Spectrally Selective Photocapacitance Modulation in Plasmonic Nanochannels for Infrared Imaging

Abstract

The optical response of subwavelength plasmonic structures can be used to monitor minute changes in their physical, chemical, and biological environments with high performance for sensing. The optical response in the far field is governed by the near-field properties of plasmon resonances. Sharp, tunable resonances can be obtained by controlling the shape of the structure and by using resonant cavities. However, microintegration of plasmonic structures on chips is difficult because of the readout in the far field. As such, structures that form an electrical microcircuit and directly monitor the near-field variation would be more desirable. Here, we report on an electronically readable photocapacitor based on a plasmonic nanochannel structure with high spectral resolution and a large modulation capability. The structure consists of metallic U-cavities and semiconductor channels, which are used to focus and confine light at the semiconductor-metal interfaces. At these interfaces, light is efficiently converted into photocarriers that change the electrical impedance of the structure. The capacitance modulation of the structure in response to light produces a light-to-dark contrast ratio larger than 10(3). A reflectance spectrum with a bandwidth of 16 nm and a 6% modulation depth is detected using a reactance variation of 3 kΩ with the same bandwidth. This photocapacitor design offers a practical means of monitoring changes induced by the near field and thus could be deployed in pixel arrays of image sensors for miniaturized spectroscopic applications.

Recent improvement of silicon absorption in opto-electric devices

“…Using a three dimensional plasmonic resonator, a photocapacitance structure was developed to detect the charge generation at the Schottky barrier with higher efficiency (Fig. 4(b)) 44 .…”

Low-Dimensional Materials and State-of-the-Art Architectures for Infrared Photodetection

“…The more important thing here is reflectance and absorptance bandwidth, and intensity depends upon nanochannel cross-sectional width and material. Likewise, with various particular designs of a metal coupler, spectral selectivity has been transformed into polarization and color detection [148,152,156].…”

“…Three-dimensional plasmonic nanochannel/semiconductor structure. ( a ) Nanochannel/semiconductor with U-shaped vertical plasmonic cavities structured at semiconductor substrate, ( i ) SEM image of Si channel fin on SiO 2 substrate, ( ii ) simulation of light concentration of EM radiations at right side; and ( b ) optical spectra showing the plasmonic coupled mode at different angles (θ) (Reproduced with the permission of [156], Copyright 2016, American Chemical Society).…”

Hot electron photodetection with spectral selectivity in the C-band using a silicon channel-separated gold grating structure

“…Plasmonic nanostructures have received extensive attention due to their ability to increase the harvesting of incident light from free space and concentrate electromagnetic energy to nanoscale volumes through the excitation of surface plasmons (SPs). With this outstanding property, plasmonic nanostructures have been widely used to enhance the performance of optoelectronic devices, such as photocatalysis devices [1,2], solar energy harvesting devices [3,4], lasing devices [5,6], imaging devices [7], monitoring devices [8], and photodetectors [9][10][11][12][13][14]. SP-based photodetectors generally have higher external quantum efficiencies and responsivities than conventional photodetectors because of the enhanced light absorption and the ability to generate hot electrons through the nonradiative decay of SPs [15,16].…”