Surface plasmon enhanced GeSn photodetectors operating at 2 µm

Area of Science:

• Optoelectronics
• Materials Science
• Nanotechnology

Background:

• Germanium-Tin (GeSn) metal-semiconductor-metal (MSM) photodetectors are crucial for infrared applications.
• Enhancing photodetector responsivity at 2 µm is essential for optical communication and sensing.

Purpose of the Study:

• To design and integrate plasmonic structures (Au-hole array and Au-GeSn grating) into GeSn MSM photodetectors.
• To investigate the impact of these plasmonic structures on photo detection performance at 2 µm.
• To evaluate the polarization dependence and responsivity enhancement offered by the plasmonic structures.

Main Methods:

• Design and fabrication of GeSn MSM photodetectors incorporating gold (Au) hole-array and Au-GeSn grating structures.
• Utilizing surface plasmon resonance (SPR) for optical confinement near the photodetector surface.
• Characterization of photodetector responsivity under varying conditions, including polarization.

Main Results:

• Both Au-hole array and Au-GeSn grating structures provide optical confinement and enhance responsivity.
• The Au-hole array structure offers polarization-insensitive responsivity enhancement (∼50%).
• The Au-GeSn grating structure achieves a 3× enhanced responsivity (0.455 A/W at 1.5V) under TM-polarized illumination, among the highest for 2 µm GeSn photodetectors.

Conclusions:

• Plasmonic engineering with Au-hole arrays and Au-GeSn gratings significantly improves GeSn photodetector performance at 2 µm.
• These plasmonic photodetectors present a viable alternative for high-efficiency 2 µm photo detection.
• The developed photodetectors show great potential for 2 µm optical communication and emerging applications.