Mid-Infrared Sensing and Ultrafast Photoresponse in Silicon-Based Plasmonic Detectors.

Area of Science:

• Photonics and Optoelectronics
• Materials Science
• Semiconductor Devices

Background:

• Mid-infrared (MIR) photonics is crucial for sensing and communication but limited by the lack of efficient, room-temperature photodetectors.
• Current technologies often require bulky cooling systems or are not compatible with standard semiconductor manufacturing.

Purpose of the Study:

• To present a novel Al-Si-Al planar heterostructure as a plasmonic photodetector for MIR light.
• To demonstrate CMOS-compatible, room-temperature operation for sub-bandgap photon detection (5-7 μm).

Main Methods:

• Fabrication of a monolithic Al-Si-Al heterostructure with abrupt interfaces, avoiding epitaxy.
• Utilizing an electrostatically tunable Schottky barrier for hot-carrier generation and detection.
• Characterization of photodetector performance, including responsivity, dark current, spectral response, and dynamic response.

Main Results:

• Detection of sub-bandgap MIR photons (5-7 μm) with a responsivity of ~0.9 mA/W.
• Achieved low dark current density (<0.4 mA/cm²) and broad spectral response without cooling.
• Observed fast internal dynamics (3.7 ps and 1.4 ns time constants) at 1560 nm, indicating high-speed potential.
• Successfully detected and spectrally characterized water molecule absorption lines.

Conclusions:

• The Al-Si-Al heterostructure offers a scalable, CMOS-compatible platform for room-temperature MIR photodetectors.
• This technology enables cost-effective, high-speed infrared sensing for integrated photonic systems.
• The device demonstrates significant potential for applications in chemical sensing, medical diagnostics, and environmental monitoring.