Tunable infrared hot-electron photodetection by exciting gap-mode plasmons with wafer-scale gold nanohole arrays

Due to the strongly concentrated electromagnetic field and the ability to detect the below-bandgap photon energies, surface-plasmon-based photodetections have attracted considerable attention. However, the manipulation of plasmonic resonance is complicated with a high cost in fabrication; moreover, the performance of hot-electron photodetectors is generally unsatisfactorily low. Here, we demonstrated that a tunable absorption can be realized by using the nanohole patterned metal-spacer-metal (MSM) structure, which can be wafer-scale fabricated by the nanosphere lithography technology. The angle- and polarization-insensitive absorption is realized under the excitation of the gap-mode plasmons, which can be facilely manipulated in the near-infrared band by varying the thicknesses and material of the spacer as well as the diameter and period of the nanohole arrays. An asymmetrically bended electrical system is proposed to efficiently convert the highly absorbed photon energies into the photocurrent. Results show that the responsivity of the prepared MSM structure can be up to ∼2.82 mA/W at the wavelength of 1150 nm.