Sn-based waveguide p-i-n photodetector with strained GeSn/Ge multiple-quantum-well active layer.

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Photodetectors are crucial for optical communication systems.
• Germanium-based photodetectors are limited in their detection range.
• Germanium-tin (GeSn) alloys offer tunable bandgaps for extended infrared detection.

Purpose of the Study:

• To develop Sn-based p-i-n waveguide photodetectors (WGPD) with a pseudomorphic GeSn/Ge multiple-quantum-well (MQW) active layer.
• To investigate the impact of Sn-alloying on the photodetector's performance, including dark current and responsivity.
• To demonstrate the feasibility of GeSn/Ge MQW WGPDs for telecommunication and optical interconnection applications.

Main Methods:

• Fabrication of Sn-based p-i-n WGPDs on a Ge-buffered Si substrate.
• Characterization of dark current density under reverse bias.
• Measurement of responsivity across telecommunication bands (O, E, S, C, L).
• Band structure analysis of pseudomorphic GeSn/Ge quantum well structures.

Main Results:

• Achieved a reduced dark-current density of 59 mA/cm² at 1 V reverse bias.
• Demonstrated complete photodetection across O, E, S, C, and L telecommunication bands.
• Observed extended absorption edge to longer wavelengths by increasing Sn content in GeSn/Ge MQW.
• Confirmed suppressed strain relaxation in the GeSn/Ge active layer.

Conclusions:

• Sn-alloying in GeSn/Ge MQW effectively shifts the absorption edge for infrared photodetection.
• GeSn/Ge MQW WGPDs exhibit promising performance for telecommunication applications.
• These photodetectors are viable building blocks for electronic-photonic integrated circuits.