GeSn/SiO₂ Multilayers by Magnetron Sputtering Deposition for Short-Wave Infrared Photonics

Area of Science:

• Semiconductor Physics
• Materials Science
• Nanotechnology

Background:

• Short-wave infrared (SWIR) photonics are crucial for applications like the Internet of Things and pollution monitoring.
• Manufacturing crystalline germanium-tin (GeSn) alloys is challenging due to low Ge and Sn miscibility.
• Embedded GeSn nanocrystals (NCs) offer a viable solution for relaxed growth conditions.

Purpose of the Study:

• To investigate GeSn/SiO2 multilayer deposition for controlled GeSn nanocrystal formation.
• To analyze the impact of multilayer structure on nanocrystal size, insulation, and SWIR properties.
• To fabricate and characterize SWIR photodetectors based on GeSn NCs.

Main Methods:

• Fabrication of 20×(11nm_GeSn/1.5nm_SiO2) multilayers using magnetron sputtering.
• In situ prenucleation followed by ex situ rapid thermal annealing for nanocrystallization.
• Characterization using ellipsometry and spectral photosensitivity measurements; device fabrication (ITO/GeSn NC/SiO2/p-Si/Al diodes).

Main Results:

• Formation of GeSn NCs with ~16% Sn concentration and ~9 nm size within SiO2 matrix.
• Vertically correlated GeSn dome formation observed, aiding nanocrystallization.
• SWIR absorption limit of ~0.4 eV and spectral photosensitivity up to >2200 nm demonstrated.
• Multilayer diodes exhibited higher photocurrent efficiency than monolayer devices.

Conclusions:

• GeSn/SiO2 multilayers effectively control GeSn NC size and insulation for SWIR applications.
• The developed diodes show significant SWIR photosensitivity, particularly at longer wavelengths.
• This approach offers a promising pathway for cost-effective SWIR photonic devices.