Self-diffusion of (31)Si and (71)Ge in relaxed Si(0.20)Ge(0.80) layers

Area of Science:

• Materials Science
• Solid-State Physics
• Semiconductor Research

Background:

• Understanding diffusion mechanisms in semiconductor alloys is crucial for device fabrication.
• Silicon-germanium (SiGe) alloys offer tunable electronic properties.
• Accurate self-diffusion data informs material modeling and process optimization.

Purpose of the Study:

• To investigate the self-diffusion behavior of silicon-31 and germanium-71 in relaxed Si(0.20)Ge(0.80) layers.
• To determine the diffusion coefficients, activation enthalpies, and preexponential factors for Si and Ge self-diffusion.
• To elucidate the dominant diffusion mechanism in SiGe alloys.

Main Methods:

• Utilized a modified radiotracer technique for precise diffusion measurements.
• Performed experiments within a controlled temperature range of 730-950 °C.
• Analyzed diffusion profiles to extract diffusion parameters.

Main Results:

• Identified Arrhenius-type temperature dependence for both Si-31 and Ge-71 diffusion.
• Obtained activation enthalpies of 3.6 eV for Si-31 and 3.5 eV for Ge-71.
• Found Ge-71 diffusion to be only slightly faster than Si-31 diffusion.

Conclusions:

• Concluded that both Si-31 and Ge-71 diffuse via a vacancy mechanism in Si(0.20)Ge(0.80), similar to pure Germanium.
• Suggested that Ge-71 radioisotopes can serve as a practical substitute for the short-lived Si-31 tracer in self-diffusion studies of Si-Ge.
• Highlighted the importance of vacancy-mediated diffusion in SiGe alloys.