Raman scattering study of GeSn under 〈1 0 0〉 and 〈1 1 0〉 uniaxial stress.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Strain engineering in Germanium-Tin (GeSn) alloys is key for modulating electronic and photonic properties.
• Accurate strain determination in GeSn is challenging due to a lack of established Raman coefficients.

Purpose of the Study:

• To investigate and quantify the Raman-strain function of GeSn alloys along specific crystallographic directions.
• To establish fundamental parameters for the design of novel electronic and photonic devices utilizing strained GeSn.

Main Methods:

• Fabrication of GeSn nanomembranes (NMs) with varying tin compositions.
• Application of uniaxial tensile strain via bending on polyethylene terephthalate substrates.
• Strain analysis using Raman spectroscopy to measure Raman-strain coefficients and ROLC.

Main Results:

• Measured Raman-strain coefficients for Ge$_{0.96}$Sn$_{0.04}$ and Ge$_{0.94}$Sn$_{0.06}$ along $\langle 100\rangle$ and $\langle 110\rangle$ directions.
• Experimental Ratio of Linear Coefficients (ROLC) determined for Ge, Ge$_{0.96}$Sn$_{0.04}$, and Ge$_{0.94}$Sn$_{0.06}$, showing good agreement with theoretical calculations.
• Qualitative analysis of the compositional dependence of phonon deformation potentials (PDPs).

Conclusions:

• The study provides crucial Raman-strain calibration for GeSn alloys.
• The determined parameters, including ROLC and PDPs, are vital for the precise engineering of strained GeSn-based devices.
• This work facilitates the development of next-generation electronic and photonic applications.