Molecular Beam Epitaxy of GeSn on III-V Material Substrates for Photonic Applications

Student: Calbi Gunder

Degree: Ph.D., May 2023

Major Professor: Dr. Gregory Salamo and Dr. Fisher Yu

Research Area(s):

Microelectronic-Photonic Materials & Devices

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Background/Relevance

  • Currently infrared imaging sensors are rather large and expensive which could be alleviated though research into GeSn systems on III-V material substrates.

  • Germanium (Ge) has higher optical absorption efficiency in a range of interest between 1.3-1.6 μm wavelengths for near infrared applications however it has an indirect bandgap. Through the incorporation of Sn, it is possible to shift Ge to a direct bandgap material to become a direct bandgap.

    Innovation

    • Growth of GeSn using MBE on III-V substrates such as InAs and GaAs.

    Approach

    • Through the use of MBE (Molecular Beam Epitaxy), deposit epitaxial GeSn films on InAs and GaAs substrates.
    • Use buffer layers to reduce strain
    • Use substrate growth temperatures to affect Sn incorporation

    Key Results

    • XRD data shows a Sn content of up to ≈ 4.12% in the GeSn structure.

    Conclusions

    • Sn incorporation is rather low. More experimentation needs to be done to increase Sn percent.

    • Low film quality

    Future Work

    • Increase composition of max GeSn composition and film quality on InAs

    • Investigate separately the growth of Ge and Sn on InAs

    • Growth GeSn on InGaAs