Band-gap and strain engineering in GeSn alloys using post-growth pulsed laser melting

Area of Science:

• Materials Science
• Semiconductor Physics
• Nanotechnology

Background:

• Pseudomorphic growth of Germanium-Tin (GeSn) alloys on Germanium (Ge) substrates induces in-plane compressive strain.
• This compressive strain negatively impacts the desirable properties of GeSn alloys, necessitating strain engineering solutions.

Purpose of the Study:

• To present strain and band-gap engineering in GeSn alloys grown on Ge virtual substrates.
• To investigate the effects of post-growth nanosecond pulsed laser melting (PLM) on strain and material properties.

Main Methods:

• Utilized nanosecond pulsed laser melting (PLM) for post-growth treatment of GeSn alloys on Ge virtual substrates.
• Employed Micro-Raman spectroscopy, X-ray diffraction (XRD), Rutherford Backscattering spectrometry (RBS), and cross-sectional transmission electron microscopy (TEM) for material characterization.
• Conducted low-temperature photoreflectance measurements to analyze band structure changes.

Main Results:

• PLM successfully removed the initial in-plane compressive strain in GeSn alloys.
• Tensile strain was induced in Ge0.89Sn0.11 layers at PLM energy densities above 0.5 J cm⁻².
• Crystalline quality and tin distribution were minimally affected by the PLM treatment.
• Band structure modifications were confirmed post-PLM.

Conclusions:

• Post-growth nanosecond pulsed laser melting (PLM) is a viable method for strain and band-gap engineering in highly mismatched GeSn alloys.
• PLM offers a pathway to overcome strain-induced property degradation in GeSn/Ge heterostructures.
• The technique allows for controlled strain modulation while preserving material integrity.