Germanium metasurface assisted broadband detectors.

Area of Science:

• Optoelectronics
• Materials Science
• Nanotechnology

Background:

• High responsivity broadband near-infrared photodetectors are in demand but challenging to realize.
• Existing Germanium (Ge) photodetectors face limitations in absorption and responsivity for broadband applications.

Purpose of the Study:

• To design, fabricate, and characterize a novel broadband Germanium (Ge) photodetector.
• To enhance light absorption and detector responsivity in the 1000-1600 nm range.
• To explore the impact of nanostructure geometry on photodetector performance.

Main Methods:

• Fabrication of a broadband Ge photodetector using densely packed Ge disks (255-500 nm diameters) on a thin Ge layer.
• Characterization of the photodetector's performance, including transmission, absorption, and responsivity spectra.
• Analysis of light-matter interactions, specifically the excitation of magnetic dipole resonances.

Main Results:

• Achieved a broadband photodetector operating from 1000-1600 nm.
• Demonstrated a nearly two orders of magnitude increase in absorption and detector responsivity compared to unstructured Ge photodetectors.
• Observed enhanced performance attributed to the excitation of magnetic dipole resonances in Ge disks.
• Maintained a relatively low dark current.

Conclusions:

• The proposed nanostructured Ge photodetector design significantly boosts broadband near-infrared detection capabilities.
• The excitation of magnetic dipole resonances in Ge disks is key to enhanced absorption and responsivity.
• This simple, adaptable approach can improve photodetector performance across various material platforms and wavelengths.