Absorption enhancement in LWIR detector via waveguide and plasmonic modes engineering.

Area of Science:

• Optoelectronics
• Materials Science
• Nanophotonics

Background:

• Long-wavelength infrared (LWIR) photodetectors are crucial for thermal imaging and sensing.
• Achieving high optical absorption in thin photodetector structures remains a challenge.
• Type-II superlattices (T2SL) offer tunable bandgaps for infrared applications.

Purpose of the Study:

• To demonstrate enhanced optical absorption in a thin InAs/InAsSb type-II superlattice (T2SL) photodetector.
• To investigate the role of waveguide and surface plasmon polariton (SPP) modes in absorption enhancement.
• To explore the impact of a highly doped semiconductor contact (HDSC) layer on photodetector performance.

Main Methods:

• Fabrication of a thin InAs/InAsSb T2SL absorber layer.
• Integration of an adjacent highly doped semiconductor contact (HDSC) layer.
• Characterization of optical absorption enhancement through mode excitation (waveguide and SPP).

Main Results:

• Demonstrated enhanced optical absorption in the LWIR photodetector.
• Observed significant absorption from guided modes between 7 µm and 9 µm.
• SPP modes contributed to resonance near 10 µm.
• The absorber-HDSC interface provided tunable Fresnel reflection phase.

Conclusions:

• The developed photodetector design enables efficient absorption in thin structures.
• Excitation of waveguide and SPP modes is key to enhanced absorption.
• The configuration advances subwavelength photonic design for infrared applications.