GaAs to Si Nano-Bonding at T<220°C - Optimizing Nano-Contacting and Surface Energy Engineering for Interphase Formation
POSTER
Abstract
Bonding GaAs to Si yields highly efficient tandem solar cells. However, the use of high temperatures in heterostructure formation and native oxides create defects that inhibit bonding.
This work uses instead low temperature Nano-BondingTM, 1 (NB), via Surface Energy Engineering (SEE), to create 2D Precursor Phases leading to a high density of molecular cross-bonds and interphase formation. SEE is based on surface energy (SE) characterization via Three Liquid Contact Angle Analysis (3LCAA), and on composition by Ion Beam Analysis (IBA), and X-Ray Photoelectron Spectroscopy (XPS).
IBA yields absolute O coverages while XPS measures the distribution of oxidation states.
After Nano-Bonding, Surface Acoustic Wave Microscopy (SAM) and Cross-Sectional Transmission Electron Microscopy (TEM) image the bonded interface. SAM reveals that 98±1% of GaAs successfully nano-bonds to Si at T<220°C with compression and 48±1% bonds without compression.
TEM further reveals that both GaAs and Si are so reactive after SEE, that they oxidize very significantly without pressure applied in gaps found in the 48±1% bonded interphase.
1 Herbots et al. US Pat. 6613677 (2003), 7,851,365 (2010), 9,018,077 (2015), 9,589,801 (2017), pend. (2020)
This work uses instead low temperature Nano-BondingTM, 1 (NB), via Surface Energy Engineering (SEE), to create 2D Precursor Phases leading to a high density of molecular cross-bonds and interphase formation. SEE is based on surface energy (SE) characterization via Three Liquid Contact Angle Analysis (3LCAA), and on composition by Ion Beam Analysis (IBA), and X-Ray Photoelectron Spectroscopy (XPS).
IBA yields absolute O coverages while XPS measures the distribution of oxidation states.
After Nano-Bonding, Surface Acoustic Wave Microscopy (SAM) and Cross-Sectional Transmission Electron Microscopy (TEM) image the bonded interface. SAM reveals that 98±1% of GaAs successfully nano-bonds to Si at T<220°C with compression and 48±1% bonds without compression.
TEM further reveals that both GaAs and Si are so reactive after SEE, that they oxidize very significantly without pressure applied in gaps found in the 48±1% bonded interphase.
1 Herbots et al. US Pat. 6613677 (2003), 7,851,365 (2010), 9,018,077 (2015), 9,589,801 (2017), pend. (2020)
*SiO2 Innovates LLC
AccuAngle Analytics LLC
Presenters
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Siddarth Jandhyala
- Dpt of Physics/Eyring Materials Center, Arizona State University
- Physics Dpt/Eyring Materials Cr, Arizona State University