Germanium Tin (GeSn)
- Germanium Tin (GeSn) is an alloy between pure Ge and Sn
- Adding Sn to the Ge lattice transitions pure Ge into a direct bandgap semiconductor and offers the ability to control the bandgap itself
- Applications include: IR LEDs, LASERs and detectors for various communication applications with the ability to tune photodiode wavelength between 1550-3000nm
- Typical device structures include pure GeSn or hybrid Ge/GeSn PiN photodiodes as well as GeSn/Ge/Si APDs
- Advanced Epi is one of the only global providers of GeSn epitaxy on (100, 150 and 200mm) diameter wafers offering significant cost savings over III-V material technologies and a great contender for new low-cost LIDAR detectors
Germanium Tin Growth
- Advanced Epi can grow high quality GeSn (strained or relaxed) up to ~13% Sn content
- Advanced Epi grow GeSn alloys on relaxed Ge buffers grown on Si(100) substrates with buffer thicknesses typically 600-1000nm
- GeSn Epilayers can be grown on 100, 150 and 200mm diameter substrates
- Electrically active doping is possible with both n-type (P) and p-type (B) dopants
Material Characterisation
![Schematic2 Schematic2](https://vkta7e.n3cdn1.secureserver.net/wp-content/uploads/2021/06/Schematic2.png)
Cross sectional schematic for GeSn epilayers grown on Ge buffers (virtual substrates).
![GeSn XRD GeSn XRD Coupled Scan](https://vkta7e.n3cdn1.secureserver.net/wp-content/uploads/2021/06/XRD-3.png)
X-ray diffraction (XRD) coupled scans of fully strained GeSn epilayers of 5% and 10% Sn composition.
![GeSn RSM GeSn RSM](https://vkta7e.n3cdn1.secureserver.net/wp-content/uploads/2023/03/RSM-e1679582938202.png)
Reciprocal Space Map (RSM) of relaxed GeSn epilayer suitable for photonic applications.
![GeSn AFM GeSn AFM Surface Morphology](https://vkta7e.n3cdn1.secureserver.net/wp-content/uploads/2021/06/AFM-1.png)
The surface roughness of GeSn epilayers tends to increase with Sn content, thickness and relaxation although films with RMS roughness <2nm are possible.
![GeSn TEM GeSn TEM Micrograph](https://vkta7e.n3cdn1.secureserver.net/wp-content/uploads/2021/06/TEM-1.png)
Cross-sectional TEM image showing high quality GeSn epilayer grown on a relaxed Ge buffer.