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Surface Energy Engineering of GaAs and Si for NanoBonding in Tandem Solar Cells

POSTER

Abstract



Semiconductor heterostructures are essential to create highly efficient tandem solar cells. But native oxides and high temperatures can inhibit bonding and limit efficiency.
This work uses Surface Energy Engineering (SEE) of Si and GaAs to modify surfaces and reduce oxides prior to NanoBonding™. SEE is based on characterization of surfaces via Three Liquid Contact Angle Analysis (3LCAA), Ion-Beam Analysis (IBA), and X-ray Photoelectron Spectroscopy (XPS).
3LCAA measures contact angles to calculate total surface energy before and after SEE. Results from 3LCAA reveal that after SEE, GaAs shifts from hydrophobic to super-hydrophilic while Si is the converse. SEE alters both surface energies by a magnitude of two.
IBA combined with Nuclear Resonance and <111> channeling shows that absolute O coverage decreases by 12% ± 3% on Si and 49% ± 4% on GaAs.
XPS quantifies changes in Ga and As oxidation levels. The most significant difference is that of the 20% of As bound oxygen, about 40% is bound as Oxygen-poor As2O3 after SEE, twice as much as before. XPS shows that the Ga:As ratio remains 1:1 before and after etching.
SEE is found to modify surfaces into far-from-equilibrium states that facilitate efficient Nano-Bonding™.

Presenters

  • Pranav Penmatcha

    Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University

Authors

  • Pranav Penmatcha

    Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University

  • Aashi R Gurijala

    Physics, Arizona State University, Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University, Physics and Eyring Materials Center, Arizona State University

  • Siddarth Jandhyala

    Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University

  • Nikhil Suresh

    Physics, Arizona State University, Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University, Physics and Eyring Materials Center, Arizona State University

  • Amber A Chow

    Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University

  • Shaurya Khanna

    Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University

  • Wesley Peng

    Physics, Arizona State University, Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University, Physics and Eyring Materials Center, Arizona State University

  • Thilina Balasooriya

    Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University, Physics and Eyring Materials Center, Arizona State University

  • Mohammed Sahal

    Physics, Arizona State University, SiO2 Innovates LLC, Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University, SiO2 Innovates, LLC

  • Sukesh Ram

    Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University

  • Robert J Culbertson

    Physics, Arizona State University, Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University, Physics and Eyring Materials Center, Arizona State University

  • Nicole Herbots

    Physics, Arizona State University, Dpt of Physics/Eyring Materials Center, Arizona State University, Physics Dpt/Eyring Materials Cr, Arizona State University, Physics and Eyring Materials Center, Arizona State University