Quantum Efficiency Enhancement in Simulated Nanostructured Negative Electron Affinity GaAs Photocathodes
Journal of Applied Physics
Nanostructured negative electron affinity GaAs photocathodes for a polarized electron source are studied using finite difference time domain optical simulation. The structures studied are nanosquare columns, truncated nanocones, and truncated nanopyramids. Mie-type resonances in the 700–800 nm waveband, suitable for generation of polarized electrons, are identified. At resonance wavelengths, the nanostructures can absorb up to 99% of the incident light. For nanosquare columns and truncated nanocones, the maximum quantum efficiency (QE) at 780 nm obtained from simulation is 27%, whereas for simulated nanopyramids, the QE is ∼21%. The high photocathode quantum efficiency is due to the shift of Mie resonance toward the longer wavelength, leading to increased light absorption. The field profile distribution shows the excitation of dipole and quadrupole modes within the nanostructures at resonant frequencies. This leads to enhanced photoabsorption and photoelectron generation closer to emission surfaces than for a flat photocathode. The enhanced photoabsorption and reduced electron transport distance for the nanostructured photocathode enhance its QE compared to that for the flat surface wafer.
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Rahman, M. A. A., Zhang, S., & Elsayed-Ali, H. E. (2023). Quantum efficiency enhancement in simulated nanostructured negative electron affinity GaAs photocathodes. Journal of Applied Physics, 133(2), 1-13, Article 023105.
and may be found at https://doi.org/10.1063/5.0130884.
Article states: The data that support the findings of this study are available from the corresponding author upon reasonable request.
Original Publication Citation
Rahman, M. A. A., Zhang, S., & Elsayed-Ali, H. E. (2023). Quantum efficiency enhancement in simulated nanostructured negative electron affinity GaAs photocathodes. Journal of Applied Physics, 133(2), 1-13, Article 023105. https://doi.org/10.1063/5.0130884
Rahman, Md Aziz Ar; Zhang, Shukui; and Elsayed-Ali, Hani E., "Quantum Efficiency Enhancement in Simulated Nanostructured Negative Electron Affinity GaAs Photocathodes" (2023). Physics Faculty Publications. 717.
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