Room-temperature plasmonic mid-infrared photodetector based on PtSi/p-Si low Schottky-barrier junction

Abstract

In this study, a low Schottky-barrier photodetector with a plasmonic assist using a two-dimensional (2D) nanohole array was demonstrated, which receives mid-infrared (MIR) light at room temperature. In the structural design, it was confirmed that the 2D nanohole-array photodetector has high absorbance in the MIR region using rigorous coupled-wave analysis. The result showed that the nanoholes formed in p-type silicon (p-Si), platinum silicide (PtSi), to form Schottky barriers, and gold (Au), for photocurrent extraction, had high absorbance in the MIR region along with the Fabry–Perot resonance mode toward the depth of the nanohole. The 2D nanohole array, with Au/PtSi/p-Si layers, has high absorbance for illuminating MIR light near 3.46 µm from the backside. The current–voltage characteristics indicated a low Schottky barrier of 0.32 eV, confirming the photoresponsive potential in the MIR photodetection. The photocurrent response to the modulation signal was obtained at room temperature. In addition, signal processing through transimpedance and lock-in amplifiers enabled us to obtain characteristics with high linearity for light intensities in milliwatts. Light acquisition for 2.5–3.8-µm-long MIR wavelength became possible, and applications in gas sensing, including vibrational absorption bands of alkane groups, are expected.

Near-infrared gas spectroscopy based on plasmonic photodetector applied for multiple gas species

“…In our group, we have already modified the Schottky metal to PtSi in a similar configuration to the proposed plasmonic photodetector and extended the measurable wavelength to 3.4 μm. 37) Introducing this technology and the design optimization make it possible for the plasmonic photodetector to perform mid-IR spectroscopy where gases significantly absorb the light, which will be a key to bridging the resolution gap.…”