Structural Characteristics of Au-GaAs Nanostructures for Increased Plasmonic Enhancement

Student: Grant Abbey

Major Professor: Dr. Joseph B Herzog

Research Area(s):

Photonics

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Background/Relevance

 

  • Free electrons in metallic structures receiving an incident electric field have been shown to exhibit collective oscillations and produce increased electromagnetic fields (i.e. plasmons). 

  • Deposition of metallic micro/nanostructures on a semiconducting substrate allow for generation of greater photocurrent in the device.

Innovation

  • Enhanced structure design and accurate nanofabrication techniques will lead to greatly improved photovoltaic and photodetection applications.

Approach

  • Generate Au/GaAs models in COMSOL FDTD software for nanoscale and microscale devices.
  • Develop script in MATLAB to calculate and plot optical flux and photocurrent given raw data from COMSOL.
  • Perform various parametric sweeps to vary structural aspects of the structure.
  • Analyze and compare results to experimental data and publications involving similar structures.

Key Results

  • Demonstrated computationally that a reduction in the gap between structures will generate an increase in optical enhancement due to plasmonic effects.
  • Verified with experimental data that reduction of the thickness of both Au and Ti will generate more optical enhancement in the GaAs substrate.

Conclusions

 

  • Smaller nanogaps between structures increases the optical enhancement produced.

  • Complete removal of the Ti layer significantly increases device performance.
  • Decreasing the thickness of the Au layer increases photocurrent produced in the GaAs.