Broadband hot-electron photodetection in near-infrared based on plasmonic disordered nanowires

Abstract

Hot-electron photodetectors are attracting increasing interests due to the outstanding capability of detecting low-energy photons below the semiconductor bandgap, operating under room temperature without electrical bias and the potential to be integrated on a chip, which have unique advantages in the field of infrared photodetection. As an emerging strategy for photodetection, the realization of the broadband/efficient absorption and photodetection with easily constructed metal-semiconductor (M-S) nanosystems is of significance. In this study, we propose a hot-electron photodetector based on a thin Au film with a thickness of 10 nm on the disordered silicon nanowires (SiNWs), which is fabricated by the metal-assisted chemical etching. The average absorption of the hot-electron photodetector across the broad wavelength spectral band (i.e., 1200−2400 nm) is higher than 85%, which is contributed from the multiple localized plasmonic resonances in the disordered Au/Si NWs. Benefited from the small thickness of Au film (shorter than the hot electron mean free path), the generated hot electrons have a high transport probability to reach Schottky interface and participate in the interfacial charge transfer process. As a result, the hot-electron photodetector shows a broadband photodetection capability to the wavelength of 2000 nm under the room temperature. The unbiased responsivity reaches 1.2 mA/W at the wavelength of 1300 nm, which is twice of the grating-based hot-electron photodetector. Our proposed hot-electron photodetector based on disordered Au/Si NWs opens up an alternate path to further extend the detection wavelength of Si-based photodetectors with a low-cost and large-area fabrication process, promoting the practical application of hotelectron devices.