Au NPs) induces localized plasmonic resonance, significantly enhancing the photocurrent over a broadband wavelength range while maintaining the dark current. This leads to superior weak light detection capabilities for the plasmonic device compared to the reference device without Au NPs. At the enhancement peak (under 860-nm laser illumination), the plasmonic device achieves a minimum detectable power density of 0.488$\mu$W/cm$^{\text{2}}$. Notably, the plasmonic PD exhibits a 3260% increase in the photo-to-dark current ratio (PDCR), with an external quantum efficiency (EQE) enhancement factor reaching a maximum of 3166%. These results lay a foundation for advancing the development of UV-SWIR broadband SiC PDs.