Plasmonic gap resonances of electrically excited MIS-AgNR hybrid system

Abstract In this paper, a kind of light-emitting tunnel junction composed of three layers of metal–insulator-semiconductor (MIS, Au-Al2O3-Si) is introduced and this structure mainly relies on electron tunneling to excite SPPs. The finite element method is used to calculate the electric field distribution and extinction spectrum of the silver nanorod (AgNR) placed on the metal–insulator-semiconductor tunnel junction (MIS-AgNR). In the simulation, the influence of tunneling current on the strength of SPPs propagating along the metal surface is quantitatively studied by changing the thickness of the insulator layer of the MIS tunnel junction and the bias voltage across it. The AgNR is placed on the tunnel junction, and the gap distance between the gold surface of the MIS structure and the AgNR is changed to qualitatively study the relationship between the extinction characteristics of the AgNR and the gap distance. The study found that the amount of the tunneling current is proportional to the intensity of the SPPs on the metal surface. In the range of 4 nm–20 nm gap distance, the adjustment of the resonance peak position in the 500 nm–700 nm range of the extinction spectrum is realized. As the gap distance increases, the position of the resonant peak in the AgNR extinction spectrum will undergo blue-shift, and at the same time the intensity of the extinction peak will decrease. It is worth noting that the change of the blue-shift displacement is exponentially related to the change of the gap distance.